What is an Ecosystem?

Term proposed by British ecologist A. G. Tansley in 1935.

An Ecosystem is a Natural unit.

Consisting of all Plants, Animals and Micro- organisms in an area functioning together with all the physical & chemical (soil, climate, water and light) factors of the environment.

An ecosystem is formed by the interactions between all living and non-living things.

Eco = the Environment; System = regularly interacting and interdependent components forming a unified whole.

Ecosystem = an Ecological system; = A community and its physical environment

treated together as a functional system.

An Ecosystem

Fundamental Characteristics of Ecosystem:

Structure:– Living/Biotic (Plants, Animals and Micro- organisms )

– Non-living/Abiotic (soil, climate, water and light ) Process:

– Energy flow– Cycling of matter (chemicals)

Change:– Dynamic/ Changing (not static)

Types of Ecosystem:

The kind of organism which can live in a particular ecosystem depends upon their physical and metabolic adaptations to the environment.

On earth there are number of ecosystems within a geographical region which are exposed to same climatic conditions & having dominant species with similar life cycle, climatic adaptations and physical structure.

This set of ecosystems is called “BIOME” In the Biosphere, there are – Natural & Artificial biomes.

Natural Biomes (Ecosystems): Natural ecosystems operate by themselves under natural conditions

without interference of man They carry out many functions for us.

Wastewater is converted to drinkable water by filtration through natural ecosystems, such as soils.

Air pollutants from industries & automobiles are often trapped on leaves or converted to harmless compounds by forests.

On the basis of particular type of habitat, they are further sub divided as:

Terrestrial Ecosystems (Biomes): They are often defined by the vegetation types that dominate the

community. Terrestrial vegetation has a rapid exchange of oxygen, water &

carbon dioxide. Moisture is the major limiting factor, faces the problem of

dehydration. Extremes of temperature are more pronounced. Soil acts as highly developed ecological subsystem.

Types of Ecosystem:

Examples of terrestrial ecosystem are: Forest ecosystem. Grassland ecosystem Desert ecosystem. Aquatic Ecosystems (Biomes): Aquatic ecosystems deal with biotic community present in water

bodies. Aquatic organisms have the same basic needs as the terrestrial

organisms However difference lies in the form in which they are made

available to them. In terrestrial ecosystem, carbon dioxide and oxygen are present in

gaseous form, but in aquatic ecosystem these are made available in dissolved state.

Types of Ecosystem:

Aquatic ecosystems fall into two categories: Freshwater Ecosystem and Marine Ecosystem. Freshwater ecosystem may be:

Lotic (Running water) Example: Streams, Rivers, Springs

Lentic (Standing water) Examples: Lakes, ponds, swamps

Marine ecosystems includes Deep sea and Oceans.

Types of Ecosystem:

Components of Ecosystem:

Abiotic components: Abiotic components are non - living chemical & physical

factors in the environment. They practically provides all the energy for ecosystems. They are of two forms:

(i) Climatic:

Temperature, humidity, precipitation, light etc. (ii) Edaphic:

Topography, pH, minerals, back-ground.

Components of Ecosystem: Biotic components: Biotic components refer to the living world of an ecosystem. They are in entirety, any living component that affects

another organism. They are of two forms:

Autotrophs: Organisms that produce their own food from an energy

source, such as the sun, and inorganic compounds. They are also called “PRODUCERS”

Examples; Green Plants.Heterotrophs:

Organisms that consume other organisms as a food source.Examples: Cows; Lions; Vultures

Structure of an Ecosystem:

Ecosystem can be described according to its Trophic structure.

The trophic structure constitutes the levels of feeding (trophic = food) and the feeding relationships of the components of the ecosystem.

• Trophic structure is the pattern of movement of energy and matter through an ecosystem.

All ecosystems must be based upon “Autotrophs”.

Autotrophs (Self feeders) produce organic food for themselves and all members of their community.

The green plants (with chlorophyll) & certain bacteria produce food.

Since these organisms produce food for all the other organisms, they are known as “Producers”

Autotrophs (Greek; auto = self & trophe = nutrition) take energy from the environment in the form of sunlight or inorganic chemicals and use it to create energy-rich molecules such as Carbohydrates.

Green plants & photosynthtic bacteria are able to do this by means of Photosynthesis, where the sun provides the necessary energy.

Therefore these green plants are the autotrophic organisms or primary producers in most ecosystems.

Structure of an Ecosystem:

Examples of producers:

Photosynthetic Photosynthetic BacteriaBacteria

GrassesGrasses ShrubsShrubs

TreesTrees

A Heterotrophs (Greek; heteros = another & trophe = nutrition) are an organisms that uses organic substrates to get its chemical energy for its life cycle.

It is the component in which utilization, rearrangement & break down of complex organic substances predominate.

They are dependant upon autotrophic organisms. The members (organisms) of heterotrophic component are called

“Consumers” The heterotrophs are further categorized as: Macro- Consumers: Heterotrophs, which in an order as they occur in a food chain are:

Structure of an Ecosystem:

1) Herbivores: Also primary consumers, feed directly on living plants or plant residues. They have vegetarian diet.

Structure of an Ecosystem:

2) Carnivores: Also secondary/ tertiary consumers, which feed on consumers, i.e. they have non- vegetarian diet.

They are also called “Predators”

Structure of an Ecosystem:

3) Omnivores: Consumers, which feed on producers as well as on primary consumers, i.e. they have vegetarian as well as non- vegetarian diet.

Structure of an Ecosystem:

Micro-consumers: Also Saprotrophs/ Detritivores . They are popularly known as decomposers, such as bacteria, fungi, flagellates & actinomyctes.

They feed on organic compounds of dead or living protoplasm of plants and animals for their food and energy

They absorb some of the decomposition or breakdown products & release inorganic compounds (nutrients) in the ecosystem, making them available again to producers.

Structure of an Ecosystem:

In simple words, structure of an ecosystem means: The composition of biological community including species,

population, biomass, life history. The quantity & distribution of abiotic materials The range of conditions of existence, such as temperature, light,

humidity, wind, wave action etc.

Structure of an Ecosystem: