All the organisms of one species living in the same place at the same time.

All the populations of different species living in the same place at the same time.

A community together with the non-living components of its environment.

What is the difference between a habitat and a niche?

A habitat is where an organism lives; a niche is its role in the ecosystem, governed by adaptation to abiotic and biotic conditions.

What governs a species' niche?

Its adaptation to both abiotic and biotic conditions.

Give three abiotic factors.

Temperature, light intensity and pH (also oxygen concentration, water availability, salinity).

Give three biotic factors.

Competition, predation and parasitism (also disease and food supply).

How can a population affect an abiotic factor?

For example, beavers building a dam change water depth, flow and temperature.

How do predator and prey populations affect each other?

More prey supports more predators; more predators then reduce the prey population.

What range of sizes can ecosystems be?

From very small (a rock pool) to very large (an ocean).

Ecosystems, populations and nichesAQA A-Level Biology: Flashcards

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Define a population.

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Define a population.: All the organisms of one species living in the same place at the same time.
Define a community.: All the populations of different species living in the same place at the same time.
Define an ecosystem.: A community together with the non-living components of its environment.
What is the difference between a habitat and a niche?: A habitat is where an organism lives; a niche is its role in the ecosystem, governed by adaptation to abiotic and biotic conditions.
What governs a species' niche?: Its adaptation to both abiotic and biotic conditions.
Give three abiotic factors.: Temperature, light intensity and pH (also oxygen concentration, water availability, salinity).
Give three biotic factors.: Competition, predation and parasitism (also disease and food supply).
What does abiotic mean?: Non-living (physicochemical).
How can a population affect an abiotic factor?: For example, beavers building a dam change water depth, flow and temperature.
How do predator and prey populations affect each other?: More prey supports more predators; more predators then reduce the prey population.
What range of sizes can ecosystems be?: From very small (a rock pool) to very large (an ocean).

Exam questions on Ecosystems, populations and niches

A woodland contains oak trees, caterpillars, blackbirds, mites that live on the blackbirds, and fungi and bacteria in the soil. The woodland also has non-living components such as soil pH, light intensity and temperature.
Explain the difference between a community and an ecosystem.2 marks
Two species of barnacle live on a rocky shore. Species X is found on the upper shore, where it is exposed to air and drying out for long periods. Species Y is found on the lower shore, which is covered by the sea for most of the time. When species Y was removed from an area of the lower shore, species X spread into that area and survived there. When species X was removed from the upper shore, species Y still did not survive there.
Explain why species X is found only on the upper shore.2 marks
In a northern forest, the population of snowshoe hares rises and falls in a cycle. The population of lynx, which prey on the hares, follows the same cycle about a year later. The hares feed on young plant shoots and twigs.
Explain how an increase in the hare population leads to changes in the lynx population and then in the hare population.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).