Genetic adaptations and diversity

• An allele is a different version of the same gene
• Recessive alleles are only expressed in homozygous
• Dominant alleles are expressed in heterozygous or homozygous
• Homozygous is a pair with 2 of the same alleles
• Heterozygous is a pair with 2 different alleles
• Different alleles are formed by mutation. Substitution, deletion and addition.
• Genetic diversity is the total number of different alleles in a reproducing population
• A population is a group of individuals of the same species that live in the same area and can reproduce
• Species is a group of individuals that can breed to produce fertile offspring.
• A population bottle neck is an evolutionary event in which a specific % of the population of a species is lost leading to a decrease in genetic diversity
• The founder effect is a type of genetic drift that occurs when a small group of individuals colonise a new area and reproduce within their reduced gene pool.
• Organisms of the same species differ in there alleles not genes because species have the same number of chromosomes
• The greater the genetic diversity the more likely a species will be able to adapt to changes. This is because greater genetic diversity

  • increases genetic diversity to disease
  • higher range of tolerance to environmental changes
  • greater probability that individuals will have the beneficial gene
• Genetic diversity can be increased by

  • mutations bad and good
  • migrating populations introduce new alleles into a population
  • increasing frequency of beneficial allele in the population
• factors reduce genetic diversity

  • genetic bottle necks
  • selective breeding
  • founder effect
• Genetic bottleneck is when a large number of the population dies out and leaves a small number of individuals with a small gene pool to reproduce. They produce offspring that have a reduced genetic diversity.
• Selective breeding is when you breed individuals with desired specific physical and behavioural traits. You then breed the offspring who posses those desired traits and don’t let the offspring without the desired traits breed.
• Selective breeding produces future generations that share similar genes which risks interbreeding.
• Interbreeding can cause lower resistance to disease and can cause genetic diseases caused by recessive alleles.
• An example of the founder effect is the Amish
• Natural selection works by individuals within a population containing a beneficial allele to survival, survive the others individuals who do not have the beneficial allele, and reproduce to create a generation of offspring having the beneficial allele.
• Types of adaptation

  • behavioural
  • physiological
  • anatomical
• Behavioural adaptations is how an organism acts in order to survive
• Physiological adaptations are the processes inside the organisms body which allows them to survive
• Anatomical adaptations are physical changes that allow an organism to survive
• Types of selection

  • directional
  • stabilising
• Example directional is antibiotic resistance
• stabilising example is human birth weight
• Directional selection is when the phenotype best suited to new conditions after a change in environment are most likely to survive.
• Antibiotics help kill prokaryotes by inhibiting enzymes needed for cell wall synthesis which leaves the prokaryote vulnerable to osmotic lysis.
• Antibiotic resistance happens when there is a mutation that changes enzyme shape changing the substrate specificity so it can break down the antibiotics
• Stabilising selection is natural selection that favours the average individuals of a population not the extreme phenotypes