AQA GCSE Combined Science: Trilogy · 4.7

Ecology

50 revision questions with answers for 4.7 Ecology in AQA GCSE Combined Science: Trilogy (spec 8464). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 4.7.1.1
Define population, community and ecosystem.
Answer:
Population: one species in an area. Community: interacting populations. Ecosystem: the community interacting with non-living environmental factors.
Question 2 · Spec 4.7.1.1
What does interdependence mean in a community?
Answer:
Species depend on one another for resources or services, such as food, shelter, pollination and seed dispersal.
Question 3 · Spec 4.7.1.1
What is a stable community?
Answer:
A community in which species and environmental factors are in balance, so population sizes remain fairly constant over time.
Question 4 · Spec 4.7.1.1
What do plants commonly compete for?
Answer:
Light, space, water and mineral ions from the soil.
Question 5 · Spec 4.7.1.1
What do animals commonly compete for?
Answer:
Food, mates and territory.
Question 6 · Spec 4.7.1.2
What is an abiotic factor? Give examples.
Answer:
A non-living environmental factor, such as temperature, light intensity, moisture, soil pH, wind or carbon dioxide concentration.
Question 7 · Spec 4.7.1.2
How could reduced light affect a plant population?
Answer:
It can reduce photosynthesis and growth, lowering survival or reproduction and changing population size.
Question 8 · Spec 4.7.1.2
Why can soil pH affect species distribution?
Answer:
Different plants tolerate different pH conditions, so unsuitable pH can limit their growth and survival.
Question 9 · Spec 4.7.1.3
What is a biotic factor? Give examples.
Answer:
A living influence, such as food availability, competition, new predators or new pathogens.
Question 10 · Spec 4.7.1.3
How could a newly introduced predator affect an ecosystem?
Answer:
It may reduce prey numbers, affecting food availability for other predators and altering other populations through interdependence.
Question 11 · Spec 4.7.1.4
Distinguish structural, behavioural and functional adaptations.
Answer:
Structural: physical features; behavioural: actions; functional: internal processes that improve survival or reproduction.
Question 12 · Spec 4.7.1.4
Why can thick fur and a small surface area to volume ratio help in cold habitats?
Answer:
They reduce heat loss, helping an animal maintain a suitable internal temperature.
Question 13 · Spec 4.7.1.4
How can a small leaf area help a desert plant?
Answer:
It reduces the surface for water loss through transpiration.
Question 14 · Spec 4.7.1.4
Give a behavioural adaptation to an extreme temperature.
Answer:
An animal may be active at night or shelter during the hottest part of the day, reducing overheating and water loss.
Question 15 · Spec 4.7.1.4
What is an extremophile?
Answer:
An organism adapted to extreme conditions, such as high temperature, pressure or salt concentration.
Question 16 · Spec 4.7.2.1
Why do most food chains start with a green plant or alga?
Answer:
These producers make biomass through photosynthesis, using energy transferred from sunlight.
Question 17 · Spec 4.7.2.1
What do arrows in a food chain represent?
Answer:
The direction in which biomass and the energy associated with it pass when one organism eats another.
Question 18 · Spec 4.7.2.1
In grass → rabbit → fox, identify producer, prey and predator.
Answer:
Grass is the producer; rabbits are prey of foxes; foxes are predators. Rabbits are also primary consumers.
Question 19 · Spec 4.7.2.1
Why can predator numbers rise after prey numbers increase?
Answer:
More prey provides more food, supporting greater predator survival and reproduction, usually after a time delay.
Question 20 · Spec 4.7.2.1 · Required practical
How can quadrats estimate plant abundance in a field?
Answer:
Place quadrats at randomly selected positions, count plants in each and calculate a mean per unit area.
Question 21 · Spec 4.7.2.1 · Required practical
How can you choose quadrat positions without selection bias?
Answer:
Use random coordinates on a measured grid, rather than selecting places that appear typical.
Question 22 · Spec 4.7.2.1 · Required practical
A 0.25 m² quadrat contains a mean of 6 daisies. Estimate the total in 100 m².
Answer:
Density = 6 / 0.25 = 24 daisies/m². Estimated total = 24 × 100 = 2,400.
Question 23 · Spec 4.7.2.1 · Required practical
How can a transect show the effect of distance from a tree?
Answer:
Sample at measured intervals along a line away from the tree and record abundance alongside an abiotic factor such as light intensity.
Question 24 · Spec 4.7.2.1 · Required practical
Why use many quadrats or repeat transects?
Answer:
They capture variation across the habitat, reduce the effect of unusual samples and improve the estimate's representativeness.
Question 25 · Spec 4.7.2.1 · Required practical
Does a correlation between light and plant abundance prove light caused the pattern?
Answer:
