What is an Ecosystem?

1. 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.

2. Ecosystem = an Ecological system; = A community and its physical environment treated together as a functional system. An Ecosystem

3. 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)‏

4. 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.

5. Types of Ecosystem: • 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.

6. 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.

7. 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.

8. 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.

9. 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

10. 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”

11. Structure of an Ecosystem: • 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.

12. Examples of producers: Photosynthetic Bacteria Shrubs Grasses Trees

13. Structure of an Ecosystem: • 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:

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

15. 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”

16. 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.

17. 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.

18. 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.