POPULATION GENETICS

POPULATION GENETICS The science of genetic change in

populations. Population- interbreeding single-

species group individuals of the same species, living in

the same place at the same time Populations are the smallest unit that

can evolve.

HOW CAN WE MEASURE EVOLUTION? As a change in the prevalence of certain

traits in a population over several generations

Evolution is only apparent when a population is tracked over time

HOW DOES IT HAPPEN?Spontaneous mutations may produce new

traitsSegregation & independent assortment

produce variations in gametes & offspringGenes are passed through gametes from

parents to offspring

MODERN SYNTHESIS Theory developed in the 1940’s Includes genetics and evolution

MICROEVOLUTION GENE POOL = where all members of the next generation get their genes!

When allele frequencies in a population change over generations, evolution is occurring at its smallest scale.

WHERE THE SPECIES LIVE MATTERS! Species distributed over a geographic range –> have different gene pool

THAN Species localized due to water, islands, mountains etc.!!!

THERE ARE SEVERAL POTENTIAL CAUSE OF MICROEVOLUTION:

1. genetic drift2. bottleneck effect

3. founder effect4. gene flow5. mutation

GENETIC DRIFT A change in the gene pool of a small population due to chance!

Ex: flipping coin 10X

BOTTLENECK EFFECT

THE FOUNDER EFFECT Type of genetic drift -colonization of a new location by a small number of individuals small size, less representative of the gene pool.

GENE FLOW Fertile individuals move into or out of a

population Gametes are transferred between

populations.

HARDY-WEINBERG EQUILIBRIUM

Allele frequency with ONLY sexual reproduction involved!

NO OUTSIDE AGENTS

VARIABLESp = dominantq = recessive2pq = heterozygousp + q = 1p2 + 2pq + q2 = 1

5 CONDITIONS ARE REQUIRED FOR HARDY-WEINBERG EQUILIBRIUM

1. very large population

2. population is isolated

3. mutations (changes in genes) do not alter the gene pool

CONTINUE… 4. mating is random 5. all indiv. Are equal in reproductive success NO NATURAL SELECTION OCCURS!

HARDY-WEINBERG EQUILLIBRIUM

Conditions rarely met by a natural population

Gives us a basis to compare nonevolving population vs. actual ones with gene pools that are changing!