unit 1 key area 7 Flashcards
(22 cards)
what is evolution
the changes in organisms over generations as a result of genomic variations
what is a gene pool
the total of all the different genetic sequences present in a population
what is natural selection
the non-random in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences
what is a selection pressure
the environmental conditions which allow natural selection to take place e.g. predation climate competition
what is a polygenic trait
controlled by several genes
what are the 3 types of natural selection which change phenotype frequency
disruptive stabilising directional
what is stabilising selection
average phenotype is selected for
what is disruptive selection
when two or more phenotypes are selected for
what is directional selection
when one extreme of the phenotype range is selected for
what cell type is natural selection most rapid in
prokaryote
what is vertical inheritance
the transfer of genetic material from one generation to another by sexual/asexual reproduction
what is horizontal inheritance
the transfer of genetic material within the same generation
how do prokaryotes exchange genetic material
horizontally
what is speciation
the generation of a new species by evolution
what is speciation a result of
isolation mutation natural selection
what is a species
a group of organisms that can interbreed to produce fertile offspring
what are the two types of speciation
allopatric and sympatric
what is allopatric speciation
a geographical barrier that physically isolates a population initially blocking gene flow
what happens during allopatric speciation
gene flow occurs between 2 populations which is interrupted by a geographical barrier and mutations occur in each population
different selection pressures cause divergence between isolated pools
reproductive isolation exists despite barrier being removed
what is sympatric speciation
genetic isolation occurs without a physical barrier e.g. behavioural or ecological
what happens during sympatric speciation
one population
differences between individuals cause them to choose different habitats and prevents gene flow
non random matin results in 2 genetically distinct and sperate populations that become different species
when will a new species be formed
if organisms can no longer interbreed to produce fertile offspring
