GCSE Biology revision

How materials are cycled

Organisation of an ecosystem

AQA 4.1.1.1

Your specification

AQA student objectives

Learning pathway

All · Most · Some

ALL 🎯

Identify and describe Why Materials Are Cycled, Overview of the Water Cycle and Evaporation and Transpiration in the context of how materials are cycled.

MOST 🎯🎯

Explain the relationships between Why Materials Are Cycled, Overview of the Water Cycle and Evaporation and Transpiration and how they contribute to how materials are cycled.

SOME 🎯🎯🎯

Apply and analyse knowledge of Why Materials Are Cycled, Overview of the Water Cycle and Evaporation and Transpiration to interpret unfamiliar information about how materials are cycled.

Revision summary

Key knowledge

Read on screen, then print for Cornell-style active revision.

Why Materials Are Cycled

Atoms and compounds are not created or destroyed — they are continuously cycled into different forms throughout the ecosystem.
The same water molecules that existed in Jurassic times are still being cycled through the environment today.

Overview of the Water Cycle

The water cycle moves water through the ecosystem, cycling it between the atmosphere, land, and bodies of water such as lakes and oceans.
The cycle has no fixed starting point, as it is a continuous process that can be followed from any stage.

Evaporation and Transpiration

Evaporation occurs when liquid water changes state to water vapour from bodies of water such as lakes, oceans, and ponds, driven by light energy from the Sun.
Transpiration returns water to the atmosphere as water vapour through the stems and leaves of plants, using water absorbed by the roots.
Both evaporation and transpiration are key processes by which water is returned to the atmosphere.

3. Evaporation and TranspirationAQA

Notes

Evaporation occurs when liquid water changes state to water vapour from bodies of water such as lakes, oceans, and ponds, driven by light energy from the Sun.
Transpiration returns water to the atmosphere as water vapour through the stems and leaves of plants, using water absorbed by the roots.
Both evaporation and transpiration are key processes by which water is returned to the atmosphere.

Condensation, Precipitation, and Infiltration

Water vapour cools in the atmosphere and condenses to form liquid clouds, which can be carried long distances by wind.
Precipitation — including rain, snow, sleet, and hail — falls from clouds back into bodies of water and onto land.
Surface run-off occurs when large amounts of precipitation cause water to flow along the ground into bodies of water.
Infiltration is the process by which water is absorbed into the ground and may be stored in aquifers, which are underground permeable rocks.

4. Condensation, Precipitation, and InfiltrationAQA

Notes

Water vapour cools in the atmosphere and condenses to form liquid clouds, which can be carried long distances by wind.
Precipitation — including rain, snow, sleet, and hail — falls from clouds back into bodies of water and onto land.
Surface run-off occurs when large amounts of precipitation cause water to flow along the ground into bodies of water.
Infiltration is the process by which water is absorbed into the ground and may be stored in aquifers, which are underground permeable rocks.

Overview of the Carbon Cycle

The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide, which is then used by plants during photosynthesis.
There are four key processes in the carbon cycle that you need to know: combustion, photosynthesis, respiration, and decomposition.

Combustion and Photosynthesis in the Carbon Cycle

Combustion (burning) releases carbon dioxide into the atmosphere when carbon-containing compounds, such as fossil fuels, are burned.
During photosynthesis, plants absorb carbon dioxide from the atmosphere and convert the carbon into glucose, removing carbon from the atmosphere.

6. Combustion and Photosynthesis in the Carbon CycleAQA

Notes

Combustion (burning) releases carbon dioxide into the atmosphere when carbon-containing compounds, such as fossil fuels, are burned.
During photosynthesis, plants absorb carbon dioxide from the atmosphere and convert the carbon into glucose, removing carbon from the atmosphere.

Respiration in the Carbon Cycle

Animals consume plants, taking in carbon compounds that are then broken down during respiration, releasing carbon dioxide back into the atmosphere.
Respiration adds carbon dioxide to the atmosphere — it does not remove it.

Decomposition and Decomposers

When plants and animals die, microorganisms called decomposers break down their bodies, releasing carbon dioxide back into the atmosphere.
Decomposers also break down dead organisms into mineral ions, which are returned to the soil and can be absorbed by plants.
Organisms that feed on dead and decaying material are known as detritivores, and they play a key role in decomposition.

8. Decomposition and DecomposersAQA

Notes

When plants and animals die, microorganisms called decomposers break down their bodies, releasing carbon dioxide back into the atmosphere.
Decomposers also break down dead organisms into mineral ions, which are returned to the soil and can be absorbed by plants.
Organisms that feed on dead and decaying material are known as detritivores, and they play a key role in decomposition.

Key Processes Summary

The four essential processes of the carbon cycle are combustion, photosynthesis, respiration, and decomposition.
The key processes returning water to the atmosphere in the water cycle are evaporation and transpiration.

Common Exam Mistakes to Avoid

Infiltration refers to water being absorbed into the ground — not a process in the carbon cycle.
Combustion is part of the carbon cycle, not the water cycle.
Rain is an example of precipitation, not condensation — condensation is the process that forms clouds.