chapter 11

• biodiversity


  variety or living organisms present in an area, including plants, animals, fungi and other living things
• importance of biodiversity

  essential in maintaining a balanced ecosystem as all species are interconnected, for example trees provide animal habitats and fungi and microorganisms decompose dead plants and animals
• biodiversity in different areas of the earth

  UK's temperate climate has less biodiversity, generally the regions closer to the Equator have a higher biodiversity, e.g 40,000 species live in the Amazon, and only 3000 live in northern canada
• Environmental Impact Assessment (EIA)


  before a major project starts, such as building a new road or building, an EIA is taken to predict the positive and negative effects of a project on the biodiversity in that area
• biodiversity can be studied at 3 different levels

  1. habitat
  2. species
  3. genetic
• habitat biodiversity


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

  two different components

  1. species richness - number of different species living in an area
  2. species evenness - comparison of numbers of individuals of each species living in a community
• genetic biodiversity


  refers to the variety of genes that make up a species, many are the same but there are many alleles, which lead to variation within a species, and can lead to very different type of characteristics, the greater the genetic biodiversity, the easier it is for adaptation so more can resist to changes
• sampling


  taking measurements of a limited number of individual organisms present in a particular area
• how can sampling be used

  can be used to estimate the number of organisms in an area without counting them all, and can be used to measure a particular characteristic of an organism by calculating averages
• random sampling


  selecting individuals by chance where each individual in the population has an equal likelihood of selection e.g by a grid:

  • marking out a grid on the grass
  • determining random numbers to coordinate x and y axis
  • take sample at random coordinate
• non-random sampling, opportunistic

  weakest form as it may not be representative of the population and only uses organisms that are conveniently available
• non-random sampling, stratified


  some populations can be divided into a number of strata (sub-groups) based on particular characteristics, e.g separated into male and female
• non-random sampling, systematic

  different areas with an overall habitat are identified and then sampled separately, usually carried out using a line or belt transect
• line transect


  involves marking a line along the ground between 2 poles and taking samples at specified points, and can include describing all of the organisms which touch the line or distances of the sample from the line
• belt transect


  two parallel lines are marked, and samples are taken of the area between the 2 lines
• reliability when it comes to sampling


  a sample is never entirely representative of the organisms present in a habitat, due to sampling bias and chance
• sampling-bias


  selection process may be biased, by accident or deliberately, the effects can be reduced using random sampling where human involvement in choosing sample area is removed
• sampling - chance


  organisms selected may not be representative of the whole population, can never be completely removed from the process but can be minimised by using a greater sample size
• pooter


  used to catch small insects by sucking on a mouthpiece, there they are drawn into holding chamber via the inlet tube, a filter before the mouthpiece prevents them from being sucked into the mouth
• sweep nets


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


  used to catch small, crawling invertebrates such as beetles, spiders and slugs, a hole is dug into the ground where the insects fall into and they are left overnight
• tree beating


  to sample invertebrates living in a tree or bush, a tree is shaken or beaten to dislodge them and the animals will fall out, and can be collected and studied
• kick sampling


  used to study organisms living in a river, the river bed is kicked for a period of time to disturb the substrate and a net is held downstream in order to capture any organisms released into the flowing water
• sampling plants

  usually sampled using a quadrat, which can also be used to pin point an area in which the sample of plants should be collected, and can also sample slow-moving animals such as limpets and sea anemones
• point quadrat


  consists of a frame containing a horizontal bar, and at set intervals along the bar, long pins can be pushed through the bar to reach the ground, each species of the plant the pin touches is recorded

  
• frame quadrat


  consists of a square frame divided into a grid of equal sections, the type and number of species within each section of the quadrat is recorded

  
• measuring species richness


  a list should be compiled of each species identified, then a total number can be calculated, to allow accuracy, identification keys are often used, they may contain images and identifiable characteristics
• using a frame quadrat

  three main ways:

  1. density - counting organisms in a 1x1 m2 to calculate density per m2
  2. frequency - counting number of squares where a species is present
  3. percentage cover - estimate by eye of the area within a quadrat
• sample sizing and reliability when sampling

  the larger the number of samples, the more reliable the results will be, then mean should be calculated to get an average value, and to work out the total population, the mean value per m2 should be multiplied by the total area
• estimating animal population size

  using capture-mark-release-recapture, organisms are captured and marked then released back into the community to give them time to re-distribute themselves, and then re captured. the greater the number of marked individuals recaptured, the smaller the population
• abiotic factors

  non living conditions in a habitat, have a direct effect on the living organisms that reside there, many can be measured quickly and accurately:

  • rapid changes can be detected
  • human error in reading is reduced
  • high degree of precision
  • data can be stored and tracked
• simpson's index of diversity

  measure of biodiversity as it takes into account both species richness and evenness

  
• simpson's index values

  values always from 0 and 1, where 0 represents no diversity and a value of 1 represents infinite diversity
• biodiversity values

  although some have a low value, some areas cannot support a large species diversity due to the extremities of that environment
• human influence on biodiversity

  increased growth rate of human population is linked to improvements in medicine and infrastructure, but humans are severely damaging the ecology of many areas
• within a species, individuals have very little variation within their DNA
• all members of the same species have the same genes but different alleles (different variations of the genes) and these create genetic biodiversity within a species or population
• the more alleles present in a population, the more genetically biodiverse the population
• species that contain greater genetic biodiversity are likely to adapt better to environment changes because within the population there are more likely to have the existing allele to combat the change, so are likely to survive leading to survival of the species