Food Chains and Predator-Prey Cycles

Food Chains

• Food chains show feeding relationships in a community.

• Example 1: Grass → Rabbit → Fox

• Example 2: Tree → Caterpillar → Bird

• All food chains start with a producer (green plants or algae).

• Producers make glucose by photosynthesis, forming biomass.

• Biomass is passed along the food chain.

Consumers

• Primary consumers = eat producers (e.g., rabbits, caterpillars).

• Secondary consumers = eat primary consumers.

• Tertiary consumers = eat secondary consumers.

Predators and Prey

• Predator = animal that kills and eats other animals.

• Prey = animal that is eaten.

• Example:

  • Rabbit = prey, Fox = predator.

  • Caterpillar = prey, Bird = predator.

Predator–Prey Cycles

• Predator and prey numbers rise and fall in cycles:

  • Prey increase → more food for predators.

  • Predator numbers increase → more prey eaten.

  • Prey numbers fall → predator numbers fall.

  • Cycle repeats.

• This happens in a stable community where biotic and abiotic factors are balanced.

• If conditions change (e.g., drought, new predator), cycles are disrupted.

✅ Key Concepts

• Producers = make biomass (glucose).

• Consumers = eat other organisms (primary, secondary, tertiary).

• Predator–prey populations are interdependent and cycle over time.

• Stable communities keep these cycles balanced.