IGCSE Biology Organisms & environment topical questions

The food chain below shows feeding in a grassland ecosystem. grass → grasshopper → frog → snake

1. (a)Name the producer.[1]
2. (b)Name the secondary consumer.[1]
3. (c)State the trophic level of the snake.[1]
4. (d)Name the group of organisms that would break down the dead bodies of these organisms.[1]

Match each term to its definition.

1. (a)All the populations of different species in an ecosystem.[1]
2. (b)A group of organisms of one species in the same area at the same time.[1]
3. (c)An animal that eats other animals.[1]
4. (d)The number of different species living in an area.[1]

Name the process in the carbon cycle described.

1. (a)Removes carbon dioxide from the air, using light energy.[1]
2. (b)Releases carbon dioxide from living organisms.[1]
3. (c)Releases carbon dioxide when fuels are burned.[1]
4. (d)Passes carbon along food chains.[1]

A food web in a meadow contains: grass; caterpillars and rabbits (which eat grass); frogs (which eat caterpillars); and hawks (which eat frogs and rabbits).

1. (a)Name the producer in this web.[1]
2. (b)Name the trophic level of the frog in the chain grass → caterpillar → frog → hawk.[1]
3. (c)A disease kills all the caterpillars. Explain what happens to the frogs and the rabbits in the short term.[2]
4. (d)Name the trophic level of the hawk when it eats a rabbit.[1]

A pyramid of numbers for an oak tree food chain is inverted: 1 tree, 500 aphids, 5 ladybirds.

1. (a)Draw or describe the shape of this pyramid of numbers.[1]
2. (b)Explain why a pyramid of biomass gives a more useful picture of this food chain.[3]
3. (c)State the trophic level of the ladybird.[1]

Explain why it is more energy efficient for humans to eat rice than to eat beef from cattle fed on rice.

1. (a)State how many energy transfers each diet involves from the producer.[2]
2. (b)Explain why each transfer wastes most of the energy.[3]

A new population of rabbits is introduced to an island with plenty of grass and no rabbit predators.

1. (a)Name the four phases of the sigmoid growth curve this population is expected to follow.[2]
2. (b)Explain what limits the population in the stationary phase. (Extended)[3]

The energy trapped by the producers of a grassland ecosystem, and the energy reaching the next trophic levels, is shown in the table.

1. (a)Calculate the percentage of energy transferred from the producers to the primary consumers. Show your working.[2]
2. (b)Calculate the percentage transferred from primary to secondary consumers.[2]
3. (c)State two ways in which energy is lost between trophic levels.[1]
4. (d)Use the data to explain why food chains rarely have more than four or five trophic levels.[1]

The total dry biomass of each trophic level in a grassland was measured in kilograms per hectare.

1. (a)Calculate the percentage of biomass passed from producers to primary consumers. Show your working.[2]
2. (b)Calculate the percentage passed from primary to secondary consumers.[2]
3. (c)State one situation in which a pyramid of biomass is more useful than a pyramid of numbers.[1]

A bacterial population growing in a flask of nutrient broth was counted every two hours.

1. (a)Name the growth phase between 0 and 2 hours, and the phase between 8 and 10 hours.[2]
2. (b)Calculate how many times the population grew between 0 and 4 hours. Show your working.[1]
3. (c)Explain why the population stopped growing between 8 and 10 hours.[2]

Explain how excess fertiliser washed from fields into a lake can kill the fish living there. (Extended)

1. (a)Describe the chain of events in order.[6]
2. (b)State the name of this process.[1]

Explain how forests and fish stocks can be conserved sustainably. (Extended)

1. (a)Explain two methods of conserving forests.[4]
2. (b)Explain two methods of conserving fish stocks.[3]

Nitrogen moves between the air, the soil, plants and animals in an ecosystem. (Supplement)

1. (a)State why plants cannot absorb the nitrogen gas in the air through their roots.[1]
2. (b)Name the type of microorganism that converts nitrogen gas into usable nitrogen compounds.[1]
3. (c)Describe the sequence that takes nitrogen from the protein in a dead animal to nitrogen taken up by a plant.[3]
4. (d)Name the microorganisms that return nitrogen to the air, reducing soil fertility.[1]

A country’s fishing fleet may catch 3000 tonnes of fish per year from a stock of 10000 tonnes whose fish reproduce and replace 2000 tonnes per year.

1. (a)Calculate the total mass of fish caught in three years at this rate.[1]
2. (b)Calculate how much the annual catch exceeds the stock’s yearly replacement.[1]
3. (c)Ignoring other losses, predict the size of the stock after three years, and state whether this fishing is sustainable.[2]
4. (d)Define a sustainable resource.[1]
5. (e)State one measure that would make this fishery sustainable.[1]