10.1

• Define ecosystem

  All the organisms living in a particular area, and all the non-living conditions found there. Can vary from very large e.g. biome, to very small e.g. microhabitat.
• Define and name the trophic levels

  Describes an organism's feeding relationships with other organisms i.e. its position in a food chain.

  
  

  Producer, primary consumer, secondary consumer, tertiary consumer, decomposer.
• Give three ways we can represent ecosystem structure

  • Pyramids of number (counting)
  • Pyramids of biomass (weighing)
  • Pyramids of energy
• Suggest methods of assessing abundance and distribution of organisms

  1. Quadrats; square frames placed at random in area to be investigated

  2. Transects; line or belt that runs across the area to be investigated
• Suggest different ways abundance can be quantified

  • Percentage cover
  • Frequency (individual counting)
  • ACFOR scale (abundant, common, frequent, occasional, rare)
• Why might we calculate a Spearman's rank correlation coefficient?

  To measure correlation between two variables, i.e. the extent to which changing one variable affects the other variable
• Explain how Spearman's rank results are interpreted

  Closer to 1= more positive correlation.

  Closer to -1= more negative correlation.

  Around 0= no correlation.
• Interpreting t-test results

  The t value obtained is compared to a critical value (found in a table) for a particular p value chosen by the researcher. If the t value is greater than the critical value, the difference is said to be statistically significant.
• What are the pros and cons of pyramids of numbers?

  + easiest to measure

  – can be distorted by large organisms
• What are the pros and cons of pyramids of biomass?

  + more accurate than pyramid of numbers

  – dry mass has to be used

  – don’t account for the rate of production of biomass
• What are the pros and cons of pyramids of energy?

  + most accurate out of the pyramids

  – hardest to measure

  – uses an outdated definition of energy
• What is a line transect?

  It‘s where a line is placed down across the habitat and species in contact with the line are recorded
• What is a quadrat?

  It’s a square frame of a given size, randomly placed in the area being sampled. The species inside the quadrat are identified. The species can be counted or an estimate of percentage cover can be produced.
• Why might we calculate a t-test?

  To determine if the means (averages) of two sets of data are significantly different from each other
• Define biomass


  The dry mass of all the living organisms in an area
• Define genetic diversity 


  A measure of the variety of genes that make up a species
• Define habitat biodiversity 


  A measure of the number of different habitats found within an area