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| Climatic Factors - Rainfall and Water |
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| Rainfall is a source for ground water and relative humidity. The amount of rainfall greatly affects the vegetation as well as animal population of a particular region. |
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 In tropical areas with heavy rainfall throughout the year, vegetation mainly include evergreen forests and abundant fauna. |
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 In countries with heavy rainfall during winter and low during summer, there are present sclerophyllous forests. The plants are shrubs, stunted in height with leathery, thick, evergreen leaves. |
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 The areas with heavy rainfall during summer and low during winter are characterized by the presence of grasslands. |
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 The regions where rainfall is scanty, are seen with deserts and xerophytic vegetation. |
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| Water is essential for life. The types of plants and animals distributed in water bodies greatly depends upon the nature of water, fresh water or sea water. The organisms have to face different problems of water scarcity or abundance, so osmoregulation is required for their proper functioning. |
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| Water in the soil is present either as hygroscopic water, capillary water or gravitational water. Out of these water forms, only capillary water is available water to plants. |
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| In aquatic ecosystem, organisms have to face the problem of excess water. These maintain water balance in different ways. |
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| The aquatic animals are classified into 2 categories on the basis of nature of water in which they can live. |
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| Example: Stenohaline - which can withstand only freshwater, or seawater and Euryhaline, which can live in waters of different concentration. |
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| Water problem in terrestrial ecosystem is a major limiting factor. Land organisms having to face the problem of deficiency of water, develop various devices to minimize the loss of water. |
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| Hydrological cycle |
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| It is the movement of water between aquatic systems, air and land water vapour condenses to form clouds, and eventually rainfall. Plants play an important role in this cycle by the process of transpiration. |
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| The upper limit (maximum) of water availability of a soil is called field capacity. |
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| The lower limit of water availability soil is known as wilting point. |
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The zones in lake water as determined by gradients of light, oxygen
and temperature from the water surface to lake bottom |
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