Ecosystem: Definition, Structure, Functions & Types

What is an Ecosystem?

Ecosystem Definition: Any geographic area where plants, animals, and other living organisms, as well as non-living elements like weather and landscape, work together to form a bubble of life is called an ecosystem.

Define Ecosystem

The ecosystem is the interrelationship between the living organisms and the environment in a particular unit of space. An ecosystem contains all the biotic (soil, water, mineral, sunlight, etc), abiotic constituents, and nonliving elements.

Who coined the term ‘Ecosystem’? The term ‘ecosystem’ was coined in 1935 by the Oxford ecologist A.G.Tensely to encompass the interactions among biotic and abiotic components of the environment at a given site.

Structure of an Ecosystem: The structure of an ecosystem is basically a description of the organisms and physical features of the environment including the amount and distribution of nutrients in a particular habitat.It is said to consist ofabiotic components i.e. inorganic materials like air, water and soil and biotic components which are the autotrophs (producers) and heterotrophs (consumers and decomposers). The structure of an ecosystem is related to its species diversity in the sense that complex ecosystems have high species diversity.

components of ecosystem

Structure of Ecosystems

Let us have a look at the structure of ecosystem one by one:

1. Abiotic Components: These include the physiochemical environment or basic inorganic elements and compounds, such as soil, water, oxygen, calcium carbonates, phosphates, and a variety of organic compounds.

Functions of abiotic components:

a. The atmosphere supplies carbon and nitrogen.

b. Soil minerals and dissolved nutrients in the water are a source of nutrients required by living organisms.

c. The organic compounds such as proteins, carbohydrates, lipids, and other complex molecules, form a link between biotic and abiotic components of the system.

d. The climatic factors like solar radiation and temperature determine the abiotic conditions within which organisms carry out their life functions.

e. Soil is a medium of plant growth representing a mixture of minerals and organic matter, capable of supplying all the essential nutrients and water.

2. Biotic Components: These include all living organisms present in the environmental system. These can be grouped into two categories as explained:

a. Autotrophs: These are the chlorophyll bearing organisms which produce their own food by assimilating the solar energy and making use of the simple inorganic abiotic substances. Example plants, trees etc. that grow on land.

b. Heterotrophs: These are the organisms, which cannot manufacture their own food and they are further divided into the following:

(i) Phagotrophs or macroconsumers: They include mainly the animals that ingest other organisms or particulate organic matter (e.g., snails that ingest organic particles). They may be herbivores (ingesting plants, e.g., goat, deer), or carnivores (ingesting other animals – e.g., tiger, lion) or omnivores (ingesting both plants and animals, e.g. bear, man).

(ii) Saprotrophs or microconsumers: These are certain types of bacteria and fungi, also called decomposers, which break down complex dead organic matter into simple inorganic forms, absorb some of the decomposition products, and release inorganic nutrients that are reused by the producers.

Types of Ecosystem

Ecosystem varies greatly in size from a small pond to a large forest or a sea. Many ecologists regard the entire biosphere as a global ecosystem, as a composite of all local ecosystems on Earth. For the sake of convenience, we divide it into two basic categories namely:

1. Natural: Land-based or Terrestrial like the Forest, grassland, desert etc. and Aquatic like pond, lake, wetland, river, estuary etc.

2. Man-made: Crop fields and an aquarium are considered as man-made ecosystems.

types of ecosystem

Example of Ecosystem

Let us now try to understand the ecosystem through an example:

Taking a small pond as an example. This is a fairly self-sustainable unit and rather a simple example that can explain even the complex interactions that exist in an aquatic ecosystem.

A pond is a shallow water body in which all the above mentioned components and functionalities of an ecosystem are well exhibited.

The abiotic component is the water with all the dissolved inorganic and organic substances and the rich soil deposit at the bottom of the pond. The solar input, the cycle of temperature, day-length and other climatic conditions regulate the rate of function of the entire pond.

The autotrophic components include the phytoplankton, some algae and the floating, submerged and marginal plants found at the edges. The consumers are represented by the zooplankton, the free swimming and bottom dwelling forms.

The decomposers are the fungi, bacteria and flagellates especially abundant in the bottom of the pond. This system performs all the functions of any ecosystem and of the biosphere as a whole, i.e., conversion of inorganic into organic material with the help of the radiant energy of the sun by the autotrophs; consumption of the autotrophs by heterotrophs; decomposition and mineralisation of the dead matter to release them back for reuse by the autotrophs, these events are repeated over and over again. There is unidirectional movement of energy towards the higher trophic levels and its dissipation and loss as heat to the environment.

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