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Topic 8: Biosphere and Global Vegetation Belts

Topic 8: Biosphere and Global Vegetation Belts. What is an Ecosystem? Components of an Ecosystem Functions of an Ecosystem - Flow of Energy (Food Chain) - Flow of Materials (Biogeochemical Cycles). Topic 8: Biosphere and Global Vegetation Belts.

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Topic 8: Biosphere and Global Vegetation Belts

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  1. Topic 8: Biosphere and Global Vegetation Belts • What is an Ecosystem? • Components of an Ecosystem • Functions of an Ecosystem- Flow of Energy (Food Chain)- Flow of Materials (Biogeochemical Cycles)

  2. Topic 8: Biosphere and Global Vegetation Belts • Environmental Influences in Biota Survival and Distribution- Environmental Influences- Biota Range of Tolerance- Environmental Adaptations of Plants & Animals

  3. Topic 8: Biosphere and Global Vegetation Belts • Types of Biome        -    Forest Biome        -    Grassland Biome        -    Desert Biome        -    Tundra Biome

  4. What is an Ecosystem? • It is a self-sustaining community of plants and animals as well as the ways they interact with one another and with the non-living physical environment surrounding them • Ecosystem gross structural components: - Biotic Components- Abiotic Components

  5. What is an Ecosystem? • Biotic Components consist of:-    Producers (autotrophs)-    Consumers (heterotrophs) • Abiotic Components consist of:-    inorganic substances (nutrients)-    physical environment

  6. What is an Ecosystem? • Ecosystem functions through the unending flow of energy and materials to its various components • The study of the structure and functions of ecosystems is called Ecology • Biogeography is the study of the variation of ecosystems from place to place

  7. What is an Ecosystem? • Ecosystems are grouped into:- Aquatic ecosystems (water-based ecosystem) • marine ecosystems - open ocean, coastal estuaries, coral reef, etc • freshwater ecosystems - lakes, bogs, marshes - Terrestrial ecosystems (land-based ecosystem)

  8. What is an Ecosystem? • Terrestrial ecosystems (land-based ecosystem):- Biome is the largest recognizable unit of terrestrial ecosystem appropriate for understanding how plants and animals are distributed on the globe- A biome is named on the basis of its dominant plant associations

  9. What is an Ecosystem? - The main types of biome are: • Forest biome (dominated by trees) • Grassland biome (dominated by grasses) • Desert biome (dominated by xerophytes and xeric animals) • Tundra biome (dominated by biota adapted to long & cold climates) - The transition zone between adjoining biomes is called an Ecotone

  10. Ecosystem

  11. Ecosystems

  12. What is an Ecosystem? • Ecosystems exist at various spatial scales • Small to medium scale ecosystem examples include communities of plants & animals in:- a person’s mouth • - a discarded coke can- Cougar lake

  13. Components of An Ecosystem • Components of an ecosystem consist of:- Biotic Components - Abiotic Components • Biotic components consists of:- Primary producers (autotrophs): • Organisms able to produce own food by photosynthesis • They include green plants & algae

  14. Components of An Ecosystem - Consumers (heterotrophs) are organisms that feed on other organisms and they consist of: • Macro-consumers:- herbivores (Plant eaters - sheep)- carnivores (Animal eaters - lion)- omnivores (Plant & animal eaters - humans)

  15. Components of An Ecosystem • Micro-consumers:- decomposers (feed on detritus or decaying organics, e.g. bacteria) - Several levels of consumers: • Primary Consumers:- lowest level of consumers feeding directly on green plants- includes all herbivores

  16. Components of An Ecosystem • Secondary Consumers:- organisms feeding on primary consumers, e.g. frog, medium-sized fish • Abiotic components consist of: • Macro-nutrients:- all nutrients required in large quantity by plants & animals

  17. Components of An Ecosystem • Abiotic components consist of: • Macro-nutrients:- all nutrients required in large quantity by plants & animals, such as • Nitrogen (N) • Phosphorus (P) • Potassium (K) • Calcium (Ca) • Magnesium (mg) • Sulphur (S)

  18. Components of An Ecosystem • Micro-nutrients:- all nutrients required in small quantity but very essential to the functioning of organisms- For example: without molybdenum, soil micro-organisms are unable to transform atmospheric nitrogen into nitrates

  19. Components of An Ecosystem • The Micro-nutrients include: • Boron (B) • Iron (Fe) • Manganese (Mn) • Copper (Cu) • Zinc (Zn) • Cobalt (Co) • Molybdenum (Mo) • Chlorine (Cl)

  20. Components of An Ecosystem • Organic Nutrients consists of:- humus • Physical Environmental Components:- landforms- soils- drainage- rocks- elevation- climatic elements

  21. Functions of An Ecosystem: Food Chain • Ecosystems function through the flow of:- energy (food chain)- materials (biogeochemical cycles • Energy Flow – Food Chain- energy flows from one organism to another in a pathway referred to as the food chainHawkSnakeFrogGrasshopperGrass

  22. Energy Flow in the Biosphere

  23. Functions of An Ecosystem: Food Chain • But energy flow is not orderly linked in nature rather it is best represented as a food web of primary and secondary consumers • Energy is used for sustenance by each organism and only the balance passes on to the next in the food chain or web • hence, energy transfer from one trophic level to another is <100% efficiency

  24. Functions of An Ecosystem: Food Chain • Herbivores store 10%, carnivores store about 10% and decreasing progressively up the trophic levels • Significant loss of energy occurs and wasted as heat energy • Energy is burnt through respiration to produce chemical energy needed to keep the organism operating

