Year 7 Biology: Food Chains and Food Webs

Introduction to Food Chains

A food chain is a simple way to show how energy and nutrients move through an ecosystem. It shows who eats whom. Here’s how it works:

1. Producers: These are usually plants that make their own food using sunlight, water, and carbon dioxide. They are at the beginning of the food chain. For example, grass and trees are producers.
2. Consumers: These are animals that eat other organisms. There are different types of consumers:
   • Primary consumers: These animals eat producers. For example, a rabbit eats grass.
   • Secondary consumers: These animals eat primary consumers. For example, a fox eats rabbits.
   • Tertiary consumers: These eat secondary consumers. For example, an eagle eats a fox.
3. Decomposers: These break down dead plants and animals, returning nutrients to the soil. Examples include fungi and bacteria.

Example of a Food Chain

Let’s look at a simple food chain:

• Grass (producer) → Rabbit (primary consumer) → Fox (secondary consumer) → Eagle (tertiary consumer)

In this chain, energy moves from the grass to the rabbit, then to the fox, and finally to the eagle.

Introduction to Food Webs

A food web is a more complex way of showing how different food chains are connected in an ecosystem. It illustrates how various plants and animals are interlinked through feeding relationships.

Example of a Food Web

Imagine a small forest. Here’s how a food web might look:

• Grass (producer) → Rabbit (primary consumer)
• Grass → Deer (primary consumer)
• Rabbit → Fox (secondary consumer)
• Deer → Wolf (secondary consumer)
• Fox → Eagle (tertiary consumer)
• Wolf → Eagle (tertiary consumer)

In this web, many animals eat the same plants, and some animals are eaten by more than one predator.

Key Rules, Tips, and Tricks

1. Start with Producers: Always begin your food chain with a plant or producer.
2. Arrow Direction: The arrows in a food chain or web show the direction of energy flow. They point from what is being eaten to the eater.
3. Multiple Chains: Remember that food webs consist of many interconnected food chains.
4. Decomposers Matter: Don’t forget about decomposers! They play a crucial role in recycling nutrients.
5. Use Diagrams: Draw food chains and webs to visualise connections. It makes understanding easier!

Questions

Easy Level Questions

1. What is a producer?
2. Name a primary consumer.
3. What do decomposers do?
4. Who eats the rabbit in our example?
5. What is the first part of a food chain?
6. Give an example of a tertiary consumer.
7. What direction do the arrows in a food chain point?
8. Are grass and trees producers or consumers?
9. Name a secondary consumer.
10. What do plants use to make their own food?
11. Who is at the top of the food chain: fox, rabbit, or grass?
12. What do we call animals that eat plants?
13. What role do fungi play in a food chain?
14. Are food webs more complex than food chains?
15. Can a food chain have more than one producer?
16. Who is a primary consumer in a food web?
17. What happens to energy as it moves up the food chain?
18. Name two types of consumers.
19. What is an example of a decomposer?
20. Who eats the deer in our food web example?

Medium Level Questions

1. Explain the difference between a food chain and a food web.
2. Why are producers important in an ecosystem?
3. Describe how energy flows through a food chain.
4. Give an example of a food chain with three links.
5. What role do secondary consumers play?
6. Can one animal be both a primary and secondary consumer? Give an example.
7. Why are decomposers crucial for the environment?
8. How does a food web show relationships better than a food chain?
9. Why might a food chain be shorter in a desert than in a rainforest?
10. How do humans fit into food chains and webs?
11. What would happen if all the producers died?
12. Name a tertiary consumer in the ocean.
13. What do you think would happen if a top predator is removed from a food web?
14. Can a herbivore be a secondary consumer in some situations? Explain.
15. Why is it important to maintain biodiversity in food webs?
16. How can pollution affect food chains?
17. What is the role of a quaternary consumer?
18. Explain how energy is lost at each level of a food chain.
19. What happens to dead organisms in an ecosystem?
20. How do plants contribute to the food chain?

Hard Level Questions

1. Discuss how energy pyramids relate to food chains and webs.
2. Explain the term “trophic levels” in relation to food chains.
3. Describe how a change in one species can impact the entire food web.
4. How might climate change affect food chains? Give an example.
5. What is biomagnification and how does it relate to food chains?
6. Discuss the concept of keystone species in a food web.
7. How does the introduction of an invasive species affect local food webs?
8. Explain how food chains can illustrate the transfer of toxins in an ecosystem.
9. Discuss the importance of producers in carbon cycling.
10. Why might a food web be more resilient than a food chain?
11. Describe an example of a food chain in a marine ecosystem.
12. How do scavengers differ from decomposers?
13. Explain the impact of overfishing on food webs.
14. How does energy transfer differ between herbivores and carnivores?
15. Discuss the role of detritivores in ecosystems.
16. How can deforestation impact local food webs?
17. Describe a scenario that could lead to a collapse of a food web.
18. How do seasonal changes affect food chains and webs?
19. Discuss the role of symbiosis in food webs.
20. How can technology help us understand and protect food webs?

Answers and Explanations

Easy Level Answers

1. A plant that makes its own food.
2. Rabbit.
3. They break down dead matter.
4. The fox eats the rabbit.
5. The producer.
6. Eagle.
7. They point from the food to the eater.
8. Producers.
9. Fox.
10. Sunlight.
11. The fox.
12. Herbivores.
13. They decompose dead matter.
14. Yes.
15. Yes.
16. Rabbit.
17. Energy is lost as heat.
18. Two: primary and secondary.
19. They decompose dead organisms.
20. The fox or wolf.

Medium Level Answers

1. A food chain is simple; a food web is complex and interconnected.
2. They provide energy for consumers.
3. Energy flows from producers to consumers.
4. Grass → Rabbit → Fox.
5. They eat primary consumers.
6. Yes, a bear can eat both plants and herbivores.
7. They recycle nutrients.
8. It shows many relationships.
9. Fewer producers and consumers exist in deserts.
10. Humans can be primary, secondary, or tertiary consumers.
11. The food chain would collapse.
12. Shark.
13. The population of prey may increase.
14. Yes, if it eats both plants and animals.
15. Biodiversity ensures stability.
16. It can harm species in food chains.
17. A quaternary consumer eats tertiary consumers.
18. Energy is lost as heat or waste.
19. They return nutrients to the soil.
20. They provide energy for consumers.

Hard Level Answers

1. Energy pyramids show energy loss at each level.
2. Trophic levels indicate the position of organisms in a food chain.
3. It can disturb the balance of the ecosystem.
4. It can change habitats and food availability.
5. It’s the accumulation of toxins in organisms at higher levels.
6. Keystone species support many other species.
7. It can disrupt the food web balance.
8. It shows how toxins move up the food chain.
9. They help in taking in carbon dioxide.
10. It can adapt better to changes.
11. Phytoplankton → Small fish → Large fish → Shark.
12. Scavengers eat dead animals; decomposers break down any organic matter.
13. It can reduce fish populations and disrupt predators.
14. Herbivores convert plant energy into body mass.
15. They break down organic matter and recycle nutrients.
16. It can eliminate food sources for many species.
17. Changes in prey or habitat can disrupt balance.
18. They change food availability and reproduction cycles.
19. It can provide mutual benefits in food webs.
20. Technology can help monitor and manage ecosystems effectively.

This structured approach should help Year 7 students understand the concepts of food chains and food webs in a clear and engaging way!