zoology genetic drift
 

[FONT=Verdana][SIZE=2][COLOR=black][B]Genetic drift

[/B][/COLOR] [COLOR=black]In [/COLOR][URL="http://en.wikipedia.org/wiki/Population_genetics"][COLOR=black]population genetics[/COLOR][/URL][COLOR=black], [B]genetic drift[/B] (or more precisely [B]allelic drift[/B]) is the [/COLOR][URL="http://en.wikipedia.org/wiki/Statistics"][COLOR=black]statistical[/COLOR][/URL][COLOR=black] effect that results from the influence that chance has on the survival of [/COLOR][URL="http://en.wikipedia.org/wiki/Allele"][COLOR=black]alleles[/COLOR][/URL][COLOR=black] (variants of a [/COLOR][URL="http://en.wikipedia.org/wiki/Gene"][COLOR=black]gene[/COLOR][/URL][COLOR=black]). The effect may cause an allele, and the [/COLOR][URL="http://en.wikipedia.org/wiki/Biological_trait"][COLOR=black]biological trait[/COLOR][/URL][COLOR=black] that it confers, to become more common or rare over successive generations. Ultimately, the drift may either remove the allele from the [/COLOR][URL="http://en.wikipedia.org/wiki/Gene_pool"][COLOR=black]gene pool[/COLOR][/URL][COLOR=black] or remove all other alleles. Whereas [/COLOR][URL="http://en.wikipedia.org/wiki/Natural_selection"][COLOR=black]natural selection[/COLOR][/URL][COLOR=black] is the tendency of beneficial alleles to become more common over time (and detrimental ones less common), genetic drift is the fundamental tendency of any allele to vary randomly in frequency over time due to statistical variation alone, so long as it does not comprise all or none of the distribution.

[/COLOR] [COLOR=black]Chance affects the commonality or rarity of an allele, because no trait guarantees survival of a given number of offspring. This is because survival depends on non-genetic factors (such as the possibility of being in the wrong place at the wrong time). In other words, even when individuals face the same odds, they will differ in their success. A rare succession of chance events — rather than [/COLOR][URL="http://en.wikipedia.org/wiki/Natural_selection"][COLOR=black]natural selection[/COLOR][/URL][COLOR=black] — can thus bring a trait to predominance, causing a population or species to evolve.

[/COLOR] [COLOR=black]An important aspect of genetic drift is that its rate is expected to depend strongly on population size as a consequence of the [/COLOR][URL="http://en.wikipedia.org/wiki/Law_of_large_numbers"][COLOR=black]law of large numbers[/COLOR][/URL][COLOR=black]. When many individuals carry a particular allele, and all face equal odds, the number of offspring they collectively produce will only slightly differ from the expected value, which is the expected average per individual times the number of individuals. But with a small effective breeding size, a departure from the norm in one individual causes a disproportionately greater deviation from the expected result. Therefore small populations are subject to more drift than large ones.This is also the basis for the [/COLOR][URL="http://en.wikipedia.org/wiki/Founder_effect"][COLOR=black]founder effect[/COLOR][/URL][COLOR=black], a proposed mechanism of [/COLOR][URL="http://en.wikipedia.org/wiki/Speciation"][COLOR=black]speciation[/COLOR][/URL][COLOR=black].

[/COLOR] [COLOR=black]By definition, genetic drift has no preferred direction. A neutral allele may be expected to increase or decrease in any given generation with equal probability. Given sufficiently long time, however, the mathematics of genetic drift (cf. [/COLOR][URL="http://en.wikipedia.org/wiki/Galton-Watson_process"][COLOR=black]Galton-Watson process[/COLOR][/URL][COLOR=black]) predict the allele will either die out or be present in 100% of the population, after which time there is no random variation in the associated [/COLOR][URL="http://en.wikipedia.org/wiki/Gene"][COLOR=black]gene[/COLOR][/URL][COLOR=black]. Thus genetic drift tends to sweep gene variants out of a population over time, such that all members of a species would eventually be [/COLOR][URL="http://en.wikipedia.org/wiki/Homozygous"][COLOR=black]homozygous[/COLOR][/URL][COLOR=black] for this gene. In this regard, genetic drift opposes [/COLOR][URL="http://en.wikipedia.org/wiki/Genetic_mutation"][COLOR=black]genetic mutation[/COLOR][/URL][COLOR=black] which introduces novel variants into the population according to its own random processes.

[/COLOR] [B][COLOR=black]Allele frequencies

[/COLOR] [/B][COLOR=black]From the perspective of [/COLOR][URL="http://en.wikipedia.org/wiki/Population_genetics"][COLOR=black]population genetics[/COLOR][/URL][COLOR=black], drift is a "sampling effect." To illustrate: on average, coins turn up heads or tails with equal probability. Yet just a few tosses in a row are unlikely to produce heads and tails in equal number. The numbers are no more likely to be exactly equal for many tosses in a row, but the discrepancy in number can be very small (in percentage terms). As an example, ten tosses turn up at least 70% heads about once in every six tries, but the chance of a hundred tosses in a row producing at least 70% heads is only about one in 25,000.

[/COLOR] [COLOR=black]Similarly, in a breeding population, if an allele has a frequency of [I]p[/I], probability theory dictates that (if natural selection is not acting) in the following generation, a fraction [I]p[/I] of the population will inherit that particular allele. However, as with the coin toss above, allele frequencies in real populations are not probability distributions; rather, they are a random sample, and are thus subject to the same statistical fluctuations ([/COLOR][URL="http://en.wikipedia.org/wiki/Sampling_error"][COLOR=black]sampling error[/COLOR][/URL][COLOR=black]).

[/COLOR] [COLOR=black]When the alleles of a gene do not differ with regard to fitness, on average the number of carriers in one generation is proportional to the number of carriers in the previous generation. But the average is never tallied, because each generation parents the next one only once. Therefore the frequency of an allele among the offspring often differs from its frequency in the parent generation. In the offspring generation, the allele might therefore have a frequency [I]p'[/I], slightly different from [I]p[/I]. In this situation, the allele frequencies are said to have [B]drifted[/B]. Note that the frequency of the allele in subsequent generations will now be determined by the new frequency [I]p'[/I], meaning that drift is a memoryless process and may be modeled as a [/COLOR][URL="http://en.wikipedia.org/wiki/Markov_process"][COLOR=black]Markov process[/COLOR][/URL][COLOR=black].

[/COLOR] [COLOR=black]As in the coin toss example above, the size of the breeding population (the [/COLOR][URL="http://en.wikipedia.org/wiki/Effective_population_size"][COLOR=black]effective population size[/COLOR][/URL][COLOR=black]) governs the strength of the drift effect. When the effective population size is small, genetic drift will be stronger.

[/COLOR] [COLOR=black]Drifting alleles usually have a finite lifetime. As the frequency of an allele drifts up and down over successive generations, eventually it drifts until fixation - that is, it either reaches a frequency of zero, and disappears from the population, or it reaches a frequency of 100% and becomes the only allele in the population. Subsequent to the latter event, the allele frequency can only change by the introduction of a new allele by a new [/COLOR][URL="http://en.wikipedia.org/wiki/Mutation"][COLOR=black]mutation[/COLOR][/URL][COLOR=black].[/COLOR]
[COLOR=black]The lifetime of an allele is governed by the effective population size. In a very small population, only a few generations might be required for genetic drift to result in fixation. In a large population, it would take many more generations. On average, an allele will be fixed in 4[I]Ne[/I] generations, where [I]Ne[/I] is the effective population size.

[/COLOR] [COLOR=black]According to the [/COLOR][URL="http://en.wikipedia.org/wiki/Hardy-Weinberg_Principle"][COLOR=black]Hardy-Weinberg Principle[/COLOR][/URL][COLOR=black], which holds that allele frequencies in a gene pool will not change over time, a population must be sufficiently large to prevent genetic drift from changing allele frequencies over time. This is why the law is unstable in a small population.

[/COLOR] [B][COLOR=black]Drift versus selection

[/COLOR] [/B][COLOR=black]Genetic drift and [/COLOR][URL="http://en.wikipedia.org/wiki/Natural_selection"][COLOR=black]natural selection[/COLOR][/URL][COLOR=black] rarely occur in isolation from each other; both forces are always at play in a population. However, the degree to which alleles are affected by drift and selection varies according to circumstance.

[/COLOR] [COLOR=black]In a large population, where genetic drift occurs very slowly, even weak selection on an allele will push its frequency upwards or downwards (depending on whether the allele is beneficial or harmful). However, if the population is very small, drift will predominate. In this case, weak selective effects may not be seen at all as the small changes in frequency they would produce are overshadowed by drift.

[/COLOR] [B][COLOR=black]Genetic drift in populations

[/COLOR] [/B][COLOR=black]Drift can have profound and often bizarre effects on the evolutionary history of a population. These effects may be at odds with the survival of the population.

[/COLOR] [COLOR=black]In a [/COLOR][URL="http://en.wikipedia.org/wiki/Population_bottleneck"][COLOR=black]population bottleneck[/COLOR][/URL][COLOR=black], where the population suddenly contracts to a small size (believed to have occurred in the history of human evolution), genetic drift can result in sudden and dramatic changes in allele frequency that occur independently of selection. In such instances, many beneficial adaptations may be eliminated even if population later grows large again.[/COLOR]
[COLOR=black]Similarly, migrating populations may see a [/COLOR][URL="http://en.wikipedia.org/wiki/Founder_effect"][COLOR=black]founder effect[/COLOR][/URL][COLOR=black], where a few individuals with a rare allele in the originating generation can produce a population that has allele frequencies that seem to be at odds with natural selection. Founder's effects are sometimes held to be responsible for high frequencies of some genetic diseases.[/COLOR][/SIZE][/FONT]

zoology nitrogen cycle
 

[B][SIZE=6][CENTER][SIZE=3][COLOR=black]The Nitrogen Cycle[/COLOR][/SIZE][/CENTER]
[/SIZE][/B][SIZE=6]
[/SIZE][COLOR=black]All life requires nitrogen-compounds, e.g., proteins and nucleic acids. [/COLOR]
[COLOR=black]Air, which is 79% nitrogen gas (N2), is the major reservoir of nitrogen. [/COLOR]
[COLOR=black]But most organisms cannot use nitrogen in this form. [/COLOR]

[COLOR=black]Plants must secure their nitrogen in "fixed" form, i.e., incorporated in compounds such as: [/COLOR][LIST][*][COLOR=black]nitrate ions (NO3−) [/COLOR][*][COLOR=black]ammonia (NH3) [/COLOR][*][COLOR=black]urea (NH2)2CO [/COLOR][/LIST][COLOR=black]Animals secure their nitrogen (and all other) compounds from plants (or animals that have fed on plants). [/COLOR]

[COLOR=black]Four processes participate in the cycling of nitrogen through the biosphere: [/COLOR][LIST=1][*][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NitrogenCycle.html//lNitrogen_Fixation"][COLOR=black]nitrogen fixation[/COLOR][/URL][*][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NitrogenCycle.html//lDecay"][COLOR=black]decay[/COLOR][/URL][*][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NitrogenCycle.html//lNitrification"][COLOR=black]nitrification[/COLOR][/URL][*][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/N/NitrogenCycle.html//lDenitrification"][COLOR=black]denitrification[/COLOR][/URL][/LIST][COLOR=black]Microorganisms play major roles in all four of these.
[/COLOR]
[B][COLOR=black]Nitrogen Fixation[/COLOR][/B]

[COLOR=black]The nitrogen molecule (N2) is quite inert. To break it apart so that its atoms can combine with other atoms requires the input of substantial amounts of energy. [/COLOR]

[COLOR=black]Three processes are responsible for most of the nitrogen fixation in the biosphere: [/COLOR][LIST][*][COLOR=black][B]Atmospheric fixation[/B] by lightning [/COLOR][*][COLOR=black][B]Biological fixation[/B] by certain microbes — alone or in a [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Symbiosis.html"][COLOR=black]symbiotic[/COLOR][/URL][*][B][COLOR=black]Industrial fixation[/COLOR][/B][/LIST][B][COLOR=black]Atmospheric Fixation[/COLOR][/B]

[COLOR=black]The enormous energy of lightning breaks nitrogen molecules and enables their atoms to combine with oxygen in the air forming nitrogen oxides. These dissolve in rain, forming nitrates, that are carried to the earth. [/COLOR]

[COLOR=black]Atmospheric nitrogen fixation probably contributes some 5– 8% of the total nitrogen fixed. [/COLOR]

[B][COLOR=black]Industrial Fixation[/COLOR][/B]

[COLOR=black]Under great pressure, at a temperature of 600°C, and with the use of a catalyst, atmospheric nitrogen and hydrogen (usually derived from natural gas or petroleum) can be combined to form ammonia (NH3). Ammonia can be used directly as fertilizer, but most of its is further processed to [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/U/UreaCycle.gif"][COLOR=black]urea[/COLOR][/URL][COLOR=black] and ammonium nitrate (NH4NO3). [/COLOR]

[B][COLOR=black]Biological Fixation[/COLOR][/B]

[COLOR=black]The ability to fix nitrogen is found only in certain [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Eubacteria.html"][COLOR=black]bacteria[/COLOR][/URL][COLOR=black] and [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Archaea.html"][COLOR=black]archaea[/COLOR][/URL][COLOR=black]. [/COLOR]

[COLOR=black]Some live in a symbiotic relationship with plants of the legume family (e.g., soybeans, alfalfa). [/COLOR]

[COLOR=black]Some establish symbiotic relationships with plants other than legumes (e.g., alders). [/COLOR]

[COLOR=black]Some establish symbiotic relationships with animals, e.g., [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/Insects.html"][COLOR=black]termites[/COLOR][/URL][COLOR=black] and "shipworms" (wood-eating [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/I/Invertebrates.html//lMollusks"][COLOR=black]bivalves[/COLOR][/URL][COLOR=black]). [/COLOR]

[COLOR=black]Some nitrogen-fixing bacteria live free in the soil. [/COLOR]

[COLOR=black]Nitrogen-fixing [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Eubacteria.html//lCyanobacteria"][COLOR=black]cyanobacteria[/COLOR][/URL][COLOR=black] are essential to maintaining the fertility of semi-aquatic environments like rice paddies.[/COLOR]

[COLOR=black]Biological nitrogen fixation requires a complex set of enzymes and a huge expenditure of ATP. [/COLOR]

[COLOR=black]Although the first stable product of the process is ammonia, this is quickly incorporated into protein and other organic nitrogen compounds. [/COLOR]

[B][COLOR=black]Decay[/COLOR][/B]

[COLOR=black]The proteins made by plants enter and pass through food webs just as carbohydrates do. At each [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html//lFood_Chains"][COLOR=black]trophic level[/COLOR][/URL][COLOR=black], their metabolism produces organic nitrogen compounds that return to the environment, chiefly in excretions. The final beneficiaries of these materials are microorganisms of decay. They break down the molecules in excretions and dead organisms into [B]ammonia[/B]. [/COLOR]

[B][COLOR=black]Nitrification[/COLOR][/B]

[COLOR=black]Ammonia can be taken up directly by plants — usually through their roots. However, most of the ammonia produced by decay is converted into [B]nitrates[/B]. This is accomplished in two steps: [/COLOR]

[COLOR=black]Bacteria of the genus [B]Nitrosomonas[/B] oxidize NH3 to [B]nitrites[/B] (NO2−). [/COLOR]
[COLOR=black]Bacteria of the genus [B]Nitrobacter[/B] oxidize the nitrites to [B]nitrates[/B] (NO3−).[/COLOR]
[COLOR=black]These two groups of autotrophic bacteria are called [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Eubacteria.html//lNitrifying_bacteria"][B][COLOR=black]nitrifying bacteria[/COLOR][/B][/URL][COLOR=black]. Through their activities (which supply them with all their energy needs), nitrogen is made available to the roots of plants. [/COLOR]

[COLOR=black]Many soils also contain archaeal microbes, assigned to the [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/Archaea.html//lCrenarchaeota"][COLOR=black]Crenarchaeota[/COLOR][/URL][COLOR=black], that convert ammonia to nitrites. While more abundant than the nitrifying bacteria, it remains to be seen whether they play as important a role in the nitrogen cycle. [/COLOR]

[COLOR=black]Many legumes, in addition to fixing atmospheric nitrogen, also perform nitrification — converting some of their organic nitrogen to nitrites and nitrates. These reach the soil when they shed their leaves. [/COLOR]

[B][COLOR=black]Denitrification[/COLOR][/B]

[COLOR=black]The three processes above remove nitrogen from the atmosphere and pass it through ecosystems.[/COLOR]

[COLOR=black]Denitrification reduces nitrates to nitrogen gas, thus replenishing the atmosphere. [/COLOR]

[COLOR=black]Once again, bacteria are the agents. They live deep in soil and in aquatic sediments where conditions are [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/A.html//lanaerobic"][COLOR=black]anaerobic[/COLOR][/URL][COLOR=black]. They use nitrates as an alternative to oxygen for the final electron acceptor in their [/COLOR][URL="http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CellularRespiration.html//lrespiratory_chain"][COLOR=black]respiration[/COLOR][/URL][COLOR=black]. [/COLOR]
[COLOR=black]Thus they close the nitrogen cycle. [/COLOR]

[B][COLOR=black]Are the denitrifiers keeping up?[/COLOR][/B]

[COLOR=black]Agriculture may now be responsible for one-half of the nitrogen fixation on earth through [/COLOR][LIST][*][COLOR=black]the use of fertilizers produced by industrial fixation [/COLOR][*][COLOR=black]the growing of legumes like soybeans and alfalfa.[/COLOR][/LIST][COLOR=black]This is a remarkable influence on a natural cycle. [/COLOR]

[COLOR=black]Are the denitrifiers keeping up the nitrogen cycle in balance? Probably not. Certainly, there are examples of nitrogen enrichment in ecosystems. One troubling example: the "blooms" of algae in lakes and rivers as nitrogen fertilizers leach from the soil of adjacent farms (and lawns). The accumulation of dissolved nutrients in a body of water is called [B]eutrophication.[/B][/COLOR]

zoology cell bio- mitochondria
 

[SIZE=4][CENTER][SIZE=3][COLOR=darkred][B]Mitochondria[/B][/COLOR][/SIZE][/CENTER]


