ap bio evolytion of populations

Population

A Localized Group of individual capable of producing fertile offspring

Locus

The location of a gene that n the chromosome

What is a locus

A locus is fixed if all individuals in a population are homozygous for the same allele

Fixed

A gene where only one allele is present in all members of a population

Gene pool

Consists of all the alleles for all loci in a population

Where do variation of a population come from

Sexual reproduction and mutations

Pokymorphism

Coexistence of 2 or more distinct forms of individuals with the same population

Gene pool

The total sum of all the different genes of their alternative forms (alleles)

Mutations

Changes in the nucleotide sequenceS of DNA

Sexual reproduction

Can shuffle existing alleles into new combinations

Pro of sexual reproduction

Creates much more variety with less side effects

Genetic drift

Describes how allele frequencies change unpredictably from one generation to the next

Genetic drift does what

Reduces genetic variation in smaller populations

The founder effect

Occurs when a few indices become isolated from a larger population

Alleles frequencies in the founder effect

in small founder populations they can be different from those in the larger parent population

The bottleneck effect

Is a sudden reduction in population size due to change in the environment

In the bottleneck effect

The resulting gene pool may no longer be reflective of the original populations gene pool

Effects of genetic drift

It is significant in small populations, genetic drift causes allele sequences to change at random, can lead to a loss of genetic variation within populations, can cause harmful alleles to become fixed

Gene flow

Consists of the movement of alleles among populations

Gene flow can

The movement of unfavorable alleles into a population results in a decrease in in fig between organisms and environment

Gene flow can also increase

Fitness of a population

Selection acts on

Any grist’s that affects survival or reproduction

Predation selection

Act on both predator and prey (speed, camouflage)

Physiological selection

Acting on body functions (disease resistance)

Sexual selection

Acting on reproductive success (attractiveness to potential mate)

Heterozygous advantage

Occurs when heterozygous Have a higher fitness than do both homozygote

artificial selection

Can use variations in population to create vastly different breeds and varieties

Selective breeding

The raw genetic material

Directional selection

Favors indicated at one end of the phenotypic range

Disruptive selection

Favors individuals at both extremes of the phenotypic range

Stabilizing selection

Favors intermediate variants and acts against extreme phenotypes

Why selection cannot fashion perfect organisms

Selection can act only on existing variants, evolution is limited by historical constraints, adaptions are often compromises, chance, natural selection, and the environment interact

The hardy Weinberg principle states

That frequencies of alleles and genotypes in a population remain constant from generation to generation

Conditions to hardy

No mutations random mating no natural selection extremely large population size no gene flow

Three major factors alter allele frequency and bring about the most evolutionary change

Natural selection, genetic drift, gene flow

Genetic drift tip

By chance more yellow butterflies than blue and yellow becomes more popular

Gene flow tip

Yellow hangs out with blue and adds their genes to the Liz