Ecosystems Biodiversity and Food Webs Cheat Sheet

A printable reference covering ecosystems, biodiversity, food chains, food webs, energy pyramids, and population interactions for grades 6-8.

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This cheat sheet covers how ecosystems work, how organisms depend on each other, and why biodiversity matters. Students need these ideas to understand food chains, food webs, energy flow, and changes in populations. It connects living things with nonliving factors such as sunlight, water, soil, and temperature. These concepts help explain how ecosystems stay balanced or become disrupted.

Key Facts

Population density = number of individuals ÷ area, such as 120 deer ÷ 30 square kilometers = 4 deer per square kilometer.
A food chain shows one path of energy flow, such as grass -> rabbit -> fox.
A food web shows many connected food chains and gives a more realistic picture of feeding relationships.
Only about 10% of energy passes from one trophic level to the next, so energy at next level = energy at current level × 0.10.
Producers make their own food using sunlight, water, and carbon dioxide through photosynthesis.
Consumers get energy by eating producers or other consumers, and decomposers recycle nutrients from dead organisms and waste.
Biodiversity includes species richness, which is the number of different species, and species evenness, which is how balanced their populations are.
A stable ecosystem usually has high biodiversity because more species can help maintain food web balance after a disturbance.

Vocabulary

Ecosystem: A community of living organisms interacting with each other and with nonliving parts of their environment.
Biodiversity: The variety of living things in an area, including different species, genes, and ecosystems.
Producer: An organism, such as a plant or algae, that makes its own food and forms the base of most food webs.
Consumer: An organism that gets energy by eating plants, animals, fungi, or other organisms.
Decomposer: An organism, such as a fungus or bacterium, that breaks down dead matter and returns nutrients to the ecosystem.
Trophic Level: A feeding position in a food chain or food web, such as producer, primary consumer, or secondary consumer.

Common Mistakes to Avoid

Confusing food chains with food webs is wrong because a food chain shows one feeding path, while a food web shows many connected feeding paths.
Drawing arrows toward what gets eaten is wrong because arrows show the direction energy moves, from the food source to the organism that eats it.
Assuming all energy transfers to the next trophic level is wrong because only about 10% of energy is passed on and most is used or lost as heat.
Ignoring decomposers is wrong because decomposers recycle nutrients that producers need to grow and keep the ecosystem functioning.
Thinking high biodiversity only means many individuals is wrong because biodiversity depends on the number of species and how evenly individuals are spread among them.

Practice Questions

1 A pond has 240 frogs living in an area of 60 square meters. What is the frog population density?
2 If producers in an energy pyramid have 10,000 energy units, about how many energy units are available to the primary consumers?
3 In the food chain algae -> small fish -> heron, identify the producer, primary consumer, and secondary consumer.
4 A disease removes most of one plant species from a meadow. Explain why a meadow with higher biodiversity may recover better than a meadow with low biodiversity.