Unit V:Population Genetics (Hardy Weinberg Equilibrium)

Ms. BuechlerInt. Sci. 4/Biology

EW5/7

Q: In the “Zonkeys” reading you were asked if hybrids help or hurt the “gene pool”… what’s a gene pool?

Genetic Diversity is a good thing!

Population Genetics VocabularyPopulation= members of

the same species that share a habitat

Fitness=how good a particular genotype is at leaving offspring in the next generation relative to how good other genotypes are at it◦ Depends on the environment

Allele frequency= how often a specific allele for a trait appears in a population

Gene Pool= the total number of genes in an interbreeding population◦ The greater # of genes in

a population the more genetic diversity Increases the “fitness” of the population in the environment

◦ Reduces the chance of extinction increases survival rate in the population

Hardy-Weinberg Equilibrium

Genetic variation introduced by the processes of meiosis (crossing over) and random fertilization does not, itself, alter a population’s overall gene pool.

The frequencies of alleles in a population’s gene pool will remain constant indefinitely (i.e. will be in equilibrium) unless a “disturbing” influence is introduced.

A theoretical non-evolving population is said to be in Hardy-Weinberg equilibrium.

When does evolution occur?Evolution occurs when populations deviate

from the Hardy-Weinberg equilibrium.The mechanisms that drive evolution are:

◦ Natural Selection◦ Sexual Selection◦ Mutation◦ Genetic drift◦ Gene Flow

Natural SelectionNatural

Selection= selective pressures causing a change in allele frequency.◦ Heritable phenotypes

that cause an advantage in the population’s fitness become more common in a population.

Sexual SelectionSexual Selection=

the more attractive members of a population are more likely to mate and pass on their genes◦ Non-random mating

occurs◦ This changes the allele

frequency as the “more attractive” members of the population pass on more alleles than the “non-attractive” members

Male Elephant seals fight for the right to breed with ALL the females in the colony

MutationsMutation= is a

random permanent change in an organism’s DNA.

Heritable mutations can lead to changes in the gene pool of a population.

New mutations can be:◦ harmful◦ neutral◦ advantageous

Due to their lack of camouflage, albino alligators generally do not survive to adulthood in the wild.

Genetic DriftGenetic Drift=

Population change due to random changes in genotypic frequencies.◦The smaller the

population, the greater the effect of genetic drift on the population’s gene pool.

EX> Suppose a natural disaster randomly kills a large portion of the population; ◦the remaining

survivors may have allele frequencies that were very different from the previous population

Gene Flow

Gene Flow=Transfer of genes from one population to another of the same species

◦Migration/ Immigration

◦Seed/pollen/larva dispersal

Changes allele frequency◦New alleles can be

introduced into a population or alleles can be removed from a population.

MigrationMigration into or out of

a population can cause deviations from Hardy-Weinberg expectations.◦New alleles can be

introduced into a population or alleles can be removed from a population.

◦The frequencies of alleles and genotypes in a population can be altered.

The arctic tern migrates longer distances than any other known bird.

VideosCrash Course: Population GeneticsBill Nye: Biodiversity

Prep for Vocab Quizzes M 5/12

Vocab 5 Mutation Genetic Recombination

/Crossing Over Phylogenetic Species

Concept Morphology Natural selection Evolution Extinction Camouflage Claim Evidence

Vocab 6 Adaptation Classify Common Ancestor Extinction Fitness Natural Selection Sexual Selection Speciation Species

Prep for Benchmark & Unit ExamBenchmark 5 on T 5/13 Use Firefox eLearning BM Testing/EOC Select Benchmark #5 2 Free Response

◦ One of those is a conclusion question

25 MC or T/F Questions Score a 3.5 or higher and

you are excused from the unit exam

Unit V Exam on Th 5/15

18 total matching (in two sections) over Evolution Key Terms and Classification Key Terms.

27 MC questions

Good Sources of Review of Classification/Evolution Exam

Study Guide Unit V

http://apesnature.homestead.com/chapter5.html

http://www.biology-online.org/2/10_natural_selection.htm

http://www.visionlearning.com/library/module_viewer.php?mid=68&l

http://www.bio200.buffalo.edu/labs/nomenclature.html

http://learn.genetics.utah.edu/content/variation/sources/