Energy Flow in Ecosystems: Food Chains and Predator-Prey Cycles

Overview

• Food Chains: Simplified representation of energy transfer in an ecosystem, showing the sequence of organisms, each feeding on the previous one.
• Food Web: More complex, showing all interactions.
• Predator-Prey Cycles: Graphical representation of how predator and prey populations cycle over time.

Food Chains

• Definition: Sequence showing what eats what in an ecosystem.
• Starts with Producers:
  • Photosynthetic organisms (e.g., green plants or algae).
  • Example: Grass, which uses sunlight to produce glucose (photosynthesis) and biomass.
• Primary Consumers:
  • Herbivores that eat producers.
  • Example: Mice.
• Secondary Consumers:
  • Predators that feed on primary consumers.
  • Example: Owls.
• Tertiary Consumers: Feed on secondary consumers; some ecosystems may have more levels.

Energy Transfer in Food Chains

• Energy loss at each level:
  • Approx. 10% of energy is transferred to the next level.
  • Example: 1000 joules in grass ➔ 100 joules to mice ➔ 20 joules to owls.
• Arrows in Food Chains: Represent the flow of energy from one level to the next.

Predator-Prey Cycles

• Concept: Populations of predators and prey are interdependent and influence each other.
• Graphing the Cycle:
  • Predator population lags behind prey population.
  • Populations cycle up and down.
  • Example: Field mice (prey) and owls (predators).
• Cycle Explanation:
  • Low predator population allows prey population to increase.
  • High prey population leads to increased predator population due to more available food.
  • High predator population reduces prey population.
  • Declining prey population leads to reduced predator numbers, allowing prey to increase again.
• Reason for Cycles: Population changes take time over multiple generations.

Conclusion

• Understanding food chains and predator-prey cycles highlights the interconnectedness of organisms in ecosystems.
• These concepts are crucial for studying ecological dynamics and energy flow.