What is a Food Chain?
A food chain shows the linear path of energy through an ecosystem, starting with plants (producers) and flowing through herbivores and carnivores (consumers). A food web is a more realistic model showing how multiple food chains overlap.
A food chain is a sequence: producer → primary consumer → secondary consumer → tertiary consumer. A food web connects multiple chains to show how organisms depend on each other.
- 1↓Producers (Plants)Capture solar energy through photosynthesis. Base of all food chains.
- 2↓Primary Consumers (Herbivores)Eat plants and gain ~10% of the plant's energy.
- 3↓Secondary Consumers (Carnivores)Eat primary consumers and gain ~10% of their energy.
- 4↓Tertiary Consumers (Top Predators)Feed on secondary consumers. Smallest population and highest energy concentration.
- 5Decomposers (Bacteria, Fungi)Break down dead organisms and return nutrients to soil.
Step-by-step worked examples
Describe the food chain: grass → rabbit → hawk.
Grass (producer) captures solar energy. Rabbit (primary consumer) eats grass and gains ~10% of its energy. Hawk (secondary/tertiary consumer) eats rabbit and gains ~10% of rabbit's energy.
In an ocean food chain, phytoplankton → zooplankton → small fish → shark, what percent of phytoplankton energy reaches the shark?
Phytoplankton → zooplankton: 10% Zooplankton → small fish: 10% of 10% = 1% Small fish → shark: 10% of 1% = 0.1%
Why is the population of predators always smaller than prey?
Each trophic level transfers only ~10% of energy to the next. Higher trophic levels must support their population on less energy. Fewest organisms at the top; most at the producer level.
Flashcards
Quick quiz
Q1.In the food chain plant → mouse → owl, which organism is the secondary consumer?
Q2.Why do ecosystems need decomposers?
Q3.In a food web with many interconnected chains, what happens if bees disappear?
Q4.Which trophic level has the most total biomass?
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Common mistakes
All organisms in a food chain are equally important. — Correct: Producers are the energy foundation; losing them collapses the entire chain.
More trophic levels = more total energy in the ecosystem. — Correct: More levels means less total energy; each transfer loses ~90%.
Decomposers are just scavengers with no important role. — Correct: Decomposers are essential; they recycle nutrients back into the soil.
Omnivores (eating both plants and meat) don't fit in food chains. — Correct: Omnivores occupy multiple trophic levels and are part of complex food webs.
FAQ
What is a food chain?
A linear sequence showing how energy flows from one organism to the next, starting with producers and ending with top predators.
What is the difference between a food chain and a food web?
A food chain is one path (e.g., grass → deer → wolf). A food web shows all interconnected food chains in an ecosystem.
What is a trophic level?
A step in the food chain based on the organism's role: producer (level 1), primary consumer (level 2), secondary consumer (level 3), etc.
Why are top predators always rare?
Each energy transfer loses ~90%. By the time energy reaches top predators, there is very little left to support large populations.