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Global ecosystems and the biosphere
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An ecosystem is a community of plants and animals and the environment they live in. Large ecosystems are called biomes.
World biomes
Tropical rainforest: near the equator; hot and wet all year.
Tropical grassland (savanna): between rainforests and deserts; a wet and a dry season.
Hot desert: near 30° north and south; very little rain.
Temperate deciduous forest: mid-latitudes such as the UK; four seasons.
Temperate grassland: continental interiors, such as the prairies.
Boreal forest (taiga): cold northern lands; conifers.
Tundra: near the Arctic; very cold, frozen ground (permafrost).
Tropical grassland (savanna): between rainforests and deserts; a wet and a dry season.
Hot desert: near 30° north and south; very little rain.
Temperate deciduous forest: mid-latitudes such as the UK; four seasons.
Temperate grassland: continental interiors, such as the prairies.
Boreal forest (taiga): cold northern lands; conifers.
Tundra: near the Arctic; very cold, frozen ground (permafrost).
What controls them
Climate is the main control: temperature and rainfall decide what can grow.
Local factors also matter: altitude (it gets colder higher up), soils and rock type, and drainage.
Ecosystems have biotic (living) parts, such as plants and animals, and abiotic (non-living) parts, such as climate, soil and water.
Local factors also matter: altitude (it gets colder higher up), soils and rock type, and drainage.
Ecosystems have biotic (living) parts, such as plants and animals, and abiotic (non-living) parts, such as climate, soil and water.
The biosphere as a life-support system
The biosphere gives people food, medicines, building materials and fuel.
For example, the rosy periwinkle from Madagascar is used to make medicines that treat leukaemia.
It is also exploited commercially for energy, water and minerals, which can damage ecosystems.
It regulates the atmosphere, the water cycle and soils.
For example, the rosy periwinkle from Madagascar is used to make medicines that treat leukaemia.
It is also exploited commercially for energy, water and minerals, which can damage ecosystems.
It regulates the atmosphere, the water cycle and soils.
Explain why hot deserts are found near 30° north and south.
- Air sinks in the global circulation at about 30°.
- Sinking air creates high pressure, so clouds rarely form.
- With very little rain, only plants adapted to drought can grow.
Answer: Sinking air, high pressure and very low rainfall.
Biomes are large ecosystems controlled mainly by climate, with local factors such as altitude and soil. Main biomes: tropical rainforest, savanna, hot desert, temperate deciduous forest, temperate grassland, boreal forest and tundra. The biosphere provides food, medicine, materials, fuel and vital services.
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