– A species is a group of organisms with the same morphological features, potentially able to breed among themselves but not with any other species
– first step is splitting of a population into two or more demes
– each deme has its own gene pool
– each gene pool is isolated from the other
– mutation and selection take place independently on isolated population produce new species
– mechanism involved included
*Ecological isolation
– all environmental barriers e.g geographical location, mountain, rain, rivers, etc.
– even within the same geographical location differences in habitat
– or the same habitat, but different seasons of the years
*Reproductive isolation
– populations may not be ecologically separated
– still cannot interbreed due to lack of attraction between male and female (e.g courtship behaviors in animals)
– incompatibility of genitalia due to size or shape of animals or genitalia
– in flowering plants, specific pollinating agents/mechanisms/flower behaviors
*Genetic Isolation
– even if mating is possible between populations
– fundamental differences in genetic constitution may prevent successful reproduction
– genetics may be prevented from fusing
– e.g incompatibility reaction between pollen grains and stigma in flowering plants
– even if fertilization occurs, the zygote (hybrid) may be unviable or short lived
– even viable surviving hybrids may be sterile e.g the mule