How is the Earth system divided, and what controls where the world's biomes are found?
The four Earth systems (geosphere, hydrosphere, atmosphere and biosphere) and how they interact; the global distribution of biomes and the climate factors that determine them.
An SQA National 5 Environmental Science answer on the Earth systems and biomes, covering the geosphere, hydrosphere, atmosphere and biosphere and how they interact, the global distribution of major biomes, and the climate factors that determine where each biome is found.
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What this dot point is asking
The SQA wants you to name the four Earth systems (geosphere, hydrosphere, atmosphere and biosphere), describe what each contains and how they interact, and explain how the world's major biomes are distributed and which climate factors decide where each one is found.
The four Earth systems
Environmental science studies the Earth as four connected systems, often called the four spheres.
- Geosphere. The rock, minerals and soil that make up the solid Earth. It is the source of resources such as metal ores, building stone, fossil fuels and the mineral part of soil.
- Hydrosphere. All the water on Earth: oceans, seas, rivers, lakes, groundwater and ice. Most is salt water in the oceans; only a small fraction is fresh water available for use.
- Atmosphere. The mixture of gases held around the Earth by gravity, mainly nitrogen and oxygen, plus carbon dioxide, water vapour and others. It supplies gases for life and shields the surface.
- Biosphere. Every living thing - plants, animals, fungi and microbes - and the zones where they live. It overlaps with the other three spheres.
How the systems interact
The four systems are not separate: matter and energy move constantly between them, and a change in one affects the others.
A practical example: burning fossil fuels (taken from the geosphere) releases carbon dioxide into the atmosphere, which warms the climate, which affects the hydrosphere (melting ice, sea-level rise) and the biosphere (shifting where species can live). One human activity ripples through all four systems.
Biomes and their distribution
Biomes are part of the biosphere, but their pattern across the globe is controlled by climate. The main climate factors are:
- Temperature, which is largely set by latitude (hot near the equator, cold near the poles) and by altitude (colder higher up).
- Precipitation (rainfall), which decides how much water is available for plant growth.
Together, temperature and rainfall decide which plants can grow, and the plants then determine which animals the biome supports. Where it is warm and wet you find dense rainforest; where it is warm and dry you find desert; cold regions give tundra; and intermediate conditions give grassland or temperate forest.
Examples in context
Example 1. Altitude mimicking latitude on a mountain. Climbing a tall tropical mountain, you pass from warm forest at the base, through cooler woodland, to cold alpine vegetation near the top, even though latitude has not changed. This shows that altitude, like latitude, lowers temperature and so changes the biome.
Example 2. A river linking all four spheres. A river (hydrosphere) erodes rock and carries sediment (geosphere), exchanges gases with the air (atmosphere), and provides a habitat for fish and plants (biosphere). It is a clear example of the four Earth systems interacting in one place.
Try this
Q1. Name the Earth system that contains all the water on the planet. [1 mark]
- Cue. The hydrosphere.
Q2. State the two main climate factors that determine where a biome is found. [2 marks]
- Cue. Temperature (set largely by latitude and altitude) and precipitation (rainfall).
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 style4 marksName the four Earth systems and give one example of a resource or component found in each.Show worked answer →
A 4-mark name-and-example answer needs all four systems, each with a correct example, so plan one mark per system.
Geosphere: the solid Earth, the rocks, minerals and soil. Example: metal ores, rock or soil.
Hydrosphere: all the water on Earth. Example: oceans, rivers, lakes, groundwater or ice.
Atmosphere: the layer of gases around the Earth. Example: oxygen, nitrogen or carbon dioxide.
Biosphere: all the living things on Earth. Example: plants, animals, fungi or bacteria.
Markers reward each system named with a correct example. A wrong example for a named system, such as putting water in the geosphere, loses that mark.
SQA N5 style3 marksExplain why tropical rainforests and hot deserts, which lie at similar latitudes, support very different biomes.Show worked answer →
This asks you to link climate factors to biome type, so each point should name a factor and its effect.
The key difference is rainfall (precipitation). Tropical rainforests receive very high rainfall all year, which supports dense, varied plant growth and high biodiversity.
Hot deserts receive very little rainfall, so very few plants can survive and biodiversity is low, even though both are warm.
A third mark could note that temperature is similarly high in both, so it is mainly the difference in available water that determines the biome. Climate (especially temperature and precipitation) decides which biome forms in a region.
Markers reward identifying precipitation as the main factor and linking high and low rainfall to the contrasting vegetation.
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