[/SIZE][CENTER]Mitochondria are rod-shaped organelles that can be considered the power generators of the cell, converting oxygen and nutrients into adenosine triphosphate ([B]ATP[/B]). ATP is the chemical energy "currency" of the cell that powers the cell's metabolic activities. This process is called [B]aerobic respiration[/B] and is the reason animals breathe oxygen. Without mitochondria (singular, mitochondrion), higher animals would likely not exist because their cells would only be able to obtain energy from anaerobic respiration (in the absence of oxygen), a process much less efficient than aerobic respiration. In fact, mitochondria enable cells to produce 15 times more ATP than they could otherwise, and complex animals, like humans, need large amounts of energy in order to survive.[/CENTER]

The number of mitochondria present in a cell depends upon the metabolic requirements of that cell, and may range from a single large mitochondrion to thousands of the organelles. Mitochondria, which are found in nearly all eukaryotes, including plants, animals, fungi, and protists, are large enough to be observed with a light microscope and were first discovered in the 1800s. The name of the organelles was coined to reflect the way they looked to the first scientists to observe them, stemming from the Greek words for "thread" and "granule." For many years after their discovery, mitochondria were commonly believed to transmit hereditary information. It was not until the mid-1950s when a method for isolating the organelles intact was developed that the modern understanding of mitochondrial function was worked out.
The elaborate structure of a mitochondrion is very important to the functioning of the organelle. Two specialized membranes encircle each mitochondrion present in a cell, dividing the organelle into a narrow [B]intermembrane space[/B] and a much larger internal [B]matrix[/B], each of which contains highly specialized proteins. The outer membrane of a mitochondrion contains many channels formed by the protein [B]porin[/B] and acts like a sieve, filtering out molecules that are too big. Similarly, the inner membrane, which is highly convoluted so that a large number of infoldings called [B]cristae[/B] are formed, also allows only certain molecules to pass through it and is much more selective than the outer membrane. To make certain that only those materials essential to the matrix are allowed into it, the inner membrane utilizes a group of transport proteins that will only transport the correct molecules. Together, the various compartments of a mitochondrion are able to work in harmony to generate ATP in a complex multi-step process.
Mitochondria are generally oblong organelles, which range in size between 1 and 10 micrometers in length, and occur in numbers that directly correlate with the cell's level of metabolic activity. The organelles are quite flexible, however, and time-lapse studies of living cells have demonstrated that mitochondria change shape rapidly and move about in the cell almost constantly. Movements of the organelles appear to be linked in some way to the microtubules present in the cell, and are probably transported along the network with motor proteins. Consequently, mitochondria may be organized into lengthy traveling chains, packed tightly into relatively stable groups, or appear in many other formations based upon the particular needs of the cell and the characteristics of its microtubular network.The mitochondrion is different from most other organelles because it has its own circular DNA (similar to the DNA of prokaryotes) and reproduces independently of the cell in which it is found; an apparent case of [B]endosymbiosis[/B]. Scientists hypothesize that millions of years ago small, free-living prokaryotes were engulfed, but not consumed, by larger prokaryotes, perhaps because they were able to resist the digestive enzymes of the host organism. The two organisms developed a symbiotic relationship over time, the larger organism providing the smaller with ample nutrients and the smaller organism providing ATP molecules to the larger one. Eventually, according to this view, the larger organism developed into the eukaryotic cell and the smaller organism into the mitochondrion.
Mitochondrial DNA is localized to the matrix, which also contains a host of enzymes, as well as ribosomes for protein synthesis. Many of the critical metabolic steps of cellular respiration are catalyzed by enzymes that are able to diffuse through the mitochondrial matrix. The other proteins involved in respiration, including the enzyme that generates ATP, are embedded within the mitochondrial inner membrane. Infolding of the cristae dramatically increases the surface area available for hosting the enzymes responsible for cellular respiration.
Mitochondria are similar to plant chloroplasts in that both organelles are able to produce energy and metabolites that are required by the host cell. As discussed above, mitochondria are the sites of respiration, and generate chemical energy in the form of ATP by metabolizing sugars, fats, and other chemical fuels with the assistance of molecular oxygen. Chloroplasts, in contrast, are found only in plants and algae, and are the primary sites of photosynthesis. These organelles work in a different manner to convert energy from the sun into the biosynthesis of required organic nutrients using carbon dioxide and water. Like mitochondria, chloroplasts also contain their own DNA and are able to grow and reproduce independently within the cell.
In most animal species, mitochondria appear to be primarily inherited through the maternal lineage, though some recent evidence suggests that in rare instances mitochondria may also be inherited via a paternal route. Typically, a sperm carries mitochondria in its tail as an energy source for its long journey to the egg. When the sperm attaches to the egg during fertilization, the tail falls off. Consequently, the only mitochondria the new organism usually gets are from the egg its mother provided. Therefore, unlike nuclear DNA, mitochondrial DNA doesn't get shuffled every generation, so it is presumed to change at a slower rate, which is useful for the study of human evolution. Mitochondrial DNA is also used in forensic science as a tool for identifying corpses or body parts, and has been implicated in a number of genetic diseases, such as Alzheimer's disease and diabetes

zoology Ecosystem
 

[SIZE=4][FONT=Georgia][SIZE=3][COLOR=darkred][B]What is a Biome?

[/B][/COLOR][/SIZE][/FONT] [/SIZE][FONT=Georgia]A biome is a large geographical area of distinctive plant and animal groups, which are adapted to that particular environment. The climate and geography of a region determines what type of biome can exist in that region. Major biomes include deserts, forests, grasslands, tundra, and several types of aquatic environments. Each biome consists of many ecosystems whose communities have adapted to the small differences in climate and the environment inside the biome.[/FONT]
[FONT=Georgia]All living things are closely related to their environment. Any change in one part of an environment, like an increase or decrease of a species of animal or plant, causes a ripple effect of change in through other parts of the environment. [/FONT]
[FONT=Georgia]The earth includes a huge variety of living things, from complex plants and animals to very simple, one-celled organisms. But large or small, simple or complex, no organism lives alone. Each depends in some way on other living and nonliving things in its surroundings.[/FONT]


[SIZE=4][FONT=Georgia][SIZE=3][COLOR=darkred][B]Deciduous forests

[/B][/COLOR][/SIZE][/FONT] [/SIZE][FONT=Georgia]Deciduous forests can be found in the eastern half of North America, and the middle of Europe. There are many deciduous forests in Asia. Some of the major areas that they are in are southwest Russia, Japan, and eastern China. South America has two big areas of deciduous forests in southern Chile and Middle East coast of Paraguay. There are deciduous forests located in New Zealand, and southeastern Australia also. [/FONT]

[FONT=Georgia]The average annual temperature in a deciduous forest is 50° F. The average rainfall is 30 to 60 inches a year. [/FONT]

[FONT=Georgia]In deciduous forests there are five different zones. The first zone is the Tree Stratum zone. The Tree Stratum zone contains such trees as oak, beech, maple, chestnut hickory, elm, basswood, linden, walnut, and sweet gum trees. This zone has height ranges between 60 feet and 100 feet. [/FONT]

[FONT=Georgia]The small tree and sapling zone is the second zone. This zone has young, and short trees. The third zone is called the shrub zone. Some of the shrubs in this zone are rhododendrons, azaleas, mountain laurel, and huckleberries. The Herb zone is the fourth zone. It contains short plants such as herbal plants. The final zone is the Ground zone. It contains lichen, club mosses, and true mosses. [/FONT]

[FONT=Georgia]The deciduous forest has four distinct seasons, spring, summer, autumn, and winter. In the autumn the leaves change color. During the winter months the trees lose their leaves. [/FONT]

[FONT=Georgia]The animals adapt to the climate by hibernating in the winter and living off the land in the other three seasons. The animals have adapted to the land by trying the plants in the forest to see if they are good to eat for a good supply of food. Also the trees provide shelter for them. Animal use the trees for food and a water sources. Most of the animals are camouflaged to look like the ground.[/FONT]
[FONT=Georgia]The plants have adapted to the forests by leaning toward the sun. Soaking up the nutrients in the ground is also a way of adaptation. [/FONT]

[FONT=Georgia]A lot of deciduous forests have lost land to farms and towns. Although people are trying to protect the forests some poachers are trying to kill the animals in the forests. The animals are losing their homes because of people building their homes.[/FONT]


[FONT=Georgia][SIZE=3][COLOR=darkred][B]DESERT ECOSYSTEM.


[/B] [/COLOR][/SIZE][/FONT][FONT=Georgia]A Hot and Dry Desert is, as you can tell from the name, hot and dry. Most Hot and Dry Deserts don't have very many plants. They do have some low down plants though. The only animals they have that can survive have the ability to burrow under ground. This is because they would not be able to live in the hot sun and heat. They only come out in the night when it is a little cooler.[/FONT]

[FONT=Georgia]A cold desert is a desert that has snow in the winter instead of just dropping a few degrees in temperature like they would in a Hot and Dry Desert. It never gets warm enough for plants to grow. Just maybe a few grasses and mosses. The animals in Cold Deserts also have to burrow but in this case to keep warm, not cool. That is why you might find some of the same animals here as you would in the Hot and Dry Deserts.[/FONT]

[FONT=Georgia]Deserts cover about one fifth of the Earth's land surface. Most Hot and Dry Deserts are near the Tropic of Cancer or the Tropic of Capricorn. Cold Deserts are near the Arctic part of the world.[/FONT]
[FONT=Georgia]Hot and Dry Deserts temperature ranges from 20 to 25° C. The extreme maximum temperature for Hot Desert ranges from 43.5 to 49° C. Cold Deserts temperature in winter ranges from -2 to 4° C and in the summer 21 to 26° C a year[/FONT]
[FONT=Georgia]The precipitation in Hot and Dry Deserts and the precipitation in Cold Deserts is different. Hot and Dry Deserts usually have very little rainfall and/or concentrated rainfall in short periods between long rainless periods. This averages out to under 15 cm a year. Cold Deserts usually have lots of snow. They also have rain around spring. This averages out to 15 - 26 cm a year.[/FONT]

[FONT=Georgia]Hot and Dry Deserts are warm throughout the fall and spring seasons and very hot during the summer. the winters usually have very little if any rainfall. Cold Deserts have quite a bit of snow during winter. The summer and the beginning of the spring are barely warm enough for a few lichens, grasses and mosses to grow.[/FONT]
[FONT=Georgia]Hot and Dry Deserts vegetation is very rare. Plants are almost all ground-hugging shrubs and short woody trees. All of the leaves are replete (packed with nutrients). Some examples of these kinds of plant are Turpentine Bush, Prickly Pears, and Brittle Bush. For all of these plants to survive they have to have adaptations. Some of the adaptations in this case are the ability to store water for long periods of time and the ability to stand the hot weather. [/FONT]

[FONT=Georgia]Cold Desert's plants are scattered. In areas with little shade,about 10 percent of the ground is covered with plants. In some areas of sagebrush it reaches 85 percent. The height of scrub varies from 15 cm to 122 cm. All plants are either deciduous and more or less contain spiny leaves. [/FONT]

[FONT=Georgia]Hot and Dry Deserts animals include small nocturnal (only active at night) carnivores. There are also insects, arachnids, reptiles, and birds. Some examples of these animals are Borrowers, Mourning Wheatears, and Horned Vipers. Cold Deserts have animals like Antelope, Ground Squirrels, Jack Rabbits, and Kangaroo Rats.[/FONT]

Grassland ecosytem
 

[SIZE=3][COLOR=darkred][B]Grassland Ecosystem[/B][/COLOR][/SIZE]

[FONT=Georgia]Grassland biomes are large, rolling terrains of grasses, flowers and herbs. Latitude, soil and local climates for the most part determine what kinds of plants grow in a particular grassland. A grassland is a region where the average annual precipitation is great enough to support grasses, and in some areas a few trees. The precipitation is so eratic that drought and fire prevent large forests from growing. Grasses can survive fires because they grow from the bottom instead of the top. Their stems can grow again after being burned off. The soil of most grasslands is also too thin and dry for trees to survive. [/FONT]

[FONT=Georgia]When the settlers of the United States moved westward, they found that the grasslands, or prairies as they called them, were more than just dry, flat areas. The prairies contained more than 80 species of animals and 300 species of birds, and hundreds of species of plants. [/FONT]

[FONT=Georgia]There are two different types of grasslands; tall-grass, which are humid and very wet, and short-grass, which are dry, with hotter summers and colder winters than the tall-grass prairie. The settlers found both on their journey west. When they crossed the Mississippi River they came into some very tall grass, some as high as 11 feet. Here it rained quite often and it was very humid. As they traveled further west and approached the Rocky Mountains, the grass became shorter. There was less rain in the summer and the winters got colder. These were the short-grass prairies.[/FONT]

[FONT=Georgia]Grassland biomes can be found in the middle latitudes, in the interiors of continents. They can have either moist continental climates or dry subtropical climates. In Argentina, South America, the grasslands are known as pampas. The climate there is humid and moist. Grasslands in the southern hemisphere tend to get more precipitation than those in the northern hemisphere, and the grass tends to be the tall-grass variety.[/FONT]

[FONT=Georgia]There is a large area of grassland that stretch from the Ukraine of Russia all the way to Siberia. This is a very cold and dry climate because there is no nearby ocean to get moisture from. Winds from the arctic aren't blocked by any mountains either. These are known as the Russian and Asian steppes.[/FONT]
[FONT=Georgia]In the winter, grassland temperatures can be as low as -40° F, and in the summer it can be as high 70° F. There are two real seasons: a growing season and a dormant season. The growing season is when there is no frost and plants can grow (which lasts from 100 to 175 days). During the dormant (not growing) season nothing can grow because its too cold. [/FONT]

[FONT=Georgia]In tropical and subtropical grasslands the length of the growing season is determined by how long the rainy season lasts. But in the temperate grasslands the length of the growing season is determined by temperature. Plants usually start growing when the daily temperature reached about 50° F.[/FONT]
[FONT=Georgia]In temperate grasslands the average rainfall per year ranges from 10-30 inches. In tropical and sub-tropical grasslands the average rainfall per year ranges from 25-60 inches per year The amount of rainfall is very important in determining which areas are grasslands because it's hard for trees to compete with grasses in places where the uppers layers of soil are moist during part of the year but where deeper layer of soil are always dry. [/FONT]

[FONT=Georgia]The most common types of plant life on the North American prairie are Buffalo Grass, Sunflower, Crazy Weed, Asters, Blazing Stars, Coneflowers, Goldenrods, Clover, and Wild Indigos. [/FONT]

[FONT=Georgia]Some common animals in the grasslands are Coyotes, Eagles, Bobcats, the Gray Wolf, Wild Turkey, Fly Catcher, Canadian Geese, Crickets, Dung Beetle, Bison, and Prairie Chicken.[/FONT]

Taiga and Rainforest ecosystem
 

[SIZE=3][COLOR=darkred][B]Rain forest Ecosystem[/B][/COLOR][/SIZE]

[FONT=Georgia]The tropical rain forest can be found in three major geographical areas around the world.[/FONT]
[FONT=Georgia]Central America in the the Amazon river basin. [/FONT]
[FONT=Georgia]Africa - Zaire basin, with a small area in West Africa; also eastern Madagascar. [/FONT]
[FONT=Georgia]Indo-Malaysia - west coast of India, Assam, Southeast Asia, New Guinea and Queensland, Australia. [/FONT]

[FONT=Georgia]The tropical rain forest is a forest of tall trees in a region of year-round warmth. An average of 50 to 260 inches (125 to 660 cm.) of rain falls yearly. [/FONT]
[FONT=Georgia]Rain forests belong to the tropical wet climate group. The temperature in a rain forest rarely gets higher than 93 °F (34 °C) or drops below 68 °F (20 °C); average humidity is between 77 and 88%; rainfall is often more than 100 inches a year. There is usually a brief season of less rain. In monsoonal areas, there is a real dry season. Almost all rain forests lie near the equator.[/FONT]

[FONT=Georgia]Rainforests now cover less than 6% of Earth's land surface. Scientists estimate that more than half of all the world's plant and animal species live in tropical rain forests. Tropical rainforests produce 40% of Earth's oxygen.[/FONT]

[FONT=Georgia]A tropical rain forest has more kinds of trees than any other area in the world. Scientists have counted about 100 to 300 species in one 2 1/2-acre (1-hectare) area in South America. Seventy percent of the plants in the rainforest are trees.[/FONT]
[FONT=Georgia]About 1/4 of all the medicines we use come from rainforest plants. [/FONT][URL="http://www.blueplanetbiomes.org/curare.htm"][U][COLOR=#0000ff][FONT=Georgia]Curare[/FONT][/COLOR][/U][/URL][FONT=Georgia] comes from a tropical vine, and is used as an anesthetic and to relax muscles during surgery. Quinine, from the cinchona tree, is used to treat malaria. A person with lymphocytic leukemia has a 99% chance that the disease will go into remission because of the rosy periwinkle. More than 1,400 varieties of tropical plants are thought to be potential cures for cancer.[/FONT]

[FONT=Georgia]All tropical rain forests resemble one another in some ways. Many of the trees have straight trunks that don't branch out for 100 feet or more. There is no sense in growing branches below the canopy where there is little light. The majority of the trees have smooth, thin bark because there is no need to protect the them from water loss and freezing temperatures. It also makes it difficult for [/FONT][URL="http://www.blueplanetbiomes.org/glossary.htm//lepiphyte"][U][COLOR=#0000ff][FONT=Georgia]epiphytes[/FONT][/COLOR][/U][/URL][FONT=Georgia] and plant parasites to get a hold on the trunks. The bark of different species is so similar that it is difficult to identify a tree by its bark. Many trees can only be identified by their flowers. [/FONT]

[FONT=Georgia]Despite these differences, each of the three largest rainforests--the American, the African, and the Asian--has a different group of animal and plant species. Each rain forest has many species of monkeys, all of which differ from the species of the other two rain forests. In addition, different areas of the same rain forest may have different species. Many kinds of trees that grow in the mountains of the Amazon rain forest do not grow in the lowlands of that same forest. [/FONT]


[B][FONT=Georgia]Layers of the Rainforest[/FONT][/B]

