An ecosystem is an area made up of living things and their non living environment. For example, a pond or a forest.
A biome is a world scale ecosystem. It covers a huge area and examples include tropical rainforests, hot deserts and the polar ice caps.
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Factors affecting biome location
Average temperature is the main factor affecting plant growth. Temperature gradually decreases as you move away from the equator. This is because the Sun's rays are at a high angle in the sky all year round which means they are concentrated into a smaller area.
This provides a lot of sunlight and heat so plants grow well. That is why there is dense vegetation in the tropics. In polar areas the sun's rays are less concentrated, and the lack of heat and light limits vegetation growth. The plants are stunted and low growing.
Precipitation is more likely to happen in some places around the world than in others. Precipitation happens in low-pressure belts, where air masses meet and air rises. Two main areas of all year round rainfall occur at the Equator and at mid-latitudes (such as the UK). Forests grow in both these areas. In polar and desert regions, high pressure zones occur causing very dry conditions. Pressure belts change with the seasons. For example Mediterranean & tropical areas sometimes become low pressure zones and get rainfall for nearly half the year.
Video looking at what biomes are and where we can find them.
