(i) Terrestrial Ecosystems:

They are known by the type of main vegetation in them. For example, grassland ecosystems have grass as main vegetation.

(ii) Aquatic Ecosystems:

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They are known by the type of habitat. They can be of estuarine, marine and freshwater types of ecosystems.

The freshwater ecosystems can be of standing freshwater ecosystems (or lentic ecosystems) or Running freshwater ecosystems (or lotic ecosystems).

Examples Ponds, lakes etc. are examples of lentic ecosystems and river, springs etc. are examples of lotic ecosystems.

2. Artificial Ecosystems:

These ecosystems are controlled and manipulated by humans. These are created by humans in order to fulfill certain needs. Broadly they are sub-classified into following two types:

(i) Agriculture ecosystem

(ii) Aquaculture ecosystem

Similarities between Natural and Arificial Ecosystems: Both are open systems with no constraints of boundaries.

Both have all the essential components such as abiotic and biotic members. Both permit constant interaction between biotic and abiotic components.

Components of Ecosystems

I. The different components of the forest ecosystems are:

(i) Abiotic components:

The minerals present in the forest and all organic (litters, debris) and inorganic substances present in the soil and the atmosphere constitute the abiotic components.

(ii) Biotic components:

All living components viz. producers, consumers and decomposers constitute the biotic components of forest.

(a) Producers:

Big trees, medium sized bush, small herbaceous plants, or any vegetation of the forest is the producer, which performs photosynthesis.

(b) Consumers:

Primary Consumers:

They graze over the primary producer. Examples Elephants, mongooses, squirrels, deer; birds and insects like flies, spiders, ants, etc.

Secondary Consumers:

They are the predators of primary consumers. They regulate the population size of primary consumers and thereby their grazing activity. Examples Jackal, fox, eagle, snake, etc

Tertiary Consumers:

They feed on secondary consumers and are also known as top carnivores. Examples lions, tigers, etc

(c) Decomposers

They have the ability to degrade all dead organisms to release nutrients into the soil which are again used by producer. They remain confined to the soil of the forest floor. Examples Earthworms, bacteria, fungi, protozoa, nematodes, etc

II. Aquatic Ecosystem :

An aquatic ecosystem is an ecosystem located in a body of water.

Biotic and abiotic components (which are self-regulating and self-sufficient) constitute an aquatic ecosystem. About 70% of the earth’s total surface is under the aquatic ecosystem. Broadly, an aquatic ecosystem is of following three types: Freshwater ecosystem, marine ecosystem and estuarine ecosystem.

Pond Ecosystem (or freshwater ecosystem)

The different components of a pond ecosystem are as follows:

(i) Abiotic components:

Oxygen, carbon dioxide, water, nitrogen, phosphorus, calcium, amino acids, etc. are abiotic components of a pond ecosystem.

(ii) Biotic components:

They consist of the following:

(a) Producers:

Some photosynthetic bacteria and the autotrophic green plants fix the solar energy with the help of nutrients obtained from the mud of the pond.

(b) Consumers:

I. Primary Consumers:

They feed on the producers. Examples Herbivores like zoo plankton and small invertebrates like copepod.

II. Secondary Consumers:

They feed on primary consumers. Examples Small carnivores like small fishes. H Tertiary Consumers: They feed on secondary consumers. Examples Large fishes

(c) Decomposers

They help in the release and recycling of nutrients. They decompose the organisms and are present at the base of the pond. Examples Bacteria, Fungi, etc

Functions of Aquatic Ecosystem

Aquatic ecosystem performs following environmental functions:

i. They recycle nutrients.

ii. They purify water.

iii. They recharge ground water.

iv. They provide habitats for wildlife.

v. They attenuate floods.

vi. They are used for human recreation.

III. Grassland Ecosystem:

Grasslands are areas where the vegetation is dominated by grasses and other non-woody plants.

Grassland ecosystem is a biological community that contains grasslands.

About 32% of the plant cover of the world is covered with grasslands. The most fertile and productive soils in the world have developed under grassland. Generally, the natural species have been replaced by cereals (cultivated grasses).

Grasslands occur in regions too moist for deserts and too dry for forests. The annual rainfall in grasslands is usually seasonal. It ranges between 25 cm to 75 cm.

The principal grasslands include:

(i) Steppes (Europe and Asia)

(ii) Prairies (Canada, USA)

(iii) Pampas (South America)

(iv) Veldts (Africa)

The dominant animal species in grassland ecosystems include large mammals in highest abundance and greatest diversity.

Examples Horses, asses, antelope, Herds of Bison, etc.

Various Components of a Grassland Ecosystem are given below:

(i) Biotic Components

(1) Producer organisms:

Mainly grasses and a few herbs and shrubs contribute to primary production of biomass.

(2) Consumers:

Three main types of consumers in grassland are:

(a) Primary Consumers:

They are herbivores feeding directly on grasses. These are grazing animals. Examples Cows, buffaloes, goats, sheeps, deer, rabbits, etc.

(b) Secondary Consumers:

They are carnivores that feed on herbivores. Examples Frogs, snakes, birds, foxes, lizards, etc

(c) Tertiary Consumers:

They feed on secondary consumers. Examples Hawks, tigers, lions, etc

(3) Decomposers:

They attack the dead or decayed bodies of organisms, and play an active role in their decomposition. In this decomposition process, nutrients are released for reuse by producers. Examples Bacteria, Fungi, Actinomycetes, etc

(ii) Abiotic Components:

Abiotic components include inorganic and organic compounds present in the soil and aerial environment.

The essential elements like C, H, N, O, P, S, etc. are supplied by water, nitrates, sulphates, phosphates present in soil and nitrogen present in atmosphere.

IV. Desert Ecosystem

Desert refers to a region or landscape in which the rainfall is negligible; annual rainfall is less than 250 millimeters. They occupy about 17% of the earth’s surface.

Deserts are characterized by:

(i) Scanty flora and fauna,

(ii) Hot days and cold nights,

(iii) Soils with abundant nutrients but little or no organic matter.

The structure and functions of desert ecosystem

The structure and functions of biotic and abiotic components of a desert ecosystem are as follows:

(i) Abiotic Components:

Nutrients present in the soil and air are abiotic components. The organic substances are poorly present in the soil because of very low rainfall and high temperature.

(ii) Biotic Components:

Biotic components are producer, consumer and decomposers.

(1) Producers:

In a desert, producers are mainly shrubs/bushes, some grasses and a few trees. Examples Water retaining plants adapted to arid climate or soil conditions (Succulents), hard grasses.

(2) Consumers:

They include animals which are capable of living in xeric conditions. Examples Insects, reptiles, etc

Some nocturnal rodents, birds and some mammalians like Camel etc. are also found.

(3) Decomposers:

In desert ecosystems, decomposers are very less due to less vegetation and very low amount of dead organic matter. Examples Bacteria and thermophillic bacteria.