Sec 4 Combined Science (Biology) Organisms & their Environment topical questions

Name the role described: (a) makes food by photosynthesis; (b) eats primary consumers; (c) breaks down dead matter.

State why energy flow through an ecosystem is described as non-cyclical.

Name two processes that return carbon dioxide to the atmosphere and one that removes it.

In the food chain grass → rabbit → fox, state the trophic level of (a) the rabbit and (b) the fox, and draw the arrows correctly.

Producers in a habitat contain 20 000 kJ of energy. Assuming 10% transfer per level, calculate the energy reaching (a) primary consumers, (b) secondary consumers, (c) tertiary consumers. (d) State two ways energy is lost at each step.

A numbers pyramid reads 1 tree → 800 aphids → 5 ladybirds. (a) Sketch/describe its shape. (b) Explain why it is inverted at the base. (c) State and justify the likely shape of the biomass pyramid for the same chain.

Describe the role of decomposers in an ecosystem and state what would accumulate without them.

Explain how a forest acts as a carbon sink, and what happens to that role when the forest is cleared and burned.

A student writes: "Since energy cannot be destroyed, the energy in a food chain is conserved, so nothing is really lost." Evaluate this statement carefully.

A country clears large areas of rainforest for farmland and burns the timber. (a) State two effects on atmospheric carbon dioxide. (b) Explain how the cleared land)s soil carbon can also reach the air. (c) Suggest two national actions that would reduce the country)s carbon dioxide output.

Two food chains in the same meadow: A (grass → rabbit → fox) and B (grass → grasshopper → frog → snake → hawk). (a) Which chain delivers more energy to its top consumer, and why? (b) Why might the hawk population in chain B be smaller than the fox population in chain A? (c) What advantage do meadow organisms gain from both chains existing in a web?

Explain the sentence: "Energy flows through an ecosystem, but carbon cycles within it." Use photosynthesis, respiration, feeding, decomposition and combustion in your answer, and state one consequence of the difference for global warming policy.