Different Modes Of Nutrition
Although all organisms need nutrients for their survival, they do not obtain nutrition in the same way. There are a wide variety of ways or modes by which different organisms derive their nutrition.
Autotrophic: Organisms that derive nutrition from simple molecules with the help of sunlight or chemical reactions are known as autotrophic, e.g. plants. This is further classified as follows:
- Phototrophic (photoautotrophic): Autotrophs that derive nutrition by using energy from sunlight to convert CO2 and water into organic substances are known as phototrophic. This type of nutrition is also called holophytic, e.g. green plants.
- Chemotrophic (chemoautotrophic): Autotrophs that prepare organic substances using energy of oxidation, without the requirement of light energy from sun, are known as chemotrophic, e.g. chemosynthetic bacteria such as Thiobacillus.
Heterotrophic: Organisms that cannot synthesise their own food and, hence, obtain its nutrition by intake of organic substances of plant or animal origin are known as heterotrophic, e.g. animals.
- Holozoic: Organisms that ingest solid or liquid food are known as holozoic.
- Herbivores: These are organisms that obtain nutrition from plants and plant products, e.g. deer.
- Carnivores: These are organisms that derive nutrition from animal tissues (meat), e.g. lion.
- Omnivore s: These are organisms that derive nutrition by feeding on all types of food (both plant and animal) material, e.g. crow.
- Saprotrophic: These are organisms that obtain nutrition from dead and decaying organic matter, e.g. mushrooms.
- Parasitic: These are organisms that obtain nutrition from a living host. Parasites can be ectoparasites or endoparasites. Here, the parasite is benefited at the expense of the host, e.g. tapeworm.