Measuring biodiversity

• 2 steps to calculating biodiversity:

  • assesment of species diversity in an area using sampling techniques
  • measurment of species diversity using species richness, endemism and Simpon's Index of Diversity (SID)
• the choice of method to assess biodiversity depends on factirs including the nature of the species or the habitat being studied
• sampling is gaining information about a part of the area or population in order to make reasonable assumptions about the entire area or population
• count or collect a small representative quantity of the environment, and to analyse the data, and form conclusions about the entire area
• grid sampling is collecting samples according to a system (vegetation)
• transect sampling is observing change along a line (vegetation)
• quadrat sampling is collectling samples from random locations (vegetation)
• capture-mark-recapture is counting organisms that move within a known ranger (animals)
• grid cell is a collection of samples throughout each cell
• grid point is the collection of material at specific points within the grid
• transect sampling


  mark a straight line on the site and record every organism on the transect line
• quadrat sampling


  mark out a square on the site to be sample and record the organisms
• capture-mark-recapture


  random sample of the population is tagged, released into the wild to mix with other animals, then another group is captured, percentage of tagged animals in the captured group can be used to calculate the overall population numbers
• capture-mark-recapture equation

  • overall population number = number of animals captured / no. of tagged animals recaptured as proportion of no. ofof animals in second capture
• ethical considerations need to be considered when research is conducted to ensure that organism welfare is not affected
• scientist complete a risk assesment task before forming an investigation
• information gathered in sampling can be compromised if there are significant sources of measurement error
• measuring diversity is necessary for the following to occur:

  • appreaciation of the importance of the Earth's biodiversity
  • understanding of how biodiversity has changed over time
  • assessment of threats to biodiversity
  • evaluation of management sratergies for maintaining biodiversity
• species richness measure:

  • ignores genetic variation within species
  • only partially represents ecosystem diversity
  • ranks oall species equally, regardless of how many individuals and whether the species is native or introduced
• if there are many individuals of one species an very few individuals of a lot of other species, then species richness may be high but species diversity is not
• species diversity ish high when species are occurring in roughly equal numbers within each trophic level
• to measure species diversity a calculation is mafe that produces a diversity index
• SID ranges from 0 (low diversity) to 1 (high diversity)
• the greater the spread of numbers across the species that are present, with less species that either dominate or are found in very low numbers, the higher the result when using SID
• species are naturally endemic to particular areas
• species can become endemic to particular locations due to destruction of existing native habitat
• a country of megadiversity has a high total number of species including a specific percentage of endemic species
• the criteria for a megadiverse classification is two fold:

  • have atleast 5,000 endemic plants
  • have a marine ecosystem within the borders
• 70% of the world's flora and fauna exist in only 17 countries
• grid sampling = systematic collection of samples from specific points across a piece of land
• transect sampling = a useful way of obtaining quantitative information about the organisms you want to sample
• quadrat sampling = useful to obtain quantiative information about small organisms
• capture-mark-recapture = used for moblie animals within a confined area
• ethics = a set of moral obligations that define right or wrong in scientific practice
• sampling error = statistical phenomenon and is always present in some degree in any research
• species richness = the number of different species present in a particular location
• species diversity = calculations take into account the relative abundance of each species, as well as, the number of different species
• quantitative data = data that is countable or measureable
• qualitative data = data that is descriptive
• accuracy = a measurement value is considered too be accurate if it is judged to be close to the 'true' value of that quantity being measured