Ecosystem notes UPSC JKSSB by home academy

 Ecosystem notes UPSC JKSSB  by home academy

The term ‘ecosystem’ was coined by A.G. Tansley in 1935. 

An ecosystem is a functional unit of nature encompassing complex interaction between its biotic (living) and abiotic (non-living) components. 

For example- a pond is a good example of ecosystem.

Components of an ecosystem

They are broadly grouped into:- (a) Abiotic and (b) Biotic components

(a) Abiotic components (Nonliving): The abiotic component can be grouped into following three categories:- 

(i) Physical factors: Sun light, temperature, rainfall, humidity and pressure. They sustain and limit the growth of organisms in an ecosystem.

(ii) Inorganic substances: Carbon dioxide, nitrogen, oxygen, phosphorus, sulphur, water, rock, soil and other minerals. 

(iii) Organic compounds: Carbohydrates, proteins, lipids and humic substances. They are the building blocks of living systems and therefore, make a link between the biotic and abiotic components.  

(b) Biotic components (Living) 

(i) Producers: The green plants manufacture food for the entire ecosystem through the process of photosynthesis. Green plants are called autotrophs, as they absorb water and nutrients from the soil, carbon dioxide from the air, and capture solar energy for this process.

 (ii) Consumers: They are called heterotrophs and they consume food synthesized by the autotrophs. Based on food preferences they can be grouped into three broad categories. Herbivores (e.g. cow, deer and rabbit etc.) feed directly on plants, carnivores are animals which eat other animals (eg. lion, cat, dog etc.) and omnivores organisms feeding upon both plants and animals e.g. human,  sparrow.

(iii) Decomposers: Also called saprotrophs. These are mostly bacteria and fungi that
feed on dead decomposed and the dead organic matter of plants and animals by
secreting enzymes outside their body on the decaying matter.They play a very importantrole in recycling of nutrients. They are also called detrivores or detritus feeders

Functions of ecosystem

Energy flow through food chain

• Nutrient cycling (biogeochemical cycles)
• Ecological succession or ecosystem development
• Homeostasis (or cybernetic) or feedback control mechanisms

Types of ecosystems

Ecosystems are classified as follows:
(i) Natural ecosystems (ii) Man made ecosystems

(i) Natural ecosystems 

(a) Totally dependent on solar radiation e.g. forests, grasslands, oceans, lakes, rivers and deserts. They provide food, fuel, fodder and medicines.
(b) Ecosystems dependent on solar radiation and energy subsidies (alternative sources)
such as wind, rain and tides. e.g tropical rain forests, tidal estuaries and coral reefs 

Ponds, lakes, meadows, marshlands, grasslands, deserts and forests are examples of
natural ecosystem

(ii) Man made ecosystems

(a) Dependent on solar energy-e.g.Agricultural fields and aquaculture ponds.

(b) Dependent on fossil fuel e.g. urban and industrial ecosystems.

aquarium; a garden or a lawn etc.These are man made ecosystem.

NOTE: A pond is an example of a complete, closed and an independent ecosystem

(a)Abiotic components
(i) Light: Solar radiation provides energy that controls the entire system. Penetration of
light depends on transparency of water, amount of dissolved or suspended particles in
water and the number of plankton. 

On the basis of extent of penetration of light a pond can be divided into

euphotic (eu=true,photic=light),mesophotic and aphotic zones.
Plenty of light is available to plants and animals in euphotic zone. 

No light is available in the aphotic zone.

(ii) Inorganic substances: These are water, carbon, nitrogen, phosphorus, calcium and

a few other elements like sulphur depending on the location of the pond. The inorganic
substances like O2 and CO2 are in dissolved state in water. All plants and animals
depend on water for their food and exchange of gases- nitrogen, phosphorus, sulphur
and other inorganic salts are held in reserve in bottom sediment and inside the living
organisms.A very small fraction may be in the dissolved state.

(iii) Organic compounds: The commonly found organic matter in the pond are amino
acids and humic acids and the breakdown products of dead animals and plants. They
are partly dissolved in water and partly suspended in water.

(b) Biotic components
(i) Producers or autotrophs: synthesize food for all the heterotrophs of the pond. They
can be categorized into two groups:-
(a) Floating microorganisms and plants
(b) Rooted plants
(a) Floating microorganisms (green) and plants are calledphytoplankton (“phyto”-plants, “plankton” –floating). They are microscopic organisms. Sometimes they are so abundant in pond that they make it look green in colour e.g. Spirogyra, Ulothrix, Cladophora, Diatoms, Volvox.
(b) Rooted plants: These are arranged in concentric zones from periphery to the deeper layers. Three distinct zones of aquatic plants can be seen with increasing deapth of water in the following order:
i) Zone of emergent vegetation: . eg. Typha, Bulrushes and Sagittaria
ii) Zone of rooted vegetation with floating leaves . eg. Nymphaea 

iii) Zone of submergent vegetation: eg. All pond weeds like Hydrilla , Rupia,
musk grass etc.

(ii) Consumers/Heterotrophs are animals which feed directly or indirectly on autotrophs eg. Tadpole, snails, sunfish, bass etc.
Pond animals can be classified into the following groups
(a) Zooplanktons are floating animals. Cyclops, Cypris
(b) Nektons are the animals that can swim and navigate at will. Eg. fishes
(c) Benthic animals are the bottom dwellers: beetle, mites, mollusks and
some crustaceans.

(iii) Decomposers: They are distributed through out the entire in the whole pond but in the sediment most abundant. There are bacteria and fungi. (Rhizopus, Penicillium,
Curvularia ,Cladosporium) found at the bottom of the pond.

 

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