[FONT=Georgia]There are four very distinct layers of trees in a tropical rain forest. These layers have been identified as the emergent, upper canopy, understory, and forest floor.[/FONT]
[URL="http://www.blueplanetbiomes.org/glossary.htm//lemergent"][FONT=Georgia][COLOR=#0000ff]Emergent[/COLOR][/FONT][/URL][FONT=Georgia] trees are spaced wide apart, and are 100 to 240 feet tall with umbrella-shaped canopies that grow above the forest. Because emergent trees are exposed to drying winds, they tend to have small, pointed leaves. Some species lose their leaves during the brief dry season in monsoon rainforests. These giant trees have straight, smooth trunks with few branches. Their root system is very shallow, and to support their size they grow buttresses that can spread out to a distance of 30 feet. [/FONT]

[FONT=Georgia]The upper canopy of 60 to 130 foot trees allows light to be easily available at the top of this layer, but greatly reduced any light below it. Most of the rainforest's animals live in the upper canopy. There is so much food available at this level that some animals never go down to the forest floor. The leaves have "drip spouts" that allows rain to run off. This keeps them dry and prevents mold and mildew from forming in the humid environment. [/FONT]

[FONT=Georgia]The understory, or lower canopy, consists of 60 foot trees. This layer is made up of the trunks of canopy trees, shrubs, plants and small trees. There is little air movement. As a result the humidity is constantly high. This level is in constant shade. [/FONT]

[FONT=Georgia]The forest floor is usually completely shaded, except where a canopy tree has fallen and created an opening. Most areas of the forest floor receive so little light that few bushes or herbs can grow there. As a result, a person can easily walk through most parts of a tropical rain forest. Less than 1 % of the light that strikes the top of the forest penetrates to the forest floor. The top soil is very thin and of poor quality. A lot of litter falls to the ground where it is quickly broken down by decomposers like termites, earthworms and fungi. The heat and humidity further help to break down the litter. This organic matter is then just as quickly absorbed by the trees' shallow roots. [/FONT]


[B][FONT=Georgia]Plant Life[/FONT][/B]

[FONT=Georgia]Besides these four layers, a shrub/sapling layer receives about 3 % of the light that filters in through the canopies. These stunted trees are capable of a sudden growth surge when a gap in the canopy opens above them. [/FONT]

[FONT=Georgia]The air beneath the lower canopy is almost always humid. The trees themselves give off water through the pores (stomata) of their leaves. This process, called transpiration, can account for as much as half of the precipitation in the rain forest. [/FONT]

[FONT=Georgia]Rainforest plants have made many adaptations to their environment. With over 80 inches of rain per year, plants have made adaptations that helps them shed water off their leaves quickly so the branches don't get weighed down and break. Many plants have drip tips and grooved leaves, and some leaves have oily coatings to shed water. To absorb as much sunlight as possible on the dark understory, leaves are very large. Some trees have leaf stalks that turn with the movement of the sun so they always absorb the maximum amount of light. Leaves in the upper canopy are dark green, small and leathery to reduce water loss in the strong sunlight. Some trees will grow large leaves at the lower canopy level and small leaves in the upper canopy. Other plants grow in the upper canopy on larger trees to get sunlight. These are the epiphytes such as orchids and bromeliads. Many trees have buttress and stilt roots for extra support in the shallow, wet soil of the rainforests.[/FONT]

[FONT=Georgia]Over 2,500 species of vines grow in the rainforest. Lianas start off as small shrubs that grow on the forest floor. To reach the sunlight in the upper canopy it sends out tendrils to grab sapling trees. The liana and the tree grow towards the canopy together. The vines grow from one tree to another and make up 40% of the canopy leaves. The rattan vine has spikes on the underside of its leaves that point backwards to grab onto sapling trees. Other "strangler" vines will use trees as support and grow thicker and thicker as they reach the canopy, strangling its host tree. They look like trees whose centers have been hollowed out.[/FONT]

[FONT=Georgia]Dominant species do not exist in tropical rainforests. Lowland dipterocarp forest can consist of many different species of Dipterocarpaceae, but not all of the same species. Trees of the same species are very seldom found growing close together. This bio diversity and separation of the species prevents mass contamination and die-off from disease or insect infestation. Bio diversity also insures that there will be enough pollinators to take care of each species' needs. Animals depend on the staggered blooming and fruiting of rainforest plants to supply them with a year-round source of food.[/FONT]


[B][FONT=Georgia]Animal Life[/FONT][/B]

[FONT=Georgia]Many species of animal life can be found in the rain forest. Common characteristics found among mammals and birds (and reptiles and amphibians, too) include adaptations to a life in the trees, such as the [/FONT][URL="http://www.blueplanetbiomes.org/glossary.htm//lprehensile"][FONT=Georgia][COLOR=#0000ff]prehensile[/COLOR][/FONT][/URL][FONT=Georgia] tails of New World monkeys. Other characteristics are bright colors and sharp patterns, loud vocalizations, and diets heavy on fruits.[/FONT]

[FONT=Georgia]Insects make up the largest single group of animals that live in tropical forests. They include brightly colored butterflies, mosquitoes, camouflaged stick insects, and huge colonies of ants.[/FONT]

[FONT=Georgia]The Amazon river basin rainforest contains a wider variety of plant and animal life than any other biome in the world. The second largest population of plant and animal life can be found in scattered locations and islands of Southeast Asia. The lowest variety can be found in Africa. There may be 40 to 100 different species in 2.5 acres ( 1 hectare) of a tropical rain forest.[/FONT]


[FONT=Georgia][SIZE=3][COLOR=darkred][B]TAIGA ECOSYSTEM[/B][/COLOR][/SIZE][/FONT]

[FONT=Georgia]A biome is the type of habitat in certain places, like mountain tops, deserts, and tropical forests, and is determined by the climate of the place. The taiga is the biome of the needleleaf forest. Living in the taiga is cold and lonely. Coldness and food shortages make things very difficult, mostly in the winter. Some of the animals in the taiga hibernate in the winter, some fly south if they can, while some just cooperate with the environment, which is very difficult. (Dillon Bartkus)[/FONT]
[FONT=Georgia]Taiga is the Russian word for forest and is the largest biome in the world. It stretches over Eurasia and North America. The taiga is located near the top of the world, just below the tundra biome. The winters in the taiga are very cold with only snowfall. The summers are warm, rainy, and humid. A lot of coniferous trees grow in the taiga. The taiga is also known as the boreal forest. Did you know that Boreal was the Greek goddess of the North Wind?[/FONT]

[FONT=Georgia]The taiga doesn't have as many plant and animal species as the tropical or the deciduous forest biomes. It does have millions of insects in the summertime. Birds migrate there every year to nest and feed.[/FONT]

[FONT=Georgia]Here is some information about the temperatures and weather in the taiga. The average temperature is below freezing for six months out of the year. The winter temperature range is -54 to -1° C (-65 to 30° F). The winters, as you can see, are really cold, with lots of snow.[/FONT]

[FONT=Georgia]Temperature range in the summer gets as low as -7° C (20° F). The high in summer can be 21° C (70° F). The summers are mostly warm, rainy and humid. They are also very short with about 50 to 100 frost free days. The total precipitation in a year is 30 - 85 cm (12 - 33 in) . The forms the precipitation comes in are rain, snow and dew. Most of the precipitation in the taiga falls as rain in the summer. [/FONT]

[FONT=Georgia]The main seasons in the taiga are winter and summer. The spring and autumn are so short, you hardly know they exist. It is either hot and humid or very cold in the taiga.[/FONT]

[FONT=Georgia]There are not a lot of species of plants in the taiga because of the harsh conditions. Not many plants can survive the extreme cold of the taiga winter. There are some [/FONT][URL="http://www.blueplanetbiomes.org/caribou_moss.htm"][U][FONT=Georgia][COLOR=#0000ff]lichens[/COLOR][/FONT][/U][/URL][FONT=Georgia] and mosses, but most plants are coniferous trees like pine, [/FONT][URL="http://www.blueplanetbiomes.org/white_spruce.htm"][U][FONT=Georgia][COLOR=#0000ff]white spruce[/COLOR][/FONT][/U][/URL][FONT=Georgia], hemlock and [/FONT][URL="http://www.blueplanetbiomes.org/douglas_fir.htm"][U][FONT=Georgia][COLOR=#0000ff]douglas fir[/COLOR][/FONT][/U][/URL][FONT=Georgia]. [/FONT]

[FONT=Georgia]Coniferous trees are also known as evergreens. They have long, thin waxy needles. The wax gives them some protection from freezing temperatures and from drying out. Evergreens don't loose their leaves in the winter like deciduous trees. They keep their needles all year long. This is so they can start photosynthesis as soon as the weather gets warm. The dark color of evergreen needles allows them to absorb heat from the sun and also helps them start photosynthesis early.[/FONT]

[FONT=Georgia]Evergreens in the taiga tend to be thin and grow close together. This gives them protection from the cold and wind. Evergreens also are usually shaped like an upside down cone to protects the branches from breaking under the weight of all that snow. The snow slides right off the slanted branches. [/FONT]

[FONT=Georgia]The taiga is susceptible to many wildfires. Trees have adapted by growing thick bark. The fires will burn away the upper canopy of the trees and let sunlight reach the ground. New plants will grow and provide food for animals that once could not live there because there were only evergreen trees.[/FONT]

[FONT=Georgia]Animals of the taiga tend to be predators like the [/FONT][URL="http://www.blueplanetbiomes.org/canadian_lynx.htm"][U][FONT=Georgia][COLOR=#0000ff]lynx[/COLOR][/FONT][/U][/URL][FONT=Georgia] and members of the weasel family like [/FONT][URL="http://www.blueplanetbiomes.org/wolverine.htm"][U][FONT=Georgia][COLOR=#0000ff]wolverines[/COLOR][/FONT][/U][/URL][FONT=Georgia], [/FONT][URL="http://www.blueplanetbiomes.org/bobcat_taiga.htm"][U][FONT=Georgia][COLOR=#0000ff]bobcat[/COLOR][/FONT][/U][/URL][FONT=Georgia], minks and ermine. They hunt herbivores like [/FONT][URL="http://www.blueplanetbiomes.org/snowshoe_rabbit.htm"][U][FONT=Georgia][COLOR=#0000ff]snowshoe rabbits[/COLOR][/FONT][/U][/URL][FONT=Georgia], red squirrels and voles. Red deer, elk, and moose can be found in regions of the taiga where more deciduous trees grow.[/FONT]

[FONT=Georgia]Many insect eating birds come to the taiga to breed. They leave when the breeding season is over. Seed eaters like finches and sparrows, and omnivorous birds like crows stay all year long. [/FONT]

Savanna,Alpine,chaparral ecosystem
 

[SIZE=3][COLOR=darkred][B]
Savanna ecosystem[/B][/COLOR][/SIZE]

A savanna is a rolling grassland scattered with shrubs and isolated trees, which can be found between a tropical rainforest and desert biome. Not enough rain falls on a savanna to support forests. Savannas are also known as tropical grasslands. They are found in a wide band on either side of the equator on the edges of tropical rainforests.

Savannas have warm temperature year round. There are actually two very different seasons in a savanna; a very long dry season (winter), and a very wet season (summer). In the dry season only an average of about 4 inches of rain falls. Between December and February no rain will fall at all. Oddly enough, it is actually a little cooler during this dry season. But don't expect sweater weather; it is still around 70° F.

In the summer there is lots of rain. In Africa the monsoon rains begin in May. An average of 15 to 25 inches of rain falls during this time. It gets hot and very humid during the rainy season. Every day the hot, humid air rises off the ground and collides with cooler air above and turns into rain. In the afternoons on the summer savanna the rains pour down for hours. African savannas have large herds of grazing and browsing hoofed animals. Each animal has a specialized eating habit that reduces compitition for food.
There are several different types of savannas around the world. The savannas we are most familiar with are the East African savannas covered with acacia trees. The Serengeti Plains of Tanzania are some of the most well known. Here animals like lions, zebras, elephants, and giraffes and many types of ungulates(animals with hooves) graze and hunt. Many large grass-eating mammals (herbivores) can survive here because they can move around and eat the plentiful grasses. There are also lots of carnivores (meat eaters) who eat them in turn.

South America also has savannas, but there are very few species that exist only on this savanna. In Brazil, Colombia, and Venezuela, savannas occupy some 2.5 million square kilometers, an area about one-quarter the size of Canada. Animals from the neighboring biomes kind of spill into this savanna. The Llanos of the Orinoco basin of Venezuela and Columbia is flooded annually by the Orinoco River. Plants have adapted to growing for long periods in standing water. The capybara and marsh deer have adapted themselves to a semi-aquatic life.

Brazil's cerrado is an open woodland of short twisted trees. The diversity of animals is very great here, with several plants and animals that don't exist anywhere else on earth.

There is also a savanna in northern Australia. Eucalyptus trees take the place of acacias in the Australian savanna. There are many species of kangaroos in this savanna but not too much diversity of different animals
Plants of the savannas are highly specialized to grow in this environment of long periods of drought. They have long tap roots that can reach the deep water table, thick bark to resist annual fires, trunks that can store water, and leaves that drop of during the winter to conserve water. The grasses have adaptations that discourage animals from grazing on them; some grasses are too sharp or bitter tasting for some animals, but not others, to eat. The side benefit of this is that every species of animal has something to eat. Different species will also eat different parts of the grass. Many grasses grow from the bottom up, so that the growth tissue doesn't get damaged by grazers. Many plants of the savanna also have storage organs like bulbs and corms for making it though the dry season.

Most of the animals on the savanna have long legs or wings to be able to go on long migrations. Many burrow under ground to avoid the heat or raise their young. The savanna is a perfect place for birds of prey like hawks and buzzards. The wide, open plain provides them with a clear view of their prey, hot air updrafts keep them soaring, and there is the occasional tree to rest on or nest in. Animals don't sweat to lose body heat, so they lose it through panting or through large areas of exposed skin, or ears, like those of the elephant.

The savanna has a large range of highly specialized plants and animals. They all depend on the each other to keep the environment in balance. There are over 40 different species of hoofed mammals that live on the savannas of Africa. Up to 16 different species of browsers (those who eat leaves of trees) and grazers can coexist in one area. They do this by having their own food preferences, browsing/grazing at different heights, time of day or year to use a given area, and different places to go during the dry season.

These different herbivores provide a wide range of food for carnivores, like lions, leopards, cheetahs, jackals and hyenas. Each species has its own preference, making it possible to live side by side and not be in competition for food.

In many parts of the savannas of Africa people have started using it to graze their cattle and goats. They don't move around and soon the grasses are completely eaten up. With no vegetation, the savanna turns into a desert. Huge areas of savanna are lost to the Sahara desert every year because of overgrazing and farming.


[SIZE=3][COLOR=darkred][B]Alpine ecosystem[/B][/COLOR][/SIZE]

Cold, snowy, windy. When you hear those words they make you think of mountains. The Alpine biome is like winter is to people in New England; snow, high winds, ice, all the typical winter things. In Latin the word for 'high mountain' is 'alpes'. That is where today's word alpine comes from.
Alpine biomes are found in the mountain regions all around the world. They are usually at an altitude of about 10,000 feet or more. The Alpine biome lies just below the snow line of a mountain. As you go up a mountain, you will travel through many biomes. In the North American Rocky Mountains you begin in a desert biome. As you climb you go through a deciduous forest biome, grassland biome, steppe biome, and taiga biome before you reach the cold Alpine biome.

In the summer average temperatures range from 10 to 15° C . In the winter the temperatures are below freezing. The winter season can last from October to May. The summer season may last from June to September. The temperatures in the Alpine biome can also change from warm to freezing in one day.

Because the severe climate of the Alpine biome, plants and animals have developed adaptations to those conditions. There are only about 200 species of Alpine plants. At high altitudes there is very little CO2, which plants need to carry on photosynthesis. Because of the cold and wind, most plants are small perennial groundcover plants which grow and reproduce slowly. They protect themselves from the cold and wind by hugging the ground. Taller plants or trees would soon get blown over and freeze. When plants die they don't decompose very quickly because of the cold. This makes for poor soil conditions. Most Alpine plants can grow in sandy and rocky soil. Plants have also adapted to the dry conditions of the Alpine biome. Plant books and catalogs warn you about over watering Alpine plants.

Alpine animals have to deal with two types of problems: the cold and too much high UV wavelengths. This is because there is less atmosphere to filter UV rays from the sun. There are only warm blooded animals in the Alpine biome, although there are insects. Alpine animals adapt to the cold by hibernating, migrating to lower, warmer areas, or insulating their bodies with layers of fat. Animals will also tend to have shorter legs, tails, and ears, in order to reduce heat loss. Alpine animals also have larger lungs, more blood cells and hemoglobin because of the increase of pressure and lack of oxygen at higher altitudes. This is also true for people who have lived on mountains for a long time, like the Indians of the Andes Mountains in South America and the Sherpas of the Himalayas in Asia.


[SIZE=3][COLOR=darkred][B]chaparral Ecosystem[/B][/COLOR][/SIZE]

The chaparral biome is found in a little bit of most of the continents - the west coast of the United States, the west coast of South America, the Cape Town area of South Africa, the western tip of Australia and the coastal areas of the Mediterranean.

Lay of the land: The chaparral biome has many different types of terrain. Some examples are flat plains, rocky hills and mountain slopes. It is sometimes used in movies for the "Wild West".

Chaparral is characterized as being very hot and dry. As for the temperature, the winter is very mild and is usually about 10 °C. Then there is the summer. It is so hot and dry at 40 °C that fires and droughts are very common.

Fortunately, the plants and animals are adapted to these conditions. Most of the plants have small, hard leaves which hold moisture. Some of these plants are poison oak, scrub oak, Yucca Wiple and other shrubs, trees and cacti.

