Species
Group of organisms with similar characteristics which can reproduce to produce fertile offspring
Speciation
Forming new species form existing ones
Gene flow between populations occurs through interbreeding
For speciation must be barrier preventing gene flow causing reproductive isolation and genetic divergence
Isolating mechanism
Barrier preventing gene flow between populations
Geographical - physical barriers
Ecological - occupying different habitats in same area
Temporal - different breeding seasons
Behavioural - failure to mate due to different courtship behaviour
Mechanical - anatomical differences
Gametic - gametes prevented from meeting so no fertilisation
Hybrid sterility - hybrids from fusion of gametes of different species with odd chromosome number cannot form more gametes
Types of speciation
Allopatric - geographical isolation prevents gene flow between isolated populations so are reproductively isolated
Sympatric- isolating mechanism disrupts gene flow in population residing in same geographical area
Allopatric speciation
Geographical isolation of populations
Variation already present due to mutations
Different selection pressures
Different features/alleles selected
Different frequency of alleles
Produce separate gene pools with no interbreeding
Genetic drift
Change in allele frequencies in population from generation to generation
Will always be genetic drift between generations but continual, substantial genetic drift causes evolution
Smaller populations are impacted more as allele frequency changes have bigger proportional impact so evolution occurs more rapidly in smaller populations
Evolution
Change in allele frequencies in a population
