B4

• Give 3 molecules which are cycled through ecosystems.

  • Oxygen
  • Carbon dioxide
  • Water
• Briefly describe how water is cycled through an ecosystem.

  • Water evaporates from rivers and lakes and from transpiration.
  • Water condenses as clouds.
  • Water is returned through precipitation.
• Briefly describe how carbon dioxide is cycled through an ecosystem.

  • Carbon dioxide is fixed through photosynthesis.
  • Respiration releases carbon dioxide.
  • Decomposition releases carbon dioxide.
  • Combustion releases carbon dioxide.
• Briefly describe how nitrogen is cycled through an ecosystem.

  • Nitrogen is fixed by lightning, the Haber process and bacteria.
  • Denitrifying bacteria releases nitrogen back to the atmosphere.
• Why is recycling in ecosystems necessary?

  • To create a continuous flow of nutrients.
  • To provide fresh water.
• How would a decrease in oxygen availability affect the rate of decomposition?

  • Lack of oxygen causes microorganisms to respire anaerobically.
  • Anaerobic decay is slower than aerobic decay.
• How would a decrease in water availability affect the rate of decomposition?

  • Decomposing microorganisms need water for chemical processes.
  • The less water available, the slower the rate of these processes.
• How would a change in temperature affect the rate of decomposition?

  • A decrease in temperature slows the rate of decomposition reactions.
  • A large increase in temperature will denature enzymes, slowing or even stopping decomposition.
• Give 4 abiotic factors that affect communities.

  • Light intensity
  • Temperature
  • Soil pH
  • Moisture levels
• Give 4 biotic factors that affect communities.

  • Number of predators
  • Food availability
  • Disease
  • Human activity
• What are the 3 types of interdependence?

  • Mutualism
  • Parasitism
  • Predation
• What is parasitism?

  • Where one organism lives on another and takes nutrients from the other organism.
  • This is beneficial to the parasite and detrimental to the host.
• What is mutualism?

  • Two organisms depend on each other.
  • Both of the organisms benefit from the relationship.
• What is predation?

  • The act of one organism (predator) hunting, killing, and consuming another organism (prey).
  • Only one organism in he relationship gains, the other suffers.
• Give 4 things animals compete for.

  • Mates
  • Space
  • Food
  • Water
• Give 4 things that plants compete for.

  • Light
  • Water
  • Minerals
  • Space
• What is a producer?

  An organism that makes its own food.
• What is a primary consumer?

  An organism that feeds on producers.
• What is a secondary consumer?

  An organism that feeds on primary consumers.
• What is biomass?

  The dry mass of all of the living organisms in an area.
• Why is dry mass used for biomass?

  Because the wet mass varies as the amount of water in the organism varies.
• How do you calculate the efficiency of biomass transfer?

  efficiency = (energy transferred / total energy available) x 100
• Why are biomass transfers not 100% efficient?

  Energy is lost through:

  • Egestion (removal of faeces)
  • Excretion (removal of urine)
  • Respiration
  • The production of inedible bones and shells
• How does the efficiency of biomass transfers affect the number of trophic levels in a biomass pyramid?

  The less efficient the transfers, the fewer trophic levels and the fewer organisms in higher trophic levels.