The animals are all mainly grassland and desert types adapted to hot, dry weather. A few examples: coyotes, jack rabbits, mule deer, alligator lizards, horned toads, praying mantis, honey bee and ladybugs.
So, if you ever go somewhere that is like chaparral, make sure to bring some sunscreen and lots of water!
[FONT=Times New Roman]

[/FONT]

Zoology Notes
 

[B][FONT=Arial][SIZE=4]Placental Structure and Classification[/SIZE][/FONT][/B]

[B][FONT=Times New Roman][SIZE=4]Placenta[/SIZE][/FONT][/B]

[FONT=Arial][SIZE=3]the vascular (supplied with [COLOR=black][URL="http://www.britannica.com/EBchecked/topic/69887/blood-vessel"][COLOR=black]blood vessels[/COLOR][/URL][/COLOR]) organ in most mammals that unites [COLOR=black]the [URL="http://www.britannica.com/EBchecked/topic/205520/fetus"][COLOR=black]fetus[/COLOR][/URL][/COLOR] to the uterus of the mother. It mediates the metabolic exchanges of the developing individual through an intimate association of embryonic tissues and of certain uterine tissues, serving the functions of nutrition, respiration, and excretion[/SIZE][/FONT]

[FONT=Arial][SIZE=3]The placentas of all eutherian (placental) mammals provide common structural and functional features, but there are striking differences among species in gross and microscopic structure of the placenta. Two characteristics are particularly divergent and form bases for classification of placental types:[/SIZE][/FONT][LIST=1][*][FONT=Arial][SIZE=3]The gross shape of the placenta and the distribution of contact sites between fetal membranes and endometrium. [/SIZE][/FONT][*][FONT=Arial][SIZE=3]The number of layers of tissue between maternal and fetal vascular systems. [/SIZE][/FONT][/LIST][FONT=Arial][SIZE=3]Differences in these two properties allow classification of placentas into several fundamental types. [/SIZE][/FONT]

[B][FONT=Arial][SIZE=3]Classification Based on Placental Shape and Contact Points[/SIZE][/FONT][/B]

[FONT=Arial][SIZE=3]Examination of placentae from different species reveals striking differences in their shape and the area of contact between fetal and maternal tissue: [/SIZE][/FONT][LIST][*][SIZE=3][B][FONT=Arial]Diffuse[/FONT][/B][FONT=Arial]: Almost the entire surface of the allantochorion is involved in formation of the placenta. Seen in [URL="http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/equine.html"][COLOR=black]horses[/COLOR][/URL] and [URL="http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/pigs.html"][COLOR=black]pigs[/COLOR][/URL]. [/FONT][/SIZE][*][SIZE=3][B][FONT=Arial]Cotyledonary[/FONT][/B][FONT=Arial]: Multiple, discrete areas of attachment called cotyledons are formed by interaction of patches of allantochorion with endometrium. The fetal portions of this type of placenta are called cotyledons, the maternal contact sites (caruncles), and the cotyledon-caruncle complex a placentome. This type of placentation is observed in [URL="http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/ruminants.html"][COLOR=black]ruminants[/COLOR][/URL]. [/FONT][/SIZE][*][SIZE=3][B][FONT=Arial]Zonary[/FONT][/B][FONT=Arial]: The placenta takes the form of a complete or incomplete band of tissue surrounding the fetus. Seen in carnivores like [URL="http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/dog_cat.html"][COLOR=black]dogs and cats[/COLOR][/URL], seals, bears, and elephants. [/FONT][/SIZE][*][SIZE=3][B][FONT=Arial]Discoid[/FONT][/B][FONT=Arial]: A single placenta is formed and is discoid in shape. Seen in [URL="http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/primates.html"][COLOR=black]primates[/COLOR][/URL] and [URL="http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/rodents.html"][COLOR=black]rodents[/COLOR][/URL]. [/FONT][/SIZE][/LIST][FONT=Arial][SIZE=3][FONT=Arial]

[CENTER][IMG]http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/plac_types.jpg[/IMG][/CENTER]
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[B][FONT=Arial][SIZE=3]Classification Based on Layers Between Fetal and Maternal Blood[/SIZE][/FONT][/B]

[FONT=Arial][SIZE=3]Just prior to formation of the placenta, there are a total of six layers of tissue separating maternal and fetal blood. There are three layers of fetal extraembryonic membranes in the chorioallantoic placenta of all mammals, all of which are components of the mature placenta: [/SIZE][/FONT][LIST=1][*][FONT=Arial][SIZE=3]Endothelium lining allantoic capillaries [/SIZE][/FONT][*][FONT=Arial][SIZE=3]Connective tissue in the form of chorioallantoic mesoderm [/SIZE][/FONT][*][FONT=Arial][SIZE=3]Chorionic epithelium, the outermost layer of fetal membranes derived from trophoblast [/SIZE][/FONT][/LIST][FONT=Arial][SIZE=3]There are also three layers on the maternal side, but the number of these layers which are retained - that is, not destroyed in the process of placentation - varies greatly among species. The three potential maternal layers in a placenta are: [/SIZE][/FONT][LIST=1][*][FONT=Arial][SIZE=3]Endothelium lining endometrial blood vessels [/SIZE][/FONT][*][FONT=Arial][SIZE=3]Connective tissue of the endometrium [/SIZE][/FONT][*][FONT=Arial][SIZE=3]Endometrial epithelial cells [/SIZE][/FONT][/LIST][CENTER][IMG]http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/layers.jpg[/IMG][/CENTER]


[CENTER][IMG]http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/microtypes.jpg[/IMG][/CENTER]





[FONT=Arial][SIZE=3]In humans, fetal chorionic epithelium is bathed in maternal blood because chorionic villi have eroded through maternal endothelium. In contrast, the chorionic epithelium of horse and pig fetuses remains separated from maternal blood by 3 layers of tissue. One might thus be tempted to consider that exchange across the equine placenta is much less efficient that across the human placenta. In a sense this is true, but other features of placental structure make up for the extra layers in the diffusion barrier; it has been well stated that "[I]The newborn foal provides a strong testimonial to the efficiency of the epitheliochorial placenta.[/I]" [/SIZE][/FONT]
[B][FONT=Arial][SIZE=3]Summary of Species Differences in Placental Architecture[/SIZE][/FONT][/B]

[FONT=Arial][SIZE=3]The placental mammals have evolved a variety of placental types which can be broadly classified using the nomenclature described above. Not all combinations of those classification schemes are seen or are likely to ever be seen - for instance, no mammal is known to have a diffuse, endotheliochorial, or a hemoendothelial placenta. Placental types for "familiar" mammals are summarized below, with supplemental information provided for a variety of "non-familiar" species. [/SIZE][/FONT]

Mammals
 

[B][COLOR=black][FONT=Arial]Mammals[/FONT][/COLOR][/B]

[COLOR=black][FONT=Arial]There are approximately 4,260 different mammalian species that have been discovered to date, although this figure varies because not all scientists agree that certain organisms are a distinct species.[/FONT][/COLOR]
[COLOR=black][FONT=Arial]In addition, new species are always being discovered, therefore this figure of how many different mammals exist is always changing.[/FONT][/COLOR]
[COLOR=black][FONT=Arial]Mammals are all warm-blooded, and all mammals are vertebrates (meaning they have vertebrae, forming a spine), but there are also other animals, like birds, that have these characteristics, so there are additional traits that set mammals apart.[/FONT][/COLOR]
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[B]Characteristics of Mammals[/B][/FONT][/COLOR]

[COLOR=black][FONT=Arial]Mammals have six key characteristics that can be seen in each and every mammal, and it’s these traits that set mammals apart from other types of creatures:[/FONT][/COLOR]
[COLOR=black][FONT=Arial]1. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]Mammals produce milk to feed their young.[/FONT][/COLOR][/I][COLOR=black][FONT=Arial] Female mammals possess a modified sweat gland – a mammary gland – that is activated by hormonal changes that occur with pregnancy. In fact, this trait is what inspired the term “mammal,” a derivation of “mammary.” [/FONT][/COLOR]
[COLOR=black][FONT=Arial]2. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]Mammals all have one single bone comprising their lower jaw. [/FONT][/COLOR][/I][COLOR=black][FONT=Arial]In all other animals, more than one bone comprises the jaw. [/FONT][/COLOR]
[COLOR=black][FONT=Arial]3. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]All mammals have three tiny bones in the middle portion of the ear.[/FONT][/COLOR][/I]
[COLOR=black][FONT=Arial]4. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]All mammals have a diaphragm. [/FONT][/COLOR][/I][COLOR=black][FONT=Arial]The mammal's diaphragm is a thin muscular wall that separates the upper and lower portions of the torso. [/FONT][/COLOR]
[COLOR=black][FONT=Arial]5. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]All mammals have fur or hair.[/FONT][/COLOR][/I][COLOR=black][FONT=Arial] Hair or fur is a characteristic that's [I]only[/I] seen in mammals. All mammals develop fur or hair at some point during their development, though not all keep their fur or hair throughout their lifespan. [/FONT][/COLOR]
[COLOR=black][FONT=Arial]6. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]Mammals have a unique heart. [/FONT][/COLOR][/I][COLOR=black][FONT=Arial]The heart of a mammal is unique in that it has one primary artery leaving the heart bending to the left, whereas other animals either have multiple arteries in the heart or the heart's main artery bends in a different direction.[/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=2]Categories of Mammals[/SIZE][/FONT][/COLOR][/B]

[COLOR=black][FONT=Arial]Within the class of animals considered mammals, there are three categories: eutheria, metatheria and prototheria.[/FONT][/COLOR]
[COLOR=black][FONT=Arial]The three categories of mammals can be described as follows:[/FONT][/COLOR]
[COLOR=black][FONT=Arial]1. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]Eutheria[/FONT][/COLOR][/I][COLOR=black][FONT=Arial] - Eutheria are mammals possessing a placenta, like a human or dog. [/FONT][/COLOR]
[COLOR=black][FONT=Arial]2. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]Metatheria[/FONT][/COLOR][/I][COLOR=black][FONT=Arial] - Metatheria are also known as marsupials or pouch-bearing mammals like the kangaroo. [/FONT][/COLOR]
[COLOR=black][FONT=Arial]3. [/FONT][/COLOR][I][COLOR=black][FONT=Arial]Prototheria[/FONT][/COLOR][/I][COLOR=black][FONT=Arial] - Prototheria are also known as monotremes or egg-laying mammals like the duckbill platypus.[/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=2]Exclusive Traits of Mammals[/SIZE][/FONT][/COLOR][/B]

[COLOR=black][FONT=Arial]In addition, there are a few characteristics that are exclusive to mammals, meaning only animals have these traits. But, in each case, there are some mammals that don't have these traits, which is why they're different from the characteristics of mammals (the mammal characteristics are seen in each and every mammal).[/FONT][/COLOR]
[COLOR=black][FONT=Symbol]· [/FONT][/COLOR][COLOR=black][FONT=Arial]The vast majority of female mammals have a placenta, used to protect and nourish the offspring prior to birth. Marsupials and monotremes do not have a placenta. [/FONT][/COLOR]
[COLOR=black][FONT=Symbol]· [/FONT][/COLOR][COLOR=black][FONT=Arial]In their lifetime, a mammal will not have more than two sets of teeth. Typically, mammals grow one set of teeth as juveniles, and then a new permanent set grows in as they near adulthood. [/FONT][/COLOR]
[COLOR=black][FONT=Symbol]· [/FONT][/COLOR][COLOR=black][FONT=Arial]A mammal is warm blooded, meaning it has the ability to generate its own body heat and maintain a steady body temperature, despite ambient temperature changes. [/FONT][/COLOR]
[COLOR=black][FONT=Symbol]· [/FONT][/COLOR][COLOR=black][FONT=Arial]Mammals also have a separation between their mouth and nasal cavity. Other animals, like reptiles do not have an upper palate; this allows the nasal cavity to remain open regardless of whether there is something inside the mouth.[/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=2]Multituberculates - An Extinct Category of Mammals[/SIZE][/FONT][/COLOR][/B]

[COLOR=black][FONT=Arial]In addition to the three categories of mammals — eutheria, metatheria and prototheria — there was once a fourth mammal category that is now completely extinct.[/FONT][/COLOR]
[COLOR=black][FONT=Arial]Multituberculates are a category of mammal that arose during the late Jurassic period 160 million years ago and they survived up until about 35 million years ago.[/FONT][/COLOR]
[COLOR=black][FONT=Arial]Multituberculates have no living descendants today, but fossil records indicate that they were similar to modern rodents.[/FONT][/COLOR]
[COLOR=black][FONT=Arial]Multituberculates were named for their teeth. These mammals had one pair of incisors on the lower jaw and their molars had numerous cusps forming numerous rows of teeth. These mammals also lacked canine teeth on the upper jaw, like many rodents of today.[/FONT][/COLOR]
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Birds
 

[COLOR=black][FONT=Arial][B]Birds, an Introduction[/B][/FONT][/COLOR]

[COLOR=black][FONT=Arial][COLOR=black][FONT=Arial][SIZE=3]Birds are ‘warm-blooded’ vertebrates, with fore-limbs modified to wings, and skins covered with feathers. Vertebrates are characterised by having a spinal column and a skull. ‘Warm blooded’ or [I]homoiothermic[/I] (constant temperature) means that their body temperature is kept more or less constant and above that of their surroundings. Typically, the forelimbs as wings give birds the power of flight although there are some flightless birds. In some cases (e.g. penguins and puffins) the wings are used for swimming under water.[/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]All birds reproduce by laying eggs which are fertilised internally before laying.[/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The skull and lower jaw are extended forward into mandibles which make a beak. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The bird's legs and toes are covered with overlapping scales. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]Birds possess a third, transparent eyelid, the [I]nictitating membrane[/I], which can move across the eye. [/SIZE][/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=3]Feathers[/SIZE][/FONT][/COLOR][/B]


[COLOR=black][FONT=Arial][SIZE=3]The feathers are the single external feature that distinguish birds from other vertebrates. The feathers are produced from the skin which is loose and dry, without sweat glands, and they form an insulating layer round the bird's body, helping to keep its temperature constant, and repelling water. The wings are specially developed for flight, having a large surface area and very little weight. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The barbules of the feathers interlock in such a way that should a feather be damaged in flight, preening with the beak will re-form it perfectly. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The feather quills have attached to them muscles which can alter the angles of the feathers; for example, when a bird fluffs its feathers out in cold weather. They also have a nerve supply which, when the feathers are touched, is stimulated in a similar way to a cat's whiskers. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The down feathers are fluffy, trapping a layer of air close to the body. The flight feathers and coverts are broad and flat and offer resistance to the passage of air. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The shape of the bird and the lay of its feathers make it streamlined in flight. [/SIZE][/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=3]Features which adapt the bird for flying[/SIZE][/FONT][/COLOR][/B]


[COLOR=black][FONT=Arial][SIZE=3]1. The fore-limbs are wings with a large surface area provided by feathers. However, rather than being an ‘adaptation to flight’ they are essential for flight to take place.[/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]2. Large pectoral muscles for depressing the wings. They may account for as much as one-fifth of the body weight in some birds. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]3. A deep, keel-like extension from the sternum (breast bone) provides for the attachment of the pectoral muscles. Well-developed coracoid bones transmit the lift of the wings to the body.[/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]4. A rigid skeleton giving a firm framework for attachment of muscles concerned with flying movements. Many of the bones which can move in mammals are fused together in birds; for example, the vertebrae of the spinal column in the body region. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]5. Hollow bones, which reduce the bird's weight. [/SIZE][/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=3]Locomotion[/SIZE][/FONT][/COLOR][/B]


[COLOR=black][FONT=Arial][SIZE=3]The flight of a bird can be divided into flapping, and gliding or soaring, different species of birds using the two types to varying extents. In flapping flight the [I]pectoralis major[/I] muscle contracts, pulling the fore-limb down. The resistance of the air to the wing produces an upward reaction on the wing. This force is transmitted through the coracoid bones to the sternum and so acts through the bird's centre of gravity, lifting it as a whole. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]In addition to the lift, forward momentum is provided by the slicing action of the wing, particularly near the tip. In the down-stroke the leading edge is below the trailing edge so that the air is thrust backwards and the bird moves forward. The secondary feathers provide much of the lifting force and the primaries most of the forward component. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The [I]bastard wing[/I] (a group of feathers attached to the first digit) may be important during take-off for giving a forward thrust. During flight it may function as a slot maintaining a smooth flow of air over the wing surface. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]The up-stroke of the wing is much more rapid than the down-stroke. The [I]pectoralis minor[/I] muscle contracts and raises the wing, since its tendon passes over a groove in the coracoid to the upper side of the humerus. Often the arm is simply rotated slightly so that the leading edge is higher than the trailing edge and the rush of air lifts the wing. The wing is bent at the wrist during the up-stroke thus reducing the resistance. In addition, the way in which the primary and secondary feathers overlap produces maximum resistance during the down-stroke and minimum resistance on the up-stroke. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]In gliding flight the wings are outspread and used as aerofoils, the bird sliding down a 'cushion' of air, losing height and gaining forward momentum. Sometimes upward thermal currents or intermittent gusts of wind may be used to gain height without wing movements; in seagulls and buzzards for example. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]Generally, the fast-flying birds have a small wing area and a large span, with specially well-developed primaries, while the slower birds have shorter, wider wings with well-developed secondaries. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]Estimates of speed vary from 160 km/h in swifts to 60 km/h in racing pigeons. The tail feathers help to stabilize the bird in flight and are particularly important in braking and landing. [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]In walking, the posture of the bird brings the centre of gravity of the bird below the joint of the femur and pelvis. [/SIZE][/FONT][/COLOR]

[B][COLOR=black][FONT=Arial][SIZE=3]Reproduction[/SIZE][/FONT][/COLOR][/B]


[COLOR=black][FONT=Arial][SIZE=3]The detailed pattern of reproduction and parental care varies widely in different species but, in general, it follows the course outlined below. [/SIZE][/FONT][/COLOR]

[SIZE=3][B][COLOR=black][FONT=Arial]Pairing.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] A sequence of behavioural activities, e.g. courtship display, leads to pair formation; a male and female bird pairing at least for the duration of the breeding season. [/FONT][/COLOR][/SIZE]

[SIZE=3][B][COLOR=black][FONT=Arial]Nest building.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] One of the pair or both birds construct a nest which may be an elaborate structure woven from grass, leaves, feathers, etc., or little more than a hollow scraped in the ground.[/FONT][/COLOR][/SIZE]

[SIZE=3][B][COLOR=black][FONT=Arial]Mating.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] Further display leads to mating. The male mounts the female, applies his reproductive openings to hers and passes sperm into her oviduct, thus enabling the eggs to be fertilized internally. [/FONT][/COLOR][/SIZE]

[SIZE=3][B][COLOR=black][FONT=Arial]Egg laying.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] The fertilized egg is enclosed in a layer of albumen and a shell during its passage down the oviduct and is finally laid in the nest. Usually, one egg is laid each day and incubation does not begin until the full clutch has been laid. [/FONT][/COLOR][/SIZE]

[SIZE=3][B][COLOR=black][FONT=Arial]Incubation.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] The female bird is usually responsible for incubation, keeping the eggs at a temperature approximating to her own by covering them with her body and pressing them against her brooding patches, i.e. areas devoid of feathers which allow direct contact between the skin and the eggshell. Incubation also reduces evaporation of water from the shell. At this temperature, the eggs develop and hatch in a week or two.[/FONT][/COLOR][/SIZE]

[SIZE=3][B][COLOR=black][FONT=Arial]Development.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] The living cells in the egg divide to make the tissues and organs of the young birds. The yolk provides the food for this and the albumen is a source of both food and water. The eggshell and shell membranes are permeable, and oxygen diffuses into the air space, being absorbed by part of the network of capillaries which spread out over the yolk and over a special sac, the [I]allantois[/I], which has become attached to the air space. The blood carries the oxygen to the embryo. Carbon dioxide is eliminated by the reverse process through the eggshell. When the chicks are fully developed, they break out of the shell by using their beaks.[/FONT][/COLOR][/SIZE]

[SIZE=3][B][COLOR=black][FONT=Arial]Parental care.[/FONT][/COLOR][/B][COLOR=black][FONT=Arial] The chicks of large, ground-nesting birds, e.g. pheasant, are covered with downy feathers and can run about soon after hatching. They peck at objects on the ground and soon learn to discriminate material suitable for food. They stay close to the hen, responding to her calls by taking cover or seeking her out according to the circumstances.[/FONT][/COLOR][/SIZE]
[COLOR=black][FONT=Arial][SIZE=3]In most other species, the chicks hatch with few or no feathers, helpless and with closed eyelids. Having no feathers, they are very susceptible to heat loss and desiccation, and the parents brood them, covering the nest with the body and wings, so reducing evaporation and temperature fluctuations. Both parents will collect suitable food, often worms, caterpillars, insects and other materials equally rich in protein. The sound or sight of the parents approaching the nest causes the nestlings to stretch their necks and gape their beaks. The bright orange colour inside the beaks induces the parent to thrust the food it is carrying into the open beaks.[/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Arial][SIZE=3]After a week or two, the young birds begin to climb out of the nest and sit in the bush or tree but the parents still find and feed them. When the primary and secondary feathers have developed, the fledglings begin short practice flights. This is one of the most dangerous periods of their lives since they can feed themselves to only a limited extent and cannot escape from predators such as cats and hawks. Some estimates suggest that only 25 per cent of the eggs laid in open nests of this kind reach the stage of fully independent birds. [/SIZE][/FONT][/COLOR]




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lectures in biology
 

lectures in biology,covers many topics of zoology.i hope you find this link useful.

[URL="http://www.jochemnet.de/fiu/BSC1011/BSC1011_LN.html"]http://www.jochemnet.de/fiu/BSC1011/BSC1011_LN.html[/URL]

regards.

Vertebrates
 

[B]Vertebrates[/B]
This is a link to 60 slide power point presentation about vertebrates.

[URL="http://www.scribd.com/doc/7748247/Vertebrates"]http://www.scribd.com/doc/7748247/Vertebrates[/URL]

regards

Protozoans
 

[B]Protozoans[/B]

[SIZE=3][FONT=Times New Roman][B][COLOR=black]Protozoa[/COLOR][/B][COLOR=black] is a subkingdom (formerly a phylum) comprised of organisms with eucaryotic cells that have many of the intracellular components characteristic of higher forms of life. Such other organisms as bacteria do not have this nucleus and are referred to as prokaryotes. Protozoa also have some form of active locomotion, which is a distinguishing feature in classifying them. Even though there are about 50,000 species of protozoa, relatively few are able to cause disease in humans. Protozoal diseases used to be limited to tropical, subtropical, and underdeveloped nations. Now, however, they are becoming a worldwide concern. Protozoa are generally free-living, but some exist as parasites or in a commensal relationship with another organism. The protozoa that are pathogenic parasites are of major interest because they cause such diseases in humans as malaria, trypanosomiasis, toxoplasmosis, and dysentery. [/COLOR][/FONT][/SIZE]
[COLOR=black][SIZE=3][FONT=Times New Roman]Protozoa generally exist in two basic forms: the active, growing form called the "trophozoite;" and the dormant, resistant form called the "cyst." The trophozoite form proliferates tissues, causing damage that results in clinical disease. The cyst is able to survive in an external environment and is usually the form that is transmitted from host to host. Some protozoa go through an intermediate stage in blood-sucking insects. [/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]Protozoology is the scientific study of protozoa. Classification of the organism is divided into seven phyla: Sarcomastigophora, Labyrinthomorpha, Apicoplexa, Microspora, Acetospora, Myxozoa, and Aliophora. In 1985, an extensive classification scheme was proposed for protozoa that included various phyla, subphyla, classes, etc. [/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]The four groups of protozoa that are mainly responsible for human disease include the following: sarcodina, ciliophora, mastigophora, and sporozoa -- all grouped according to their form of locomotion. [/FONT][/SIZE][/COLOR][LIST=1][*][SIZE=3][FONT=Times New Roman][B]Sarcodina[/B], commonly known as amoebas, move by extending a section of their cytoplasm (called a pseudopodium or false foot) in one direction, causing the remainder to follow. They are usually found in marine and fresh water. Members include eight species (see Endoparasites). Three are parasitic to humans, with one causing more of a problem than the others. ([I]Entamoeba histolytica[/I] causes the disease amebiasis.) [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Ciliophora[/B], or Ciliates, move by using the many fine cilia that beat in rhythmic patterns to propel the organism. Members include and [I]Paramecium[/I], but only one species causes disease in humans; and that is of a dysentery nature. [I]Balantidium coli[/I] is a large oval-shaped cell that is the largest intestinal protozoa found in humans. Increasingly, it is showing up in the human intestinal tract, where it can invade and destroy the intestinal lining. Its normal habitat is the intestinal tract of hogs, but it can also be found in marine and fresh water worldwide, causing the disease known as balantidiasis. The life cycle is similar to that of the amoeba [I]E. histolytica[/I] and has been associated with chronic fatigue syndrome. [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Mastigophora[/B] is a subphylum of protozoa that has one or more whiplike flagella that propel the organism like swimmers. They are commonly known as Flagellates and are normally found in fresh water. Two relatively mild diseases, trichomoniasis and giardiasis, are produced from them, as well as the more serious diseases of trypanosomiasis and leishmaniasis. [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Sporozoa[/B] (singular sporozoon) is a class of parasitic protozoa that include [I]Plasmodium[/I] and [I]Toxoplasma[/I]. These two are commonly known as the parasites, found in vectors responsible for malaria and toxoplasmosis. They have both a sexual and asexual phase. They mainly target the epithelial cells of the intestinal tract, but can also be found in the liver and other organs.[/FONT][/SIZE][/LIST][COLOR=black][SIZE=3][FONT=Times New Roman]Other, yet unclassified, sporozoa on the rise are [I]Pneumocystis carinii[/I] and [I]Cryptosporidium[/I]. They are of particular concern to the immunocompromised, particularly those with AIDS, cancer, or a recipient of transplants. [I]P. carinii[/I] is responsible for a type of pneumonia, while [I]Cryptosporidium[/I] produces a profuse watery diarrhea.[/FONT][/SIZE][/COLOR]

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Protozoa
 

[B]Protozoa [/B]

[B][URL="http://www.scribd.com/doc/4361572/Phylum-Protozoa"]click here[/URL][/B]

[B]Disease causing protozoans.[/B]
[B]regards[/B]

Reproduction in Protozoa
 

[B]Reproduction in Protozoa[/B]

[B]Asexual Reproduction[/B]

[SIZE=2][COLOR=black][COLOR=black][COLOR=black]Asexual reproduction[/COLOR][/COLOR][COLOR=black] is the most common means of replication by protozoans. The ability to undergo a sexual phase is confined to the ciliates, the apicomplexans, and restricted taxa among the flagellates and sarcodines. Moreover, sexual reproduction does not always result in an immediate increase in numbers but may simply be a means of exchanging [/COLOR][COLOR=black][FONT=Arial][FONT=Verdana][COLOR=black]important genetic [/COLOR]material[/FONT][/FONT][/COLOR][/COLOR][/SIZE][SIZE=2][COLOR=black]between individuals of the same species (conjugation). Free-living protozoans normally only resort to sexual reproduction when environmental conditions become adverse, because this mode of reproduction enhances the fitness of the population and increases the chance of mutation. When food and other conditions are favourable, asexual reproduction is practiced.[/COLOR]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]Asexual reproduction in free-living species usually involves [/COLOR][COLOR=black][COLOR=black]nuclear division[/COLOR][/COLOR][COLOR=black] and the division of the cell into two identical [/COLOR][COLOR=black][COLOR=black]daughter cells[/COLOR][/COLOR][COLOR=black] of equal size by [/COLOR][COLOR=black][COLOR=black]binary fission[/COLOR][/COLOR][COLOR=black]. In parasitic protozoa and some free-living species, multiple fission, resulting in the production of many offspring that may not resemble the parent cell, is normal. During the cycle of growth and division, the protozoan undergoes a series of identifiable phases: a division phase, a [/COLOR][COLOR=black][COLOR=black]growth phase[/COLOR][/COLOR][COLOR=black] during which the cell increases substantially in size, a phase of DNA synthesis, and a phase of preparation for division, which extends from the end of DNA synthesis until the initiation of division. The division of the cytoplasm is preceded by the division of the nucleus or nuclei.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]The plane of division in protozoan cells varies among the different groups and is of taxonomic significance. The flagellates normally divide in a longitudinal plane. The usual process starts at the front end with the division of the flagella and the associated structures; simultaneously, the nucleus divides. The cytoplasm then splits from front to back into two identical daughter cells. The ciliates normally divide in an equatorial, or transverse, plane, thereby maintaining the correct number of ciliary rows, or kineties. The cell mouth and any specialized cilia around it are replicated in different ways among the various ciliate groups, depending on the complexity of the cytostome. The replication of the cytostome precedes the division of the cytoplasm. Some ciliates ([I]e.g.,[/I] [I]Colpoda[/I]) divide within thin-walled reproductive cysts into two daughter ciliates, each of which then divides so that the cyst contains four progeny, which are released when the cyst wall ruptures.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]The sedentary suctorians do not reproduce by binary fission because the production of an identical, nonswimming offspring would rapidly lead to overcrowding. They instead produce single ciliated offspring called swarmers by a process called [/COLOR][COLOR=black][COLOR=black]budding[/COLOR][/COLOR][COLOR=black]. Budding can occur endogenously, in which the bud forms within the parent and is ejected when mature, or exogenously, in which the swarmer is formed outside the parent. The swarmers swim away from the parent, settle on a substrate, lose their cilia, and develop feeding tentacles and an attaching stalk.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]Naked amoebas (rhizopods) have no fixed plane of division but simply round up and divide into two basically equal halves. The [/COLOR][COLOR=black][COLOR=black]testate amoebas[/COLOR][/COLOR][COLOR=black] (also rhizopods), which live in single-chambered shells, or [/COLOR][COLOR=black][COLOR=black]tests[/COLOR][/COLOR][COLOR=black], exude the daughter from the aperture of the shell. In species that have a shell formed from silica plates, the daughter contains the plates used to produce the shell but remains attached to the mother cell until the shell is fully formed, when the final severing of the cytoplasm between the individuals occurs. Some of the testate amoebas live inside proteinaceous shells. There, too, the new shell is secreted before binary fission is completed.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]The foraminiferan and radiolarian sarcodines have evolved [/COLOR][COLOR=black][COLOR=black]multiple fission[/COLOR][/COLOR][COLOR=black]. Both produce many flagellated swarmers, or [/COLOR][COLOR=black][COLOR=black]zoospores[/COLOR][/COLOR][COLOR=black]. The common planktonic foraminiferan [I]Globigerinoides sacculifer[/I], for example, can produce 30,000 swarmers at one time. Each swarmer is about 5 micrometres (0.005 millimetre) long. In planktonic species the parent usually loses buoyancy and sinks by shedding spines and withdrawing the complicated pseudopodial network into the shell. The swarmers are produced in deep water and migrate upward as they mature. Each secretes a shell around itself, which is added to as the organism grows.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]The foraminiferans are unusual among free-living protozoans in that a sexual phase is a regular part of the life cycle, alternating with an asexual phase. During the life cycle two types of swarmer are produced. One type, zoospores, have half the number of chromosomes of the parent ([I]i.e.,[/I] they are haploid); they grow until they become mature adults and can produce and release large numbers of gametic swarmers. These gametes are identical (isogamous) but are comparable to the eggs and sperm of higher organisms. The gametic swarmers fuse in pairs, thus restoring the full complement of chromosomes ([I]i.e.,[/I] they are diploid), and each individual grows, matures, and ultimately produces haploid zoospores.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]Sexual reproduction among the flagellates is not widespread and can involve identical gametes (isogamy) or distinct male and female gametes (anisogamy). The female gametes are larger and are stationary, whereas the male gametes are smaller, produced in larger numbers, and motile.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black][B]Sexual Reproduction[/B][/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]Sexual reproduction among the ciliated protozoans takes the form of [/COLOR][COLOR=black][COLOR=black]conjugation[/COLOR][/COLOR][COLOR=black]. The process does not result in an increase in numbers, but is a simple exchange of genetic material between two individual cells. Conjugation occurs only between compatible mating strains within a species, and each species may contain many mating strains. Before conjugation occurs, special chemical signals, called gamones, are released by some ciliates. The gamones cause compatible mating strains to undergo processes that facilitate conjugation. In other ciliates, such as [I]Paramecium[/I], gamones are bound to the cell surface and elicit their responses when the ciliates make physical contact.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]During conjugation, two ciliates line up side by side. The macronucleus, which plays no part in the process, disintegrates. A series of nuclear divisions of the micronuclei in each ciliate then ensues, including a meiosis, during which a number of haploid micronuclei are produced in both cells. All but one of these haploid micronuclei disintegrate. The remaining haploid micronucleus in each cell then divides through mitosis into two haploid nuclei (gamete nuclei). A bridge of cytoplasm forms between the two ciliates, and one gametic nucleus from each cell passes into the other cell. The two gametic nuclei in each cell unite, thus restoring the diploid number of chromosomes. The micronucleus undergoes two mitotic divisions to produce four micronuclei; two of these will form the new micronuclei of the cell and two are destined to become the macronucleus. Following the process of conjugation, normal binary fission proceeds. The number of macronuclei and micronuclei formed is dependent on the species and remains the same as the original number.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]When no suitable mating partner is available, ciliates may undergo a form of conjugation called [/COLOR][COLOR=black][COLOR=black]autogamy[/COLOR][/COLOR][COLOR=black], in which all of the nuclear processes described above occur. But, because only one individual is involved, there is no exchange of gametic nuclei; instead, the two gametic nuclei within the cell unite to form the restored micronucleus.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]Specialized sedentary [/COLOR][COLOR=black][COLOR=black]suctorian[/COLOR][/COLOR][COLOR=black] ciliates practice a modified form of conjugation. The conjugating individuals differ in appearance. The macroconjugants resemble the normal feeding individuals, and the microconjugants resemble the swarmers, although smaller. When a microconjugant locates a macroconjugant, it enters and fuses with it. This is quite different from the temporary association between two cells that occurs in most ciliates.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]As is common with other parasitic organisms, parasitic protozoans face the problem of how to disperse from one host to another. In order to increase the probability of finding more hosts, most parasitic protozoa reproduce in high numbers. A representative life cycle of a parasitic protozoan can be found in members of the parasitic phylum Apicomplexa. These protozoans have a complex life cycle that involves a series of stages characterized by episodes of asexual multiple division called [/COLOR][COLOR=black][COLOR=black]schizogony[/COLOR][/COLOR][COLOR=black]. In the parasite [I]Plasmodium[/I], for example, this phase of the life cycle occurs in the liver and red blood cells of humans. The parasite (sporozoite) enters the host’s cells and grows while feeding on the cell contents. It then undergoes a multiple asexual division (schizogony) into many individuals ([/COLOR][COLOR=black][COLOR=black]merozoites[/COLOR][/COLOR][COLOR=black]). The host’s cell wall ruptures, permitting each individual to invade a new red blood cell and repeat the process.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]In certain merozoites a sexual cycle is eventually initiated inside the red blood cell, and male and female gametes are produced. The male gametes (microgametocytes) are small, while the female gametes (macrogametocytes) are larger. The life cycle continues if the gametocytes are taken up by a feeding female mosquito of the genus [I]Anopheles[/I]. Only the gametocytes can infect the mosquito. Inside the mosquito’s gut the haploid gametes fuse to form a diploid zygote, which then undergoes [/COLOR][COLOR=black][COLOR=black]sporogony[/COLOR][/COLOR][COLOR=black], a process of multiple divisions in which many [/COLOR][COLOR=black][COLOR=black]sporozoites[/COLOR][/COLOR][COLOR=black] are produced. The sporozoites migrate to the [/COLOR][COLOR=black][COLOR=black]salivary glands[/COLOR][/COLOR][COLOR=black] of the insect and are injected into a new host when the mosquito next feeds. They are carried by the blood to the liver, where they undergo their first schizogony inside liver cells, thereafter invading the red blood cells for repeated cycles of schizogony.[/COLOR][/COLOR][/SIZE][SIZE=2]

[/SIZE][SIZE=2][COLOR=black][COLOR=black]The parasitic flagellates reproduce entirely by asexual means and do not appear to have a sexual phase in their life cycles. There is, however, evidence of [/COLOR][COLOR=black][FONT=Arial][FONT=Verdana][COLOR=black]genetic[/COLOR][/FONT][/FONT][/COLOR][/COLOR][/SIZE][SIZE=2][COLOR=black] exchange between certain subspecies of [I]Trypanosoma brucei[/I], although the process by which this occurs is not known.[/COLOR][/SIZE]


