Organisation of an Ecosystem

• Give one way in which food production might be more efficient from battery chickens than from free-range chickens. Give a reason for your answer

  Limiting their movement reduces energy transfer
• One product of anaerobic respiration is methane. Name two other products of anaerobic respiration.

  Ethanol

  Lactic acid
• Deforestation results in an increase in carbon dioxide levels in the atmosphere. Give two reasons why.

  fewer trees to take in carbon dioxide for photosynthesis

  decomposers respire releasing carbon dioxide
• Explain why the presence of air results in a high concentration of carbon dioxide in the biogas.

  Oxygen is present

  Aerobic respiration occurs

  Carbon dioxide from respiration
• The bladder wrack has many air bladders. The air bladders help the bladder wrack to float upwards when the sea covers it. Suggest how this helps the bladder wrack to survive.

  Gets more light so there’s more photosynthesis
• eutrophication

  
  

  Waste water flows into stream

  contains mineral ions increasing growth of algae

  the algae underneath die due to lack of light

  decomposers feed on decaying matter

  the respiration of decomposers uses up all the oxygen so invertebrates die due to lack of oxygen
• Define habitat

  The place in which an organism lives.
• Define community

  Populations of different species interacting.
• Define ecosystem

  The interactions between the biotic and abiotic factors in an area.
• What do food chains show?

  Food chains show the feeding relationships of

  different organisms and the flow of energy between

  the organisms.
• Define biomass

  The total mass of living material.
• What are trophic levels?

  The stages in a food chain.
• What do arrows in a food chain represent?

  The direction of biomass transfer.
• Describe a simple food chain

  producer → primary consumer → secondary consumer → tertiary consumer.
• What is a producer?

  An organism that makes its own food.
• What types of organisms are primary producers?

  Photosynthetic organisms like green plants and algae that trap energy from the sun.
• 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 a tertiary consumer?

  An organism that feeds on secondary

  consumers.
• What is a predator?

  A consumer that kills and eats other

  animals.
• What is prey?


  An animal that is killed and eaten by

  another animal.
• Describe the pattern of predators and prey in a

  stable community

  The numbers of predators and prey rise

  and fall in cycles.
• Why are producers the first trophic level?

  ● Producers provide all biomass for the food

  chain (production of glucose via

  photosynthesis).

  ● The rest of the food chain involves the transfer

  of this biomass.
• What piece of apparatus is used to measure the

  abundance and distribution of organisms in an area?

  Quadrat
• What piece of apparatus is used to study the

  distribution of organisms across a gradient?

  Belt transect
• When considering the abundance of organisms,

  what is meant by the term "mean"?


  The average number of organisms.
• How is the arithmetic mean calculated?

  Sum of each number of each

  organism/the total number of each type

  of organism.
• When considering the abundance of different

  organisms, what is meant by the term "mode"?

  The most populous organism
• When considering the abundance of organisms,

  what is meant by the term "median"?


  The organism that represents the middle

  value when the numbers of each

  organism are arranged from lowest to

  highest.
• Describe how materials cycle through the living and

  non-living components of an ecosystem

  ● Organisms take in elements from their surroundings e.g. soil, air.

  ● Elements converted to complex molecules which become biomass.

  ● Elements transferred along food chains.

  ● Elements returned to environment during excretion and

  decomposition of dead organisms.
• Give 3 molecules which are cycled through

  ecosystems

  Oxygen, carbon dioxide and water.
• Describe the carbon cycle


  - Plants fix carbon dioxide into organic molecules during

  photosynthesis.

  - The organic carbon-containing molecules are passed onto organisms

  that eat the plants.

  - Carbon dioxide is released back into the atmosphere by respiration

  from animals and plants.

  - Burning fossil fuels also releases carbon dioxide into the atmosphere.
• Why is the carbon cycle important?

  Carbon-containing molecules such as

  glucose are important for living

  organisms to grow and provide energy

  for vital functions within cells.
• Describe the water cycle

  - Water from lakes and oceans evaporates.

  - The evaporated water condenses into clouds and returns

  to earth as precipitation.

  - The water from precipitation is useful for life on land.

  - The water then returns to rivers and oceans through

  surface runoff.
• Why is the water cycle important?

  Living organisms require water and the

  water cycle provides organisms on land

  with a continuous supply of water.
• Why are microorganisms important for the cycling of

  materials through an ecosystem?

  Microorganisms (bacteria and fungi) return carbon to the

  environment by releasing carbon dioxide through

  respiration while they decompose dead matter. The

  decomposition of dead matter in soil returns mineral ions to

  the environment for other organisms to use e.g. plants use

  mineral ions for growth.
• What is meant by decomposition? (biology only)


  The breakdown of dead materials into

  simpler organic matter
• How do decomposers break down dead matter?

  (biology only)

  Decomposers release enzymes which

  catalyse the breakdown of dead material

  into smaller molecules.
• What are the two types of decomposition?

  (biology only)

  Aerobic decomposition (with oxygen)

  Anaerobic decomposition (without

  oxygen)
• What factors affect the rate of decomposition?

  (biology only)

  ● Oxygen availability

  ● Temperature

  ● Water content