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๐ฌ Think about it
Imagine a chain of dominoes. Push one and the next falls. Eating in nature works like a chain too. Grass feeds the hare, the hare feeds the fox. Let us trace these eating chains.
What is a food chain?
- It shows the feeding relationship among organisms.
- It is a simple sequence of who eats whom.
- The arrows point from the eaten to the eater.
A Grassland Food Chain
Grass
Producer that makes its own food.
↓
Grasshopper
Eats the grass.
↓
Frog
Eats the grasshopper.
↓
Snake
Eats the frog.
↓
Eagle eats the snake
In this Activity, we will draw feeding relationships among grassland organisms to make a food chain.
Materials needed
The grassland figure (Fig. 12.8), pencil and notebook.
Procedure
1. Take an example of a grassland ecosystem.
2. List the organisms — grass, frog, hare, grasshopper, snake and eagle.
3. See the who-eats-whom shown in Fig. 12.8.
4. Draw arrows for the remaining organisms, like the ones shown.
2. List the organisms — grass, frog, hare, grasshopper, snake and eagle.
3. See the who-eats-whom shown in Fig. 12.8.
4. Draw arrows for the remaining organisms, like the ones shown.
Observation
Grass is eaten by the hare, and the hare is eaten by the leopard. Another chain is: Grass → Grasshopper → Frog → Snake → Eagle.
Explanation
Feeding relationships can be shown as a linear chain. A food chain shows who eats whom in an ecosystem.
โ Summary
- Grassland organisms listed
- Arrows drawn
- Who eats whom
- Food chain made
What is a trophic level?
- It is the position an organism has in a food chain.
- Producers like green plants are at the first level.
- Herbivores like hares and deer are at the second level.
- Small carnivores are third; large carnivores come next.
Trophic Levels
First level
Producers, like green plants.
↓
Second level
Herbivores, like hares and deer.
↓
Third level
Small carnivores, like frogs.
↓
Next level: large carnivores, like tigers
In this Activity, we will count organisms in a crop field and arrange them to form a pyramid.
Materials needed
The crop field figure (Fig. 12.10a), notebook and pencil.
Procedure
1. Count the number of each type of organism in the crop field.
2. Make a table and write the number against each organism.
3. Arrange numbers with the highest at the base and lowest at the top.
4. Place the mouse, millet and eagle in the correct positions.
5. See what figure you get — it looks like a pyramid.
2. Make a table and write the number against each organism.
3. Arrange numbers with the highest at the base and lowest at the top.
4. Place the mouse, millet and eagle in the correct positions.
5. See what figure you get — it looks like a pyramid.
Observation
There are many millet plants, fewer mice, and only one eagle. Arranged by number, they form a pyramid shape.
Explanation
Producers are most in number and form the base. The top carnivore is least in number. This is why the food chain looks like a pyramid.
โ Summary
- Organisms counted
- Numbers arranged
- Producers at base
- Pyramid formed
What is a food web?
- One organism may be eaten by two or more types.
- So food chains in an ecosystem are interlinked.
- This network of linked food chains is a food web.
In this Activity, we will add arrows to a diagram to complete the missing who-eats-whom links in a food web.
Materials needed
The food web figure (Fig. 12.11), pencil and notebook.
Procedure
1. Look at the food web figure.
2. Put more arrows for the missing who-eats-whom links.
3. Count how many organisms one organism is connected to.
4. Check if the different food chains are interlinked.
2. Put more arrows for the missing who-eats-whom links.
3. Count how many organisms one organism is connected to.
4. Check if the different food chains are interlinked.
Observation
Each organism may be eaten by two or more organisms. The food chains are joined to each other.
Explanation
When food chains are interlinked, they form a network. This network is called a food web.
โ Summary
- Arrows added
- Many links found
- Chains interlinked
- Food web formed
Important Points
- A food chain is a single line of who eats whom.
- A food web is many food chains linked together.
- Trophic levels are the positions in a food chain.
๐ก Ever heard of ...
- India has diverse habitats and seasons.
- Many migratory birds fly thousands of miles to reach India.
- They come to avoid harsh climate and find food.
- They act as pollinators or seed dispersers along their path.
- They are predators of insect pests and help farmers.
- Demoiselle Cranes visit Khichan village in Jodhpur in winter.
โ Test Yourself
-
What is a food chain?
View Answer
A simple sequence showing who eats whom in an ecosystem. -
Which organisms are at the first trophic level?
View Answer
Producers, like green plants. -
How is a food web different from a food chain?
View Answer
A food web is many food chains interlinked, not a single line. -
Why does a food chain look like a pyramid?
View Answer
Producers are most in number at the base; top carnivores are fewest at the top. -
Name one job of migratory birds.
View Answer
They pollinate, disperse seeds, or eat pest insects to help farmers.
Important Definitions
- Food chain — a simple sequence showing who eats whom in an ecosystem.
- Food web — a network of many interlinked food chains.
- Trophic level — the position an organism holds in a food chain.
๐ NCERT Question 4 — Look at this food
In the chain grass → grasshopper → frog → snake, what happens to grasshoppers and snakes if frogs vanish?
View Answer →
๐ NCERT Question 9 — If the Indian hare
If the Indian hare population drops because of disease, how does it affect other organisms in the food web?
View Answer →
