Biodiversity

• random sampling


  sampling where each individual in the population has an equal likelihood of selection.
• how does random sampling work

  random number tables or computers are used - mark out a grid using two tape measures laid at right angles, use random numbers to generate the x and y coordinate on your grid, take a sample at each of the coordinate pairs measured
• measuring biodiversity


  habitat biodiversity, species biodiversity, genetic biodiversity
• habitat biodiversity


  the number of different habitats found within an area (greater habitat biodiversity, greater species biodiversity)
• species biodiversity


  species richness and species evenness
• non-random sampling


  an alternative sampling method to random sampling, where the sample is not chosen at random. It can be opportunistic, stratified or systematic.
• sampling


  taking measurements of a limited number of individual organisms present in a particular area
• abundance of organisms


  number of individuals of a species present in an area
• sampling uses


  can estimate abundance (without having to count them all) and can measure a particular characteristic (mean height of plants for example)
• opportunistic sampling


  sampling using the organisms that are conveniently available. The weakest form of sampling as it may not be representative of the population.
• stratified sampling


  sampling where populations are divided into sub-groups (strata) based on a particular characteristic. A random sample is then taken from each of these strata proportional to its size.
• systematic sampling


  different areas of a habitat are identified and sampled separately. Often carried out using a line or belt transect.
• line transect


  Marking a line along the ground between points and taking samples at specific points
• belt transect


  two parallel lines are marked along the ground and samples are taken of the area

  at specified points.
• reliability


  sampling bias (reduced by random sampling) and chance (reduced by large sample)
• pooter


  used to catch small insects by sucking a mouthpiece, insects drawn into holding chamber via inlet tube
• sweep nets


  used to catch insects in areas of long grass
• pitfall traps


  hole dug has roof to prevent rainwater filling it, used to catch small, crawling invertebrates such as beetles, spiders and slugs
• kick sampling


  river bank and bed is 'kicked' for a period of time to disrupt substrate, net catches organisms released into water
• quadrat


  it can be used to sample plants and slow-moving animals
• catching organisms


  kick sampling, pitfall traps, sweep nets, pooter
• point quadrat


  a frame has a horizontal bar - set intervals aong the bar long pins can be pushed through the bar to reach ground, each plant that touches the pin is recorded
• species richness


  the number of different species in an area
• species evenness


  a comparison of the number of individuals of each species living in a community
• frame quadrat sample calclations

  density, frequency, percentage cover
• estimating animal population size

  capture-mark-release-(time)-recapture, compare numbers of marked individuals with number of unmarked in second sample
• abiotic factors


  non-living conditions in a habitat e.g. wind speed, light intensity, temperature etc.
• biotic factors


  All the living organisms that inhabit an environment
• Simpson's Index of Diversity

  0 to 1, species richness and species evenness., n = total number of organisms of a particular species, N = total number of organisms of all species

  
• genetic biodiversity


  the total number of alleles of different genes in a population
• high genetic biodiversity


  more alleles, more likely to have advantageous characteristics, more likely to adapt to changes in the environment, hence are less likely to become extinct
• factors that increase genetic biodiversity

  mutations in the dna, gene flow
• factors that decrease genetic biodiversity

  selective breeding, captive breeding programmes, artificial cloning, natural selection, genetic bottlenecks, founder effect, genetic drift
• gene flow


  an individual migrates from one population and breeds with a member of another population, alleles are transferred between the two populations
• genetic bottlenecks


  a few individuals within a population survive an event or change thus reducing the 'gene pool', alleles coding for less advantageous characteristics will be lost from a population
• founder effect


  a small number of individuals create a new colony, geographically isolated from the original, the gene pool for this population is small
• genetic drift


  the random nature of alleles being passed on from parents to their offspring, the frequency of occurrence of an allele will vary - some alleles may disappear
• polymorphic genes


  genes that have more than one allele,
• monomorphic genes


  genes with only one allele
• why is too much variation bad? why do we have monomorphic genes?

  this ensures the basic structure of individuals within a species remains consistent