Module 4.2.1- Biodiversity

• Biodiversity


  the variety of living organisms present in an area
• Habitat biodiversity


  the number of different habitats found within an area
• The greater the habitat biodiversity...


  the greater the species biodiversity will be within that area
• Species richness


  The number of different species living in a particular area
• Species evenness


  the relative proportion of different species in a given area
• Genetic biodiversity


  refers to the variety of genes that make up a species
• Sampling


  can be used to estimate the number of organisms in an area without having to count them all
• Random sampling


  a sample that fairly represents a population because each member has an equal chance of inclusion
• How can you take a random sample- example

  1) mark out a grid on the grass using 2 tape measures at right angles

  2) use random numbers to determine the x-coordinate and y-coordinate on your grid

  3) take a sample at each of the coordinate pairs generated
• 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.
• Opportunistic sampling (NRS)


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


  the population is divided into a number of strata (subgroups) and weighted based on a particular characteristic.

  e.g. divided into male and female.

  then random sampling used for that
• Systematic sampling (NRS)


  select some starting point and then select every kth element in the population
• Line transect- systematic sampling


  a line is marked along the ground and samples are taken at specified points.
• Belt transect- systematic sampling

  2 parallel lines are marked, and samples are taken of the area between the two lines
• Sampling bias


  A problem that occurs when a sample is not representative of the population from which it is drawn. for example choosing more interesting looking flowers in an area.
• Chance


  the organisms selected may, by chance, not be representative of the whole population.The larger the sample size, the more reliable the result
• Pooters- sampling technique

  used to catch small insects. suck on a mouthpiece and insects are drawn into the holding chamber via the inlet tube. There is a filter before the mouthpiece to prevent it being sucked into the mouth.
• Sweep nets- sampling technique


  used to catch insects in areas of long grass
• Pitfall traps- sampling technique


  used to catch small, crawling invertebrates. a hole is dug in the ground which insects fall into with roof

  left overnight
• Tree beating - sampling technique


  used to take samples of the invertebrates living in a tree or bush large white cloth is stretched out under the tree

  the tree is shaken/beaten to dislodge the invertebrates onto the cloth
• Kick sampling- sampling technique


  used to study organisms living in a river. the river bank or bed is 'kicked' for a period of time to disturb the substrate

  a net is held just downstream for a set period of time in order to capture any organisms released into the flowing water
• Point quadrat (Plant sampling)


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

  
• Frame quadrat (Plant sampling)


  consists of a square frame divided into a grid of equal sectionsthe type and number of species within each section of the quadrat is recorded
• Measuring species richness


  Various techniques should be used to compile list of species in habitat. Then total is a measure of species richness
• Measuring species evenness


  Ratios of organisms in a community.

  Example:

  50 organisms under a log

  20 woodlice

  15 spiders

  15 centipedes

  This is even

  45 woodlice

  5 spiders

  This is uneven
• Frame quadrat- density


  count the number of individual large plants in a 1m x 1m square quadrat. this gives you the density per square meter. it is an absolute measure.
• Frame quadrat- frequency


  using the small grids within a quadrat, count the number of squares a particular species is present in.
• Frame quadrat- percentage cover


  It is an estimate by eye of the area within a quadrat that a particular plant species covers

  it is fast
• 2 ways to increase reliability


  take a larger sample size

  calculate mean
• Estimating animal population size: capture-mark-release-recapture method

  compare numbers of marked individuals with number of unmarked in the second sample and then the population size can therefore be estimated

  the greater the number of marked individuals recaptured, the smaller the population

  species evenness can then be calculated
• Abiotic factors


  a nonliving condition or thing, as climate or habitat, that influences or affects an ecosystem and the organisms in it
• Examples of abiotic factors


  wind speed

  light intensity

  relative humidity

  pH

  temperature

  oxygen content in water
• How to calculate biodiversity


  Simpson's index of diversity
• Simpson's index of diversity


  a measure of biodiversity that takes into account both species richness and species evenness

  a higher value means there is more diversity

  
• Species diversity


  takes into account both the number of different species present (species richness) and the number of individuals of each species
• Importance of genetic diversity


  Diverse gene pool gives a population more flexibility to survive in a changing environment and is less likely to become extinct

  The more genetically diverse a population, the more ways it has to adapt
• Factors that increase genetic diversity


  mutation

  interbreeding between different populations (gene flow)
• Factors that decrease genetic diversity


  selective breeding (artificial selection)

  captive breeding programmes are breeds artificial cloning

  natural selection

  genetic bottlenecks

  founder effect

  genetic drift
• Polymorphism


  the existence of two or more forms of individuals within the same animal species (independent of sex differences)