Organisms and Population


Earth has a web of biological interactions between organisms, population and the communities enabling them to survive mutually. A group of individuals inhabiting in a specific geographic location determines a population. A similar type of organisms inhabiting in a particular territory is called species, for example, all Homo sapiens live in and around the city. On the other hand, a  number of different populations form a biotic community, for example, a group of 100 different types of animals and thousands of plants. The ecosystem is the consequence of the interaction between living organisms with the abiotic factors surrounding them. Some of them are water, sunlight,  temperatures, nutrients and pollutants. These ecosystems can be, tropical, aquatic,  deserts etc which we will discuss in the next section. Furthermore, many ecosystems combining together to guide to a landscape. A landscape is a variable set of biotic and abiotic factors. A landscape can be a tropical rain forest, deciduous forest, desert or sea coast. The screenshot below is the depiction of how organisms are organized in their hierarchy.







Organisms and their environment

Organisms and the environment coexist to bring in harmony. They both complement and influence each other alongside many abiotic factors .“An Organism is a living entity that relates itself to the environment. An organism can be a plant, animal, microbe etc that has the ability to respond and adapt to the environment provided there is a balanced ecosystem. For example, polar bear’s thick fur is an adaptation against the harsh cold weather in its territory, similarly, the long beak of waterbird aid in picking up the fish from deep inside the lake water. However, in both cases, chances of survival can be affected by many other adverse environmental conditions. The environment is an inclusive term used for the structural and organisational setup that it provides for the biological processes to happen. The way the environment and the organisms interact with each other encourage the organisms to develop specific modifications. Such modifications are nothing but the defence mechanisms, for example, camouflaging is the structural adaptation by many organisms to escape from their predators by hiding themselves.  



Organisms in their biome  

The complex association of plants and animals with their environment lead to a biome. Biomes vary across different geographical regions as each geographical province differs in its levels of drought, sunshine, wind, landscape, rainfall etc. Hence, a biome in itself is indigenous and unique. Some of the common biomes and their definitions are as under


Common biome types

  1. Desert - Very dry with no or minimum water source.

  2. Tundra – Very cool but dry with no trees in it.

  3. Temperate Deciduous Forest - cool and rainy, with lots of deciduous trees within.

  4. Grassland - Windy, partly dry, grass with few trees. For example, tropical savanna, prairie, steppe, pampas, etc.

  5. Mountain biomes have a variety of mountains with grasslands at low altitudes and taiga (coniferous forests).

  6. Temperate Rain Forest - cool and wet

  7. Tropical Rain Forest - warm and very wet

  8. Land Cave - cool and dark

  9. Wetlands - swamps, marshes, moors, bogs, fens, sloughs, etc.

  10. Freshwater Marsh - a wetland located near creeks, streams, rivers and lakes

  11. Marine (ocean or sea) – including euphotic (sunlit) zone, littoral or intertidal zones and coral reef (warm shallow salt-water environments based on coral formations).



Biomes in India

India has a rich heritage of natural sources including a variety of plants, trees and animals that are highly different between different regions. Such variations result in different biomes. The most commonly recognised biomes in India are the tropical rain forests, deciduous forests, deserts and sea coasts. Each biome varies in its living conditions or climatic factors and these differences are due to the varying levels of temperature, water, light, soil and many other abiotic factors. The climatic factors help in moulding the living conditions of biomes that suits the organisms living in an area. It is important to understand how biomes are distributed across the country and the way they can influence the individuals. The picture below depicts the biome distribution and their proportions in relation to the types of biomes.







Factors influencing biomes

Abiotic Factors

Some of the abiotic factors include water, sunlight, oxygen, soil and temperature.  Plants and animal respond differently to diverse abiotic factors. Abiotic factors are the non-living conditions prevailing in a specified geographic area. The picture below is the depiction of the variety of abiotic factors that affect plants , however animals are also influenced by the same conditions.  


Abiotic Factors             



1. Temperature as an abiotic factor

Temperature is a more comprehensive term used differently in a variety of contexts.  Temperature is the feeling of heat or cold in a given region. It is one of the most important factors determining the kind of organisms exist in a habitat. As global warming is increasing at an alarming phase, the organisms in each geographic location respond differently against the heat. the temperature surrounding us is highly volatile as the highest desert temperatures could reach more than 5000 Celsius and the lowest could be -2210 in the polar regions making it very difficult for the survival of all organisms. However, the organism`s ability to adapt as per the climatic conditions can assist in the survival. For instance, a penguin can survive in the coldest polar regions but not in the desert. Organisms proving their ability to adapt to a wide range of temperatures are known as Eurythermal organisms.  If the organisms fail tot adapt resulting in their restriction to only specified areas are called stenothermal organisms.



