 What is an Ecosystem?  Term proposed by British ecologist A. G. Tansley in  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.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 Bacteria Grasses Shrubs Trees

 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: