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Practise 34 exam-style questions on Communities for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Define 'ecosystem'.
An ecosystem is the interaction of a community of organisms (biotic) with the non-living (abiotic) parts of their environment.
Ecosystem includes both biotic and abiotic components and their interactions, such as energy flow and nutrient cycling.
community of living organisms interacting with abiotic environment
Why is random sampling important when estimating species abundance with quadrats?
Random sampling prevents biased placement of quadrats and ensures samples are representative of the whole area, improving accuracy and reliability.
Choosing quadrat locations at random avoids targeting particular patches and gives an unbiased estimate of abundance across a habitat.
prevents bias in location of samples
makes results more representative of the whole area
A stable pond community suddenly loses its top predator. Predict and explain two likely short-term effects on the community.
Increase in prey population (less predation) leading to overgrazing of plants or increase in a herbivore which may reduce plant biomass; secondary effects could include disease spread from overcrowding or declines in species that depended on balanced conditions.
Top predators control prey. Removing them allows prey to increase, which can reduce vegetation and cause ripple effects through the food web.
prey population increases due to reduced predation
overgrazing or depletion of plant species leading to changes in habitat
secondary effects such as disease from overcrowding or decline of dependent species
Design a simple field investigation to compare species richness between two habitats (woodland and grassland). Include how you would sample and one control to make it fair.
Use random quadrat sampling in each habitat, place 20 quadrats at random in each, record number of species per quadrat, calculate mean species richness; control by sampling same area size, same time of day and similar weather.
Random quadrats reduce bias; equal sampling effort and controls (time, weather) ensure fair comparison of species richness between habitats.
random quadrat sampling in each habitat
record species present in each quadrat and count species richness
use same quadrat size and number of samples in each habitat (e.g., 20 random quadrats)
control: sample at same time of day / similar weather or same inspector
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