Topic 9

• What is the definition of an ecosystem?

  All organisms and non-living factors in an area
• What defines a population of organisms?

  All individuals of one species in an area
• What is a community of organisms?

  All populations interacting in a particular area
• What does a food web illustrate?

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

  1. Place quadrats randomly in an area
  2. Count individuals in each quadrat
  3. Use the formula:

  $\text{Total number of organisms in all quadrats} =$$\frac{\text{Total area size}}{\text{Total area of quadrats}}$
• What is another term for non-living factor?

  Abiotic factor
• Name three abiotic factors.

  Temperature, soil pH, rainfall
• What is the difference between abundance and distribution of organisms?

  Abundance is how many organisms; distribution is where they are found
• How might a scientist measure the effect of an abiotic factor on species distribution?

  Use a belt transect
• Where should quadrats be placed along a transect line?

  At regular intervals
• What should a scientist do at each quadrat?

  Measure the abiotic factor and record abundance
• What is a pollutant?

  A substance that harms organisms in the environment
• What does interdependence in an ecosystem mean?

  Organisms need each other for food or resources
• What is a biotic factor?

  A living factor that affects other organisms
• Name two biotic factors.

  Competition and predation
• What do organisms compete for?

  Resources like food, water, and mates
• How might increased competition affect the abundance of an organism?

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

  Regular variation in numbers of predators and prey
• What word describes a feeding relationship where one organism benefits and the other is harmed?

  Parasitism
• Define parasite.

  An organism that feeds off a host
• What word describes a feeding relationship where both organisms benefit?

  Mutualism
• What is biodiversity?

  The variety of species in an area
• What are the advantages and disadvantages of fish farming?

  Advantages:

  • Prevents overfishing
  • Produces more fish

  
  

  Disadvantages:

  • Harmful waste to wild organisms
  • Parasites can infect wild organisms
• What is a non-indigenous species?

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

  They compete for resources with indigenous species
• What can happen if too many nutrients enter an aquatic ecosystem?

  Eutrophication occurs
• How can humans maintain biodiversity?

  1. Reforestation
  2. Conservation efforts
• What are the benefits of maintaining biodiversity?

  • Protects human food supply
  • Protects other organisms in the food web
  • Provides future medicines
  • Promotes ecotourism and jobs
  • Offers aesthetic and cultural benefits
• Why do humans need to maintain food security?

  To meet the nutrition needs of the growing population
• Define sustainability.

  Meeting today's needs without affecting future generations
• Name two factors that affect food security.

  Increasing meat consumption and environmental change
• Through which parts of the ecosystem do water, carbon, and nitrogen cycle?

  Both biotic and abiotic parts
• What important role do microorganisms play in the carbon cycle?

  They act as decomposers breaking down waste
• How is carbon taken out of the air?

  Through photosynthesis
• How does carbon move through food chains?

  Through feeding and decomposition
• How is carbon returned to the air?

  Through respiration and combustion
• How is nitrogen taken out of the air?

  Through nitrogen-fixation by lightning or bacteria
• How does nitrogen return to the air?

  Through denitrifying bacteria
• What role do nitrifying bacteria play in the nitrogen cycle?

  They convert ammonia into nitrites and nitrates
• What role do decomposers play in the nitrogen cycle?

  They break down waste into ammonia