  25. Functions of An Ecosystem: Food Chain • The food pyramid shows the number of organisms required to support successive levels of consumers in the food chain • In the food pyramid, the primary producers are largest in number and they occupy the bottom of the pyramid • The number of consumers becomes progressively lower towards the top

  26. Food Pyramid

  27. Functions of An Ecosystem: Food Chain • The next higher level is occupied by primary consumers (e.g. herbivores) feeding on primary producers directly • There are many levels of consumers, with secondary consumers feeding on primary consumers and so on • HawkSnakeFrogGrasshopperGrass(4th consumer)(3rd consumer)(2nd consumer)(1st consumer) (primary producer)

  28. Mass of Living Materials per Unit Area in Different Trophic Levels of an Ecosystem

  29. Functions of An Ecosystem: Food Chain • The decomposers feed on detritus or decaying organic matter and constitute the final link in the pyramid • since every other members of the food chain are dependent on the bottom level, they occur in large quantity, e.g. planktons

  30. Functions of An Ecosystem: Food Chain • For example, it takes a ton of planktons to provide a pound weight gain for a human • But energy flow is not orderly linked in nature rather it is best represented as a food web of primary and secondary consumers

  31. Functions of An Ecosystem: Food Chain • A large number of producers are needed to support a smaller number of herbivores and even fewer carnivores • To obtain enough food, animals at higher trophic levels must have large territorial areas that provide enough of the species at the lower trophic level they eat

  32. Functions of An Ecosystem: Food Chain • Food and energy move along a chain in one direction • Hence, the whole system collapses if an earlier link of the food chain is broken • Example: Removal of a plant species in the food chain may eliminate all higher trophic level species that feed on it

  33. Functions of An Ecosystem: Food Chain • Also, the one direction flow of food in the chain causes materials to be passed along from a lower trophic level to a higher level and their concentrations magnified towards the top by the ecosystem • Hence, the 0.02 ppm of insecticide DDT sprayed on Clear Lake, CA produced higher concentrations at higher trophic level

  34. Functions of An Ecosystem: Food Chain • Clear Lake example shows a progressive increase in DDT density with increasing trophic level:Grebes (Birds)FishSmall herbivoresPlankton • Planktons 5ppm DDT density • Herbivores 15ppm DDT density • Fish 100ppm DDT density • Grebes (birds) 1600ppm DDT density

  35. Functions of An Ecosystem: Food Chain • The grebes that ate the fish died due to biomagnifications of the insecticide by the ecosystem • Non-biodegradable pollutants tend to accumulate in the body of organisms over time  

  36. Functions of An Ecosystem: Biogeochemical Cycles Material Flow Through the Ecosystem • Life in ecosystem is sustained by a number of chemical elements transmitted through the biogeochemical cycles • Examples of Biogeochemical Cycles:- Nitrogen Cycle- Carbon Cycle- Phosphorus Cycle, etc

  37. Functions of An Ecosystem: Biogeochemical Cycles • While energy could be lost from the biosphere during its flow through the ecosystem, materials in biogeochemical cycles are conserved and re-used or re-cycled

  38. Functions of An Ecosystem: Biogeochemical Cycles Nitrogen Cycle: • Only few soil bacteria and blue-green algae use gaseous nitrogen directly • For other species, nitrogen must first be converted into nitrogen compounds (nitrates) (nitrogen fixation)before they could be used

  39. Nitrogen Cycle

  40. Nitrogen Cycle

  41. Functions of An Ecosystem: Biogeochemical Cycles • Nitrogen fixation is accomplished by:-    lighting, cosmic radiation, marine organisms in very small amount-    soil micro-organisms (Azotobacter bacteria) and others in plant root nodules (Rhizobia bacteria) in large amount • Usable nitrogen is assimilated by green plants in the form of nitrates

  42. Rhizobia Bacteria in Root Nodules Nodules

  43. Nitrogen Cycle

  44. Functions of An Ecosystem: Biogeochemical Cycles • Animals feeding on plants assimilate the usable nitrogen indirectly • Unused nitrates return to the soil as animal wastes, dead plants and animals • Certain bacteria convert the nitrates in the wastes into nitrites and some species convert the nitrites into nitrates for re-use by green plants

  45. Functions of An Ecosystem: Biogeochemical Cycles • Some bacteria (coliform, rhizobium, citrobacter, clostridium) convert the nitrates into nitrogen gas in a process called denitrification • Nitrogen returns to the atmosphere where it will go through another cycle

  46. Carbon Cycle

  47. Functions of An Ecosystem: Biomass • Biomass is the dry organic matter weight of an ecosystem given in gm/m2/yr • It’s the net productivity (photosynthesis minus respiration) of an ecosystem or accumulated organic matter • Tropical lowland rainforests have the highest biomass (2200gm/m2/yr)

  48. Functions of An Ecosystem: Biomass • Biomass is lowest in deserts, highlands, and high latitudes • Biomass from different climates:- Tropical Rainforest 2200 gm/m2/yr- Temperate Evergreen forest 1300 gm/m2/yr- Boreal forest 800 gm/m2/yr- Tropical Grassland 900 gm/m2/yr- Temperate Grassland 600 gm/m2/yr- Cultivated Land 650 gm/m2/yr

  49. Annual Global Pattern of Biomass

  50. Ecosystem of a Pond

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