Ecosystem

History of EcosystemHistory of Ecosystem The term ecosystem first appeared in a 1935 The term ecosystem first appeared in a 1935

publication by the British ecologist Arthur Tansley publication by the British ecologist Arthur Tansley (1935). However, the term had been coined already (1935). However, the term had been coined already in 1930 by Tansley's colleague Roy Clapham.in 1930 by Tansley's colleague Roy Clapham.

Tansley (1939) expanded on the term in his later Tansley (1939) expanded on the term in his later work, adding the Ecotope concept to define the work, adding the Ecotope concept to define the spatial context of ecosystemsspatial context of ecosystems

According to woodbury (1954)According to woodbury (1954) Ecosystem is a complex in Ecosystem is a complex in which habitat, plants and animals are considered as one which habitat, plants and animals are considered as one interesting unit, the materials and energy of one passing interesting unit, the materials and energy of one passing in and out of the others.in and out of the others.

According to E.P. OdumAccording to E.P. Odum, the ecosystem is the basic , the ecosystem is the basic functional unit of organisms and their environment functional unit of organisms and their environment interaction with each other and with their own interaction with each other and with their own components.components.

e.g. One square meter of grassland, a large lake, a large e.g. One square meter of grassland, a large lake, a large tract of forest, balanced aquarium, a certain area of river tract of forest, balanced aquarium, a certain area of river and ocean. All the ecosystems of the earth are connected and ocean. All the ecosystems of the earth are connected to one another, like, river ecosystem is connected with to one another, like, river ecosystem is connected with the ecosystem of ocean, and a small ecosystem of dead the ecosystem of ocean, and a small ecosystem of dead logs is a part of large ecosystem of a forest. A complete logs is a part of large ecosystem of a forest. A complete self-sufficient ecosystem is rarely found in nature but self-sufficient ecosystem is rarely found in nature but situations approaching self-sufficiency may occur. situations approaching self-sufficiency may occur.

Structure of EcosystemStructure of EcosystemThe structure of an ecosystem is basically a The structure of an ecosystem is basically a

description of the organisms and physical description of the organisms and physical features of environment including the features of environment including the amount and distribution of nutrients in a amount and distribution of nutrients in a particular habitat. From the particular habitat. From the structure point structure point of view, all ecosystems consist of the of view, all ecosystems consist of the following basic components:following basic components:

1.1. Abiotic componentsAbiotic components

2.2. Biotic componentsBiotic components

Abiotic Components:Abiotic Components: An ecosystem possesses both An ecosystem possesses both biotic (living) and abiotic non-living components. biotic (living) and abiotic non-living components. The The abiotic componentsabiotic components include soil, water, light, include soil, water, light, inorganic nutrients and weather inorganic nutrients and weather

Biotic Components:Biotic Components: The The biotic components biotic components of the of the ecosystem can be categorized as either producers or ecosystem can be categorized as either producers or consumers. Producers are autotrophic organisms with consumers. Producers are autotrophic organisms with the capability of carrying out photosynthesis and the capability of carrying out photosynthesis and making food for themselves, and indirectly for the making food for themselves, and indirectly for the other organisms as well. In terrestrial ecosystems the other organisms as well. In terrestrial ecosystems the producers are predominantly green plants, while in producers are predominantly green plants, while in freshwater and marine ecosystems the dominant freshwater and marine ecosystems the dominant producers are various species of algae. producers are various species of algae.

Biotic componentsBiotic componentsThe biotic components include all living The biotic components include all living

organisms present in the environmental organisms present in the environmental system. From system. From nutrition point nutrition point of view, the of view, the biotic components can be grouped into three biotic components can be grouped into three basic components:basic components:

1.1. ProducerProducer

2.2. Consumers and Consumers and

3.3. Decomposers or reducers and transformersDecomposers or reducers and transformers

1.1. ProducersProducersThe producers are the autotrophic elements –chiefly green The producers are the autotrophic elements –chiefly green

plants. They use radiant energy of sun in photosynthetic plants. They use radiant energy of sun in photosynthetic process whereby carbon dioxide is assimilated and the process whereby carbon dioxide is assimilated and the light energy is converted into chemical energy. The light energy is converted into chemical energy. The chemical energy is actually locked up in the energy rich chemical energy is actually locked up in the energy rich carbon compounds. Oxygen is evolved as byproduct in carbon compounds. Oxygen is evolved as byproduct in the photosynthesis. the photosynthesis.

