Ecology: Organisms and Their Environment

Ecology is the study of the interaction of organisms in an area with the surrounding environment. This interaction constitutes an overall adaptation of the organisms to their environment which also includes the continuity of species. However, the availability of organisms in an area is dependent on the type of environment. Thus, the availability of specific species is indirectly dependent on the various factors like annual rainfall, average temperature conditions, the position of the earth with respect to the sun, etc. These factors give rise to the existence of biomes like grasslands, rainforests, deserts, etc. The climate in the specific biome further decides the species richness in that area.

Let us now discuss the various abiotic components in the environment.

Abiotic Components in an Ecology

  1. Temperature – It is one of the major factors which directly affects life in an area. The temperature on earth follows a general geographic trend. It is highest at the equator and keeps on decreasing as we move towards the poles. Temperature affects the various enzymatic reactions in living organisms. As a result, the biodiversity observed in the planet varies along the temperature gradient.
  2. Water – It is the next important factor that affects life on earth. Water supports most of the life forms on earth. For example, 70 percent of the human body is made up of water. Similarly, all other organisms require water for temperature regulation and many other physiological activities. It has been observed that the species richness is maximum near water bodies.
  3. Light – We already know that light from the sun is the ultimate source of energy for living beings on the earth. Plants capture this energy and manufacture food by the process of photosynthesis. This energy is then passed on to the rest of the organisms in the environment by the food chain and food web.
  4. Soil – The type of soil available in an area determines the type of vegetation. This directly results in the type of organisms that can be found. It also contains all the minerals needed by various living beings including plants to support their life.

An Organism is a contiguous living system that includes archaeon, animals, plants and fungus. Organisms are capable of some degree of response to homeostasis, growth, reproduction and stimuli. Organisms consisting of more than one cell are termed as multicellular organisms and single-cell organisms are termed as unicellular organisms.

A group of cells is termed as a tissue. There are four basic types of tissues that are found in animals namely muscle tissue, connective tissue, epithelium and nerve tissue. Several types of tissue together form an organ. They perform a specific function. Some of the common characteristics of a cell include reproduction by cell division, response to internal and external stimuli, metabolism and cellular components.

Adaptation of organisms to the Environment.

All the organisms possess the ability to adapt to the environment through a process of biological variation. Adaptation may differ among different species but they have the same objective, i.e. “adjustment to variation”. This results in the enhancement of ability and chance of survival. Behaviour is one of the important aspects of adaptation. It includes the way they behave, the way they look and how they are built.

For instance, the animals living in the deserts. They retain moisture either through the food they consume or through  making burrow into the moist earth to absorb water into their bodies. Another example would be the cactus in the middle of the desert drawing nourishment from ground and air.


The population is defined as “Group of interbreeding individuals of any species that live in a distinct geographical area and compete for similar resources”. Population refers to a collection of humans in terms of sociology. For instance a population of females between the age of 30 – 50 years in a specific city.

A local population is a population inhabiting a small area locally. Meta-population is referred to a closely related local population. Population ecology is a link between ecology, evolution and population genetics.

Population Attributes

Some of the attributes of the population are stated below:

  • Age Pyramid

The population is comprised of individuals of different ages at any given time. The age pyramid shows age distribution in a population. The age pyramid of human population illustrates the age distribution of females and males in a combined diagram. The shape of the pyramids reflects the growth status of the population.

  • Death Rate

It is the rate of death of individuals per unit time due to different environmental changes, predation, competition and diseases.

  • Birth Rate

It is the addition of new individuals per unit of population per unit time. For instance, if in a garden, there are 40 rose plants and 8 new plants are added by reproduction in a year. Then the birth rate will be 0.2 offspring per rose per year (8/40 = 0.2).

  • Sex Ratio

The sex ratio is the ratio of males to females in a population.

  • Population Density or Size

Population Density is nothing but the size of a population. It is defined as the number of individuals of a species per unit area.

Population Growth

A variation occurs in the size of any population and this change depends on several factors namely pressure of predator, availability of food, weather and competition. Change in population density occurs mainly due to Immigration, Natality, Emigration, and Mortality.


The above picture illustrates the formation of a biosphere. The following figure shows the formation of the biosphere. It refers to the region of the atmosphere and surface of the earth occupied by living organisms. A community refers to the population of different organisms that interacts with each other in a specific area.

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