[CENTER][URL="http://www.tulane.edu/%7Ewiser/protozoology/notes/images/ciliate.gif"][IMG]http://www.tulane.edu/%7Ewiser/protozoology/notes/images/ciliate.gif[/IMG]
[/URL][/CENTER]



[CENTER][IMG]http://xup5matt.files.wordpress.com/2009/01/amoeba-fission-big1.jpg[/IMG][/CENTER]

Reproduction in Protozoa
 

[B]Reproduction in Protozoa[/B]

[B][URL="http://www.scribd.com/doc/4195238/Reproduction-in-Protozoa"]Click here[/URL][/B]

[B]Regards[/B]

The Phylum Porifera
 

[B][FONT=Arial][SIZE=4]The Phylum Porifera[/SIZE][/FONT][/B]


[LEFT][SIZE=3][FONT=Times New Roman][B]Etymology:-[/B] From the Latin [I]porus[/I] for pore and [I]Ferre[/I] to bear,
hence an animal with with pores. [/FONT][/SIZE]

[SIZE=3][FONT=Times New Roman][B]Characteristics of Porifera:-[/B]
1)No definite symmetry.
2)Body multicellular, few tissues, no organs.
3)Cells and tissues surround a water filled space but there is no true body cavity.
4)All are sessile, (live attached to something as an adult).
5)Reproduce sexually or asexually, sexual reproduction can be either gonochoristic or hermaphroditic.
6)Has no nervous system.
7)Has a distinct larval stage which is planktonic.
8)Lives in aquatic environments, mostly marine.
9)All are filter feeders.
10)Often have a skeleton of spicules. [/FONT][/SIZE]

[/LEFT]

[FONT=Times New Roman][SIZE=3]Sponges are one of the better known groups of invertebrates, due to their usefulness in the bath many people who care nothing for invertebrates at least know name and may even have seen a sponges skeleton on sale in a shop. One of the more amazing things about sponges is there ability to suffer damage. Because the cells are not linked in a tissue it is possible for them to be separated an then come together again. Some species such as the freshwater sponge [I]Ephydatia fluviatilis[/I] can be pushed through a sieve, then if given time the individual cells will come together again and make a new sponge.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]A sponge is a simple organism that is easy to describe. A sponge is a sedentary, filter-feeding metazoan which has a single layer of flagellated cells that drive a unidirectional current of water through its body. such a brief description though does not do them justice. Sponges are an ancient and highly successful group of animals. In the Palaeozoic they are believed to have comprised more than half the biomass in marine reefs. They have been living in the waters of the world for more than 600 million years, and can now be found in all marine and many freshwater habitats. Sponges occur in rivers and streams, from rock pools to the deep ocean depths, from frozen arctic seas to the warm tropical seas. They are perhaps at their most beautiful in tropical marine seas. There are about 10,000 known species and though their basic organisation is pretty simple and remains fairly constant throughout the all species they do manage to show a great variety of forms.[/SIZE][/FONT]
[B][FONT=Arial]Anatomy[/FONT][/B]

[FONT=Times New Roman][SIZE=3]The body of a sponge is a collection of a few different types of cells loosely arranged in a gelatinous matrix called a 'mesohyl', mesoglea or mesenchyme. This mesohyl is the connective tissue of a sponge body and it is supported by the skeletal elements. The skeletal elements of sponges are variable and important in taxonomy. Throughout this body run canals through which water flows, there is considerable variation in the complexity of these canals. The canals have openings to the outside which are called pores, where the water enters the sponge system these pores are usually small and are called 'ostia' and where the water leaves the sponge system the pores are larger, often singular and are called 'oscula' (singular osculum). Many if not most of these canals are lined with special flagellated cells called 'choanocytes'. These choanocytes keep the water flowing through the canals in the correct direction by beating their flagellum, they are also important in trapping food items.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]There are three main types of canal system in sponges. The simplest form is Asconoid, here the canals run straight through the sponge body and all the choanocytes line the central large space called the 'spongocoel'. The water enters the ostia, is drawn through to the spongocoel and leaves through a single large osculum. Asconoid sponges have cylindrical hollow bodies and tend to grow in groups attached to some object or other in relatively shallow seas.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Slightly more complicated are Syconoid sponges, externally they are fairly similar to asconoid sponges except that their body wall is thicker. The canals are branched however and do not allow the water to flow straight through in to the spongocoel. Instead the water flows a twisted route through a number of canals some of which are lined with choanocytes before being expelled into the spongocoel and out through the osculum. The spongocoel is not lined with choanocytes only the canals. Syconoid sponges go through a asconoid stage in their development suggesting that they evolved from some ancestral asconoid. Syconoid sponges do not normally form groups as do asconoid sponges.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Most modern sponge species are Leuconoid. In leuconoid sponges the canal system is more complicated again with the canals being longer and more branched, they lead to special chambers whose walls are lined by choanocytes, there are no choanocytes in the canals. There is no real spongocoel just a central exit canal leading to the osculum. Leuconoid sponges tend to live in large groups with each individual sponge having its own osculum, however the borders between individual sponges are often hard to define and the sponge may act more like a large communal organism.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Sponges are built up from relatively few cell types, the main ones being choanocytes, pinacocytes, amoebocytes and lophocytes.[/SIZE][/FONT]
[SIZE=3][FONT=Times New Roman][B]Choanocytes[/B] are vase shaped cells with a collar of fine fibrils connected by microvilli. this is a filter which strains out the smallest food items from the water such as individual bacteria. Extending from the centre of this collar is the single flagellum whose beating drives the water currents that keep the sponge alive and healthy. [/FONT][/SIZE]
[SIZE=3][FONT=Times New Roman][B]Pinacocytes[/B], these form much of the epidermis of sponges and are as close as a sponge gets to having a tissue. Generally they cover the exterior and some interior surfaces. They can change their size (they are contractile) and can therefore change the size of the openings of the ostia thus controlling the flow of water through the sponge. Pinacocytes are also implicated in the absorption into the sponge of larger food items.[/FONT][/SIZE]
[SIZE=3][FONT=Times New Roman][B]Amoebocytes[/B] come in several forms, they are alike in that they are mobile and move around within the sponge body. Archaeocytes are the basis of some asexual reproductive gemmules. If an amoebocyte secretes the spongin fibres of the skeleton they are called a spongioblast, if it secretes spicules it is called a scleroblast and if it is star shaped and secrete collagenous fibrils then it is called a collencyte.[/FONT][/SIZE]
[SIZE=3][FONT=Times New Roman][B]Lophocytes[/B] are a type of amoebocyte, they are the most motile of the sponge cells moving around relatively freely within the mesohyl where they are important in the secretion of fibrils.[/FONT][/SIZE]
[FONT=Times New Roman][SIZE=3]Sponges have skeletons, if it were not so they would be just blobs. There are two main components of a sponge skeleton, a protein called spongin which forms a tough fibrous network throughout the sponge and normally works in conjunction with the spicules. Spicules are non-living aggregates of a chemical nature, secreted and made from either silica or calcium carbonate as calcite or aragonite. These spicules are important in the classification of sponges, thus we can say that.
The Calcarea sponges have spicules of calcium carbonate that have 1,3 or 4 rays, a a skeleton that involves a single large lump of calcium carbonate rather than spicules.
The Demospongiae have their spicules made from silica and they have 1,2, or 4 rays.
The Sclerospongiae have a compound skeleton of spicules of silica that is restricted to thin layer of living sponge supported on a large basal layer of calcium carbonate.
The Hexactinellida or 'Glass sponges' have spicules made from silica that are 6 rayed.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Individual spicules can be arranged loosely within the spongin or interlocking and fused together, siliceous spicules come in two sizes called megascleres and microscleres.[/SIZE][/FONT]

[B][FONT=Arial]Ecology[/FONT][/B]

[FONT=Times New Roman][SIZE=3]All sponges are filter feeders on small to extremely small particles and most are sedentary or immobile as adults, i.e they spend their adult lives fixed to a substrate.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]The reproductive ecology of most sponges has never been studied so the following generalisation is based on the few species that are reasonably well known and should not be taken as the last word in sponge reproductive ecology.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Sponges are generally hermaphroditic, however they are only one gender at a time, being either male or female or neuter, some species such as [I]Halichondria moorei[/I] change colour when they change sexes though most do not. Sponges have no permanent gonads, instead a number of areas of the sponge will during the reproductive period become differentiated (changed) to produce either sperm or ova (eggs). Sperm is released into the canals and is then pumped out of the sponge through the osculum where it is likely to be drawn into the canal system of another sponge. Here incoming sperm of the same species are trapped by the choanocytes which then loose their flagellum and collar and migrate through the mesohyl to the ovocyte, a cell generating ova, where the sperm are transferred to the ova, assuming this is a sponge in its female form. Sperm release can be an individual act as in [I]Verongia archeri[/I] or it can be a co-ordinated affair with many sponges in an area releasing their sperm simultaneously as in [I]Neofibularia nolitangere[/I].[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]The fertilised ova are retained within the adult sponge until some unknown signal indicates it is time for their release. They are then set free into the surrounding waters. Once an adult begins expelling its larvae it continues to do so for some time, thus [I]Microciona coccinea[/I] releases 4 or 5 larvae per minute for 3 to 4 days. [/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Larval sponges are small 50 microns to 5 millimetres in diametre. all known sponge larvae are ciliated though the cilia may be longer, shorter or absent from different parts of their surface. After release they swim or crawl for a period of time before settling down to begin life as a new miniature sponge. Swimming species tend to have a crawling phase immediately before settling down. This free living stage may last as long as 18 to 20 days in [I]Polymastia[/I] spp. or be as short as 4 to 6 hours in genera such as [I]Ophlitaspongia[/I]. Larval sponges are not complicated organisms, and there is much variation between species however many species have a positive phototaxis when they first leave their parents body which switches to a negative one before they enter the presettling stage. Some species have been shown to have a preliminary negative geotaxis while most species have shown a preference for surfaces with an algal or bacterial film. As with the larval stage so the time taken for the larvae to reorganise itself into and functioning sponge varies between species so that Microciona spp. are up and running within two days while Polymastia spp. can take as long as 7 days to get themselves sorted.[/SIZE][/FONT]
[FONT=Times New Roman][SIZE=3]Sponges also reproduce asexually by releasing fragments of themselves, or special groups of cells called gemmules. These gemmules, at least in freshwater species such as [I]Ephydatia fluviatilis[/I] have protective coat of spongin and have particular environmental conditions they need to have met before they germinate.[/SIZE][/FONT]

[CENTER][SIZE=3][FONT=Times New Roman][IMG]http://www.cartage.org.lb/en/themes/Sciences/Zoology/Biologicaldiverstity/AnimalsI/sponge_1.gif[/IMG][/FONT][/SIZE][/CENTER]


[CENTER][IMG]http://www.mun.ca/biology/scarr/141995_Porifera.jpg[/IMG][/CENTER]

Porifera
 

[B]Canal System in Porifera.[/B]

[SIZE=3][FONT=Times New Roman]There are three types of [B]canal systems[/B], in the following drawings the arrows show the direction of water flow:
[B]Asconoids[/B] have the simplest, see the drawing on the left. These sponges are small and tube-shaped. The water enters through tiny ostia into one large internal cavity called a spongocoel, and is expelled through one large osculum. This type of canal system is found in the Calcarea Class .[/FONT][/SIZE]
[SIZE=3][FONT=Times New Roman][B]Synconoids[/B], like asconiods, have a single, large osculum, but their body is thicker. The drawing below left shows two synconoid systems - a simple type on the left and a more complex type on the right. The water enters through numerous small ostia, and passes through incurrent canals before reaching the large central cavity. This system is found in Calcarea and Hexactinellida .[/FONT][/SIZE]

[SIZE=3][FONT=Times New Roman][B]Leuconoids[/B] have the most complex structure . They have many small ostia. The ostia lead to numerous incurrent canals, but there is no large central cavity. [/FONT][/SIZE]
[CENTER][SIZE=3][FONT=Times New Roman]Asconoid Type [IMG]http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/images/nw0250-nn.jpg[/IMG][/FONT][/SIZE][/CENTER]

[CENTER][IMG]http://www.bumblebee.org/invertebrates/images/synconoid.jpg[/IMG][/CENTER]


[CENTER][IMG]http://www.bumblebee.org/invertebrates/images/leucaniod.jpg[/IMG][/CENTER]

Three Types of canal system

[CENTER][IMG]http://animaldiversity.ummz.umich.edu/site/resources/biodidac/spongetypes.jpg/medium.jpg[/IMG][/CENTER]

Phylum Porifera
 

[B]Phylum Porifera[/B]

The link mentioned here cantains very good presentation about porifera,structure i.e skeleton,canal system ,reproduction.... with very good figures.

[URL="http://www.scribd.com/doc/6710267/4-Porifera-Spicules-Canal-System"]Click Here.[/URL]

Regards

Phylum Protozoa
 

[B]Skeleton in Protozoa , a very good and interesting presentation on protozoa skeleton,do check it.[/B]

[B][URL="http://www.scribd.com/doc/6710280/2-Skeleton-in-Protozoa"]Click this.[/URL][/B]


[B]regards[/B]

Protozoan reproduction.
 

[B]Protozoan reproduction.[/B]
[B]Although i have given a link of rep in protozoa its not comprehensive.[/B]
[B]the link i am mentioning now has both detailed description and diagrams of asexual and sexual reproduction.[/B]

[B][URL="http://www.scribd.com/doc/6710273/3-Repd"]Clich here[/URL][/B]

[B]regards[/B]

Zoology Glossary
 

A glossary of Zoology Terms, Click [URL="http://animals.about.com/od/zoologyglossary/Glossary.htm"][B]here[/B][/URL]

Hope it helps ! :)

Diagrams
 

[B]Figures of Invertebrate phylums [/B]
[B]you can also check the glossory.[/B]

[B][URL="http://www-biol.paisley.ac.uk/biomedia/text/txt_pictures.htm#s"]Click here[/URL][/B]

[B]Regards[/B]

Porifera.
 

All about Porifera.Its a 17 page presentation and easily downloaded.
And in the end the classification is also given.
With this most of the phylum porifera is complete now.

[URL="http://cfcc.edu/rogers/courses/msc174/Lectures/Phylum%20Porifera.pdf"]Click Here[/URL]

Regards

@afrms

You mentioned in some of your post about a couple of articles published in Dawn. I tried to find that peculiar post but couldn't succeed. Would you please write again about the title and date on which they were printed?

Regards,

[quote=Lord AvaLon]@afrms

You mentioned in some of your post about a couple of articles published in Dawn. I tried to find that peculiar post but couldn't succeed. Would you please write again about the title and date on which they were printed?

Regards,[/quote]


I think you are talking about post 3 in the thread linked [B][URL="http://www.cssforum.com.pk/css-compulsory-subjects/current-affairs/21803-important-topics-current-affair-2009-a.html"]here [/URL][/B]

[quote=Lord AvaLon]@afrms

You mentioned in some of your post about a couple of articles published in Dawn. I tried to find that peculiar post but couldn't succeed. Would you please write again about the title and date on which they were printed?

Regards,[/quote]

salam
Mohsin has mentioned the link.i was going through the Dawn news articles and found a good article on Irrigation System.
The title is "giving irrigation system a facelift" By bilal hassan.(economic and bsuiness reveiw,feb 16-22 P.III.
do check it might be helpful.
regards

That was helpful afrms,
I request you to keep on pointing out the articles which appears important to you in anyway. Having the clippings would obviously help alot in the high times of exam.

Regards,

[quote=Lord AvaLon]That was helpful afrms,
I request you to keep on pointing out the articles which appears important to you in anyway. Having the clippings would obviously help alot in the high times of exam.

