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  2. 2. • You should be able to: 1. Define the terms habitat, niche, population, community and ecosystem, and describe examples of each; 2. Explain the term producer, consumer and trophic level, and state examples of these in specific food chain and food webs; 3. describe how energy is transferred through food chain and food webs; 4. explain how energy losses occur along food chains, and understand what is meant by efficiency of transfer;
  3. 3. Food Chains and Food Webs November 28, 2013 place footer here 3
  4. 4. What is a Food Chain? • A food chain is the path by which energy passes from one living thing to another. November 28, 2013 place footer here 4
  5. 5. What’s in a Food Chain? •Producers •Consumers •Decomposers November 28, 2013 place footer here 5
  6. 6. Producers • Producers make their own food • Green plants use energy from the sun to make food • Producers are on the bottom of the food chain November 28, 2013 place footer here 6
  7. 7. Consumers • Consumers hunt, gather, and store food because they cannot make their own. November 28, 2013 place footer here 7
  8. 8. Three Types of Consumers •Herbivores •Carnivores •Omnivores November 28, 2013 place footer here 8
  9. 9. Herbivores • Animals who eat plants such as: –grasshoppers –rabbits –squirrels –deer –pandas November 28, 2013 place footer here 9
  10. 10. Carnivores • Animals who only eat other animals such as: –tigers –lions –hawks –wolves –cougars November 28, 2013 place footer here 10
  11. 11. Omnivores • Animals who eat both plants and animals such as: –humans –bears November 28, 2013 place footer here 11
  12. 12. Decomposers • Microorganisms that are able to break down large molecules into smaller parts • Decomposers return the nutrients that are in a living thing to the soil November 28, 2013 place footer here 12
  13. 13. Let’s Look at a Food Chain • A food chain is a simplified way to look at the energy that passes from producers to consumers. November 28, 2013 place footer here 13
  14. 14. Types of Food Chains • Aquatic- Water-related food chains with sea plants and animals • Terrestrial- Land-related food chains with land plants and animals November 28, 2013 place footer here 14
  15. 15. Predator & Prey • Predator- An animal that captures and eats other animals • Prey- The animal that is captured and eaten November 28, 2013 place footer here 15
  16. 16. What is a Food Web? • A more realistic way of looking at the relationship of plants and animals in an environment • Several food chains linked together • A predator from one food chain may be linked to the prey of another food chain November 28, 2013 place footer here 16
  17. 17. Food Webs • How many food chains can you make from this food web? November 28, 2013 place footer here 17
  19. 19. NUTRIENT CYCLES: ECOSYSTEM TO ECOSPHERE • Nutrient cycling occurs at the local level through the action of the biota. • Nutrient cycling occurs at the global level through geological processes, such as, atmospheric circulation, erosion and weathering.
  20. 20. NUTRIENT CYCLES • The atoms of earth and life are the same; they just find themselves in different places at different times. • Most of the calcium in your bones came from cows, who got it from corn, which took it from rocks that were once formed in the sea. • The path atoms take from the living (biotic) to the non-living (abiotic) world and back again is called a biogeochemical cycle.
  21. 21. Nutrients: The Elements of Life • Of the 50 to 70 atoms (elements) that are found in living things, only 15 or so account for the major portion of living biomass. • Only around half of these 15 have been studied extensively as they travel through ecosystems or circulate on a global scale.
  22. 22. A GENERALIZED MODEL OF NUTRIENT CYCLING IN AN ECOSYSTEM • The cycling of nutrients in an ecosystem are interlinked by an a number of processes that move atoms from and through organisms and to and from the atmosphere, soil and/or rocks, and water. • Nutrients can flow between these compartments along a variety of pathways.
  23. 23. Nutrient Compartments in a Terrestrial Ecosystem • The organic compartment consists of the living organisms and their detritus. • The available-nutrient compartment consists of nutrients held to surface of soil particles or in solution. • The third compartment consists of nutrients held in soils or rocks that are unavailable to living organisms. • The fourth compartment is the air which can be found in the atmosphere or in the ground.
  24. 24. Uptake of Inorganic Nutrients from the Soil • With the exception of CO2 and O2 which enter though leaves, the main path of all other nutrients is from the soil through the roots of producers. • Even consumers which find Ca, P, S and other elements in the water they drink, obtain the majority of these nutrients either directly or indirectly from producers.
