Sec 4 Biology Organisms & the Environment topical questions

Define a producer and give one example.

State the role of decomposers in an ecosystem.

For the food chain grass → rabbit → fox, name the trophic level of each organism.

Name two processes that add carbon dioxide to the atmosphere.

A dragonfly eats a plant-eating insect, which feeds on a rose bush. Name the trophic level of the rose bush and of the dragonfly.

Explain why food chains rarely contain more than four or five trophic levels.

A food chain stores 20 000 kJ in its producers and 2 000 kJ in its primary consumers. Calculate the efficiency of transfer, and state two ways in which the remaining energy is lost.

A described pyramid of numbers shows one very wide bottom bar replaced by a single narrow bar at the producer level beneath thousands of insects. Name the kind of pyramid, explain the inversion, and state which pyramid type would not invert here.

Describe the carbon cycle by naming one process that removes CO₂ from the air and two that return it, and state why forests act as carbon sinks.

Construct a food chain from these organisms: hawk, grass, grasshopper, snake. Name the trophic level of each.

A primary consumer eats food containing 5 000 kJ. Of this, 3 500 kJ leaves in respiration and 750 kJ is egested or excreted. (a) Calculate the energy built into new tissue and its percentage of the intake. (b) State which loss is the largest and what it means for the next trophic level.

Explain why the ocean is described as a carbon sink, and state one way its capacity to absorb carbon dioxide could be reduced.

An insecticide is present at 0.02 ppm in the water of a lake, 0.2 ppm in plankton, 2 ppm in small fish and 20 ppm in fish-eating birds. Show that the concentration multiplies tenfold per level, calculate the overall increase, and explain why the birds suffer most.

Explain how deforestation and the combustion of fossil fuels each raise atmospheric carbon dioxide, and describe two human actions that would slow global warming.

Untreated sewage is discharged into a slow-moving river. Describe, in order, the events that follow and explain why fish die even though sewage is largely organic food material.

Explain what sustainable use of a tropical rainforest means, and describe how conservation of such forests maintains biodiversity and supports the fight against global warming.

A described graph of atmospheric carbon dioxide shows a concentration of 315 ppm in 1960 rising to 420 ppm in recent years. Calculate the percentage increase, name two human causes and explain one consequence of this rise.

A farm pond food chain has these biomass measurements: algae 800 g/m², zooplankton 160 g/m², small fish 24 g/m², large fish 3.6 g/m². Calculate the percentage of biomass passed on at each step, and explain why the biomass shrinks at every level.