2. Water (H2O) as an abiotic factor

Life never exists without water as every living organism need water for their survival. A variety of animals, plants and aquatic creatures live in a diversity of water sources.  The human body has approximately 70% of water content in the form of intracellular fluids, extracellular fluids such as blood and lymph. For the plants, water decodes their growth, transportation, and photosynthesis.  Apart from the availability of water, quality and chemical composition of water are also very important for a healthy living. Different organisms require different types of water. For example, some inland aquatic organisms need freshwater( sweet) lakes whereas some fishes can exist only in the highly acidic oceans. Based on this, the organisms that can tolerate diverse salinity are called euryhaline whereas other organisms living in a narrow range of salinity are called stenohaline animals.



3. Sunlight as an abiotic factor

Sunlight is the most significant demand by autotrophs, however, it is essential for almost all other organisms for a different purpose. Sunshine helps in the survival of every organism indirectly through photosynthesis. In addition, the amount of sunshine varies between specified geographic areas that can influence the quality of life of plants and animals. The amount of sunlight also influences the rate of growth. A few herbs and shrubs can grow faster in the forests under the massive trees as they are able to manage their photosynthesis even under dim-light, whereas grass and trees demand a  high-intensity temperature. With the exception of nocturnal animals, light is an indispensable factor for most of the organisms because light provides a clue on the day’s cycle for animals. The period of time in a day during which an organism receives illumination is called Photoperiod. Photoperiod determines the timing of the foraging, reproductive and migratory activities of animals. Human beings benefit from light as they can produce vitamin –D when the skin is exposed to it.



4. Oxygen as an abiotic factor

Like water, oxygen is another important abiotic factor necessary for many bodily functions. Majority of the animal population die in the absence of oxygen for a few minutes. Animals receive oxygen and give away carbon dioxide during respiration while the carbon dioxide released by animals is used for plant respiration. The levels of oxygen differ across different regions depending upon the altitude, humidity, pollution and other factors. For instance, the oxygen level decreases as we move to the high altitude regions, similarly, polar regions tend to have lesser oxygen levels than the tropical areas. The type of organisms and their morphology also differ according to the oxygen composition of a given area.


5. Soil as an abiotic factor

Soil is one of the abiotic factor act as a medium to supply water and mineral nutrition for the plants. The plant`s root system deeply submerged into different layers of soil to absorb water in it. Root system help in sucking the water and hold it temporarily. The water absorbed by the roots is transported to different parts of the plant like leaves, twigs and  stem so that the plant grows over time. As animals eat many plants, they indirectly depend on the water levels, health and composition of soil in a given area.  The type of soil and the health of the soil is the most important factor determining the growth and development of both the plants and animal. Furthermore, the type of soil in each area is different based on the colour, water holding capacity, pH and many other features.  The variety of soil help in producing a variation in the health and the growth of plants and animals in some way or the other.  The soil erosion and the excess of weedicide sprays can seriously impede the health status of animals and plants when they consume food that is grown in such soil. 



Biotic factors

Biotic factors, as the name suggest, are the living factors in an ecosystem. Biotic components are the producers, consumers or the decomposers. The way the organisms interact with these 3 factors differs in different contexts. For example, decomposers are necessary to convert dead matter into energy, at the same time they can destroy food material that we consume hence, the decomposers act in 2 different ways depending upon with whom they interact.  Following sections explain the 3 major biotic factors.



Producers are nothing but the plants, trees and related organisms that use solar energy to facilitate photosynthesis. Better the interaction of plants with the environment, greater the productivity and vice-versa.



Consumers are animals such as rabbits, deer and cows that mostly eat plant produce. They are further classified into primary and secondary type depending upon what they consume. The primary consumers are herbivores (vegetarians). The organisms that eat the primary consumers are meat eaters (carnivores) and are called secondary consumers. Secondary consumers tend to be larger but fewer in number while the primary consumers are smaller but many in numbers.



Decomposers are those help in breaking down the dead material (dead animals, dead plants ) and convert them into the soil. For example, mushrooms.



Further reading


Species on the earth and their diversity


Introduction to Ecosystems


Organisms and population attributes         


Animal Kingdom





  1. Explain the basic terminologies used in describing population'

  2. What is the difference between a species and population?

  3. What are biotic and abiotic factors?

  4. Explain the influence of temperature on the organisms.

  5. Describe the impact of rain and sunlight on the ecosystem.

  6. Explain the 3 major biotic factors in a system.




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