Components of an Ecosystem

(Organisation or Structural aspect of an ecosystem)

An ecosystem comprises of two basic components

i) Abiotic components and

ii) Biotic components

The relationship between the biotic components and abiotic components of an ecosystem is called 'holocoenosis'.

Abiotic Components

These include the non-living, physico - chemical factors such as air, water, soil and the basic elements and compounds of the environment.

Abiotic factors are broadly classified under three categories.

Climatic factors which include the climatic regime and physical factors of the environment like light, humidity, atmospheric temperature, wind, etc.

Edaphic factors which are related to the structure and composition of soil including its physical and chemical properties, like soil and its types, soil profile, minerals, organic matter, soil water, soil organisms.

Inorganic substances like water, carbon, sulphur, nitrogen, phosphorus and so on. Organic substances like proteins, lipids, carbohydrates, humic substances etc.

Biotic Components

It comprises the living part of the environment, which includes the association of a number of interrelated populations belonging to different species in a common environment.

The populations are that of animal community, plant community and microbial community.

Biotic community is distinguished into autotrophs, heterotrophs and saprotrophs.

Autotrophs (Gr: auto - self, trophos - feeder) are also called producers, convertors or transducers.

These are photosynthetic plants, generally chlorophyll bearing, which synthesize high-energy complex organic compounds (food) from inorganic raw materials with the help of sunlight, and the process is referred as photosynthesis.

Autortophs form the basis of any biotic system.

In terrestrial ecosystems, the autotrophs are mainly the rooted plants.

In aquatic ecosystems, floating plants called phytoplankton and shallow water rooted plants called macrophytes are the dominant producers.

Heterotrophs (Gr: heteros - other; trophs - feeder) are called consumers, which are generally animals feeding on other organisms.

Consumer's also referred as phagotrophs (phago - to ingest or swallow) or macroconsumers are mainly herbivores and carnivores.

Herbivores are referred as First order consumers or primary consumers, as they feed directly on plants.

For e.g., Terrestrial ecosystem consumers like cattle, deer, rabbit, grass hopper, etc.

Aquatic ecosystem consumers like protozoans, crustaceans, etc.

Carnivores are animals, which feed or prey upon other animals.

Primary carnivores or Second order consumers include the animals which feed on the herbivorous animals.

For e.g., fox, frog, predatory birds, smaller fishes, snakes, etc.

Secondary carnivores or Third order consumers include the animals, which feed on the primary carnivores.

For e.g., wolf, peacock, owl, etc.

Secondary carnivores are preyed upon by some larger carnivores.

Tertiary carnivores or Quaternary consumers include the animals, which feed on the secondary carnivores.

For e.g., lion, tiger, etc.

These are not eaten by any other animals.

The larger carnivores, which cannot be preyed upon further are called top carnivores.

Saprotrophs (Gr: sapros - rotten; trophos - feeder) are also called decomposers or reducers. They break down the complex organic compounds of dead matter (of plants and animals).

Decomposers do not ingest their food. Instead they secrete digestive enzymes into the dead and decaying plant and animal remains to digest the organic material. Enzymes act upon the complex organic compounds of the dead matter.

Decomposers absorb a part of the decomposition products for their own nourishment. The remaining substances are added as minerals to the substratum (mineralisation).

Released minerals are reused (utilised) as nutrients by the plants (producers).