Eco-System-An ecosystem is defined as a structural and functional unit of biosphere consisting of community of living beings and the physical environment, both interacting and exchanging materials between them. It includes plants, trees, animals, fish, birds, micro-organisms, water, soil, and people.

When an ecosystem is healthy (i.e. sustainable) it means that all the elements live in balance and are capable of reproducing themselves

Components of Ecosystem

The components of the ecosystem is categorised into abiotic of non-living and biotic of living components. Both the components of ecosystem and environment are same.

  1. Abiotic Components

the inorganic and non-living parts of the world. consists of soil, water, air, and light energy etc. involves a ,large number of chemicals like oxygen, nitrogen-, etc. and physical processes including volcanoes, earthquakes, floods, forest fires, climates, and weather conditions.

Abiotic factors are the most important determinants of where and how well an organism exists in its environment. Although these factors interact with each other, one single factor can-limit the range of an organism.


  1. a) Energy

Energy from the sun is essential for maintenance of life. Energy determines the distribution of organisms in the environment.

  1. b) Rainfall
  2. c) Temperature :-Temperature is a critical factor of the environment which greatly influences survival of organisms. Organisms can tolerate only a certain range of temperature and humidity.
  3. d) Atmosphere :It is made up of 21% oxygen, 78% nitrogen , 0.038% carbon dioxide and other inert gases (0.93% Argon, Neon etc).
  4. e) Substratum :Land is covered by soil and a wide variety of microbes, protozoa, fungi and small animals (invertebrates) thrive in it
  5. f) Materials:

(i) Organic compound

Such as proteins, carbohydrates, lipids, humic substances are formed from inorganic compound on decomposition.

(ii) Inorganic compound

Such as carbon, carbon dioxide, water, sulphur, nitrates, phosphates, and ions of various metals are essential for organisms to survive.

  1. g) Latitude and altitude

Latitude has a strong influence on an area’s temperature, resulting in change of climates such as polar, tropical, and temperate. These climates determine different natural biomes. From sea level to highest peaks, wild life is influenced by altitude. As the altitude increases, the air becomes colder and drier, affecting wild life accordingly.( wild life decrease as altitude increase)

  1. Biotic Components :Biotic components include living organisms comprising plants, animals and microbes and are classified according to their functional attributes into producers and consumers.

Primary producers – Autotrophs (self-nourishing) Primary producers are basically green plants (and certain bacteria and algae). They synthesise carbohydrate from simple inorganic raw materials like carbon dioxide and water in the presence of sunlight by the process of photosynthesis for themselves, and supply indirectly to other non- producers.

In terrestrial ecosystem, producers are basically herbaceous and woody plants, while in aquatic ecosystem producers are various species of microscopic algae.

  1. b) Consumers — Heterotrophs or phagotrophs (other nourishing)

Consumers are incapable of producing their own food (photosynthesis).

They depend on organic food derived from plants, animals or both.

Consumers can be divided into two broad groups

(i) Macro consumers- They feed on plants or animals or both and are categorised on the basis of their food sources.

Herbivores are primary consumers which feed mainly on plants e.g. cow, rabbit.

Secondary consumers feed on primary consumers e.g. wolves.

Carnivores which feed on secondary consumers are called tertiary consumers e.g. lions which can eat wolves.

Omnivores are organisms which consume both plants and animals e.g. man.

(ii) Micro consumers – Saprotrophs (decomposers or osmotrophs)

They are bacteria and fungi which obtain energy and nutrients by decomposing dead organic substances (detritus) of plant and animal origin.

The products of decomposition such as inorganic nutrients which are released in the ecosystem are reused by producers and thus recycled.

Earthworm and certain soil organisms (such as nematodes, and arthropods) are detritus feeders and help in the decomposition of organic matter and are called detrivores.

Classification of Eco-system

  1. Natural Ecosystem-

Terrestrial- Forests, Grasslands, Deserts

Aquatic- Fresh Waters, Saline Waters, Marine Waters

Ecotone :- a zone of junction between two or more diverse ecosystems. For e.g. the mangrove forests represent an ecotone between marine and terrestrial ecosystem.

