AQA GCSE Geography · 3.1.2

Ecosystems

50 revision questions with answers for 3.1.2 Ecosystems in AQA GCSE Geography (spec 8035). 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 3.1.2.1
What is an ecosystem?
Answer:
A community of living things (plants, animals, microorganisms) interacting with each other and with the non-living environment around them.
Question 2 · Spec 3.1.2.1
What is the difference between biotic and abiotic components?
Answer:
Biotic components are the living parts, such as plants and animals. Abiotic components are the non-living parts, such as climate, soil, water, light and rock.
Question 3 · Spec 3.1.2.1
Give examples of biotic and abiotic components in a woodland.
Answer:
Biotic: trees, fungi, insects, birds, deer. Abiotic: sunlight, temperature, rainfall, soil minerals and pH.
Question 4 · Spec 3.1.2.1
At what scales do ecosystems exist?
Answer:
From very small (a pond, a rotting log, a hedgerow) to large (a woodland) and global scale (biomes such as tropical rainforest or tundra).
Question 5 · Spec 3.1.2.1
What are producers?
Answer:
Organisms, mainly green plants and algae, that make their own food by photosynthesis. They are the start of every food chain.
Question 6 · Spec 3.1.2.1
What are consumers?
Answer:
Organisms that eat other living things. Primary consumers eat producers, secondary consumers eat primary consumers, and tertiary consumers eat secondary consumers.
Question 7 · Spec 3.1.2.1
What are decomposers?
Answer:
Bacteria and fungi that break down dead plants and animals and waste, releasing nutrients back into the soil for plants to use.
Question 8 · Spec 3.1.2.1
What is a food chain?
Answer:
A single line showing what eats what and the direction of energy flow, for example grass, then rabbit, then fox.
Question 9 · Spec 3.1.2.1
What is a food web?
Answer:
Many linked food chains showing the more complex feeding relationships in an ecosystem, where most animals eat more than one food.
Question 10 · Spec 3.1.2.1
Why is a food web more realistic than a food chain?
Answer:
Most consumers have several food sources and are eaten by several predators, so a food web shows how species depend on each other.
Question 11 · Spec 3.1.2.1
What is nutrient cycling?
Answer:
The continual movement of nutrients between soil, plants and animals. Plants absorb nutrients, which return to the soil as leaf litter and waste and are released by decomposers.
Question 12 · Spec 3.1.2.1
Describe nutrient cycling in a UK deciduous woodland.
Answer:
Trees take nutrients from the soil, then drop leaves in autumn. Decomposers break down the leaf litter and the nutrients return to the soil to be used again.
Question 13 · Spec 3.1.2.1
Why are decomposers essential in an ecosystem?
Answer:
Without them dead material would pile up and nutrients would stay locked away, so new plant growth would be starved and the food web would collapse.
Question 14 · Spec 3.1.2.1
What is meant by the balance between components of an ecosystem?
Answer:
Each part depends on the others, so populations stay roughly steady. A change to one component can alter the whole system.
Question 15 · Spec 3.1.2.1
What is interdependence in an ecosystem?
Answer:
Living things and their environment rely on each other. For example, bees feed on nectar and pollinate flowers, and plants provide food and shelter.
Question 16 · Spec 3.1.2.1
Name the parts of a UK pond ecosystem.
Answer:
Producers: algae, pondweed, water lilies. Consumers: snails, tadpoles, dragonfly nymphs, newts, fish, herons. Decomposers: bacteria and fungi. Abiotic: light, temperature, oxygen, pH.
Question 17 · Spec 3.1.2.1
Give a food chain from a UK pond.
Answer:
Pondweed, then water snail, then newt, then grass snake (or heron). The arrows show energy passing to each consumer.
Question 18 · Spec 3.1.2.1
How can fertiliser run-off damage a pond ecosystem?
Answer:
Extra nutrients cause an algal bloom that blocks light. When the algae die, decomposers use up the oxygen, and fish and other animals die (eutrophication).
Question 19 · Spec 3.1.2.1
What happens to a pond if a top predator such as a fish is removed?
Answer:
Numbers of the animals it ate rise, and these may then over-graze producers. The balance of the whole food web changes.
Question 20 · Spec 3.1.2.1
What is the effect of an invasive species in a pond?
Answer:
Non-native plants such as New Zealand pygmyweed can spread quickly, block light and oxygen, and out-compete native species, reducing biodiversity.
Question 21 · Spec 3.1.2.1
How could drought or lower water levels affect a pond?
Answer:
Shallow water warms and loses oxygen, and plants and animals die or leave. Food chains are broken and the pond may dry out.
Question 22 · Spec 3.1.2.1
Describe the layers of a UK deciduous woodland.
Answer:
Canopy (tall trees such as oak), understorey (small trees and shrubs), field layer (herbs, bluebells) and ground layer (mosses, leaf litter, fungi).
Question 23 · Spec 3.1.2.1
How could removing a component affect a woodland ecosystem?
Answer:
If predators of deer are removed, deer numbers grow and they browse seedlings, so young trees and shrubs decline, affecting insects and birds that rely on them.
Question 24 · Spec 3.1.2.1
How can a change in an abiotic factor affect an ecosystem?
Answer:
For example, a warmer, drier climate can reduce plant growth, so herbivores have less food and in turn there is less food for predators.
Question 25 · Spec 3.1.2.1
What is energy flow in a food chain?
Answer:
