The following points highlight the four main factors that influence the life of an organism. The factors are: 1. Temperature 2. Water 3. Light 4. Soil.
Factor # 1. Temperature:
It is the most ecologically significant environ mental factor. It varies seasonally. Thus, 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 > 50°C in tropical deserts in summer.
There are also certain unique habitats such as thermal springs, deep sea hydrothermal vents where, the average temperature exceeds 100°C.
Physiological functions, as well as geographical distribution of plants and animals is governed by the temperature and their thermal tolerance.
Organisms, which can tolerate and thrive in a wide range of temperatures are called eurythermal, while organisms, which can tolerate a narrow range of temperatures are called stenothermal.
Factor # 2. Water:
It is the next most important factor influencing life of an organisms. Life on earth, for the first time originated in water and cannot be sustained without it.
The productivity and distribution of plants is dependent on water. For aquatic organisms, pH, chemical composition and temperature is important. These are also affected by the salinity of water. Which is about 5% in inland water, 30-35% in sea and >100% in some lagoons.
Organisms, which can tolerate a wide range of salinity are called euryhaline, while organisms, which can tolerate a narrow range of salinity are called stenohaline. Freshwater animals cannot live in sea water due to high salinity and vice-versa.
Factor # 3. Light:
The significance of light, lies in the fact that all autotrophs depend upon light as a source of energy for preparing their food and release oxygen through photosynthesis. Therefore, it is an important factor for life to exist on earth.
Small herbs and shrubs growing in forests, are adapted to photosynthesize under very low light intensities, because they are overshadowed by the tall canopied trees.
Most plants also depend on sunlight to meet their photoperiodic requirement of flowering.
Many animals depend upon diurnal and seasonal variations in light intensity and duration (photoperiod) as cues for timing their foraging, reproductive and migratory activities.
The UV component of light is harmful for many organisms.
Red, brown and green algae are distributed at different depths. The red algae can live in very deep water.
Factor # 4. Soil:
The nature and properties of soil in different places vary significantly.
It is dependent mainly on the:
(b) Weathering process
(c) Whether soil is transported or sedimentary
(d) Soil development process
Water holding capacity and percolation of the soil is determined by its various characteristics, such as soil composition, grain size and aggregation.
The characteristics of soil like grain size, porosity, pH, mineral composition and topography determine the type of plants that can grow in a particular habitat and the type of animals that feed on them.
In aquatic environment also, the bottom sediments determine the type of benthic animals that can live there.
Responses to Abiotic Components:
The above factors are highly variable. Therefore, during the course of million years of existence, many species have evolved a relatively constant internal environment, which permit all the biochemical reactions and physiological functions to proceed with maximal efficiency and thus, enhance the overall ‘fitness’ of the species.
This constancy can be achieved in terms of optimum temperature and osmotic concentration of body fluids, i.e., the internal environment homeostasis; despite of varying external environmental conditions that tend to upset its homeostasis.