Chapter 17: Population Genetics and Evolution

Population Genetics

deals with the abundance of different alleles within a population and the manner in which the abundance of a particular allele increases, decreases, or remains the same with time.

Factors that Cause the Gene Pool to Change

Mutation

Artificial Selection

Natural Selection

because of mutation, existing alleles decrease in frequency, and new alleles increase

the most significant factor causing gene pool changes; usually described as survival of the fittest

the process in which humans purposefully change the allele frequency of a gene pool

also used to produce ornamental plants that flower more abundantly or for a longer time

often carried out in conjunction with artificial mutation

two conditions must be met before natural selection can occur

whether or not mutation is significant depends in part of on the population's size

does not include purpose, intention, planning, or voluntary decision

Rates of Evolution

Speciation

natural selection has caused a new species to evolve, a process called speciation

can occur in two fundamental ways:

Phyletic Speciation

Divergent Speciation

This movement of alleles physically through space, called gene flow, occurs in many ways, such as by pollen transfer, seed dispersal, and vegetative propagation

Abiological Reproductive Barriers

Biological Reproductive Barriers

Adaptive Radiation

a special case of divergent evolution in which a species rapidly diverges into many new species over just a few million years

any biological phenomenon that prevents successful gene flow

any physical, nonliving feature that prevents two populations from exchanging genes

Evolution and the Origin of Life

there are many species of seedless plants (lycopods, Equisetum, ferns) that have persisted for tens of millions of years without diverging into new species

equisetum

speci

mustardselection

the most seriously considered hypothesis about the origin of life on Earth is that of chemosynthesis

prezygotic isolation mechanisms

neither pollination nor fertilization occurs