BIOLOGY · Stage 8 · Chapter 7: The Health of the Environment
Biology 7.1 Ecosystems of the Earth — Biomes and Biodiversity
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Lesson summary
7.1 Ecosystems of the Earth — Biomes and Biodiversity — Alhussan International Academy — Biology (Stages 7–9) notes: Describe the main biomes, explain how climate shapes them and define biodiversity.Ecosystem — a community of living organisms together with the non-living parts of…
- Abiotic factors
- Deciding factors
- Tropical rainforests
- Temperate regions
- Aquatic ecosystems
- Desert plants
Section 1 of 6Ecosystems and the biosphere
- Ecosystem
- a community of living organisms together with the non-living parts of their environment, such as soil, water and climate.
- An ecosystem is an environment that supports life and may be as big as the Sahara or as small as a pond.
- Biosphere
- the Earth itself is the biggest ecosystem, and each part of it is an ecosystem in its own right.
- Abiotic factors
- they are non-living, such as soil, temperature and water supply.
- Biotic factors
- they are living, such as food supply, numbers of predators and prey, and diseases and parasites.
Section 2 of 6Biomes and what decides them
- Biome
- a very large ecosystem covering a huge area with a characteristic climate and type of vegetation.
- Deciding factors
- temperature and rainfall decide which biome occurs in a place.
- Temperature and rainfall depend on latitude, altitude and distance from the sea.
Section 3 of 6Major land biomes
| Biome | Climate | Typical features |
|---|---|---|
| Tropical rainforest | Hot and wet all year | Tall evergreen trees, very high biodiversity |
| Savanna | Warm, distinct wet and dry seasons | Grassland with scattered trees, grazing animals |
| Desert | Very little rain | Cacti and succulents; animals active at night |
| Temperate forest | Moderate with four seasons | Deciduous trees that lose leaves in winter |
| Taiga (coniferous forest) | Long cold winters | Evergreen conifers with needle-like leaves |
| Tundra | Very cold, frozen soil | Mosses, lichens, low shrubs |
Section 4 of 6Rainforest, desert, temperate and aquatic ecosystems
1Tropical rainforests2 points
- they grow where there is a lot of rain, sun and warmth all year.
- These ideal conditions support many species, so biodiversity is high.
2Deserts2 points
- they are very dry areas with little water.
- Hot deserts and cold deserts (where water is frozen) are both tough for living organisms.
3Temperate regions4 points
- temperature and light change a lot through the year.
- Summer has plenty of sunlight, warmth and water.
- Winter is cold with short days, so plants struggle to grow even when water is plentiful.
- They have many more species than deserts but far fewer than tropical rainforests.
4Aquatic ecosystems3 points
- about 71% of the Earth's surface is water, so there are more aquatic than land ecosystems.
- Most water is salty (oceans and seas), and a small percentage is fresh water in rivers, streams, lakes and ponds.
- Coral reefs are the tropical rainforests of the sea, found only in warm, clean, relatively shallow seas.
Section 5 of 6Adaptation to the biome
- Desert plants
- they store water in thick stems and have spines instead of leaves, which cuts water loss.
- Tundra animals
- the Arctic fox has thick fur and a rounded body to reduce heat loss.
- Rainforest trees
- they grow very tall to compete for light and have leaves with drip tips to shed heavy rain.
Section 6 of 6Biodiversity
- Biodiversity = the variety of living organisms in an area, including the number of species and the genetic variation within each species.
- Pattern
- it is highest near the equator, where warmth and water allow plants to grow all year and support many food chains.
- It is lower near the poles.
- Stability
- a high-biodiversity ecosystem is generally more stable, because other species can fill the role of a lost species.
- Human threats
- deforestation, farming and pollution reduce biodiversity, which is why conservation matters.
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