Genetic diversity and adaptation

• Define species

  A group of organisms capable of breeding to produce fertile offspring
• Define population

  A group of organisms of the same species in a particular area
• Define genetic diversity

  The number of different alleles present in a population
• Define selection pressure

  Environmental change that means a specific allele has a survival advantage
• Define evolution

  Change in frequency of alleles in a population over time
• Describe natural selection as a model answer

  -There is a natural variation in a population

  -Caused by random DNA mutations in a gene

  -State which allele has the advantage

  -Organisms with this allele are more likely to survive

  -These organisms are more likely to reproduce

  -So, these organisms pass on this allele

  -Therefore, this allele increases in frequency in the population
• Describe the 3 types of adaptation that enable a species to survive

  Anatomical adaptations = structural/physical features

  Physiological adaptations = biological processes within the organism

  Behavioural adaptations = the way an organism behaves
• Name and describe 4 aseptic techniques

  -Sterilise the work surface afterwards with disinfectant to prevent contamination of the scientist

  -Use a sterile pipette to transfer bacteria to prevent contamination of the bacteria with environmental microorganisms

  -Flame the neck of bottles and forceps to prevent contamination of the bacteria with environmental microorganisms

  -Keep the lid on the petri dish and work close to the bunsen burner for the convection currents to prevent contamination of the bacteria from environmental microorganisms
• Name and describe the 3 types of selection

  Directional = one extreme is favoured over the mean and other extreme

  Stabilising = the mean is favoured over both extremes

  Disruptive = both extremes are favoured over the mean
• How is the number of viable bacterial cells calculated?

  -Multiply the number of colonies by the dilution factor

  -Multiply by factor used to produce the spread plate (if not 1cm3)