2. WHAT IS AN ECOSYSTEM?• The term ecosystem was coined in 1930 by Roy Clapham, to denote the physical and biological components of an environment considered in relation to each other as a unit.• Ecosystem means a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit.
6. STRUCTURE AND FUNCTIONS OF AN ECOSYSTEM STRUCTURE An ecosystem usually consists of :• Biotic components• Abiotic components• Interaction between them• Source of energy
7. STRUCTURE AND FUNCTIONS OF AN ECOSYSTEMFUNCTIONS In an ecosystem there are two processes proceeding simultaneously: 1 . Energy flow 2 . Biogeochemical cycle
8. Functions Energy flow• The energy flow is in a single direction and is non-cyclic.• Energy cannot be used indefinitely and is continuously being lost to the environment in the form of heat of being used by the organism for its processes such as digestion, respiration,etc.
9. FunctionsBiogeochemical cycles :• The cyclic flow of nutrients between non- living environment (soil, rocks, air, water) and living organisms is known as biogeochemical cycle.• The major nutrient elements i.e. carbon, hydrogen, oxygen and nitrogen, which form about 95% mass of the living organism, are circulated again and again between living and non-living components of the ecosystem.
10. Carbon Cycle
11. BIOTIC COMPONENETS OF AN ECOSYSTEM• Producers• Consumers o Primary consumers o Secondary consumers o Tertiary consumers• Decomposers
12. Producers• In an ecosystem, producers are those organisms that use photosynthesis to capture energy by using sunlight, water and carbon dioxide to create carbohydrates, and then use that energy to create more complex molecules like proteins, lipids and starches that are crucial to life processes.• Producers, which are mostly green plants, are also called autotrophs.
13. Producers• Role: Producers funnel into the ecosystem the energy needed for its biological processes.• Shaping the ecosystem : The efficiency of the producers in adding energy to the ecosystem determines how robust that ecosystem will be. Efficient producers can enable an ecosystem to support secondary, tertiary or even quaternary consumers.
14. Consumers• Primary consumers: Primary consumers feed directly upon primary producers to obtain their nutrients and energy.
15. Consumers• Tertiary consumersThey feed on secondary consumers.
16. Decomposers• Decomposers are the organisms that clean up after the producers and consumers.• They obtain their own energy by breaking down the remains of the producers and consumers.
17. ENERGY FLOW• Each organism requires energy for survival.• On average about 10 percent of net energy production at one level is passed on to the next level.• Energy is not recycled during decomposition, but rather is released, mostly as heat .
18. ECOLOGICAL SUCCESSION• The process by which the structure of a biological community evolves over time is called as ecological succession.• There are two different types of ecological succession: 1. Primary succession 2.Secondary succession
19. Primary Succession• Primary succession occurs when all previous living organisms have been removed from an area.• Thus, organisms that enter into the uninhabited area start the process of ecological succession.
20. Secondary Succession• It is set in motion by disturbances in the environment which are insufficient to wipe out the previously existing species.
21. Climax Communities• The relative end point of ecological successions referred to as climax communities.• The climax community is an environmental system in which there is little or extraordinarily slow change.
22. FOOD CHAIN• A food chain shows how each living thing gets its food.• Each link in this chain is food for the next link. A food chain always starts with plant life and ends with an animal.
24. Characteristics of food chains1. There are more herbivores than carnivores.2. The further along the food chain you go, the less food (and hence energy) remains available.3. Most food chains have no more than four or five links.
25. FOOD WEB• Most animals are part of more than one food chain and eat more than one kind of food in order to meet their food and energy requirements. These interconnected food chain form a food web.• A food web differs from a food chain in that the latter shows only a portion of the food web involving a simple, linear series of species connected by feeding links
27. ECOLOGICAL PYRAMIDS• An ecological pyramid is an illustration of the reduction in energy as you move through each feeding (trophic) level in an ecosystem.
29. ECOLOGICAL PYRAMIDSThere are three ways an ecological pyramid can be represented.1. Pyramid of Numbers can be generated by counting all the organisms at the different feeding levels.
31. • Pyramid of Biomass where organisms are collected from each feeding level, dried and then weighed. This dry weight (biomass) represents the amount of organic matter (available energy) of the organisms.
33. • Pyramid of Energy Flow This approach necessitates measuring the caloric value of the different organisms that make up the community
35. Summary• Concept of an ecosystem• Structure and function of an ecosystem• Producers,consumers and decomposers.• Energy flow• Ecological succession• Food chains and food webs• Ecological pyramids