natural selection

evolution

the heritable change in phenotype, due to genetic transmission of information across generations (or environment)

how does change arise

• genetic mutation

• genetic recombination

what did Darwin observe

• observed differences between related species across the Galapagos

• saw an adaptive radiation of change

• finches differed in their feeding behaviour, reflected in the shape of their beaks (thin, large, intermediate)

• believed the finches had a common ancestor

• added a mechanism of selection to his grandfather’s hypothesis

what does artificial selection produce

heritable phenotypic diversity among domestic species

4 components needed for evolution by natural selection

• variation : individuals of a species differ

• inheritance : some of this variation is heritable

• competition : populations remain constant in size

• mutation : new variants can appear

what is darwinian fitness

a measure of the proportional change of abundance of genotype in a population

phenotype

an individual’s observable characteristics

genotype

an individual’s genetic 9heritable) constitution

trait

a phenotypic character such as colour or height

additive gene-environment ineractions

environmental effects are advantageous to all genotypes, even if one does better than the other

non-additive gene-environment interactions

only one genotype does well in each environment

neodarwinism

understanding of evolution bringing together medelian genetics and darwinian theory