The region of the earth in which all organisms live is the biosphere. The nonliving features of the environment are abiotic factors and the organisms in the environment are biotic factors. Populations and communities make up an ecosystem. The ecosystem is the base of the biosphere which influences the wellbeing of the entire earth system. It includes living things and non-living environments in a given area where plants, animals and other organisms are the living things and weather, sun, earth, climate, soil, atmosphere, etc. form non-living environments.
Any ecosystem comprises of several factors which may be following two categories:
- Abiotic components and
- Biotic components
The environment is made up of living things or organisms that depend on one another for food and shelter but those organisms also depend on factors that surround them such as calcium, potassium, magnesium, sulfur, gaseous substances like oxygen, nitrogen, carbon dioxide, soil, sunlight, water or moisture, precipitation, temperature, and air. These factors form nonliving, physical features of the environment are known as abiotic factors. Besides all these, amino acid, humic acids, are present which adds into the abiotic factors. The producers such as green plants secure these substances from soil and air in order to prepare their foods. Abiotic factors actually control the functions, behavior, distribution, structure, and inter-relationship of organisms in an environment. Organisms cannot survive without the abiotic components. Abiotic components can differ from one ecosystem to another ecosystem which mainly acts as a life supporter or limiting factors. They influence and control the growth of the population, number, and diversity of biotic factors. In the environment, if anyone factor changes slightly causing a disturbance.
The abiotic component is also divided into the following two categories:
- Climatic factors: Climatic factors include rainfall, light, temperature, humidity, wind, and air, etc.
- Edaphic factors: These factors include minerals, soil, topography, and pH, etc.
Light: Light is the primary source of energy in the living world. Various life processes are influenced directly or indirectly by this factor.
Temperature: It is of three types: such as minimum, optimum, and maximum. The temperature tolerance of a given species at different stages of its life history is variable. The optimum temperature lies towards the maximum limit of temperature and minimum temperatures. In the optimum temperature, life processes function smoothly and efficiently. The maximum temperature for some organisms is about 38 0C. The chemical constitutes of the protoplasm suffer considerable change at this temperature. The proteins, one of the chief constituent of the protoplasm, become denatured and coagulated at considerably high temperature. However, the average maximum temperature for living organisms lies between 40 and 45 0C.
Atmospheric Pressure: It has its own influence on the living world. The atmospheric pressure varies inversely with the altitude. Lower atmospheric pressure results in lower pressure of oxygen and this condition are harmful as it leads to less oxygenation of the tissues. The above conditions along with humidity of the air, etc. fall under the climatic conditions of an environment.
Soil Factor: The environmental condition of a place mainly depends on the nature of the soil, water holding capacity, percolation of water through the soil, amount of water under soil, soil air, soil temperature, nature of the soil-sap(whether it is acidic, basic or neutral, etc).
Physiographic or topographic Factors: The altitude, undulating landscape, the amount of light falling on a place or wind blowing through the region, etc. add in to form the topographic factors of an ecosystem.
From the functional point of view the living organisms of the ecosystem are divided into two components by Odum (1971):
Autotrophic Components: Those living organisms of a biotic community for the preparation of their own food depends on the environment for water, carbon dioxide and for fixation of light energy are regarded as autotrophic components. All chlorophyll-containing green plants come under this category.
Heterotrophic Components: Those living organisms utilizes, and decomposes the complex substances produced by autotrophic components as they cannot prepare their own food matters due to lack of chlorophyll are called heterotrophic components. Except for a few plants, most animals come under this category as they are directly or indirectly dependant on autotrophic components for food.
Biotic factors are the living things which direct or indirect influence on other organisms in an environment. Organisms cannot depend only on abiotic factors for survival because they do not provide everything to live. Biotic factors depend on abiotic factors for their survival and they help to form of abiotic factors such as soil, nutrients, etc. Biotic factors such as plants offer food for other organisms while the abiotic factors such as soil support the growth of the plants by providing nutrients and other key components.
Mushrooms would not be able to grow without the decaying bodies of other organisms to feed on. Honeybees could not survive without pollen from flowers. Some species of owls and woodpeckers prefer to nest in the hollow trunks of dead trees. Organisms need help from other organisms to live. In this case, one organism provides food, shelter, protection, or reproduction to other organisms. Living or once-living organisms in the environment are known as biotic factors.
Biotic components are the constituents of a community. Each biotic community comprises of:
- Consumers and
The green autotrophic plants are regarded as producers. They are able to synthesize carbohydrates, proteins, fats, etc. from certain inorganic constituents (CO2, H2O, mineral salts, etc.) of the surrounding environment with the help of chlorophyll in presence of sunlight. The producers prepare their food matters by the process of photosynthesis which is stated below:
Proteins, amino acids, and other important minerals are also produced other than glucose. Autotrophic plants may be of two types such as (i) large rooted plants growing on lands or in shallow water and (ii) small floating algae constituting what is called phytoplankton. The later is more important of the two and they may grow up to that level of a sea or in a large lake where the sunlight can reach. Phytoplankton is the main source of food of the majority of the primary consumers.
There are certain bacteria which can prepare their own food even in darkness by a special process chemosynthesis. For example, some chemosynthetic bacteria (nitrifying bacteria) can convert ammonia to nitrite and nitrite to nitrate. Certain bacteria called photosynthetic bacteria can carry out photosynthesis. Both these types of bacteria are producer organisms. Finally, producers capture energy from non-organic sources and then store them for future use.
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Consumers are heterotrophs organisms which cannot fix carbon from non-organic sources. Hence, they directly or indirectly depend on producers for their food. Consumers are a basic component of any ecosystem. Consumers are of three types:
- Primary consumers
- Secondary consumers and
- Tertiary consumers.
Primary Consumers: The plant eaters are known as primary consumers or first-order consumers. The minute animals in the upper level of water constitute zooplankton such as Daphnia, Cyclops, etc. The primary consumers in a lower level of water are known as bottom fauna such as snails, small fishes, etc. Primary consumers of land are herbivorous animals such as grasshopper, rabbit, deer, cow, etc.
Secondary Consumers: The carnivorous animals feeding on the primary consumers are known as secondary consumers or second order consumers such as spiders, toad, frog, mole, etc.
Tertiary Consumers: The animals living on the secondary consumers are known as tertiary consumers or third order consumers such as tiger, lion, shark, eagle, etc.
It is also known as reducers or microorganisms. They are saprophytic organisms which act on dead matter and decompose them for their nutrition.
Certain heterotrophic bacteria and fungi break down the complex compounds of dead protoplasm, absorb some of the decomposed products and may release certain simpler substances for further utilization by the producers. These together form the decomposers. They are very important to any ecosystem because the ecosystem could not perform very long without the presence of reducers.