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Presentation G 2

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  • 1. OPTION G ECOLOGY AND CONSERVATION G2 Ecosystems and biomes
  • 2. G.2.1 Define gross production , net production and biomass . (1)
    • Productivity refers to the quantity of energy fixed per unit area per unit time in an ecosystem by a particular trophic level. ( Biology Course Companion )
    • Gross Production = the amount of light energy converted to chemical energy by autotrophs in an ecosystem. Also called primary productivity.
    • Net Production = Energy able to be passed on by producers to consumers. The gross production is reduced by the loss of energy through cellular respiration.
    • Net production numbers are used to create the next level of an energy pyramid (also called a productivity pyramid).
  • 3. G.2.2 Calculate values for gross production and net production using the equation: gross production – respiration = net production. (2)
    • Just remember that gross energy minus energy lost equals net energy.
    • You might be asked to use this equation when interpreting or creating an energy pyramid.
    • Primary production can be used to compare biomes.
  • 4. G.2.3 Discuss the difficulties of classifying organisms into trophic levels. (3)
    • The following answers are from a sample IB test question. The question was “ Discuss, giving examples, the difficulties of placing organisms in higher trophic levels .” This was a 4 point question.
    • In food webs, organisms often occupy two levels.
    • Some organisms eat prey from different trophic levels.
    • Not all feeding habits of all organisms are known.
    • Feeding habits may vary seasonally or during the life cycle.
    • As you move up the food chain, less energy is available.
    • Broad diet is needed to ensure adequate energy intake.
    • Examples were expected.
  • 5. G.2.4 Explain the small biomass and low numbers of organisms in higher trophic levels. (3)
    • The shortness of food chains can be attributed to the loss of energy between trophic levels.
    • In general, only about 10% of the energy from one trophic level is available to the next trophic level.
    • This 10% rule of thumb also explains why few carnivores can be supported in a food web.
    • The amount of energy available to top-level consumers is small compared with that available to lower-level consumers. Only a fraction of the energy from photosynthesis flows through a food chain to top-level consumers.
  • 6. G.2.4 Explain the small biomass and low numbers of organisms in higher trophic levels. (3)
    • This explains why top-level consumers such as lions and hawks require so much territory; it takes a lot of vegetation to support trophic levels that are many steps removed from the photosynthetic level.
    • An energy pyramid also explains why meat is a luxury for humans. Producing meat for human consumption means more land be cultivated; more water, fertilizers and pesticides are needed.
  • 7. G.2.4 Explain the small biomass and low numbers of organisms in higher trophic levels. (3)
    • Energy losses between trophic levels also result in pyramids based on the number of organisms or the amount of biomass at each trophic level.
  • 8. G.2.5 Construct a pyramid of energy, given appropriate information. (3) Tertiary consumers Secondary consumers Primary consumers Producers 10 kcal 100 kcal 1,000 kcal 10,000 kcal 1,000,000 kcal of sunlight
  • 9. G.2.5 Construct a pyramid of energy, given appropriate information. (3)
    • Your pyramid of energy should look like the diagram on the previous slide.
    • Solar energy IS NOT included in pyramid, unlike the example.
    • See handout with sample question and answer rubric.
      • correct pyramid shape; correct values and unit given; (correctly calculated as energy passed to secondary consumer); producer and primary consumer values correctly inserted ;
      • Award [2 max] if there are units omitted. Award [2 max] if a bar is included for the solar energy. Do not deduct marks if the areas of the bars are not proportional to the values, although they should get smaller going up.
  • 10. G.2.6 Distinguish between primary and secondary succession, using an example of each. (2)
    • Biotic factors may actually change the abiotic factors in an environment to such extent that the environment becomes limiting to them and other species become more suited. This is known as succession .
    • Primary succession occurs in areas where there is no soil formation.
    • Secondary succession is the progression of communities where a pre-existing climax community has been disturbed but the soil is already developed.
    • During succession, initial changes are often much more rapid than subsequent changes.
  • 11. G.2.6 Distinguish between primary and secondary succession, using an example of each. (2) A pioneering group of plant species will arrive on the island contribute to the development of an ecosystem that will eventually stabilize with different dominant species. The change in dominant species with time occurs as a result of the pioneering species altering the abiotic conditions such that other species become more suited.
  • 12. G.2.7 Outline the changes in species diversity and production during primary succession. (2)
    • Gross productivity rises as small plants are replaced by larger plants. Biomass increases.
    • Increase in productivity at autotroph level is transmitted to upper trophic levels.
    • Succession increases species diversity.
  • 13. G.2.7 Outline the changes in species diversity and production during primary succession. (2) Here is one example of primary succession. Often the only life forms present are autotrophic bacteria. Lichens and mosses grow from windblown spores. Soil develops gradually as rocks weather and organic material accumulates.
  • 14. G.2.8 Explain the effects of living organisms on the abiotic environment, with reference to the changes occurring during primary succession. (3)
    • Ecologists have studied primary succession on the rocky moraines left by retreating glaciers around Glacier Bay, Alaska, and have identified a predictable pattern of changes in vegetation and soil characteristics.
    • Early pioneering species include Dryas , a mat-forming shrub, which is later replaced with stands of alder. Both of these species have symbiotic nitrogen-fixing bacteria, which improve the soil for later plant species.
    • Later spruce trees use the soil nitrogen and lower the soil pH as the trees’ acidic needles decompose.
    • By altering soil properties, pioneer plant species permit new species to grow, and the new plants in turn alter the environment.
    • By about 300 years after glacial retreat, spruce-hemlock forest dominates the area.
  • 15. G.2.9 Distinguish between biome and biosphere . (2)
    • A biome is an ecological region dominated by a certain type of ecosystem characterized by certain precipitation and temperature conditions leading to a distinctive biological community adapted t those conditions.
    • Our biosphere is composed of these biomes. Mader defines biosphere as the “zone of air, land, and water at the surface of the Earth in which living organisms are found”.
    • Atmosphere = air
    • Lithosphere = land
    • Hydrosphere = water
  • 16. G.2.10 Explain how rainfall and temperature affect the distribution of biomes. (3)
    • The distribution of biomes is determined by physical factors such as climate (principally temperature and rainfall), which varies according to latitude and altitude.
    • Use the information on the climograph for the biomes from G.2.11.
  • 17. G.2.11 Outline the characteristics of six major biomes. (2)
    • Desert
    • Grassland
    • Shrubland
    • Temperate deciduous forest
    • Tropical rainforest
    • tundra
    • Temperature
    • Moisture (rainfall)
    • Vegetation
    • Did you keep notes from your biome project?