No. Other factors, such as soil moisture, may also vary; further controlled investigation is needed.
Question 26 · Spec 4.7.2.2
Why must materials be recycled in ecosystems?
Answer:
Living organisms need a continuing supply of elements, and Earth's supply of these materials is finite.
Question 27 · Spec 4.7.2.2
How do decomposers return materials to an ecosystem?
Answer:
They break down dead organisms and waste, returning mineral ions to soil and releasing carbon dioxide through respiration.
Question 28 · Spec 4.7.2.2
How does carbon enter plant biomass?
Answer:
Plants take in carbon dioxide and use photosynthesis to make carbon-containing organic molecules.
Question 29 · Spec 4.7.2.2
How does carbon move from plants into animals?
Answer:
Animals eat plants, or eat other animals that obtained carbon from plants.
Question 30 · Spec 4.7.2.2
Name three processes returning carbon dioxide to the atmosphere.
Answer:
Respiration, decomposition involving respiring organisms, and combustion of fuels.
Question 31 · Spec 4.7.2.2
What drives evaporation in the water cycle, and what follows it?
Answer:
Energy from the Sun causes evaporation. Water vapour cools and condenses, forming clouds and eventually precipitation.
Question 32 · Spec 4.7.2.2
How do plants return water to the atmosphere?
Answer:
Water evaporates from leaf cells and diffuses out through stomata during transpiration.
Question 33 · Spec 4.7.3.1
What is biodiversity?
Answer:
The variety of different species of organisms on Earth or within an ecosystem.
Question 34 · Spec 4.7.3.1
Why can high biodiversity help ecosystem stability?
Answer:
Many interdependent species help maintain resources and conditions, reducing reliance on a small number of species.
Question 35 · Spec 4.7.3.2
Why has human population growth increased pollution pressure?
Answer:
More people and higher living standards increase resource use and waste production.
Question 36 · Spec 4.7.3.2
Name pollutants affecting water, air and land.
Answer:
Water: sewage, fertilisers or toxic chemicals. Air: smoke and acidic gases. Land: landfill and toxic chemicals.
Question 37 · Spec 4.7.3.2
How can pollution reduce biodiversity?
Answer:
It can poison organisms, damage habitats or change conditions so that fewer species survive.
Question 38 · Spec 4.7.3.3
Give three human activities that reduce available habitat.
Answer:
Building, quarrying, agriculture and waste disposal can all remove or alter habitats.
Question 39 · Spec 4.7.3.3
Why can destroying peat bogs reduce biodiversity?
Answer:
Peat bogs support distinctive communities; draining or removing peat destroys these habitats.
Question 40 · Spec 4.7.3.3
How can peat extraction and use increase atmospheric carbon dioxide?
Answer:
Peat stores carbon. Disturbance allows decomposition, and burning peat releases carbon dioxide.
Question 41 · Spec 4.7.3.4
Give two reasons for large-scale deforestation.
Answer:
Clearing land for cattle or crops, including crops grown for biofuels.
Question 42 · Spec 4.7.3.4
How does deforestation affect atmospheric carbon dioxide?
Answer:
Fewer trees remove carbon dioxide by photosynthesis, while burning or decay of cleared vegetation releases carbon dioxide.
Question 43 · Spec 4.7.3.5
Which two increasing atmospheric gases are highlighted in biological global warming?
Answer:
Carbon dioxide and methane, both greenhouse gases.
Question 44 · Spec 4.7.3.5
Give two possible biological effects of global warming.
Answer:
Changes in species distributions and migration patterns, altered habitats and increased extinction risk for some species.
Question 45 · Spec 4.7.3.5
Why is scientific consensus stronger than one isolated climate observation?
Answer:
It draws on systematic reviews of many peer-reviewed studies rather than a single local or short-term result.
Question 46 · Spec 4.7.3.6
How can breeding programmes and habitat protection conserve biodiversity?
Answer:
Breeding programmes increase threatened populations; protecting and restoring habitats provides suitable places for species to survive.
Question 47 · Spec 4.7.3.6
Why can field margins and hedgerows increase farmland biodiversity?
Answer:
They provide food, shelter and breeding sites for species that cannot thrive in a single-crop field.
Question 48 · Spec 4.7.3.6
How can recycling and reduced deforestation help ecosystems?
Answer:
They reduce waste, resource extraction and habitat destruction, helping preserve species and environmental conditions.
Question 49 · Spec 4.7.3.6
Why may biodiversity conservation conflict with economic interests?
Answer:
Protecting habitats may restrict farming, building or extraction that provides jobs, income or food.
Question 50 · Spec 4.7.3.6
How should a proposal to protect a habitat be evaluated?
Answer:
Compare evidence of biodiversity benefits with social and economic costs, consider alternatives and state a justified conclusion.

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