evolution of a species

• mutations are random changes to genetic material
• mutations change the order of the DNA bases and can result in missing proteins or produce different proteins
• mutations are random and are the only source of new alleles ( form of gene)
• mutations can be advantageous, disadvantageous or neutral
• advantageous mutations increase the organisms chance of survival and ability to reproduce
• disadvantageous mutations decrease an organisms chances of survival and ability to reproduce
• neutral mutations have no effect on an organisms chances or survival or ability to reproduce
• The rate at which mutations occur can be increased by

  o Radiation e.g. UV light

  o Some chemicals e.g. bromine and mustard gas
• Variation within a population makes it possible for a population to evolve over time in response to changing environmental conditions
• sexual reproduction is important as it introduces variation in a population
• An adaptation is an inherited characteristic that makes an organism well suited to survive in its environment
• natural selection

  • when a species produces more offspring than their environment can support, some individuals die because of factors like predation, food shortage or disease
  • some individuals are better adapted to their environment due to inherited characteristics that give them a select advantage
  • the best adapted individuals are more likely to survive and reproduce
• When a species produces more offspring than their environment can support, some individuals die

  because of factors such as predation, food shortage or disease

  o These factors are known as selection pressures, and they determine which individuals will do

  best at surviving and reproducing
• Some individuals are better adapted to their environment due to inherited characteristics that give

  them a selective advantage

  o E.g. they may have a better ability to avoid predators, compete for food, or resist disease
• The best adapted individuals are more likely to survive and reproduce

  o This is known as survival of the fittest

  o They pass on the versions of genes that produce their adaptations and the frequency of these

  alleles will increase within the population
• Speciation is the process which forms a new species
• Speciation occurs after part of a population becomes isolated by an isolation barrier
• isolation barriers;

  Geographical - physical barrier - river mountain

  Ecological - abiotic factor - PH, saltiness of water, different habitats

  Behavioural - reproductive isolation - physical differences, mating behaviours
• speciation

  • A part of the population becomes isolated by an isolation barrier
  • Different mutations occur in each sub-population
  • Natural selection selects for different mutations is each group
  • Each sub-population evolves until they become so genetically different that they are two different species and can no longer breed together to produce fertile offspring
• speciation - I'm a new species

  I - isolation

  M - mutation

  N - natural selection

  S - speciation