Biodiversity

• biodiversity


  a measure of the variation found in the living world
• habitat biodiversity 


  range of habitats in which different species live
• species 


  a group of organisms that can freely interbreed to produce female offspring
• Species consist of individual organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics

  • As a result, individuals in a species can interbreed freely to produce fertile offspring
  • the range of organisms found in a habitat contributes to species biodiversity
• two habitats have an equal number of different species, but not considered as equally diverse

  • species richness - number of plant species
  • species evenness - degree to which species are represented
• genetic biodiversity - variation between individuals belonging to the same species

  →variation found within any species that ensures we do not all look identical
• Using samples to measure biodiversity

  sampling a habitat you select a small portion + study that carefully as they should be taken as a a representative of the habitat
• Random sampling

  randomly selected ~ deciding where you want to sample - can be achieved by using randomly generated numbers as coordinates for your samples or possibly selecting coordinates from a map and using a global-positioning satellite system to find exact position

  • ensure the data are not biased by selective sampling
  • may not cover all areas of habitat equally; species with a low presence may be missed, leading to an underestimate of biodiversity
• Non-random Sampling Type 1

  Opportunistic

  when researcher makes sampling decisions based on prior knowledge or during the process of collecting data - researcher may deliberately sample an area that they know or can see contains a particular species

  • easier and quicker than random sampling
  • data may be biased ~ presence of a large or colourful species may entice researcher to include that species ; which may lead to overestimate of its importance + therefore overestimate of biodiversity
• Non-random Sampling Type 2

  Stratified

  Dividing a habitat into areas which appear different, and sampling each area separately

  • ensures all different areas of a habitat are sampled and species are not under-represented due to the possibility that random sampling misses certain areas
  • possibility of over-representation of some areas in sample e.g. a disproportionate number of samples are taken in small areas that look different
• Non-random sampling Type 3

  Systematic

  this is when samples are taken at fixed intervals across the habitat - line and belt transect are systematic techniques

  • particularly useful when the habitat shows a clear gradient in some environmental factors such as getting drier further from a pond
  • only the species on the line or within belt can be recorded - other species may be missed leading to an underestimate of biodiversity
• Genetic diversity is a measure of the genetic variation found in a particular species, in other words it is the number of alleles in a gene pool. It can be determined by calculating the heterozygosity index (H) , the higher the heterozygosity index (H), the more genetically diverse the species H= number of heterozygotes / number of individuals in the population
• Biodiversity can also be measured using the index of diversity (D) which can be calculated as following:

  • D = Diversity index
  • N = total number of organisms
  • n = total number of organisms of each species
• Sampling plants

  • Quadrats- squares randomly placed, species counted
  • Point quadrats- place the quadrat and use a point frame- species it touches are recorded
  • Line transect- walk the line and record what species are present at set intervals or walk it continuously and record what is seen
  • Belt transect – walk the line and place a quadrat at intervals