Energy enters as sunlight, is captured by producers and passes along the chain. Only about 10% is passed to the next level, which limits chain length.
Question 26 · Spec 3.1.2.1
What is a biome?
Answer:
A large-scale ecosystem with a similar climate, soil, plants and animals across a wide area, such as tropical rainforest or tundra.
Question 27 · Spec 3.1.2.1
List the major global ecosystems (biomes).
Answer:
Tropical rainforest, tropical grassland (savanna), hot desert, temperate deciduous forest, temperate grassland, Mediterranean, coniferous (boreal) forest, tundra and polar.
Question 28 · Spec 3.1.2.1
Where are tropical rainforests found?
Answer:
Close to the equator, between about 10 degrees north and south, in the Amazon basin, the Congo basin and South East Asia.
Question 29 · Spec 3.1.2.1
Describe the characteristics of tropical rainforests.
Answer:
Hot (about 27 degrees C) and wet (over 2000 mm of rain) all year, with tall evergreen trees and very high biodiversity.
Question 30 · Spec 3.1.2.1
Describe tropical grassland (savanna).
Answer:
Found 5-15 degrees from the equator, with a hot climate, a wet and a dry season, tall grasses and scattered trees such as acacia and baobab, and large herbivores.
Question 31 · Spec 3.1.2.1
Describe hot desert ecosystems.
Answer:
Found about 15-35 degrees north and south, with very low rainfall (under 250 mm), extreme temperatures and sparse, drought-adapted plants such as cacti.
Question 32 · Spec 3.1.2.1
Describe temperate deciduous forest.
Answer:
In mid-latitudes such as the UK and western Europe, with mild, moist weather, four seasons and broad-leaved trees that lose their leaves in autumn.
Question 33 · Spec 3.1.2.1
Describe temperate grassland.
Answer:
In continental interiors such as the North American prairies and Asian steppes, with hot summers, cold winters, low rainfall and few trees.
Question 34 · Spec 3.1.2.1
Describe Mediterranean ecosystems.
Answer:
Hot, dry summers and mild, wet winters, with drought-resistant shrubs and trees such as olive and cork oak. Found around the Mediterranean and in California.
Question 35 · Spec 3.1.2.1
Describe the boreal (coniferous) forest.
Answer:
Found at 50-65 degrees north in Canada, Scandinavia and Russia, with long cold winters, short summers and evergreen conifers adapted to snow.
Question 36 · Spec 3.1.2.1
Describe tundra.
Answer:
North of the boreal forest, with very cold winters, a short cool summer, frozen subsoil (permafrost) and low plants such as mosses, lichens and dwarf shrubs. No trees.
Question 37 · Spec 3.1.2.1
Describe polar ecosystems.
Answer:
Ice-covered areas such as Antarctica and the central Arctic, with extreme cold and very little plant life. Animals such as seals and penguins depend on the sea.
Question 38 · Spec 3.1.2.1
What mainly decides which biome forms in a place?
Answer:
Climate: temperature and rainfall, which vary with latitude, ocean currents, altitude and distance from the sea. Soil and wildlife follow from the climate.
Question 39 · Spec 3.1.2.1
Why are tropical rainforests found near the equator?
Answer:
Strong heating makes air rise, cool and condense, so there are high temperatures and heavy rain all year, which supports dense vegetation.
Question 40 · Spec 3.1.2.1
Why are the world's hot deserts mostly around 30 degrees north and south?
Answer:
Dry air sinks at these latitudes under high pressure, so there is little cloud or rain.
Question 41 · Spec 3.1.2.1
How does altitude affect ecosystems?
Answer:
Temperature falls with height, so vegetation changes from forest at the base to alpine plants and then bare rock and snow near the top.
Question 42 · Spec 3.1.2.1
How does climate affect soils in different biomes?
Answer:
Rainforest soils are deep but nutrient-poor because heavy rain washes nutrients out. Tundra soils are thin and frozen, and desert soils are dry and low in humus.
Question 43 · Spec 3.1.2.1
Which biome has the greatest biodiversity?
Answer:
Tropical rainforest, which has more species of plants and animals than any other biome because of its warm, wet and stable climate.
Question 44 · Spec 3.1.2.1
How do humans change large-scale ecosystems?
Answer:
Deforestation, farming, urban growth, mining, pollution and climate change alter or destroy natural ecosystems.
Question 45 · Spec 3.1.2.1
Why are some ecosystems more vulnerable to change than others?
Answer:
Those with specialised species or thin, slow-forming soils, such as rainforest and tundra, recover slowly and are easily damaged.
Question 46 · Spec 3.1.2.1
What is a trophic level?
Answer:
A feeding level in a food chain: producers, then primary, secondary and tertiary consumers.
Question 47 · Spec 3.1.2.1
Why does the loss of one species sometimes affect many others?
Answer:
Other species may depend on it for food, pollination or shelter. A keystone species such as a top predator affects the whole food web.
Question 48 · Spec 3.1.2.1
How does an ecosystem recover from damage?
Answer:
Through succession: pioneer species colonise first, then later species replace them until a stable community develops, which can take decades or centuries.
Question 49 · Spec 3.1.2.1
What is a species?
Answer:
A group of organisms that can breed together and produce fertile offspring. The number of species in an area is a measure of its biodiversity.
Question 50 · Spec 3.1.2.1
What is biodiversity?
Answer:
The variety of living things in an ecosystem, including the number of species and the genetic variety within them.

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