Characteristics of Ecotone

It may be very narrow or quite wide. It has the conditions intermediate to the adjacent ecosystems. Hence it is a zone of tension.

It is linear as it shows progressive increase in species composition of one in coming community and a simultaneous decrease in species of the other out going adjoining community.

A well developed ecotones contain some organisms which are entirely different from that of the adjoining communities.

Sometimes the number of species and the population density of some of the species is much greater in this zone than either community. This is called edge effect For example the density of birds is greater in the mixed habitat of the ecotone between the forest and the desert.


a description of all the biological, physical and chemical factors that a species needs to survive, stay healthy and reproduce. No two species have exact identical niches. Niche plays an important role in conservation of organisms.

Types of Niche

  1. Habitat niche – where it lives
  2. Food niche – what is eats or decomposes & what species it competes with
  3. Reproductive niche -how and when it reproduces.
  4. Physical & chemical niche – temperature, land shape, land slope, humidity & other requirement.


The terrestrial part of the biosphere is divisible into enormous regions called biomes, which are characterized, by climate, vegetation, animal life and general soil type.

No two biomes are alike.

The most important climatic factors are temperature and precipitation.

  1. Tundra- Northern most region adjoining the ice bound poles. Devoid of trees except stunted shrubs in the southern part of tundra biome, ground flora includes lichen, mosses and sedges.

The typical animals are reindeer, arctic fox polar bear, snowy owl, lemming, arctic hare, ptarmigan. Reptiles and amphibians are almost absent

  1. Taiga- Northern Europe, Asia and North America. Moderate temperature than tundra. Also known as boreal forest.

The dominating vegetation is coniferous evergreen mostly spruce, with some pine and firs. The fauna consists of small seed eating birds, hawks, fur bearing carnivores, little mink, elks, puma, Siberian tiger, wolverine, wolves etc.

  1. Temperate Deciduous Forest- Extends over Central and Southern Europe, Eastern North America, Western China, Japan, New Zealand etc.

Moderate average temperature and abundant rainfall. These are generally the most productive agricultural areas of the earth The flora includes trees like beech, oak, maple and cherry. Most animals are the familiar vertebrates and invertebrates.

  1. Tropical rain forest- Tropical areas in the equatorial regions, which is a bound with life. Temperature and rainfall high.

Tropical rainforest covers about 7% of the earth’s surface & 40% of the world’s plant and animal species.

Multiple storey of broad-leafed evergreen tree species are in abundance.

Most animals and epiphytic plants(An epiphyte is a plant that grows harmlessly upon another plant) are concentrated in the canopy or tree top zones

  1. Savannah- Tropical region: Savannah is most extensive in Africa

Grasses with scattered trees and fire resisting thorny shrubs.

The fauna include a great diversity of grazers and browsers such as antelopes, buffaloes, zebras, elephants and rhinoceros; the carnivores include lion, cheetah, hyena; and mongoose, and many rodents

  1. Grassland- North America, Ukraine, etc . Dominated by grasses. Temperate conditions with rather low rainfall. Grasses dominate the vegetation. The fauna include large herbivores like bison, antelope, cattle, rodents, prairie dog, wolves, and a rich and diverse array of ground nesting bird
  2. Desert- Continental interiors with very low and sporadic rainfall with low humidity. The days are very hot but nights are cold. The flora is drought resistance vegetation such as cactus, euphorbias, sagebrush. Fauna : Reptiles, Mammals and birds.

Aquatic Zones

Aquatic systems are not called biomes,

The major differences between the various aquatic zones are due to salinity, levels of dissolved nutrients; water temperature, depth of sunlight penetration.

  1. Fresh Water Ecosystem-Fresh water ecosystem are classified as lotic (moving water) or lentic (still or stagnant water).
  2. Marine Ecosystem-
  3. Estuaries-Coastal bays, river mouths and tidal marshes form theestuaries. In estuaries, fresh water from rivers meet ocean water and the two are mixed by action of tides.

Estuaries are highly productive as compared to the adjacent river or Sea

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