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Old Saturday, September 25, 2010
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Default BioDiversity

Classification of Living Organisms.
  • Thousand of Different kinds of organis,s exists on the Earth.Some organisms distinctly different from one another and share only a few common characteristics, other resembles more with each other and show only a few differences while some are even identical.
  • Classification is the arrangement of organisms into groups and sub-groups.
  • About 2 millions species of animals and 0.5 millions species of plants have been discovered so far.
  • According to 'Darwin's Theory of Common Descent'. the organisms having common ancestry in the near past would resemble one another very closely, while other those having more distant common ancestory would show more interrelationships.
  • Organisms resembling one another more are placed in the same group while other showing more differences are put in the different groups. This type of grouping is called 'evolutionary taxonomy'


BASIS AND AIMS OF CLASSIFICATION

Classification is based on such features or characters that are simmilar in one kind of organism and different in different kid of organism. The character which can be used in classification include external morphlogy, internal morphology ( anatomy), physiology, cell structure especially the number of chromosomes and chemical composition and embryology.
  • Occurrence o some common characters in different organism indicate their common ancestral origin. This similarity because of common ancestral origin is called Homology.e.g arm of monkey, flipper of a whale and wing of bat show homology. Aparently they do not look alike but their basic internal structure is almost similar. Such organs which have same basic internal structure and embronic development are called homologous organs
  • Fruits of all plants whether sweet or sour , small and dry, or large or fleshy are homologous structure because they all develop from ovary of flower and have common origin.
  • On the other hand , wings of and insect and bird despite performing the same function are not homologous because their origin is different. Such organs that are similar in function but different in basic structure are called analogous organs.

Aims and Objective
1. Determine similarities and differences between different organisms.
2. Arrange organism according to similarities and differences.
3. Identify the organisms on the basis of their structure and other prominent features and study them systematically and logically
4. Find out inter-relationship of organism.

Units of Classification
  • Species----Basic Unit---A group of organism that can bred with one another in the nature and produce fertile offspring.All member of species have same number of chromosomes in their cells and character in common.
  • Different but closely related species are grouped togather into a large category known as genus(plural genera).
  • The closely related genera are grouped into a still higher category known as family.
  • The families are grouped into an order.
  • Orders are put together into a class
  • Closely related classes are grouped into phylum (plural Phyla) which are also called divisions among plants, fungi, and algea.
  • The phyla or division are in turn grouped into Kingdom

KINGDOMS OF LIVING ORGANISMS

1. Two Kingdom System
  • Oldest Classification system.
  • Living organism are placed into just two kingdoms. Plants and Animal
  • Presence of cell wall and ability to make their own food were considered the most important characteristics of plants.
  • Lack of cell wall and inability to make food and characteristic mode of nutrition and ability to move from place to place are the most significant characteristics of animals.

1. FiveKingdom System[*]Margulis and Schwartz (1982) has proposed five kingdom classification.[*]This system claims to solved the difficulties faced in the two kingdom classification system. [*]According to this system all organism are classified into five kingdoms which are:
  • Kingdom-Monera (Prokaryotes)
  • Kingdom-Protista
  • Kingdom-Plantae
  • Kingdom-Fungi:
  • Kingdom-Animalia

    1.Kingdom-Monera (Prokaryotes)
    • The kingdom Monera includes all microorganisms with prokaryotic cells.
    • Prokaryotic cells lacking nuclear membrane, plastids, mitochondria and advanced (9 + 2 strands) flagella.
    • They are solitary, unicellular or colonial. Predominant mode of nutrition is absorption but some groups are photosynthetic or chemosynthetic.
    • Reproduction is primarily asexual by fission and budding,etc

    2.Kingdom-Protista
  • The Protista (also called Protoctista) are generally single-celled eukaryotes (cells with membrane bound nuclei) such as Euglena and Amoeba.
  • Nutrition by photosynthesis, absorption, ingestion and combination of these
  • Reproduction is asexual and sexual type. Motility by flagella or by other means or nonmotile.

3.Kingdom-Plantae[*]The members of this kingdom are mostly multicellular autotrophs, with cellulose wall and frequently vacuolated, eukaryotic cells.[*]Chloroplasts present; principal nutritive mode is photosynthetic but some absorptive.[*]Primarily nonmotile, living anchored to a substrate. Structural differentiation; reproduction primarily sexual, e.g., Rhodophyta, Phaeophyta, Chlorophyta, Bryophyta, Tracheophyta (Pteridophytes, Gymnosperms and Angiosperms).[/LIST]

4.Kingdom-Fungi[*]he fungi include multicellular heterotrophs, such as mushrooms and molds as well as unicellular yeasts with eukaryotic nuclei dispersed in a walled and often septate mycelium[*]Fungi decompose other biological materials, develop from spores, lack plastids, photosynthetic pigments and flagella. Nutrition absorptive; chitin in cell wall. Somatic tissue differentiation absent or limited.[*] Reproductive tissue differentiation and life-cycle elaboration masked in higher forms[*]Primarily nonmotile (but protoplasmic streaming in mycelium), living embedded in a medium of food supply. Reproduction asexual and sexual both types. No embryo is formed.[/LIST]
5.Kingdom-Animallia[*]The members of this kingdom are multicellular heterotrophs with wall-less eukaryotic cells, lacking plastids and photosynthetic pigments.[*]exhibit movements and develop from embryos[*] Nutrition primarily by ingestion with digestion within an internal cavity but some- forms are absorptive.[*]Sensory neuromotory system[*]Reproduction predominantly sexual[*]They include sponges, coelentrates, insects, birds, mammals,etc.[/LIST]
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