Unit 3.6 Evolution Flashcards
Mutation
A random change to genetic material.
Can have a neutral or negative effect on an organism, but sometimes gives them an advantage.
Mutagenic agent
Environmental factor that can increase the mutation rate.
Includes radiation (eg. UV radiation) and chemicals (eg. mustard gas)
Alleles
Different versions of a gene.
Mutation is the only source of new alleles.
Variation
Differences between individuals in a population, due to different alleles.
Variation allows organisms to evolve (change) over time in response to changing environmental conditions.
Overproduction
Species produce more offspring than the environment can support.
Natural selection (survival of the fittest)
The best adapted members of a population survive when the population is put under a selection pressure eg. competition or predation.
The survivors reproduce and pass on their favourable alleles to the next generation.
Allele frequency
How many times a particular allele occurs within a population.
Favourable alleles which confer an advantage increase in frequency, unfavourable ones decrease.
Evolution
Repeated natural selection over a long period of time of causes organisms to change.
High speed evolution
Occurs in pest and disease species as a result of selection pressure form humans. eg. DDT resistance in mosquitoes, antibiotic resistance in bacteria.
Speciation
The formation of a new species.
Occurs when groups within a population become isolated and no longer breed together and exchange genes.
Mutation and natural selection occur in the separated sub-populations and they evolve so that they can no longer breed to produce fertile offspring if reunited.
Isolation barrier
Separates a population into groups, preventing exchange of genes between them.
Barriers can be geographical (eg. a mountain), ecological (eg. a food source) or behavioural. (eg. different courtship behaviour)
