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SAI International School
Subject- Biology, Class-VII
Topic- Nutrition in Animals
Subtopic- Steps of Nutrition
Module-6
Lesson Notes

NUTRITION

Nutrition in animals includes the intake of food from external sources (other plants or
animals) and the utilisation of nutrients present in the food for energy, growth and
development.

Nutrition in complex animals involves following steps:

 Ingestion
 Digestion
 Absorption
 Assimilation
 Egestion

Ingestion: The intake of food is called ingestion. Method of ingestion, i.e. taking of food,
varies from one animal to another.

Different Ways of Taking Food

 Human beings swallow the food after chewing.
 Herbivores quickly swallow the grass and leaves.
 Amoeba, a unicellular animal, engulfs tiny particles of food by using
pseudopodia. Amoeba surrounds the food by pseudopodia and then makes a
food vacuole to engulf the food.
 Paramecium has small thread-like structures, called cilia (singular: cilium), all
over its body surface that help to capture the food.
 Insects like butterfly have a long tube-like structure called proboscis using which
they suck the nectar of flowers.
 A frog captures prey with its sticky tongue.
 An earthworm swallows food using its muscular pharynx.
 In spiders, the mode of ingestion is sucking after injecting venom on the prey.
 An aquatic organism like Hydra has tentacles to catch its prey.