4.2.1

• Biodiversity


  The variety of living organisms in an area
• Species

  A group of similar organisms able to reproduce to give fertile offspring
• Habitat

  The area inhabited by a species, including physical factors like soil and temperature, and living biotic factors like availability of food and presence of predators
• Areas with high biodiversity are those with lots of different species
• Levels of biodiversity

  • Habitat diversity
  • Species diversity
  • Genetic diversity
• Habitat diversity


  The number of different habitats in an area
• Species diversity

  The number of different species (species richness) and the abundance of each species (species evenness) in an area
• Genetic diversity

  The variation of alleles within a species (or a population of a species)
• Sampling to measure biodiversity

  1. Choose an area to sample

  2. Count the number of individuals of each species

  3. Repeat the process to take as many samples as possible

  4. Use the results to estimate the total number of individuals or the total number of different species in the habitat being studied

  5. When sampling different habitats and comparing them, always use the same sampling technique
• Sampling techniques

  • Quadrat (for plants)
  • Sweep net (for flying insects)
  • Pitfall trap (for ground insects)
  • Net (for aquatic animals)
• Types of sampling

  • Random
  • Non-random
• Random sampling

  To avoid bias in your results, the sample should be random, such as selecting random coordinates
• why use Non-random sampling

  when there's a lot of variety in the distribution of species in the habitat and you want to make sure all the different areas are sampled
• Types of non-random sampling

  • Systematic
  • Opportunistic
  • Stratified
• Systematic sampling

  Samples are taken at fixed intervals, often along a line/ transect
• Opportunistic sampling

  Samples are chosen by the investigator, it's simple to carry out but the data will be biased
• Stratified sampling

  Different areas in a habitat are identified and sampled separately in proportion to their part of the habitat as a whole
• why is sampling a range of organisms important?

  it can tell us the health of the habitat, the species evenness and richness and how specific species have been impacted by variables
• Species richness


  The number of different species in an area. The higher the number of species, the greater the species richness
• Measuring species richness

  Take random samples of a habitat and count the number of different species
• Species evenness

  A measure of the relative abundance of each species in an area. The more similar the population size of each species, the greater the species evenness
• Measuring species evenness

  Take random samples of a habitat and count the number of individuals of each different species
• Simpson's Index of Diversity

  • Takes into account both species richness and species evenness
  • Gives a value between 0 and 1, with 1 being the most diverse
• Calculating Simpson's Index of Diversity

  diversity = 1 - sum of [( total number of 1 species / total number of all organisms counted)^2]
• diversity calculation example

  • 3 different species of flower (red, white, blue)
  • 11 organisms total
  • 3 red, 5 white, 3 blue
  • Simpson's Index of Diversity = 0.64
• factors decreasing genetic diversity

  selective breeding, captive breeding, rare breeds, artificial cloning, natural selection, genetic bottleneck, founder effect, genetic drift
• allele


  a version of a gene
• locus


  the point on a chromosome which an allele is found
• polymorphism


  a locus has more than 2 types of allele that can occur there
• monomorphism


  a single allele exists for the gene.
• monomorphism exists to ensure

  the basic structure of an organisms remains constant
• example of monomorphic gene


  position of head relative to body and arms/ legs
• example of polymorphic gene

  eye colour
• calculating genetic diversity

  proportion of polymorphic gene loci = number of polymorphic gene loci / total number of loci
• populations where genetic diversity is low

  zoos, rare breeds, pedigree breeds
• factors affecting biodiversity

  human population, agriculture, climate change
• reasons to maintain biodiversity

  ecological, economic, aesthetic
• ecological reasons to maintain biodiversity


  protecting keystone species ( interdependence of organisms), maintaining genetic resources
• economic reasons to maintain biodiversity

  reduce soil depletion caused by continuous monoculture
• aesthetic reason to maintain biodiversity

  protecting ancient landscapes, some urban settings are not aesthetic