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What is a Biome?

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2.4.2 A biome is a group of comparable ecosystems that have developed in similar climatic conditions.

Ecosystems that have developed independently in similar conditions in different parts of the world can have many parallel features. Precipitation, temperature and insolation are major influences on the distribution of terrestrial biomes.

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This lesson builds on the tricellular model and ocean currents (2.4.5 and 2.4.6). You already understand that the tricellular model determines patterns of temperature and precipitation at different latitudes, and that these patterns determine which biome develops.

Definition:

• A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur
• The key phrase is "wherever they occur" – ecosystems in similar conditions in different parts of the world share many parallel features, even though the actual species are different
• For example, tropical rainforests in the Amazon Basin, the Congo Basin and Southeast Asia all share recognisable structural features (tall canopy, dense undergrowth, high species diversity) because similar climatic conditions produce similar selective pressures, leading to convergent structures

Three major influences on terrestrial biome distribution:

• Precipitation – water is needed for photosynthesis, transpiration and cell turgidity
• Temperature – affects the rate of photosynthesis as a chemical reaction
• Insolation – sunlight provides energy for photosynthesis

It is the combination of these factors that determines which biome develops. Together, they determine productivity, which in turn determines biome structure. For any given temperature and rainfall pattern, one natural ecosystem type is likely to develop.

[Source]

A Whittaker diagram shows how different combinations of mean annual temperature and mean annual precipitation produce different biomes.

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ArcGIS

1. Define the term biome.

2. Explain what is meant by "parallel features" in biomes found in different parts of the world.

3. State the three abiotic factors that most influence terrestrial biome distribution.

4. Using a Whittaker diagram, what biome would you expect at 25°C and 2,500 mm annual precipitation? What about 25°C and 250 mm? Explain why the same temperature produces completely different biomes.

Biome Card Sort

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2.4.4 Biome categories include freshwater, marine, forest, grassland, desert and tundra.

Students should be able to describe the characteristic limiting factors, productivity and biodiversity of tropical rainforest, hot desert, tundra, temperate deciduous forest and tropical grassland (savanna). Students should be able to create climate graphs showing annual precipitation and average temperature for different biomes.

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