Regards,[/quote]
yes i will keep on doing that.so keep an eye.yes reading newspaper helps a lot i got 50 in current just by reading dawn and shahid books

Phylum Coelenterata
 

[COLOR=black][FONT=Verdana][SIZE=2]Phylum Coelenterata [/SIZE][/FONT][/COLOR]
[COLOR=black][FONT=Verdana][/FONT][/COLOR]
[COLOR=black][FONT=Verdana][B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]The radiate animals Phylum Coelenterata ( Cnidaria )[/COLOR][/SIZE][/FONT][/COLOR][/B]

[SIZE=2][FONT=Verdana] [/FONT][FONT=Verdana][/FONT][/SIZE]
[B][COLOR=black][FONT=Verdana][SIZE=2]The Phylum Coelenterata includes the polyps, jellyfishes, sea anemones, and corals. All of these animals have a body wall consisting of two layers of cells, between which is a jellylike substance, the mesoglea. Within the body is a single gastrovascular cavity, or coelenteron. Because of the presence of two cellular layers, Coelenterates are side to have a tissue-level organization. They are also acoelomates; that is, they dont possess a second body cavity, the coelom .[/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Position in animal kingdom[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]Phylum Cnidaria are characterized by primary radial or biradial symmetry . Radial symmetry , in which the body parts are arranged concentrically around the oral-aboral axis , is particularly suitable for sessile or sedentary animals .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]The phylum has not advanced generally beyond the tissue level of organization, although a few organs occur . [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Biologic contributions[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][SIZE=2][COLOR=black][FONT=Verdana]a. [/FONT][/COLOR][COLOR=black][FONT=Verdana]The phylum has developed two well-defined germ layers , ectoderm and endoderm ; a third , or mesodermal ,layer , which is derived embryologically from the ectoderm , is present in some . The body plan is saclike , and the body wall is composed of two distinct layers , epidermis and gastrodermis , derived from the ectoderm and endoderm , respectively . The gelatinous matrix , mesoglea , between these layers may be structureless , may contain a few cells and fibers , or may be composed largely of mesodermal connective tissue and muscle fibers .[/FONT][/COLOR][/SIZE][/B]

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[B][SIZE=2][COLOR=black][FONT=Verdana]b. [/FONT][/COLOR][COLOR=black][FONT=Verdana]An internal body cavity, the gastrovascular cavity , is lined by the gastrodermis and has a single opening , the mouth , which also serves as the anus .[/FONT][/COLOR][/SIZE][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]c. Extracellular digestion occurs in the gastrovascular cavity , as does intracellular digestion in the gastrodermal cells . [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. Most radiates have tentacles , or extensible projections around the oral end , that aid in food capture .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]e. The first true nerve cells ( protoneurons ) occur in the radiates , but the nerves are arranged as a nerve net , with no central nervous system .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]f. Sense organs appear first in the radiates and include well-developed statocysts (organs of equilibrium ) and ocelli.[/SIZE][/FONT][/COLOR][/B]

[SIZE=2][FONT=Verdana] [/FONT][/SIZE][COLOR=black][FONT=Verdana][SIZE=2]g. Locomotion in the free-moving forms is achieved either by muscular contractions . However the groups are still better adapted to floating or being carried by currents than to strong swimming . [/SIZE][/FONT][/COLOR]
[B][COLOR=black][FONT=Verdana][SIZE=2]h. Polymorphism (polyp stage and medusa stage ) in the cnidarians has widened their ecologic possibilities .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]i. Some unique features are found in this phylum , such as nematocysts ( stinging organoids ) in Cnidarians .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] characteristics[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]a. Entirely aquatic , some in fresh water but mostly marine [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. Radial symmetry or biradial symmetry around a longitudinal axis with oral and aboral ends ; no definite head[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]c. Two basic types of individuals: polyps and medusae [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. Exoskeleton or endoskeleton of chitinous, calcareous , or protein components in some[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]g. Special stinging cell organoids called nematocysts in either or both epidermis and gastrodermis ; nematocysts abundant on tentacles , where they may form batteries or rings[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]h. Nerve net with symmetric and asymmetric synapses; with some sensory organs; diffuse conduction [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]e. Body with two layers, epidermis and gastrodermis, with mesoglea ( diploblastic ) ; mesoglea with cells and connective tissue ( ectomesoderm ) in some ( triploblastic )[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]f. Gastrovascular cavity (often branched or divided with septa ) with a single opening that serves as both mouth and anus; extensible tentacles usually encircling the mouth or oral region[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]i. Reproduction by asexual budding ( in polyps ) or sexual reproduction by gametes ( in all medusae and some polyps ) ; sexual forms monoecious or dioecious ; planula larva ; holoblastic cleavage . [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]j. No excretory or respiratory systems [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]k. No coelomic cavity [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]Classification[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]a. Class Hydrozoa[/COLOR][/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]This class includes the freshwater polyps , the small jellyfishes , the hydroid zoophytes, and a few stony corals .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. Class Scyphozoa [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]Most of the large jellyfishes are placed in this class .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]c. Class Anthozoa[/COLOR] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] In this class are included the sea anemones , and most of the stony and horny corals . [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Class Hydrozoa[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][SIZE=2][COLOR=sienna](1) Characteristics[/COLOR] [/SIZE][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2] a. solitary or colonial ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] b. asexual polyps and sexual medusae , although one type may be suppressed ; [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] c. hydranths with no mesenteries.[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] d. medusae ( when present ) with a velum;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] e. both fresh-water and marine .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] (2) Typical animal[/COLOR] [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2] Hydra[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] a. The structure of hydra ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] b. The physiological function of hydra ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] c. The life cycle of hydra .[/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Class Scyphozoa[/COLOR][/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna](1) Characteristics of Class Scyphozoa[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2] a. solitary ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] b. polyp stage reduced or absent ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] c. bell-shaped medusae without velum ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. gelatinous mesoglea much enlarged ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]e. margin of bell or umbrella typically with eight notches that are provided with sense organs ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]f. all marine[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]Typical animal[/COLOR][/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [I]Aurelia aurita[/I] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]a. The structure of [I]Aurelia aurita[/I] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. The life cycle of [I]Aurelia aurita[/I] [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2] [COLOR=sienna]Class Anthozoa[/COLOR] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][SIZE=2][COLOR=sienna] [B](1) characteristics[/B][/COLOR] [/SIZE][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2] a. all polyps, no medusae ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] b. solitary or colonial ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] c. enteron subdivided by at least 8 mesenteries or septa bearing nematocysts;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] d. gonads endodermal ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] e. all marine .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna](2) Typical animal[/COLOR] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] sea-anemones[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Metamorphosis[/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]Generally, after swimming for a few hours to many days the planula attaches and develops into a polyp or polypoid form , which in colonial species subsequently gives rise to the colony .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]In some hydroids the planula remains in the gonophore, developing into the tentaculate actinula larva which is liberated and creeps about . After attachment, it develops into a polyp . In many hydrozoans with no polypoid phase the planula develops into an actinula and then a medusa .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]In most scyphozoans, after attachment, the planula develops into a polypoid scyphistoma, with a stalked trumpet-shaped body . At maturity, the scyphistoma produces a free-swimming medusa stage, the ephyra larva, by transverse fission or strobilization. Ephyrae may be produced singly or several at a time, and develop to adult medusae . [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]In zoantharian anthozoans, the planula does not attach but develops into an anemone-like Edwardsia larva, then the Halcampoides larva. After attachment, tentacles develop and the adult polyp form is attained.[/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]Reproduction [/COLOR][/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]There are both dioecious and hermaphroditic species .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] Sexual reproduction [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] Asexual reproduction [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][B][SIZE=2][COLOR=sienna]Asexual reproduction[/COLOR] is common, it may occur by :[/SIZE][/B][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]a. budding ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. pedal laceration, e.g. in sea anemones ;[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]c. transverse fission, e.g. in the production of ephyrae by scyphistomae [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. longitudinal fission , e.g. in many sea anemones .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] Polymorphism [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2]In many cnidarians the life-cycle contains two morphologically dissimilar individuals , the pulp and the medusa . In colonial species, each of these types may occur in a number of different morphological forms , specialized to perform a particular function .[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]The main types of modified polyp are :[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] a. the gastrozooid ---- feeding polyp [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] b. the gonozooid ---- reproductive polyp[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] c. the dactylozooid ---- protective polyp , or tentaculozooid [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]a, b and c are found in hydrozoan colonies [/SIZE][/FONT][/COLOR][/B]

[B][SIZE=2] d. the autozooid ---- feeding and reproductive polyp[/SIZE][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] e. the siphonozooid ---- current producing polyp[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d, and e are found in some authozoan colonies[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]A colony may also bear medusoid forms in different stages of formation or degeneration, which may or may not be freed . Medusae may become modified as swimming bells, floats , protective bracts or phyllozooids, or gonophores which serve only for reproduction . [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]Phylum Ctenophora[/COLOR]
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[B][COLOR=black][FONT=Verdana][SIZE=2]About 100 species known . Ovoid forms measure up to about 5 cm , flattened forms may be up to 1 meter or more in length .[/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna](1) Characteristics[/COLOR] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=windowtext][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]a. symmetry biradial ; arrangement of internal canals and the position of the paired tentacles change the radial symmetry into a combination of the two ( radial + bilateral )[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. usually ellipsoidal or spherical in shape , with radially arranged rows of comb plates for swimming [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]c. Ectoderm , endoderm , and a mesoglea ( ectomesoderm ) with scattered cells and muscle fibers ; may be considered tripoblastic [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. Nematocysts absent ( except in one species ) , but adhesive cells ( colloblasts ) present [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]e. Digestive system consisting of mouth, pharynx , stomach , and a serious of canals [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]f. Nervous system consisting of a subepidermal plexus concentrated around the[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]mouth and beneath the comb plate rows; an aboral sense organ ( statocyst )[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]g. No polymorphism or attached stages [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]h. Reproduction monoecious, gonads ( endodermal origin ) on the walls of the digestive canals , which are under the rows of comb plates ; determinate cleavage ; cydippid larva[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]i. Luminescence common [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Comparison with Cnidaria[/COLOR] [/SIZE][/FONT][/COLOR][/B]

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[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]A. Ctenophores resemble the cnidarians in the following ways:[/COLOR][/SIZE][/FONT][/COLOR][/B]

[SIZE=2][FONT=Verdana] [/FONT][FONT=Verdana][/FONT][/SIZE]
[B][COLOR=black][FONT=Verdana][SIZE=2]a. Form of radial symmetry ; together with the cnidarians , they form the group Radiata [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. Aboral - oral axis around which the parts are arranged [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]c. Well - developed gelatinous ectomesoderm [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. No coelomic cavity [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]e. Diffuse nerve plexus [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]f. Lack of organ systems [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna]B. They differ from the cnidarians in the following ways:[/COLOR][/SIZE][/FONT][/COLOR][/B]

[SIZE=2][FONT=Verdana] [/FONT][FONT=Verdana][/FONT][/SIZE]
[B][COLOR=black][FONT=Verdana][SIZE=2]a. No nematocysts except in Euchlora [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]b. Development of muscle cells from mesenchyme[/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]c. Presence of comb plates and colloblasts [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]d. Mosaic, or determinate type of development [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]e. Presence of pharynx generally [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]f. No polymorphism[/SIZE][/FONT][/COLOR][/B]

[SIZE=2][FONT=Verdana] [/FONT][FONT=Verdana][/FONT][/SIZE]
[B][COLOR=black][FONT=Verdana][SIZE=2][COLOR=sienna] Classification[/COLOR] [/SIZE][/FONT][/COLOR][/B]

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[B][SIZE=2][FONT=Times New Roman] [COLOR=sienna] [/COLOR][/FONT][COLOR=sienna]Class Tentaculata[/COLOR] [/SIZE][/B]

[B][COLOR=windowtext][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]With tentacles. Tentacles may or may not have sheaths into which they retract . Some types flattened for creeping ; other compressed to a bandlike form . In some the comb plates may be confined to the larval form. [/SIZE][/FONT][/COLOR][/B]

[B][SIZE=2][COLOR=sienna][FONT=Times New Roman] [/FONT]Class Nuda[/COLOR][/SIZE][/B]

[B][COLOR=windowtext][FONT=Verdana][SIZE=2] [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2]Without tentacles; conical form; wide mouth and pharynx; gastrovascular canals much branched . [/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][/SIZE][/FONT][/COLOR] [/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][IMG]http://content.tutorvista.com/biology_11/content/us/class11biology/chapter10/images/img45.jpeg[/IMG][/SIZE][/FONT][/COLOR][/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][/SIZE][/FONT][/COLOR] [/B]

[B][COLOR=black][FONT=Verdana][SIZE=2][IMG]http://gurungeblog.files.wordpress.com/2008/11/obelia.jpg[/IMG][/SIZE][/FONT][/COLOR][/B]

[/FONT][/COLOR]

Free Ebook of Invertebrates by Cambridge
 

[B]Free Ebook of Invertebrates By Janet Moore(An Introduction to Invertebrates)[/B]

[B]This is a link to ebook of invertebrate zoolgy.It cantains all the phylums.Hope its helpful.[/B]

[B][URL="http://www.scribd.com/doc/4961869/Invertebrates"]Click Here.[/URL][/B]

[B]Regards[/B]

Coelenterata
 

[B]Phylum Coelenterata Presentation with brief classification[/B]

[B][URL="http://www.scribd.com/doc/6710254/6-Cnidaria"]Check this[/URL][/B]


[B]Coral Reef Presentation with types.[/B]

[B][URL="http://www.scribd.com/doc/6710249/7-Corals-Coral-Reefs"]Click here[/URL][/B]

[B]Regards[/B]

coral reef
 

[B]Coral reefs[/B]
Coral reefs are warm, clear, shallow ocean habitats that are rich in life. The reef's massive structure is formed from coral polyps, tiny animals that live in colonies; when coral polyps die, they leave behind a hard, stony, branching structure made of limestone.

The coral provides shelter for many animals in this complex habitat, including [URL="http://www.enchantedlearning.com/subjects/invertebrates/sponge/"][COLOR=black]sponges[/COLOR][/URL][COLOR=black],[/COLOR] nudibranchs, fish (like Blacktip Reef Sharks, groupers, clown fish, eels, parrotfish, snapper, and scorpion fish), jellyfish, anemones, sea stars (including the destructive Crown of Thorns), crustaceans (like crabs, shrimp, and lobsters), turtles, sea snakes, snails, and mollusks (like octopuses, nautilus, and clams). Birds also feast on coral reef animals.
[B]Types of Corals[/B]: There are two types of coral, hard coral and soft coral. Hard corals (like brain coral and elkhorn coral) have hard, limestone skeletons which form the basis of coral reefs. Soft corals (like sea fingers and sea whips) do not build reefs.

[B]Where are Coral Reefs?[/B]: Coral reefs develop in shallow, warm water, usually near land, and mostly in the tropics; coral prefer temperatures between 70 and 85 ° F (21 - 30 °C). There are coral reefs off the eastern coast of Africa, off the southern coast of India, in the Red Sea, and off the coasts of northeast and northwest Australia and on to Polynesia. There are also coral reefs off the coast of Florida, USA, to the Caribbean, and down to Brazil.

The Great Barrier Reef (off the coast of NE Australia) is the largest coral reef in the world. It is over 1,257 miles (2000 km) long.

[B]Types of Reefs[/B]: The different types of reefs include:[LIST][*][B]Fringing reefs[/B] are reefs that form along a coastline. They grow on the continental shelf in shallow water.[*][B]Barrier reefs[/B] grow parallel to shorelines, but farther out, usually separated from the land by a deep lagoon. They are called barrier reefs because they form a barrier between the lagoon and the seas, impeding navigation.[*][B]Coral Atolls[/B] are rings of coral that grow on top of old, sunken volcanoes in the ocean. They begin as fringe reefs surrounding a volcanic island; then, as the volcano sinks, the reef continues to grow, and eventually only the reef remains.[/LIST][B]Coral Reefs in Danger[/B]: Many coral reefs are dying. Major threats to coral reefs are water pollution (from sewage and agricultural runoff), dredging off the coast, careless collecting of coral specimens, and sedimentation (when silt or sand from construction or mining projects muddies the waters of a reef and kills coral, which needs light to live).

[CENTER][IMG]http://www.geographyalltheway.com/igcse_geography/natural_environments/marine_processes/imagesetc/types_of_reefs.jpg[/IMG][/CENTER]

Nematocyst
 

[LEFT][FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000][B]What is a Nematocyst?[/B][/COLOR][/SIZE][/FONT][/LEFT]



[FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000]Nematocysts are unique to the phylum; Cnidaria ( = Coelenterata)[/COLOR][/SIZE][/FONT]


[FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000]Nematocysts are individual cells usually on the outer surface of the organism which have a variety of functions, most usually in defence or capture of prey species. These cells are known as stinging cells sometimes used to inject toxins which in some cases are toxic to man.[/COLOR][/SIZE][/FONT]


[FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000]Nematocysts can be specialised to carry out a number of functions within the organism these include; Sticking to surfaces and wrapping around objects, Penetrating surfaces or secreting proteinaceous toxins. These functions are used in food collection,defense and to some extent, locomotion. [/COLOR][/SIZE][/FONT]


[FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000]Nematocysts are usually most abundant on the feeding tentacles of all species, and within the digestive cavity of some species. The individual nematocyst rarely exceed 50 um (microns) in size, but is the great number that make them effective in providing protection or as a method to capture and stun prey species.[/COLOR][/SIZE][/FONT]
[FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000]These cells are also important to the biologist in individual species recognition.[/COLOR][/SIZE][/FONT]

[FONT=Arial,Helvetica,sans-serif][SIZE=3][COLOR=#000000]Nematocyst discharge is triggered by direct contact or other external stimulus. Once the cell is discharged a new nematocyst is formed as the mechanism in each cell can only be triggered once.[/COLOR][/SIZE][/FONT]

[CENTER][IMG]http://scyphozoans.tripod.com/sitebuildercontent/sitebuilderpictures/141997.jpg[/IMG][/CENTER]


[CENTER][IMG]http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/nematocysts%20diagram.gif[/IMG][/CENTER]

Phylum Platyhelmenthis
 

[LEFT][B][COLOR=black][FONT=Times New Roman]The Phylum Platyhelminthes[/FONT][/COLOR][/B][/LEFT]

[B][COLOR=black][FONT=Times New Roman][SIZE=3]Etymology:-[/SIZE][/FONT][/COLOR][/B][COLOR=black][SIZE=3][FONT=Times New Roman] From the Greek [I]platy[/I] for flat and [I]helminthes[/I] for worms,
Hence Flat Worms. [/FONT][/SIZE][/COLOR]
[COLOR=black]
[SIZE=3][FONT=Times New Roman][B]Characteristics of Platyhelminthes:-[/B]
1)Bilaterally symmetrical.
2)Body having 3 layers of tissues with organs and organelles.
3)Body contains no internal cavity.
4)Possesses a blind gut (i.e. it has a mouth but no anus)
5)Has Protonephridial excretory organs instead of an anus.
6)Has normally a nervous system of longitudinal fibres rather than a net.
7)Generally dorsoventrally flattened.
8)Reproduction mostly sexual as hermaphrodites.
9)Mostly they feed on animals and other smaller life forms.
10)Some species occur in all major habitats, including many as parasites of other animals. [/FONT][/SIZE][/COLOR]

[B][COLOR=black][FONT=Times New Roman]Platyhelminthes = Flatworms[/FONT][/COLOR][/B]

[COLOR=black][SIZE=3][FONT=Times New Roman]Platyhelminthes are an ancient phylum, but practically nothing is known of their evolutionary history because they have very soft bodies which do not preserve well as fossils. Scientists believe that the first turbellarians evolved around 550 MYA (million years ago).[/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]Platyhelminthes are mostly worm like creatures that are dorsoventrally flattened, meaning they look like a ribbon, this is why they are called names such as Tapeworm, Flatworm, Fluke and Planarian.[/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]The Platyhelminthes are a successful phylum with around 25,000 known species divided into four classes. Most Platyhelminthes are parasites on other animals, only the Turbellarians are mostly non-parasitic. A few species are commensalists living in harmony, or mutual benefit with another, normally larger organism. Most species feed on animal material either as parasites or as scavengers, a very few species feed on algae. Although a few of the free living marine and terrestrial species are very beautiful, most species are not particularly attractive to the human mind.[/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]Platyhelminthes live nearly everywhere, on land, in both fresh and marine waters as well as inside other animals. Most of the free living species are marine with only a small number inhabiting fresh water and very few being terrestrial. Parasitic species normally move between different habitats as they change life cycle stages and hosts. A number of parasitic species are of importance to mankind because they infect either our bodies or the bodies of our livestock. A few species can be fatal to humans if not treated, but nearly all species can be treated with modern medicines. Schistosomiasis (Bilharzia) is the most important platyhelminth disease of humans, causing much suffering and some death, over 200 million people are infected with the causative agent in tropical countries.[/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]While they remain fairly morphologically simple the Platyhelminthes show several advance in body structure over the simple radial phyla that came before them. They have a definite congregation of of sensory organs(a few have light sensing organs) and nervous tissues at one end of their body giving them a distinct head and tail. They also have distinct upper and lower (dorsal and ventral) body surfaces. They have a number of organs and even the beginnings of organ systems and a more distinct 3rd layer of cells in their body plan. The evolution of this connective tissue, called parenchyma, the cells of which serve as storage reservoirs as well as protecting the internal organs, is a major step forward toward the more complex body plans of higher animals, such as humans.[/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]However they still no anus, instead they have only a blind ending gut, or no gut at all. Those species with a gut must therefore excrete there digestive waste products through their mouths.[/FONT][/SIZE][/COLOR]
[B][COLOR=black][FONT=Times New Roman]Classification [/FONT][/COLOR][/B]

