3.4.4 Genetic diversity and adaption

• Causes of genetic diversity/ variation:

  • Genetic/ chromosomal mutation
  • Meiosis- crossing over which mixes up alleles of genes, and independent segregation which mixes up maternal and paternal chromosomes
  • Random fertilisation
• Genetic diversity- the total number of different alleles of genes in a population (group of individuals of the same species that can live in the same place and can breed to produce fertile offspring)
• Allele frequency- the relative frequency of an allele (variant of a gene) at a locus in a population, expressed as a fraction/ percentage of all the chromosomes in the population that carry that allele
• Reproductive success- the passing of genes onto the next generation, in a way so they are also able to pass those genes on. In practise, it is a tally of the number of offspring produced by the individual
• Principles of natural selection:

  • Species produce more offspring than needed to maintain the population at a constant level
  • Members of a species and their offspring differ from each other, which is caused by different alleles of different genes which are originally caused by a random mutation
  • Competition for survival- individuals with a certain phenotype are more likely to survive as they have an advantage
  • Individuals who survive longer are more likely to breed, and pass their alleles onto offspring
  • Over time, advantageous alleles will become more common in the population
• Example of natural selection in bacteria (antibiotic resistance):

  A) binary

  B) fission

  C) mutation

  D) antibiotic

  E) antibiotics

  F) non-resistant

  G) resistant

  H) resistant

  I) binary

  J) fission

  K) higher