Biomes
Biomes
- The term biome can be defined as follows:
A large community of plants and animals that has developed as a result of environmental factors
- Abiotic environmental factors, such as rainfall and temperature patterns determine which biome develops in a particular location
- Regions of the world that experience similar abiotic factors will contain the same biome, e.g. desert occurs in parts of Africa, North and South America, and Australia
Biomes map
Regions of the world that experience similar abiotic factors will contain the same biome
- Biomes contain many ecosystems
- The ecosystems found in equivalent biomes in different parts of the world contain similar communities, even if the species are not exactly the same
- E.g. the ecosystems in the deserts of South America will contain similar communities to those in the deserts of Africa
- These similarities exist due to shared abiotic factors and resultant convergent evolution
- Species face similar selection pressures, so similar features provide a survival advantage
- These advantageous features become more common in the population due to natural selection
- This means that these communities are similar not because they have all evolved from a recent common ancestor, but because they have independently adapted to have similar features
- Species that are adapted to survive in the deserts of South America will not be close genetic relatives of those found in the deserts of Africa, though they may have similar morphology
 CC BY-SA 3.0, via Wikimedia Commons |
 CC BY-SA 3.0, via Wikimedia Commons |
The cacti of the South American deserts (left) and the euphorbias of the African deserts (right) share spines and succulent stems as adaptations to their desert biome environments, but the two plant groups are not closely related
Climate conditions of major biomes table
| Biome | Climate conditions | Community features |
| Tropical forest |
Annual rainfall 2000 - 10 000 mm Temperatures consistently between 20 - 25 °C Nutrient poor soil due to lack of seasonal leaf fall |
Layers of vegetation, e.g. canopy and undercanopy Highly productive, i.e. high levels of photosynthesis Very high levels of biodiversity |
| Temperate forest |
Annual rainfall 750 - 1500 mm Seasonal, but no extremes temperatures Fertile soil due to leaf fall each autumn |
Dominant deciduous trees Productive during part of the year High levels of biodiversity |
| Taiga (conifer forest) |
Annual rainfall 300 - 900 mm but high snow fall Very short summer growing period Temperatures between -40 - 20 °C |
Dominant coniferous (evergreen) trees Low productivity A small number of well-adapted species |
| Grassland |
Annual rainfall 500-950 mm Dry and wet seasons Temperatures between -20 - 30 °C (differs depending on region) |
Dominant grasses Not enough water for significant tree growth; low productivity Grazing animals and a small number of top predators |
| Tundra |
Annual rainfall 150-250 mm Dark winter periods and frozen soil Temperatures between -50 - 18 °C |
Not enough water, light, or warmth for tree growth; low productivity Hibernating or migrating animal species |
| Hot desert |
Annual rainfall less than 250 mm Hot days (up to 49 °C) and cold nights (down to 0 °C) |
Productivity very low due to lack of water A small number of well-adapted species |
 CC BY-SA 4.0, via Wikimedia Commons |
 CC BY 2.0, via Wikimedia Commons |
 Public domain, via Pix4free |
 CC BY-SA 3.0, via Wikimedia Commons |
 CC BY-SA 2.5, via Wikimedia Commons |
 CC BY-SA 2.5, via Wikimedia Commons |
Tropical forest (top left), temperate forest (top right), taiga (middle left), grassland (middle right), tundra (bottom left) and hot desert (bottom right) are all examples of biomes
