10: Ecosytems

• Define ecosystem?

  A description of a habitat and the community of organisms within it and their interactions with abiotic factors
• Define community?

  All of the different organisms living in a particular habitat
• Define population?

  All of the members of the same species living a particular habitat
• Define habitat?

  The area and resources required by a particular species for life
• Define niche?

  The role an organism plays in a community including the precise conditions it requires and its interactions with other species
• Define biotic factors?

  Variables that affect organisms (including there distribution) and are due to other living things in the environment
• Define abiotic factors?

  Physical variables that affect the distribution of organisms
• What is a trophic level?

  The position of an organism in a food chain (determined by feeding relationships)
• What is a producer?

  An organism that makes its own food
• What is another word for a producer?

  Autotroph
• What is a consumer?

  An organism which eats and digests other organisms to gain a source of organic molecules
• What is another word for a consumer?

  Heterotroph
• What is a decomposer?

  An organism that breaks down dead or decaying organisms
• What are the two types of decomposer?

  Detritivores and saprotrophs
• What do detritivores decompose?

  Animals
• What do saprotrophs decompose?

  Microorganisms
• Are decomposers autotrophs or heterotrophs?

  Heterotrophs
• What is an ecological pyramid?

  A simplified representation of the relationships between different trophic levels
• What are the three types of ecological pyramid?

  Pyramid of numbers, pyramid of biomass & pyramid of energy
• What does a pyramid of numbers show?

  The number of individual organisms at each trophic level
• What is the disadvantage of using pyramids of numbers?

  Doesn't take into account the size of organisms, meaning larger organisms are often underrepresented particularly producers e.g trees
• What does a pyramid of biomass show?

  The mass of biomass present in the organisms at each trophic level
• What are the units for a pyramid of biomass?

  grams per square metre
• What are the two disadvantages of using pyramids of biomass?

  Dry biomass has to be used meaning some organisms have to be killed and the value is based off of an estimate as only a sample is used. Organisms grow at different rates and breed at different times. meaning the biomass at one given point will not be reflective
• What does a pyramid of energy show?

  The energy content of each trophic level
• What are the units for a pyramid of energy?

  kilojoules per square metre per year
• What is the disadvantage of using pyramids of energy?

  Very time consuming to crop, dry and use calorimetry over an entire year
• What does abundance refer to?

  The size or representation of a population
• What does distribution refer to?

  Where individuals of a population are found within an environment
• What are the three main distribution categories?

  Random, uniform & clumped
• What does an ACFOR scale stand for?

  Abundant, common, frequent, occasional and rare
• What is the issue with ACFOR scales?

  Highly subjective
• When is the Chi-squared test used?

  When comparing observed and expected results (or looking at frequencies)
• When is the Student's T-test used?

  When looking for differences between measurements
• When is the Spearman's rank correlation coefficient used?

  When looking for correlation ebtween measurements
• Which statistical test should be used to identify if there is a significant difference between the expected blue:white flower value (found using genetic cross) and the actual one?

  Chi-squared test
• Which statistical test should be used to identify if there is a significant difference between the blood pressures of smokers and non-smokers
• Which statistical test should be used to identify if there is significant correlation between leaf length and width?

  Spearman's rank correlation coefficient
• What is carbon fixation?

  The process whereby autotrophs turn inorganic carbon into organic compounds
• Define gross primary productivity?

  The total amount of light energy fixed through photosynthesis in a given time