Ecosystems and biomes
- An ecosystem is made of living parts (plants and animals) and non-living parts (climate, soil and water) that interact.
- A biome is a very large ecosystem, such as tropical rainforest, hot desert, savanna, temperate deciduous forest, taiga (coniferous forest) or tundra.
- Where each biome is found depends mainly on climate: temperature and rainfall, which change with latitude.
- The British Isles' natural vegetation is temperate deciduous forest, where trees lose their leaves in winter.
Tropical rainforests
- Found near the Equator (such as the Amazon). Hot (about 27 °C) and wet all year, with over 2000 mm of rain.
- Layers: emergents, canopy, understorey and forest floor. They have the highest biodiversity of any biome.
- Plant adaptations: drip tips let heavy rain run off leaves; buttress roots support tall trees in thin soil; lianas (woody vines) climb towards the light.
- Deforestation for cattle ranching, farming (such as palm oil and soya), logging, mining and roads destroys habitats, reduces biodiversity and adds carbon dioxide to the air. Selective logging and ecotourism are more sustainable.
Hot deserts and cold environments
- Hot deserts (such as the Sahara) are found around 30° north and south of the Equator. They get less than 250 mm of rain a year, with very hot days and cold nights.
- Cacti have spines instead of leaves (so they lose less water), store water in thick stems and have roots that spread out to catch rain. Camels store fat in their humps, have wide feet for sand and long eyelashes to keep sand out.
- Tundra is very cold, with permafrost (ground frozen all year) and low biodiversity.
Key terms
- Ecosystem
- Living things and their non-living environment, interacting.
- Biome
- A very large ecosystem, such as a tropical rainforest.
- Biodiversity
- The variety of living things in an area.
- Canopy
- The dense layer of treetops in a rainforest.
- Drip tip
- A pointed leaf tip that lets rain run off quickly.
- Buttress roots
- Large roots that support tall rainforest trees.
- Deforestation
- Cutting down large areas of forest.
- Selective logging
- Cutting down only some trees, so the forest can recover.
- Adaptation
- A feature that helps a living thing survive in its environment.
- Permafrost
- Ground that stays frozen all year.