  25. 25. The Atmosphere Is a Source of Inorganic Nutrients • • • The atmosphere acts as a reservoir for carbon dioxide (CO2), oxygen (O2) and water (H2O). These inorganic compounds can be exchanged directly with the biota through the processes of photosynthesis and respiration. The most abundant gas in the atmosphere is nitrogen (N2);about 80% by volume. Its entry into and exit from the biota is through bacteria.
  26. 26. Some Processes By Which Nutrients Are Recycled • Cycling within an ecosystem involves a number of processes. • These are best considered by focusing attention on specific nutrients.
  27. 27. CARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMS • C, H & O basic elements of life; making up from about 98% of plant biomass. • CO2 and O2 enter biota from the atmosphere. • Producers convert CO2 and H2O into carbohydrates (CH2O compounds) and release O2 from water. • Producers, consumers and decomposers convert CH2O compounds, using O2, back into CO2 and H2O.
  28. 28. CARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMS • Carbon and oxygen cycle come out of the air as carbon dioxide during photosynthesis and are returned during respiration. • Oxygen is produced from water during photosynthesis and combines with the hydrogen to form water during respiration.
  29. 29. PHOSPHOROUS CYCLE IN ECOSYSTEMS • Phosphorus, as phosphate (PO4-3), is an essential element of life. • It does not cycle through atmosphere, thus enters producers through the soil and is cycled locally through producers, consumers and decomposers. • Generally, small local losses by leaching are balanced by gains from the weathering of rocks. • Over very long time periods (geological time) phosphorus follows a sedimentary cycle.
  30. 30. NITROGEN CYCLE IN ECOSYSTEMS • Nitrogen (N2) makes up 78% of the atmosphere. • Most living things, however, can not use atmospheric nitrogen to make aminoacids and other nitrogen containing compounds. • They are dependent on nitrogen fixing bacteria to convert N2 into NH3(NH4+).
  31. 31. Biological Sources of Soil Nitrogen • Only a few species of bacteria and cyanobacteria are capable of nitrogen fixation. • Some are fee-living and others form mutualistic associations with plants. • A few are lichens.
  32. 32. Atmospheric Sources of Soil Nitrogen • Lightning was the major source of soil nitrogen until recent times when the burning of fossil fuels became a major source of atmospheric deposition. • Nitrogen oxides come from a variety of combustion sources that use fossil fuels. In urban areas, at least half of these pollutants come cars and other vehicles.
  33. 33. Agricultural Supplements to Soil Nitrogen • Various forms of commercial fertilizer are added to agricultural fields to supplement the nitrogen lost through plant harvest. • Crop rotation with legumes such as soybeans or alfalfa is also practiced to supplement soil nitrogen.
  34. 34. Biological Nitrogen Fixation • Nitrogen fixation is the largest source of soil nitrogen in natural ecosystems. • Free-living soil bacteria and cyanobacteria (blue-green “algae”) are capable of converting N2 into ammonia (NH3) and ammonium (NH4+). • Symbiotic bacteria (Rhizobium) in the nodules of legumes and certain other plants can also fix nitrogen. QuickTimeª and a TIFF (Uncompressed) decompressor are needed to see this picture.
  35. 35. Nitrification • Several species of bacteria can convert ammonium (NH4+) into nitrites (NO2-). • Other bacterial species convert nitrites (NO2-) to nitrates (NO3-).
  36. 36. Uptake of Nitrogen by Plants • Plants can take in either ammonium (NH4+) or nitrates (NO3-) and make amino acids or nucleic acids. • These molecules are the building blocks of proteins and DNA, RNA, ATP, NADP, respectively. • These building blocks of life are passed on to other trophic levels through consumption and decomposition.
  37. 37. Ammonification • Decomposers convert organic nitrogen (CHON) into ammonia (NH3) and ammonium (NH4+). • A large number of species of bacteria and fungi are capable of converting organic molecules into ammonia.
  38. 38. Denitrification • A broad range of bacterial species can convert nitrites, nitrates and nitrous oxides into molecular nitrogen (N2). • They do this under anaerobic conditions as a means of obtaining oxygen (O2). • Thus, the recycling of N is complete.
  39. 39. GLOBAL NUTRIENT CYCLES • The loss of nutrients from one ecosystem means a gain for another. (Remember the law of conservation of matter.) • When ecosystems become linked in this manor, attention shifts to a global scale. One is now considering the ECOSPHERE or the whole of planet earth.
  40. 40. THANK YOU