List the various abiotic environmental factors.
A non-living conditional factor or thing of the environment that influences the survival and reproduction functions of organism is called an abiotic factor. Abiotic factors can determine which species of organisms will survive in a given environment. Some important factors are discussed below:
Temperature:
It is the most ecologically significant environmental factor. It varies seasonally on land and 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 are governed by the temperature conditions and their thermal tolerance.
Organisms which can tolerate and thrive in a wide range of temperatures are called eurythermal, e.g. most mammals and birds while organisms which can tolerate a narrow range of temperatures are called stenothermal, e.g. polar bear, amphibians.
Water:
It is the second most important factor influencing life of organisms. Life on earth is known to have originated in water and cannot sustain without it. The productivity and distribution of plants is dependent on availability of water.
For aquatic organisms, pH, chemical composition and temperature of water is important. They are also affected by the salinity of water, which is less than 5 parts per thousand in inland waters, 30-35 parts per thousand in sea and 100 parts per thousand in some hypersaline 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. Many freshwater animals cannot live for long in sea water because of osmotic problems arising due to high salinity and vice-versa.
Light:
The significance of light lies in the fact that all autotrophs depend upon light as a source of energy for preparing their food by photosynthesis and release oxygen during the process. Therefore, it is an important factor for life to exist on earth. Small herbs and shrubs growing in forests are adapted to photosynthesise under very low light intensities, because they are overshadowed by the tall, canopied trees. Most plants depend on sunlight to meet their photoperiodic requirement for flowering also.
Many animals depend upon diurnal and seasonal variations in light intensity as cues for timing their foraging, reproductive and migratory activities. The availability of light on land is closely linked with that of temperature as the sun is the source for both. However, in deep oceans (> 500m), the environment is perpetually dark.
The spectral’ quality of solar radiation is also important for life. The UV component of light is harmful for many organisms. Different components of the visible spectrum are available for marine plants living at different depths of the ocean. This is why different types of algae, i.e. green, brown and red algae occur at different depths in sea in the upper, middle and deep layers of water respectively.
Soil:
The nature and properties of soil in different places vary significantly. It is dependent mainly on the following factors:
(a) Climate
(b) Weathering process
© 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.
These characteristics of soil along with its pH, mineral composition, topography, etc., determine the type of plants that can grow in a particular habitat and the type of animals that can feed on them. In aquatic environment also, the bottom sediments and its characteristics determine the type of benthic animals that can live there.