topic 9

• Define the word ecosystem


  All the organisms and and non-living factors that interact in an area
• What is a population of organisms?


  All the individuals in one species living in the same area
• What is a community of organisms?


  All the populations interacting with one another in a particular are
• What does a food web show?


  The feeding relationships between organisms
• How can you estimate the population size of plants in an area?

  a)    Place quadrats randomly in an area.

  b)   Count the number of individuals in each quadrat.

  Total number of organisms in all quadrats X (total area size/qudrats)
• What word describes the total mass of an organism or group of organisms?

  biomass
• What is another word for a feeding level?

  trophic level
• Why are most food chains limited to 4 or 5 trophic levels?


  Energy is lost between each trophic level, so not enough energy is left to support another species
• List 3 ways energy is lost from food chains.

  • Lost in faeces/urine
  • Not all of every organism is eaten
  • Transferred to environment as heat (due to respiration)
• What diagram can be used to show the biomass of organisms in each trophic level?

  pyramid of biomass
• Why are pyramids of biomass always smaller at the top?


  Energy is transferred out of the food chain at each trophic level.
• If a primary consumer has 78 g/m2 of biomass, and a secondary consumer has 36 g/m2, what % of biomass is transferred?

  (36 / 78) x 100 = 46.2%
• What is another word for non-living factor?

  abiotic factor
• List 3 abiotic factors.


  e.g. temperature, soil pH, rainfall, light intensity, pollution level etc
• What is the difference between abundance and distribution of organisms?


  Abundance - how many organisms

  Distribution - the spread of organisms / where they are found
• How might a scientist measure the effect of an abiotic factor on the distribution of a species?


  Use a belt transect
• Where should the scientist place quadrats along the transect line?


  At regular intervals
• What should the scientist do at each quadrat? (2 things)


  1. Measure the abiotic factor
  2. Record the number (abundance) of individuals
• What is a pollutant?


  A substance that harms organisms when released into the environment
• Organisms in an ecosystem are interdependent. What does this mean?


  They need each other for food or resourcese.g. shelter
• What is a biotic factor?


  a living factor that affects other organisms
• Name two biotic factors


  Competition, predation or the presence of pathogens
• What do organisms compete for?


  Resources (e.g. food, water, mates, light etc.)
• How might increased competition affect the abundance of an organism?

  it would decrease
• What is a predator-prey cycle?


  The regular variation in numbers of predators/prey in a feeding relationship
• What word describes an organism that indicates the level of pollution in an area?

  indicator species
• List two sources of air pollution

  Sulphur dioxide and nitrogen oxides
• List two sources of water pollution

  E.g. eutrophication, sewage, mercury, detergents
• List one disadvantage of using indicator species to assess pollution levels


  Species might not be found in area

  Doesn’t give quantitative (numerical) data
• What word describes a feeding relationship where one organism benefits and the other is harmed?

  parasitism
• Define parasite.


  An organism that feeds off / lives on a host, causing it harm
• What word describes a feeding relationship where both organisms benefit?

  Mutualism
• Define biodiversity

  The variety of species in an area
• Give one advantage and one disadvantage of fish farming


  A – prevents overfishing / produces more fish

  D – uneaten food, faeces and pesticides fall from the fish pens, harming wild organisms / parasites can get out and infect wild organisms
• What is a non-indigenous(or non-native) species?

  A species that hasn’t been in an area before
• How do non-indigenous species harm biodiversity?

  Compete for resources with (or prey upon) indigenous species
• What can happen if too many nutrients (e.g. nitrates) enter an aquatic ecosystem?

  Eutrophication
• List 2 ways humans can maintain biodiversity.

  Reforestation / conservation
• List 3 benefits of maintaining biodiversity

  e.g. protects human food supply /protects other  organisms in the food web /provides future medicines /ecotourism & new jobs /aesthetic/cultural benefits
• Why do humans need to maintain food security?

  To meet the food / nutrition needs of the growing human population