the various abiotic factors are as follows:

1. Temperature: the average temperature on land varies seasonally, decreases progressively from the equator towards the poles and from plains to the mountain tops. It ranges from sub-zero levels in polar areas and high altitudes to more than 50°C in tropical deserts in summer. So, it can be stated that temperature significantly affects the

(a) Latitudinal and Attitudinal distribution of organisms

(b) Enzyme kinetics and basal metabolism.

Organisms which can tolerate and thrive a wide range of temperatures and can maintain a constant body temperature are known as Eurythermal animals. These includes Mammals, birds. Organisms which can tolerate and thrive a restricted narrow range of temperature are termed as Stenothermal. It includes Polar bears, penguins.

2. Water: The productivity and distribution of plants is dependent on water. For aquatic organisms the quality (chemical composition, pH) of water becomes important.

Organisms which tolerate a wide range of salinities are termed as euryhaline e.g. Salmon. Organisms which are restricted to a narrow range of salinities are termed as Stendhalian e.g. Shark.

3. Light: Light affects significantly the production in autotrophs, photoperiodism and behavioural and physiological adaptations in organisms living in low in intensities. For example, many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesise optimally under very low light conditions because they are constantly overshadowed by tall, canopied trees. Many plants are also dependent on sunlight to meet their photoperiodic requirement for flowering. Light also plays an important role in aquatic habitats for vertical distribution of plants in the sea.

4. Soil: Soil is an important factor affecting the distribution of organisms. Properties of soil like grain size, mineral content, percolation, pH are significant in distribution of plants and animals.