Download Evolution and Gene Frequencies

Evolution and Gene Frequencies
Chapter 5
Zoology
Populations and Gene Pools
• Population – group of individuals of the same
species occupying a given area at the same
time and sharing a common set of genes
• Gene Pool – The sum of all alleles for all traits
in a sexually reproducing population
• 4 ways the gene pool changes: independent
Assortment, crossing over, chance
fertilization, mutations
Most, if not all, Populations are
Evolving
• Hardy-Weinberg theorem states that
evolution stops only when 4 principles are
met:
• Large population size
• No migration in or out
• No mutations
• Sexual reproduction must be random
Four Mechanisms of Evolutionary
Change
• Genetic Drift - chance events influencing the
frequencies of genes
• Gene Flow - immigration or emmigration in a
population
• Mutation - changes in the structure of genes
and chromosomes
• Natural Selection - certain phenotypes having
an environmental advantage over other
phenotypes (survival of the fittest)
Types of Selection
• Disruptive Selection - produces distinct
subpopulations
• Sexual Selection - mating patterns that
produce varying degrees of success of
individuals of a population
• Stabilizing Selection - narrows the phenotypic
range
Speciation
•Speciation – the formation of a new species (can
only occur through reproductive isolation)
•Allopatric Speciation – occurs when populations
become geographically isolated
•Parapatric Speciation – occur in small, local
populations (ex. frogs in an isolated pond)
•Sympatric Speciation – occurs within a single
population (brood parasites)
Rates of Evolution
•Phyletic Gradualism – slow, continuous
change over long period of time (Darwin)
•Punctuated Equilibrium – rapid change,
followed by periods of stasis, or no change,
over long periods of time
Molecular Evolution
•Using molecular genetics to study base-paring
in DNA is a high-tech way of tracking
evolution through the genome
Mosaic Evolution