4C

• importance of biodiversity:

  • organisms are interdependent
  • large-scale ecosystems can function and self-regulate
  • air and water purification
  • decomposition
  • photosynthesis stabilises world climate
  • transpiration causes rain
  • cross-breeding and genetic engineering
  • medicine
• varying biodiversity across locations:

  • stable ecosystem allows complex relationships to develop between species
  • high levels of productivity support more niches
  • organisms can grow rapidly, so there are more mutations, which increase adaptations to exploit niches
• An area with an even abundance of species is considered to be more biodiverse than an area with the same number of species, but dominated by one of those species.
• ecosystems


  biological communities where organisms interact with one another and with their physical environment
• species richness


  number of different species in an area
• relative species abundance


  relative number of species in an area
• biodiversity hotspot


  an area with a particularly high level of biodiversity
• endemic


  species that evolves in geographical isolation and is found in only one place
• The diversity index is used as a measure of biodiversity, using species richness and abundance.

  $D =$$\frac{ N\left( N-1 \right)}{\sum_{}^{}n(n-1)}$

  D = diversity index

  N = total number of organisms of all species

  n = number of organisms of each species (abundance of each species)
• niche


  the role of an organism within the habitat in which it lives
• The heterozygosity index is an indicator of genetic variation.

  heterozygosity index = number of heterozygotes/total population

  The higher the index, the more genetically diverse a population is.
• ecology


  study of the relationships of organisms to one another and to their physical environment
• succesful adaptations:

  • anatomical adaptations - form and structure of organism is adapted to its niche
  • physiological adaptations - the way the body of the organisms works, and differences in biochemical pathways or enzymes helps the organism to adapt
  • behavioural adaptations - changes to programmed or instinctive behaviour making organisms better adapted for survival
• Selection pressure:

  1. change occurs in environment
  2. some individuals have advantageous alleles
  3. these individuals are more likely to survive and reproduce, passing on the allele
  4. individuals without the resistant allele die before reproducing, so susceptible alleles are not passed on
  5. allele frequency changes
• The amount of change that takes place in the frequency of alleles in a population shows whether it is stable or evolving. The Hardy-Weinberg equation states that allele frequency of a population is stable as long as that population is not evolving. There are 2 equations:

  • p + q = 1 ~ p - frequency of dominant alleles, q - frequency of recessive alleles
  • $p^2 +$$2pq +$$q^2 =$$1$ ~ homozygous dominant, heterozygous, homozygous recessive
• conditions of Hardy-Weinberg equation:

  • no mutations
  • random mating
  • large population
  • no migration
  • no selection pressure
• Random mating


  likelihood of any 2 individuals in a population mating is independent of their genetic makeup
• population


  breeding group of individuals of the same species occupying a particular habitat and a particular niche
• gene pool


  the total of all genes in a population at a given time
• selection pressure


  the effect of one or more environmental factors that determine whether an organism will be more or less successful at surviving and reproducing, which drives speciation
• Speciation:

  1. isolation of part of a population
  2. reduced gene flow between the 2 parts of the population
  3. different populations experience different selection pressures
  4. natural selection acts in different directions
  5. genotype and phenotype of populations change
  6. members of different populations can't interbreed
• reproductive isolation mechanisms:

  • geographical isolation - physical barrier separates individuals of a population
  • ecological isolation - two populations in the same region, but different parts of habitat
  • seasonal isolation - timing of sexual receptiveness is different in two populations
  • behavioural isolation - changes in a mating pattern so individuals do not recognise others as potential mates
  • mechanical isolation - mutation changes genitalia so only some successful mating
• allopatric speciation


  speciation that occurs when populations are physically or geographically separated and there can be no interbreeding or gene flow between populations
• hybridisation


  production of offspring as a result of sexual reproduction between individuals from two different species
• adaptive radiation


  process by which a species develops rapidly into several different species which fill different ecological niches after allopatric speciation
• sympatric speciation


  speciation that occurs between populations of a species in the same place that become reproductively isolated by mechanical, behavioural or seasonal mechanisms yet gene flow continues between the populations to some extent as speciation occurs
• population bottleneck


  the effect of an event that dramatically reduces the size of a population which causes a severe decrease in the gene pool of the population, resulting in large changes in allele frequency and a reduction in genetic diversity
• founder effect


  the loss of genetic diversity which occurs when a small number of individuals become isolated, forming a new population with allele frequencies not representative of the original poppulation
• conservation


  maintaining and protecting a living and changing environment
• ex-situ conservation


  conservation of components of biological diversity outside their natural habitats
• in-situ conservation


  conservation of ecosystems and natural habitats, and the maintenance and recovery of viable populations of species in their natural surroundings
• captive breeding programmes


  programmes where individuals of endangered species are bred in zoos in an attempt to save the species from extinction, and if possible to reintroduce them to their natural wild environment
• Ex-situ conservation of plants:

  • seeds are easily stored
  • not a lot of space needed
  • seeds can be stored for hundreds of years
  • 80% of species can be stored in seed banks
  • field gene banks for growing plants
  • tissue cultures to conserve plant DNA
• Ex-situ conservation of animals:

  • protects animals from threat in the wild
  • captive breeding programmes
  • reintroduce captive bred animals into the wild
• negatives of zoos:

  • not enough space or resources for all endangered species
  • difficult to provide correct conditions for breeding
  • reintroduction can be unsuccessful if the threat is still present
  • captive animals struggle to adjust to life in the wild
  • smaller gene pool, but artificial insemination between zoos can fix this
  • reintroduction programmes are expensive, yet could still fail