Animals are the living organisms which do not have plastids in their cell, thus are unable to perform photosynthesis ad moreover they do not have cell wall, thus they are grouped into another kingdom i.e. Animalia. Animals thus do not posses cell wall nor plastid. Lack of plastid results in a different mode of nutrition i.e. Heterotrophic mode of nutrition.
HETEROTROPHIC MODE OF NUTRITION
- This is a type of nutrition in which the living organisms feed on other living organisms for their survival either on plants or on animals.
- The energy is derived from the food they take in, normally from the plant or animal tissue.
MODES OF HETEROTROPHIC NUTRITION
- SAPROTROPHIC MODE
- In this type of nutrition the food is derived from the dead and decaying organisms.
- Example: Yeast, Fungi.
- PARASITIC MODE
- The type of nutrition in which one organism is benefited and the other one is harmed.
- The organism from which nutrition is derived is called Host body and the organism which take nutrition is called parasite.
- Example: Plasmodium, Roundworm.
- HOLOZOIC MODE
- The mode of nutrition in which the solid food is taken as a whole is termed as holozoic nutrition.
- The solid food is ingested, digested, absorbed into the cells and utilized.
- Example: Human, cow.
Nutrition In Amoeba
- Amoeba is an unicellular organism which are found in ponds, lakes and water bodies.
- Amoeba feeds unicellular plants and animals for their survival.
- The mode of nutrition of Amoeba is holozoic in nature.
- Amoeba is omnivorous.
- Amoeba do not have a specific shape.
- Steps involved in nutrition of Amoeba are as followed:
- When amoeba comes in contact with the food particles, the very first step is it sends out finger like projection around the food.
- The finger like projections are called pseudopodia. (Pseudo: False and Podia: Feet)
- The pseudopodia forms food cup which intake the food into the cup and thus engulf the food.
- This engulfing of the food by Amoeba is called endocytosis.
- Endocytosis: As amoeba is unicellular, and the cell takes in the food from the outside environment, thus got the term.
- This completes the process of ingestion.
- The digestion takes place inside the vacuole, which is formed when the food is encaptured.
- The food vacuole acts as a temporary stomach which help in the digestion of food as it secrets digestive enzymes, thus completing the process of digestion.
- ABSORBTION AND ASSIMILATION:
- The digested food gets absorbed by the process of diffusion into the cell.
- As it is unicellular through diffusion the assimilation is also completed as there is no circulation of digested food will take place.
- The undigested food is removed from the body surface or thrown out from the cell and this is known as exocytosis.