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Chapter: 11 th 12th std standard Bio Botany plant tree Biology Higher secondary school College Notes

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Organisms : Environmental Climatic Factors

1. Climatic factors 2. Edaphic factors 3. Biotic Factors. The former two factors are abiotic components that contain matter and energy. I. Climatic Factors : These are related to the aerial environment of the organisms e.g. light, precipitation, temperature, atmospheric humidity, wind, etc.

Organisms  : Environmental factors

 

All living organisms, including human beings live in some sort of abiotic component of environment, that contains matter and energy. Various environmental factors can be divided into following two groups:

 

1. Climatic factors 2. Edaphic factors 3. Biotic Factors. The former two factors are abiotic components that contain matter and energy.

I. Climatic Factors

 

These are related to the aerial environment of the organisms e.g. light, precipitation, temperature, atmospheric humidity, wind, etc.

II. Edaphic Factors

 

They include the factors related to the soil. e.g. soil composition, organic matter, soil water, soil air, soil organisms etc.


III. Climatic Factors

i) Light

 

Light is a factor of great physiological importance. It affects structure, growth and activities of organisms

 

Sunlight is the source of energy for all organisms. Light is essential for photosynthesis, a process by which green plants synthesise their food on which rest of the living world depends.

 

Development of photosynthetic pigments, pigments for floral colour, red - far red absorbing phytochrome pigments which regulate morphogenetic processes, induction and regulation of many enzymes are all light regulated processes. 'Photoperiod' is an important factor in the flowering of plants.

ii) Temperature

 

Most living organisms can survive only in a narrow range of temperature (50-350C). However, there are notable exceptions to it. Certain bacteria, cyanobacteria (blue green algae), seeds, spores and encysted protozoans can occur in hot springs or in very low temperature. Many organisms have developed physiological and behavioural adaptations to avoid extremes of temperature.

 

Temperature varies in various quarters of the earth according to latitute and altitude. It is also influenced by plant cover, atmospheric humidity, water reservoirs, air current and snow. According to the change of temperature with the increase of latitude, various vegetation zone have been recognized. Similarly , on the basis of change in temperature due to altitude, many vegetation zones can be observed.

iii) Water

 

Water is an essential requirement of life. No life can exist without water. The protoplasm of the cell contins 80-90% of water. The requirement of water varies from organism to organism. The distribution of organisms depend upon the extent of the need and specialadaptations for conserving water. Plants of dry area are called xerophytes. They develop modifications to increase water absorption, reduce transpiration and store absorbed water.

 

Plants of aquatic habitats are called hydrophytes. They possess aerenchyma (air containing parenchyma) to support themselves in water. The depth, salt content, clarity and water currents determine the growth and distribution of plants in water.

iv) Air

 

Air currents determine the weather conditions and also affect living organisms, particularly plants. Wind helps in pollination and dispersal of fruits and seeds of many plants. It increases transpiration, which may lead to desiccation and wilting of many plants. Strong winds uproot the plants and cause lodging (flattening of plants on the ground) of many crops. Areas frequented by unidirectional winds develop flag trees, which have branches on one side only. Persistent strong winds restrict the height of plants due to excessive loss of water by transpiration. The plants of such areas usually possess strong spreading roots and strong but flexible shoots.



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