Class 7 Science

Animal Nutrition


After ingestion, food is digested and then it is passed to different parts of body for the growth, repair and other vital functionins of body.

The food we take is primarily in the form of complex substances. Our body cannot use food in complex form. So, these complex substances need to be broken down into simple substances so that they can be absorbed by cells of the body. After that, cells can utilise such simple substances for various purposes, like growth & repair, and for getting energy.

The process of breaking down of complex component of food into simpler substances is called digestion. The process of digestion is different in different organisms. Digestive systems of different animals have evolved according to different dietary needs of these animals.

In case of amoeba, the digestion is intracellular, i.e. it happens inside the cell.

On the other hand, digestion in complex animals is extracellular, i.e. it happens outside the cells.

Enzymes help in the breakdown of complex molecules like carbohydrates, protein, fats, etc. into simple molecules. Enzymes are special chemicals which hasten the chemical reaction during the process of digestion.

Digestion in Amoeba

Digestion in unicellular animals, like Amoeba, is intracellular. Once the amoeba engulfs a food particle,it makes food vacuole around the food particle. The digestive enzymes are secreted in the food vacuoles. Digestion takes place inside food vacuoles. It is followed by absorption and assimilation. After that, food vacuole sticks to cell membrane, followed by egstion of undigested food.

Review Questions

Question 1: What is ingestion?

Answer: The intake of food is called ingestion.

Questions 2: What is digestion?

Answer: The breaking down of solid and complex food into simple and soluble forms is called digestion.

Question 3: What is absorption?

Answer: The process of passing of digested food into blood vessels in the intestine is called the absorption.

Question 4: What do you understand by assimilation?

Answer: The conversion of absorbed food in complex substances such as proteins and vitamins required by body is called assimilation.

Question 5: What do you understand by egestion?

Answer: Removal of waste materials from the body, time to time from anus is called egestion.

Questions 6: What are the steps of nutrition involved in animals?

Answer: There is five steps of nutrition involved in animals. These are Ingestion, Digestion, Absorption, Assimilation and Egestion.

Questions 7: What are Pseudopodia?

Answer: Finger-like outgrowths on amoeba are called pseudopodia.

(The word pseudopodia is the combination of pseudo and podus. Pseudo means false and podus means feet. Singular of pseudoposida is pseudopodium)