natural selection

• natural selection


  in any environment the individuals that have the best adaptive features are the ones most likely to reproduce and survive
• Natural selection


  1. Individuals in a species show a range of variation caused by differences in genes

  2. Organisms reproduce, producing more offspring than the environment can support

  3. Competition for food and other resources results in a 'struggle for survival'

  4. Individuals with characteristics most suited to the environment have a higher chance of survival and more chances to reproduce

  5. Alleles resulting in these characteristics are passed to offspring at a higher rate than those with less suited characteristics

  6. In the next generation, there will be a greater number of individuals with the better adapted variations in characteristics
• Survival of the fittest


  Theory of natural selection put forward by Charles Darwin
• example of natural selection - snails

  • there is variation in shell colour in the population (grey or black colour)
  • random mutations (chance mutations) produces a phenotype with a survival advantage - ( longer survival greater chance of reproduction ) (white shell snails)
  • the new variation becomes more common in the population as white shells are better camouflage
• Natural selection


  • Evolution of the peppered moths
• Evolution


  The change in adaptive features of a population over time as a result of natural selection
• If the environment does not change


  Selection does not change
• If the environment changes, or a chance mutation produces a new allele


  Selection might now favour individuals with different characteristics or with the new allele
• Evolution


  1. Individuals that survive and reproduce will have a different set of alleles that they pass on to their offspring

  2. Over time, this will bring about a change in the characteristics of the species
• Natural selection


  Results in a process of adaptation, which means that, over generations, those features that are better adapted to the environment become more common
• Populations of organisms become better suited to their environment
• Speciation


  If two populations of one species become so different in phenotype that they can no longer interbreed to produce fertile offspring, they have formed two new species