Characteristics Of Living Organisms:
Following are the main characteristics of living beings which are not present in non-living organisms.
i) Metabolism
ii) Growth
iii) Irritability
iv) Reproduction
v) Movement
vi) Nutrition
vii) Respiration
viii) Excretion
Virus:
• Viruses are the micro-organisms which are strict or obligate parasites of animals or plant cells.
• Many of the viruses are also parasites on bacteria.
• A large number of viruses cause diseases in plants and animals.
Characteristics Of Virus:
• A virus consists of two components, a protein coat and a core of nucleic acid which is either DNA or RNA.
• DNA viruses are called adenoviruses and RNA viruses are called retroviruses.
• The shape of a virus is due to its protein coat.
• Viruses are of many shapes i.e. rods, spherical, hexagonal or icosahedral.
• Sometimes their shape is complicated.
• Virus replicate inside a living cell and many viruses are synthesized along with their protein coats and nucleic acid.
• The nucleic acid contains instructions for the shape of the virus.
Diseases Caused By viruses:
i) Polio
ii) AIDS
iii) Smallpox
iv) Measles
v) Hepatitis
Bacteria:
Characteristics Of Bacteria:
• Bacteria are unicellular prokaryotic organisms which generally divide by transverse binary fission.
• They possess rigid cell walls and act as pathogens
• Nucleus is not well organised
• No definite chloroplast, chlorophyll is dissolved in chromoplasm.
• There are three forms of bacteria which are:
i) Round called Cocci
ii) Rod like called Bacilli
iii) Spiral called Spirrila
Classification Of Bactria According To Mode Of Nutrition:
According to mode of nutrition, there are three types of Bactria:
a) Parasitic:
• Devoid of chlorophyll
• Are heterotrophic and get food from living animals and plants
b) Saprophytic
• Lack chlorophyll hence cannot prepare their own food.
• Get food from dead organic remains
c) Autotrophic
• Contain chlorophyll
• Can synthesis food by photosynthesis
• Few get their food by chemosynthesis
Reproduction In Bacteria
i)
Vegetative: By Binary Fission
ii)
Asexual: By Formation of Endospores
iii)
Sexual: By Conjugation