Chapter 24 Objectives
1. Anagenesis is when a single species transforms into another due to change accumulations, and the original species has disappeared. Cladogenesis is also known as branching evolution because new species bud off from a parent species. 2. Morphospecies is using morphology to define species, which enables one to name the extinct species. It can also be applied to individuals that do not have biparental reproduction in their line of descent. Morphological definitions lumped together biological species that are distinct, as well as separated things that belong together 3. Ernst Mayr said that a species is defined as a population or group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring. Biological species cannot produce viable, fertile offspring with members of other species. 4. There are limitations of the biological species concept in form of the fact that is no way to see if interbreeding occurred in the extinct forms represented by fossils, and the biological species concept does not apply to life-forms that use asexual reproduction. 5. Allopatric Speciation takes place in populations with geographically separate ranges. Gene flow is initially interrupted or reduced between two populations because they are separated in space. Sympatric speciation, takes place in geographically overlapping populations. Here biological factors, such as chromosomal changes and nonrandom mating, reduce gene flow. 6. Prezygotic barriers are barriers that prevent the zygote from forming in the mother; fertilization does not occur.