exam questions

Cards (8)

  • explain why the value for GPP is lower than the light energy available to the ecosystem(3)
    • not all of the light falls on the leaves/plant
    • some of the light is reflected from the surface of the leaf
    • some of the light misses the chloroplasts and passes through the leaf
    • some of the light is the wrong wavelength thus not absorbed by the chlorophyll
  • explain why respiration affects the production of biomass(3)
    • GPP-R=NPP
    • organic molecules/glucose are used in respiration to provide energy
    • because some organic molecules/glucose are used in respiration, the less is available for the production of biomass
  • Succession
    The gradual changes in an ecosystem over time as new species arrive and others decline
  • Primary Succession
    1. Pioneer species colonise bare land
    2. Pioneers change environment by forming soil/humus
    3. Pioneer species germinate easily and withstand harsh conditions
    4. Environment becomes less hostile for other/new species
    5. Decomposition of pioneers helps form soil
    6. Arrival of grasses and small plants adapted to shallow/nutrient-poor soils
    7. Roots of small plants help hold soil in place
    8. Environment becomes more suitable for other/new species
    9. Soil becomes deeper/more nutrient-rich to support larger shrubs/trees
    10. Change/increase in diversity/biodiversity
    11. Final species becomes the dominant climax community
  • Succession occurs in a range of natural ecosystems
  • explain why net production of consumers is less than the net production from producers(4)
    • not all of the energy available from the producer is taken up
    • Some parts of the grass are not eaten
    • Some parts of the grass is not digestible by the deer (so the energy it contains is not passed on to the deer)
    • Some energy is lost to the environment as respiratory losses
    • Some energy is lost due to excretion from consumer
  • explain why it is rare to find a natural food chain which has more than 5 trophic levels(4)
    • Energy is lost (from organisms) at each trophic level
    • There is insufficient energy remaining to support further trophic levels
    • (Approximately) 90% of energy is lost at each tropic level
  • explain why 2 species occupying different niches is an advantage(3)
    • Reduced competition for a resources/food/shelter
    • Ensures both species survive and can reproduce