Biotic and Abiotic Definition and Meaning
The environment involves the interactions of all external factors, substances, and conditions that influence organisms without becoming their constituent part. The environment is usually divided into two parts, physical environment, and biotic environment.
The components, conditions, and forces of the environment that directly or indirectly affect the form, functioning, behavior, survival, and reproduction of organisms are called environmental factors.
These of two types- biotic and abiotic.
Biotic factors are influences produced by living organisms. All living components of the ecosystem, i.e. plants, animals and microorganisms, are called biotic factors. They can be further classified into three types:
- Producers: These are green photosynthetic plants that entrap solar energy through chlorophyll to synthesise organic food from inorganic raw materials. The green plants are thus termed autotrophs as they are capable of synthesising their food materials. They have also termed transducers as they change radiant energy into chemical energy. The complex organic substances are utilised to build up their bodies and release energy required for various metabolic and physiological activities.
- Consumers: These are the animals that cannot synthesise the food material but feed on other organisms or their parts. They are thus called heterotrophs. They are also called phagotrophic as they ingest solid food materials. The consumers are mainly of two types, i.e. herbivores and carnivores. Herbivores are termed primary consumers as they obtain food directly from plants. Cattle, deer, goat, rabbit, mouse, grasshopper, etc., are common herbivores in terrestrial ecosystems, and crustaceans, molluscs and protozoans are common herbivores in the aquatic ecosystem.
Omnivores are the group of animals who eat both plants as well as animals. Thus, they can survive on both matters—for example, bear, crow, dogs, etc. Some carnivores feed upon herbivores and thus termed secondary consumers. Other carnivores feed upon secondary consumers, not eating the herbivores. They are termed, tertiary consumers. Other large and stronger carnivores thus eat some carnivores. However, some larger and stronger carnivores never become prey to any animal and act as predators only. They are called top carnivores.
- Decomposers: These are saprophytic microorganisms deriving their food material from organic matter present in dead remains of plants and animals. They secrete digestive enzymes, which convert complex organic substances into simpler ones. The microorganisms assimilate a part of the digested organic matter, and the rest is broken down into simpler inorganic compounds for recycling. Thus, they bring about a cyclic exchange of materials between the biotic community and the environment. They are thus essential components of an ecosystem. They are also called reducers as they are capable of degrading dead organisms.
All the non-living components of the ecosystem are termed abiotic factors. Abiotic factors are divisible into three categories- atmospheric, edaphic and topographic. These are explained in detail below:
- Temperature: It is the most relevant factor as temperature variation affects the enzyme kinetics, basal metabolic activities, and organisms' physiological functions. So, thermal tolerance decides the geographical distribution of different species to a large extent.
- Water: Next to temperature, water is the most important factor influencing the life of organisms. It is an important component of protoplasm and is a universal solvent. Water is also present over more than 71% surface of the earth. Sea has a high percentage of salt content. Water present on land is called freshwater. Its salt content is low, less than 0.5%. The salt concentration is less than 5% in inland water.
- Light: It has a wide range of the spectrum. The electromagnetic spectrum is a complete range of oscillating waves that travel together through space at a 3x105 km/sec speed. Light affects photosynthesis, growth, reproduction, movements, stratification, photoperiodism and phenology in plants, affecting migration, reproduction, development, pigmentation, locomotion and period of activity in animals.
- Soil: It consists of four components, two solid and two non-solids. The solid components are mineral particles and organic matter. The two non-solid components are air and water. The fifth component of variable nature is soil organisms. Chief characteristics of soil are studied with the help of soil profile. The type of soil depends upon the climate and vegetation of the area. Following are the steps of soil formation:
- Physical weathering
- Chemical weathering
- Biological weathering
- Eluviation and Illuviation
Soil texture- three main types of soil are:
- Sandy soil
- Clay soil
- Loam soil
Soil porosity depends on the climate, weathering process, origin of the soil. Soil can have two types of pores:
- Soil micropores: with less than 20 um diameter
- Soil macrospores: with 20-50 um diameter
- Atmosphere: it is a layer of gases that surrounds all of us. It protects us from the harmful ultraviolet radiation of the sun. There are mainly five layers of the atmosphere -
- Wind: Wind is the movement of air that occurs relatively on Earth's surface. The wind is used as a source of energy for the generation of electricity. It is renewable energy and hence will never exhaust. It is a clean source of energy generation.