This is used in respiration by all living things. Algae and This is used in respiration by all living things. Algae and other hydrophytes of a pond, grasses of the field, trees of other hydrophytes of a pond, grasses of the field, trees of the forests are examples of producer. Chemosynthetic the forests are examples of producer. Chemosynthetic bacteria and carotenoid bearing purple bacteria that also bacteria and carotenoid bearing purple bacteria that also assimilate carbon-dioxide with the energy of sunlight but assimilate carbon-dioxide with the energy of sunlight but only in the presence of organic compounds also belong to only in the presence of organic compounds also belong to this category.this category.

2.2. ConsumerConsumerThose living members of ecosystem which consume the Those living members of ecosystem which consume the

food synthesized by producers are called consumers. food synthesized by producers are called consumers. Under this category are included all kinds of animals Under this category are included all kinds of animals that are found in an ecosystem. There are different that are found in an ecosystem. There are different classes or categories of consumers that are discussed classes or categories of consumers that are discussed in following.in following.

Primary consumers:Primary consumers: Those are dependent on Those are dependent on producers or green plants for their food called producers or green plants for their food called primary consumers (purely herbivorous). e.g. Insects primary consumers (purely herbivorous). e.g. Insects rodents rabbit, cow, goat for terrestrial ecosystem. On rodents rabbit, cow, goat for terrestrial ecosystem. On the other hands crustaceans, molluscs etc. for aquatic the other hands crustaceans, molluscs etc. for aquatic habitat. habitat.

According to Elton, 1939 primary consumers are the According to Elton, 1939 primary consumers are the “Key industry animals” in a particular ecosystem.“Key industry animals” in a particular ecosystem.

Secondary consumers: Those animals are adapted to consume herbivores as well as plants as their food called secondary consumers. They are carnivores and omnivores. e.g. sparrow, crow, fox etc.

Tertiary consumers: These are the top carnivores which prey upon secondary consumers as well as other carnivores, omnivores and herbivores. Lions, tigers hawk, vulture etc. are considered as tertiary or top consumers.

Parasites, scavengers and saprobes: They are consumers. The parasitic plants and animals utilize the living tissues of different plants and animals. The scavengers and saprobes utilize dead remains of animals and plants as their food.

3.3. Decomposers and transformersDecomposers and transformers Decomposers attack the dead remains of producers Decomposers attack the dead remains of producers

and consumers and degrade the complex organic and consumers and degrade the complex organic substances into simpler compounds. substances into simpler compounds.

The simple organic matters are then attacked by The simple organic matters are then attacked by another kind of bacteria, the transformers which another kind of bacteria, the transformers which change these organic compounds in to the inorganic change these organic compounds in to the inorganic forms that are suitable for reuse by producers of forms that are suitable for reuse by producers of green plants. green plants.

The decomposers and transformers play very The decomposers and transformers play very important role in maintaining the dynamic nature of important role in maintaining the dynamic nature of ecosystems.ecosystems.

Function of EcosystemFunction of Ecosystem

Action of biotic and abiotic components with the help Action of biotic and abiotic components with the help of solar energy through the ecosystem is called of solar energy through the ecosystem is called function of ecosystem. In any ecosystem we have the function of ecosystem. In any ecosystem we have the following functional components;following functional components;

1. Inorganic constituents (air, water and mineral salts)1. Inorganic constituents (air, water and mineral salts)2. Organisms (plants, animals and microbes) and 2. Organisms (plants, animals and microbes) and 3. Energy input which enters from outside ( the sun)3. Energy input which enters from outside ( the sun)

The principal steps in the operation of The principal steps in the operation of ecosystemecosystem

Thus the principal steps in the operation of ecosystem Thus the principal steps in the operation of ecosystem are as follows:are as follows:

1. Reception of radiant energy of sun.1. Reception of radiant energy of sun.2. Manufacture of organic materials from inorganic 2. Manufacture of organic materials from inorganic

ones by producers, ones by producers, 3. Consumption of producers by consumers and further 3. Consumption of producers by consumers and further

elaboration of consumed materials and elaboration of consumed materials and 4. After the death of producers and consumers, complex 4. After the death of producers and consumers, complex

organic compounds are degraded and finally organic compounds are degraded and finally converted by decomposers and converters into such converted by decomposers and converters into such forms as are suitable for reutilization by producers. forms as are suitable for reutilization by producers.

Solar energy Solar energy

producerproducer

primary consumers primary consumers primary primary carnivores carnivores

dead remains dead remains secondary secondary

carnivorescarnivores

Raw materialsRaw materials decomposersdecomposers

Flow of energy at different levels of ecosystem.Flow of energy at different levels of ecosystem.

Solar energy Solar energy

producerproducer

primary consumers primary consumers primary primary carnivores carnivores

dead remains dead remains secondary secondary

carnivorescarnivores

Raw materialsRaw materials decomposersdecomposers

Flow of energy at different levels of ecosystem.Flow of energy at different levels of ecosystem.

A

B

C

D