[FONT=Times New Roman][COLOR=black][SIZE=3]The higher classification of the Platyhelminthes, is as with so many other groups, in a state of confusion, and there is little consensus of opinion among the experts. The scheme I have used here will suffice to break the phylum into smaller, more manageable groups and will be satisfactory for teaching at secondary levels providing some mention is made of the inherent disharmony in expert opinion. However if you are considering research work, or writing as an undergraduate you should seek out and read the latest scientific papers. There is a general consensus concerning the classes Turbellaria and Cestoda, however the Monogenea, Digenea and the Aspidobothrians are somewhat confusing, you will find them all included in the Class Trematoda, and all given class status in their own right, and in schemes, like that which I have used here, that are a mixture of these two extremes.
[/SIZE][/COLOR][B][COLOR=black]Phylum Platyhelminthes[/COLOR][/B][/FONT][FONT=Times New Roman][COLOR=black][SIZE=3]
[/SIZE][/COLOR][B][COLOR=black]Class [URL="http://www.earthlife.net/inverts/turbellaria.html"][COLOR=black]Turbellaria[/COLOR][/URL][/COLOR][/B][/FONT][FONT=Times New Roman][COLOR=black][SIZE=3]
[/SIZE][/COLOR][B][COLOR=black]Class [URL="http://www.earthlife.net/inverts/monogenea.html"][COLOR=black]Monogenea[/COLOR][/URL][/COLOR][/B][/FONT][FONT=Times New Roman][COLOR=black][SIZE=3]
[/SIZE][/COLOR][B][COLOR=black]Class [URL="http://www.earthlife.net/inverts/trematoda.html"][COLOR=black]Trematoda[/COLOR][/URL][/COLOR][/B][/FONT][FONT=Times New Roman][COLOR=black][SIZE=3]
[/SIZE][/COLOR][B][COLOR=black]Class [URL="http://www.earthlife.net/inverts/cestoda.html"][COLOR=black]Cestoda[/COLOR][/URL][/COLOR][/B][/FONT]


[CENTER][FONT=Times New Roman][B][COLOR=black][IMG]http://teacherweb.com/NV/NWCTA/CarolTAdamson/Flatworms.gif[/IMG][/COLOR][/B][/FONT][/CENTER]

Phylum Platyhelminthes
 

[COLOR=black][FONT=Times New Roman][SIZE=4][B]Phylum Platyhelminthes[/B][/SIZE][/FONT][/COLOR]


[COLOR=black][FONT=Times New Roman][SIZE=4]This is a link to Power point Presentation [/SIZE][/FONT][/COLOR]


[COLOR=black][FONT=Times New Roman][SIZE=4][URL="http://faculty.evansville.edu/de3/b10802/PPoint/Platyhelminthes/sld001.htm"]Click here[/URL][/SIZE][/FONT][/COLOR]


[COLOR=black][FONT=Times New Roman][SIZE=4]This is a link to pdf file,all related to Flat worms.[/SIZE][/FONT][/COLOR]


[COLOR=black][FONT=Times New Roman][SIZE=4][URL="http://www.tamut.edu/~allard/Courses/Invertebrate_zoo/lectures/308_Lecture5.pdf"]Check this[/URL][/SIZE][/FONT][/COLOR]


[COLOR=black][FONT=Times New Roman][SIZE=4]regards[/SIZE][/FONT][/COLOR]

The life cycle of the liver fluke:
 

[COLOR=black][FONT=Times New Roman][SIZE=4][B][LEFT][FONT=Verdana, Arial, Helvetica, sans-serif][SIZE=2][COLOR=#000080][COLOR=black][B]The life cycle of the liver fluke:[/B][/COLOR] [/COLOR][/SIZE][/FONT][/LEFT]
[FONT=Verdana, Arial, Helvetica, sans-serif][SIZE=2][COLOR=#000080]
[/COLOR][/SIZE][/FONT][/B][/SIZE][/FONT][/COLOR][LIST][*][LEFT]The adult flukes ([I]Fasciola hepatica[/I]: up to 30 mm by 13 mm; [I]F. gigantica[/I]: up to 75 mm) reside in the large biliary ducts of the mammalian host. Immature eggs are discharged in the biliary ducts and in the stool. [/LEFT][*][LEFT]After development in water, each egg releases a miracidium which invades a suitable snail intermediate host. [/LEFT][*][LEFT]In the snail the parasites undergo several developmental stages (sporocysts, rediae, and cercariae). [/LEFT][*][LEFT]The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other surfaces. [/LEFT][*][LEFT]Mammals acquire the infection by eating vegetation containing metacercariae. [/LEFT][*][LEFT]After ingestion, the metacercariae excyst in the duodenum and migrate through the intestinal wall, the peritoneal cavity and the liver parenchyma into the biliary ducts, where they develop into adults.[/LEFT][*][LEFT][I]Fasciola hepatica[/I] infect various animal species, mostly herbivores. [/LEFT][*][LEFT]Humans can become infected by ingesting metacercariae-containing freshwater plants, especially watercress. [/LEFT][*][LEFT]In humans, maturation from metacercariae into adult flukes takes approximately 3 to 4 months.[/LEFT][/LIST][CENTER][IMG]http://uk.merial.com/producers/dairy/IMAGEFOLDER/life_cycle_of_liver_fluke.gif[/IMG][/CENTER]

Parasitic Adaptations in Helminths
 

[COLOR=black][FONT=Times New Roman][SIZE=4][B]Phylum Platyhelminthes[/B][/SIZE][/FONT][/COLOR]

[COLOR=black][B]Parasitic Adaptations in Helminths[/B][/COLOR]

Check this link for parasitic modification in flat worms,reproduction and life cycles.

[B][URL="http://www.scribd.com/doc/6710236/8-Parasitic-Adaptations-in-Helminths"]Click Here[/URL][/B]

regards

Importance of Trematodes
 

[B][FONT=Times New Roman][SIZE=4]Significance to humans[/SIZE][/FONT][/B]
[FONT=Arial][SIZE=3][FONT=Verdana]Trematodes pose a significant health threat to humans, particularly those living in developing countries. A common illness in developing countries is schistosomiasis. This condition, caused by three species of [I]Schistosoma[/I], affects more than 40 million individuals who live in tropical and subtropical countries, causing weakness, diarrhea, hemorrhage, fever, enlargement of the spleen, and other severe symptoms.[/FONT][/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]Other trematodes also infect humans, including the trematode [I]Opisthorchis[/I], which is transmitted to humans through eating infected fishes. Prevalent in parts of Russia, the fluke currently infects 1.2 million people, which is more than 4 percent of the region's population.[/FONT][/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]The cost for treatment of human fluke infections ranges into billions of dollars, in part because these conditions are frequently misdiagnosed. Treatment for infection by such organisms as [I]Paragonimus[/I] species costs about $1, but the patient's illness is often misinterpreted as tuberculosis, which calls for years of expensive treatment.[/FONT][/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]Trematodes that infect such household pets as rabbits, dogs, and cats may cause gastrointestinal symptoms requiring veterinary treatment. In the case of dogs, the trematode [I]Nanophyetus salmincola[/I] or so-called salmon-poisoning fluke, may cause a fatal disease resembling distemper because it carries a rickettsia (a type of bacterium) to which dogs are susceptible. The rickettsia, however, does not produce clinical disease in either humans or cats.[/FONT][/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]Trematodes can also infect livestock, sport and commercial fishes, and game mammals, which can have negative economic impacts on agriculture, sport fishing, and commercial fishing.[/FONT][/SIZE][/FONT][FONT=Arial]
[SIZE=3]Human infections are most common in the Orient, Africa, South America, or the Middle East. However, trematodes can be found anywhere that human waste is used as fertilizer.[/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]Trematodes are commonly referred to as [I]flukes[/I]. This term can be traced back to the Saxonname for Flounder, and refers to the flattened, rhomboidal shape of the worms. [/FONT][/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]There are no known cases of human infection with Aspidogastreans, therefore the use of the term "fluke" in relation to human infection refers solely to digenean infections. [/FONT][/SIZE][/FONT]
[FONT=Arial][SIZE=3][FONT=Verdana]The flukes can be classified into two groups, on the basis of the system which they infect. [B]Tissue flukes[/B], are species which infect the bile ducts, lungs, or other biological tissues. This group includes the lung fluke, [I]Paragonimus westermani[/I], and the liver flukes, [I]Clonorchis sinensis[/I] and [I]Fasciola hepatica[/I]. The other group are known as [B]blood flukes[/B], and inhabit the bloodin some stages of their life cycle. [/FONT][/SIZE][/FONT]

Phylum Aschelminthes
 

[B]Phylum Aschelminthes[/B]

[COLOR=black][FONT=Times New Roman][SIZE=3]A very large and heterogeneous cluster of [/SIZE][/FONT][URL="http://www.ucmp.berkeley.edu/phyla/phyla.html"][COLOR=black][FONT=Times New Roman][SIZE=3]animals[/SIZE][/FONT][/COLOR][/URL][SIZE=3][FONT=Times New Roman] have traditionally been classified together in a group variously known as the Aschelminthes, Nemathelminthes, and/or Pseudocoelomata. Today, these organisms are classified in about ten separate phyla. Nonetheless, it is sometimes useful to retain the name "Aschelminthes" to cover all these organisms. Opinion is divided as to whether or not the aschelminth phyla form one monophyletic group. To make matters worse, different authors have not agreed on what phyla should be considered "aschelminths." [/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]The most commonly recognized aschelminth phyla are: [/FONT][/SIZE][/COLOR][LIST][*][B][URL="http://www.ucmp.berkeley.edu/phyla/rotifera/rotifera.html"][COLOR=black][FONT=Times New Roman][SIZE=3]Acanthocephala[/SIZE][/FONT][/COLOR][/URL][/B][SIZE=3][FONT=Times New Roman] -- spiny-headed parasitic worms; about 1150 species known [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Chaetognatha[/B] -- arrowworms; about 70 species known. [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Cycliophora[/B] -- cycliophorans; 1 species known, microscopic [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Gastrotricha[/B] -- gastrotrichs; about 430 species known, all microscopic [/FONT][/SIZE][*][B][URL="http://www.ucmp.berkeley.edu/phyla/ecdysozoa/cephalorhyncha.html"][COLOR=black][FONT=Times New Roman][SIZE=3]Kinorhyncha[/SIZE][/FONT][/COLOR][/URL][/B][SIZE=3][FONT=Times New Roman] -- kinorhynchs; about 150 species known, all microscopic [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Loricifera[/B] -- loriciferans; about 10 species described, all microscopic [/FONT][/SIZE][*][B][URL="http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html"][COLOR=black][FONT=Times New Roman][SIZE=3]Nematoda[/SIZE][/FONT][/COLOR][/URL][/B][SIZE=3][FONT=Times New Roman] -- nematodes or roundworms; about 12,000 species known, but an estimated 200,000+ species extant, mostly microscopic [/FONT][/SIZE][*][SIZE=3][FONT=Times New Roman][B]Nematomorpha[/B] -- horsehair worms; about 320 species known [/FONT][/SIZE][*][B][URL="http://www.ucmp.berkeley.edu/phyla/ecdysozoa/cephalorhyncha.html"][COLOR=black][FONT=Times New Roman][SIZE=3]Priapulida[/SIZE][/FONT][/COLOR][/URL][/B][SIZE=3][FONT=Times New Roman] -- priapulid worms; 16 species known, abut half microscopic [/FONT][/SIZE][*][B][URL="http://www.ucmp.berkeley.edu/phyla/rotifera/rotifera.html"][COLOR=black][FONT=Times New Roman][SIZE=3]Rotifera[/SIZE][/FONT][/COLOR][/URL][/B][SIZE=3][FONT=Times New Roman] -- rotifers or "wheel animalcules"; about 1500 species known, all microscopic [/FONT][/SIZE][/LIST][COLOR=black][FONT=Times New Roman][SIZE=3]Of these, probably the most familiar is the Nematoda. Nematodes make up the second most diverse animal phylum, second only to the [/SIZE][/FONT][URL="http://www.ucmp.berkeley.edu/arthropoda/arthropoda.html"][COLOR=black][FONT=Times New Roman][SIZE=3]arthropods[/SIZE][/FONT][/COLOR][/URL][SIZE=3][FONT=Times New Roman]. Free-living nematodes are exteremely abundant in soils and sediments, where they feed on bacteria and detritus. Other nematodes are plant parasites and may cause disease in economically important crops. Still others parasitize animals (including humans); well-known parasitic nematodes include hookworms, pinworms, Guinea worm (genus [I]Dracunculus[/I]), and intestinal roundworms (genus [I]Ascaris[/I]). [/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]So what, if anything, is an aschelminth? Most are soft-bodied worms, and many of them are microscopic -- in fact, practically all members of the Cycliophora, Gastrotricha, Kinorhyncha, Loricifera, and Rotifera are less than 1 millimeter long, as are many nematodes and priapulids. On the other hand, one species of parasitic nematode can reach 13 meters in length -- it parasitizes the sperm whale -- and adult nematomorphs, chaetognaths, and some priapulids are also visible to the naked eye. [/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]Aschelminths used to be referred to as "[B]pseudocoelomates"[/B] -- an alternative name for the taxon is Pseudocoelomata -- because of their supposed shared internal structure. True [B]coelomates[/B] have a fluid-filled body cavity, the [B]coelom[/B], that surrounds the gut; this cavity exists within the middle tissue layer, the [B]mesoderm[/B], and the gut is suspended within it by sheets of tissue known as [B]mesenteries[/B]. "Pseudocoelomates" may also have a body cavity around the gut; in some (e.g. the gastrotrichs) it is extremely small, while in others (e.g. nematodes and priapulids) it may be quite extensive. This cavity has traditionally not been considered a true coelom, because it supposedly does not exist within the mesoderm, true mesenteries are not present, and its development in the embryo is quite different. However, this dichotomy between "coelomates" and "pseudocoelomates" appears to be false. A full discussion of this issue is beyond the scope of this exhibit; suffice it to say that some traditional "coelomates" and some traditional "pseudocoelomates" do not fit their traditional definitions. Body cavities develop in several different ways and perform many different functions within the animal kingdom. [/FONT][/SIZE][/COLOR]
[COLOR=black][SIZE=3][FONT=Times New Roman]A number of aschelminths [B]are parasitic[/B], including the Acanthocephala, which parasitize vertebrates; the Nematomorpha, which parasitize insects and other arthropods; and the Nematoda, which include parasites of plants and animals as well as many non-parasitic, free-living species. Free-living, microscopic "aschelminths" may be extremely common in moist soils and fresh-water sediments (gastrotrichs, rotifers and nematodes). Others may abound in marine sands and muds (gastrotrichs, kinorhynchs, loriciferans, nematodes, priapulids, rotifers). The arrowworms, found in marine waters, are generally planktonic and can swim; they are voracious predators on other planktonic organisms. Many small aschelminths, in particular many rotifers and nematodes, are able to suspend their life processes completely when conditions become unfavorable; in these resistant states they can survive extreme drying, heat, or cold, and then return to life when favorable conditions return. This is known as [B]cryptobiosis[/B]. [/FONT][/SIZE][/COLOR]
[COLOR=black][FONT=Times New Roman][SIZE=3]Since aschelminths all lack substantial hard parts, their fossil record is extremely spotty. Most of the microscopic phyla have no known fossil record at all, and seem unlikely ever to be found as recognizable fossils. The Rotifera are only known as far back as the [/SIZE][URL="http://www.ucmp.berkeley.edu/tertiary/oli.html"][SIZE=3][COLOR=black]Oligocene[/COLOR][/SIZE][/URL][SIZE=3]. Fossil nematodes are occasionally found in amber (fossilized tree resin) from the [/SIZE][URL="http://www.ucmp.berkeley.edu/cenozoic/cenozoic.html"][SIZE=3][COLOR=black]Cenozoic[/COLOR][/SIZE][/URL][SIZE=3], but possible fossil nematodes have been found in older rocks of the middle [/SIZE][URL="http://www.ucmp.berkeley.edu/paleozoic/paleozoic.html"][SIZE=3][COLOR=black]Paleozoic[/COLOR][/SIZE][/URL][SIZE=3]. The oldest known "aschelminth" phylum is the Priapulida. These unsegmented worms have been found in [/SIZE][URL="http://www.ucmp.berkeley.edu/cambrian/camb.html"][SIZE=3][COLOR=black]Cambrian[/COLOR][/SIZE][/URL][SIZE=3] rocks, such as the legendary Burgess Shale. Priapulids, at least, date from the earliest known evolutionary radiation of the animals, and a few trace fossils suggest that nematodes may have been around at the time as well. Evidence from the anatomy and genetic information of living "aschelminths" suggest that the aschelminth phyla are much older than their sparse fossils would indicate. However, no consensus has yet been reached as to how these phyla evolved and how they are related to each other.[/SIZE][/FONT][/COLOR]

[CENTER][COLOR=black][FONT=Times New Roman][IMG]http://content.tutorvista.com/biology_11/content/us/class11biology/chapter10/images/img69.jpeg[/IMG] [/FONT][/COLOR][/CENTER]
[COLOR=black][FONT=Times New Roman]Round Worm Anatomy[/FONT][/COLOR]