Food Chains & Food Webs

Introduction

A food chain is a linear sequence showing how energy and nutrients pass from one organism to another. A food web is a network of interconnected food chains in an ecosystem.

Energy flows from producers (plants, algae) to various levels of consumers and finally to decomposers.

Trophic Levels & Examples

• Producers: green plants, algae.
• Primary consumers (herbivores): grasshoppers, rabbits.
• Secondary consumers (carnivores): frogs, small birds.
• Tertiary consumers (top predators): snakes, hawks.
• Decomposers: fungi, bacteria, which recycle nutrients.

Detailed Food Chain Example

Grass → Grasshopper → Frog → Snake → Hawk

Explanation: Energy from sunlight is used by grass (producer) to make food. Grasshoppers eat grass and gain energy. Frogs eat grasshoppers, snakes eat frogs, and hawks eat snakes. Decomposers break down dead organisms, returning nutrients to soil.

Food Web Example

A food web shows interconnections between multiple food chains:

• Grass → Grasshopper → Frog → Hawk
• Grass → Grasshopper → Snake → Hawk
• Grass → Rabbit → Fox → Hawk

Practice Questions & Answers

• Q: Differentiate between a food chain and a food web.
  A: A food chain is linear showing energy flow from one organism to another. A food web is a network of interconnected food chains showing multiple paths of energy flow.
• Q: Draw a food chain with producers, primary, secondary, and tertiary consumers.
  A: Grass → Grasshopper → Frog → Hawk
• Q: Explain why energy decreases at higher trophic levels.
  A: Energy is lost as heat during respiration and movement; only ~10% is transferred to next trophic level.
• Q: Draw and label a simple energy pyramid.
  A: Base: producers, next level: primary consumers, then secondary consumers, top: tertiary consumers.
• Q: Give examples of decomposers and explain their importance.
  A: Fungi and bacteria. They recycle nutrients back to soil, making them available for producers.