• Everything that surrounds or affects an organism during its lifetime is collectively known as its environment.
  • It comprises of both living (biotic) and non-living components (abiotic).
  • Biotic components- Green plants, non-green plants, decomposers, parasites, symbionts, animals, etc.
  • Abiotic components- Energy, radiation, temperature & heat flow, water, atmospheric gases & wind, fire, gravity, topography, soil, geological substratum
  • Organisms are affected by both their internal as well as external environments.
  • The biosphere includes all living organisms on earth, together with the dead organic matter produced by them.
  • Habitat is the physical environment in which an organism lives (address of an organism).
  • Many habitats make up the environment.


  • Ecology is the study of interactions between organisms and their environment.
  • The term Ecology was given by Ernst Haeckel.


  • An ecosystem is a functional unit of the environment (mostly biosphere).
  • An ecosystem can be visualized as a functional unit of nature, where living organisms interact among themselves and also with the surrounding physical environment.
  • An ecosystem can be of any size but usually encompasses specific and limited species. Example- Aquatic ecosystem.
  • The term ecosystem was given by A. G. Tensley.

Components of Ecosystem

Abiotic Components-

Energy, Rainfall, Temperature, Atmosphere, Substratum, Organic and Inorganic material, Latitude and Altitude


Effect of Abiotic Components on Terrestrial Primary Producers (Plants)


  • Extremely high intensity favours root growth over shoot growth which results in increased transpiration, short stem, smaller thicker leaves.
  • On the other hand, low intensity of light retards growth, flowering and fruiting.
  • When the Intensity of light is less, the plants cease to grow due to the accumulation of CO2.
  • Of the visible part of the spectrum, only red and blue are effective in photosynthesis.
  • Plants grown in blue light are small, red light results in elongation of cells (etiolated plants).
  • Plants grown in ultraviolet and violet light are dwarf.


  • Frost results in freezing the soil moisture.
  • The plants are killed due to increased transpiration when their roots are unable to supply moisture.


  • Snow acts as a blanket, prevents a further drop in temperature and protects seedlings from excessive cold and frost.


  • High-temperature results in the death of plant due to coagulation of protoplasmic proteins (some bacteria can survive high temperatures because of their protoplasmic proteins that don’t coagulate at normally high temperatures).

Biotic Components-

1.       Primary producers- Autotrophs (self-nourishing)

2.       Consumers- Heterotrophs or phagotrophs (other-nourishing)

A) Macro consumers- feed on plants or animals or both

B) Micro consumers– bacteria and fungi that obtain energy and nutrition by decomposing dead organic material. These are also called Saprotrophs (decomposers or osmotrophs).

Q. Which one of the following is the best description of the term “ecosystem”?

a) A community of organisms interacting with one another

b) That part of the Earth which is inhabited by living organisms

c) A community of organisms together with the environment in which they live.

d) The flora and fauna of a geographical area.


(a) A community of organisms interacting with one another – no specific term.

(b) That part of the Earth which is inhabited by living organisms – biosphere.

(c) A community of organisms together with the environment in which they live-ecosystem.

(d) The flora and fauna of a geographical area –biodiversity.

Answer: (c)

Know the difference

Environment- can be almost everything or a small region

Habitat- an area where organisms live

Biosphere- the region of earth that supports life

Ecosystem- Producers, consumers, decomposers, and their relationships. It is the functional unit of the environment.

Ecology- the study of the relationship between organisms and their environment.

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