Food Chains and Food Webs

📚 Key Concepts

🔹 Food Chain

A food chain is a linear sequence showing ‘who eats whom’ in an ecosystem.

Structure of Food Chain: Producer → Primary Consumer → Secondary Consumer → Tertiary Consumer

Example: Grass → Grasshopper → Frog → Snake → Eagle

Direction of Energy Flow:

• Energy flows from producers to consumers
• Energy decreases at each level
• Cannot flow backward

🔹 Trophic Levels

Each step in a food chain is called a trophic level.

Trophic Levels:

• Level 1: Producers (plants)
• Level 2: Primary consumers (herbivores)
• Level 3: Secondary consumers (small carnivores)
• Level 4: Tertiary consumers (large carnivores)

🔹 Food Web

A food web is a network of interconnected food chains in an ecosystem.

Characteristics:

• More realistic than food chains
• Shows multiple feeding relationships
• One organism can be part of several food chains
• More stable than single food chains

Advantages of Food Webs:

• If one species disappears, alternatives exist
• Better represents ecosystem complexity
• Shows energy flow patterns
• Explains ecosystem stability

🔹 Ecological Pyramid

An ecological pyramid shows the number, biomass, or energy at each trophic level.

Types: 1. Pyramid of Numbers

• Shows number of organisms at each level
• Usually decreases from bottom to top

2. Pyramid of Biomass

• Shows total mass of organisms at each level
• Always decreases from bottom to top

3. Pyramid of Energy

• Shows energy available at each level
• Always decreases from bottom to top (10% rule)