Biodiversity

• Species - group of organisms that can breed and produce fertile offspring
• biodiversity - the variety of living organisms present in an area
• habitat - the place where an organism lives
• population - all the organisms of one species in the same place at the same time
• community - all of the different organisms of different species living together in one habitat
• ecosystem - a relatively self contained, self perpetuating system
• Habitat biodiversity:

  • each habitat can support a number of different species
  • in general the greater the habitat biodiversity, the greater the species biodiversity
• Species biodiversity:

  • species richness: the number of different species living in a particular area
  • species evenness: a comparison of the numbers of individuals of each species living in the community
  • an area can differ in species biodiversity even if it has the same number of species
• Genetic biodiversity - the variety of genes that make up a species:

  • many genes are the same for all individuals within a species, however there are also many alleles which aid genetic biodiversity
  • greater genetic biodiversity within a species allows for better adaptationsto a changing environment
  • it is more likely to result in individuals who are resistant to disease
• sampling - taking measurements of a limited number of individual organisms present in a particular area
• abundance - the number of species present in an area
• Random sampling: selecting individuals by chance

  • avoids bias
• non-random sampling

  • there are 3 main techniques:
  • opportunistic: uses organisms that are conveniently available
  • stratified: population divided into strata (sub groups) and a random sample is taken from each strata
  • systematic: different areas within an overall habitat are identified then sampled separately, often carried out with a belt or line transect
• line transect:

  • placing a line along the ground between two areas and taking samples at specified points e.g. organisms that touch the line
• belt transect:

  • two parallel lines are marked and samples are taken of the area between the two lines
• Reliability

  • a sample is never entirely representative of the organisms present in a habitat:
  • sampling bias: the selection process may be biased; this can be reduced by using random sampling techniques
  • chance: the organism selected may not represent the whole population; can be minimised by using a larger sample size
• Sampling Animals:

  • pooter: used to catch small insects by using a straw to draw small insects into holding chambers
  • sweep nets: used to catch insects in areas of long grass
  • pitfall traps: used to catch small, crawling invertebrates
  • tree beating: used to take samples of the invertebrates living in trees/bushes
  • kick sampling: used to study river organisms
• capture, mark, release, recapture:

  • used to estimate population size
  • population size = no of individuals in 1st sample x no of individuals in 2nd sample / no of recaptured marked individuals
  • assumptions:
  • population doesnt change
  • all organisms are equally likely to be caught
  • the mark has no effect on organism
  • reintegration time is allowed
• Sampling plants:

  • normally involves a quadrat
  • there are two main types of quadrat:
  • point quadrat: a frame containing a horizontal bar, pins can be pushed through to the bar to reach the ground, each species of plant that the pin touches in recorded
  • frame quadrat: a square frame divided into grids of equal sections:
  • density: count large individual plants within the quadrat for density per square metre
  • frequency: count number of squares where a particular species is found and calculate % frequency
  • percentage cover: estimate by eye, the coverage of the plant
• Measuring species richness: work out total number of different species in a specific area

  measuring species evenness: work out number of organisms per species
• Measuring abiotic factors:

  • e.g. temp, light, pH etc.
  • measure at varying sampling points
• Simpsons Diversity index: D=1-(E(n/N)^2)

  • n = number of each species
  • N = total no. of all individuals
• the more alleles present in a population, the more genetically biodiverse the population is. the more genetic biodiversity there is within a species, the more likely the species is to adapt to changes in their environment
• to increase the genetic biodiversity in a species, the no. of possible alleles in a population must increase, through:

  mutations

  interbreeding between different populations - gene flow
• to decrease genetic biodiversity, the number of possible alleles in a population must also decrease, through:

  selective breeding

  captive breeding programmes

  rare breeds - the number of the breed falls, leaving a low gene pool

  artificial cloning using cuttings

  natural selection

  genetic bottleneck

  the founder effect - small no.s of individuals create a geographically isolated colony

  genetic drift - alleles disappear from population randomly
• measuring biodiversity:

  polymorphism - more than one allele in gene e.g. blood type

  most genes aren't polymorphic to ensure that the basic structure of individuals remains constant
• proportion of polymorphic gene loci = number of polymorphic gene loci/ total number of loci

  the greater the proportion of polymorphic gene loci, the greater the genetic biodiversity
• deforestation and biodiversity:

  reduces no. of trees present

  species diversity can be decreased

  animal habitats are destroyed, affecting animals higher up the food chain - migration lowers biodiversity

  only commercially viable trees are planted
• agriculture and biodiversity:

  deforestation to clear land

  removal of hedgerows for larger fields, destroying habitats

  pesticides and herbicides decrease biodiversity and reduces supply for food chain

  monoculture - diverse area is replaced by one crop so fewer animals can survive
• climate change and biodiversity:

  melting polar ice caps

  animals have to move further north, changing location patterns of the organisms

  temperate plants and animals can live further north

  low-lying land could flood, salt water can flow up rivers

  high temperatures and low rainfall could result in non-drought resistant plants, less food for animals

  insects that carry pathogens could migrate from tropical areas
• Aesthetic reasons to maintain biodiversity:

  plants and animals provide enrichment

  inspiration for artists and writers

  health reasons; health is improved and recovery time is decreased when in a natural environment
• economic reasons for maintaining biodiversity:

  natural ecosystems have value as they regulate the climate, purify and retain water, form and fertilise soil, recycle nutrients, detoxify waste, pollenate crops and provide timber for food and fuel

  deforestation causes soil erosion and desertification, reducing a country's ability to grow crops

  if all organisms used in a specific industry are used up, the industry will collapse

  habitat destruction causes a loss of species with potential economic value
• economic reasons 2

  monoculture reduces the fertility of the soil , crops become less robust and more fertilisers are required

  high biodiversity protects against abiotic factors such as disease and extreme weather

  tourism

  a diverse ecosytem has a greater potential for future advancements e.g. medicines

  a variety of plants allows cross breeding to provide plants with greate disease resistance/increased yield - the loss of a species can affect the entire food chain
• ecological reasons:

  all organisms are dependent on others - the loss of one organism can have detrimental effect on other organisms

  keystone species: organisms that have a disproportionately large effect on their environment relative to their abundance - if they are removed then all other species in the ecosystem are affected/disappear e.g. jaguars, american alligators, sea stars
• human activity can be negative but can also promote biodiversity

  e.g. burning gorse and heather in the New Forest to prevent domination from bracken and silver birch
• conservation - management of the environment and natural resources to allow organisms to survive and reproduce
• in situ conservation: conservation within the organism's natural habitat
• ex situ conservation: conservation out of the organisms natural habitat
• extinct - no organisms of the species anywhere else in the world
• extinct in the wild - organisms of the species only exist in captivity