Mutations

• Mutations are sudden random changes in the number or structure of an organisms DNA.
• Mutations are spontaneous and occur rarely. Most are harmful but some are beneficial and the new alleles improve on organisms survival chances.
• Mutagenic agents increase the rate of mutations this can be radiation or chemicals.
• Natural selection is the survival of those organisms best adapted to the environment. Those with favourable characteristics will have a selective advantage to survive.
• The first stage of speciation is there is a large interbreeding population of one species.
• The second stage of speciation is the population is split into two by a barrier.
• The barrier in speciation can be geographical, ecological or behavioural.
• The third stage of speciation is mutations occurring at random and these different mutations will affect the two populations causing new variants to occur.
• The third stage of speciation is selection pressures acting on each population are different. Natural selection affects each population randomly.
• The fifth stage of speciation is that over a long period of time stages 3 and 4 cause the two groups to become genetically different.
• The sixth stage of speciation is when the barrier is removed the two populations are unable to interbreed successfully. There are now two different species.