CBSE Class 3 Environmental Studies Food Chain Notes Set 01

What is a food chain?

All living things need food, and they get it by eating other living things. A food chain shows who eats whom in nature. It is a line of living things in which each one is food for the next. An arrow is drawn between them. The arrow points towards the one that eats, and it shows the direction in which energy moves.

Links of a food chain

1. Producers: green plants such as grass make their own food using sunlight, air and water. Every food chain starts with a producer.

2. Primary consumers: animals that eat plants. They are herbivores. A grasshopper or a deer eating grass is a primary consumer.

3. Secondary consumers: animals that eat the herbivores. A frog that eats a grasshopper is a secondary consumer.

4. Tertiary consumers: animals that eat the secondary consumers. A snake that eats a frog is a tertiary consumer.

5. Decomposers: bacteria and fungi that break down the dead bodies of plants and animals and return nutrients to the soil.

Examples of food chains

1. Grass → Grasshopper → Frog → Snake → Eagle

2. Grass → Deer → Lion

3. Leaf → Caterpillar → Bird → Cat

4. Grain → Rat → Snake → Eagle

The sun is the first source of energy. Plants trap the energy of sunlight and make food. When a herbivore eats the plant, the energy goes to the herbivore, and so on up the chain.

Food web

In nature, an animal usually eats more than one kind of food and is eaten by more than one kind of animal. For example, a snake may eat frogs, rats and birds. So many food chains join together like a net. This network of food chains is called a food web.

Why are food chains important?

1. They show how energy passes from one living thing to another.

2. They keep the number of plants and animals in balance. If all the frogs disappeared, insects would increase a lot.

3. They show that all living things depend on each other.

Worked examples

Example 1. Complete the food chain: Grass → ____ → Snake.
A frog or a rat can be placed in the blank, because it eats grass or insects and is eaten by a snake. A better answer is Grass → Rat → Snake.

Example 2. In the chain Grass → Deer → Lion, name the producer and the consumers.
Grass is the producer. Deer is the primary consumer and lion is the secondary consumer.

Example 3. What would happen if all the grass in a forest dried up?
The deer would have no food and would die or move away. Then the lions would also lose their food.

A longer example

Let us follow the energy in a pond. Tiny green plants in the water make food using sunlight. Small fish eat these plants. A bigger fish eats the small fish, and a bird eats the bigger fish. When the bird dies, bacteria and fungi break down its body. The nutrients return to the water and help the green plants to grow again. In this way a food chain is like a circle of giving and taking, and every living thing in it is important. If any one link is lost, the others are affected too, so we must protect all plants and animals around us.

Quick Check Questions