More Natural Selection Info

• Describe Natural Selection including the 3 things needed for it to occur

• Define adaptation

• List and describe five examples of natural and artificial selection

Natural Selection

• 1. There is competition for limited resources• 2. There is natural variation (behavior, traits)• 3. The variation is inherited

• The outcome of variation in heritable traits that affect survival and reproduction

Adaptation

• The consequence of natural selection is adaptation

• Adaptation: some heritable aspect of form, function, behavior or development that improves the odds for surviving or reproducing in a given environment.

Artificial Selection

http://www.gly.uga.edu/railsback/1122/1122Dogs.jpeg

Artificial Selection

http://www.bio.miami.edu/dana/160/artificialselection.jpg

Natural Selection

http://www.museums.org.za/bio/insects/cockroaches/

http://home-supplies.best-emporium.com/cat-125/Cleaning-Sanitation/Cleaning-Chemicals/Rodenticide-Insecticides/

Natural Selection

Staphylococcus aureus: antibiotic resistance

Population Information

• Define population

• Describe the basis and source of heritable variation within a population

• If there are heritable variations within a population, when does evolution not occur?

How would you define POPULATION?

• all organisms that constitute a specific group (species) in a specific habitat/environment

Review of Genetics• Cells are the basic unit of life• Cells have DNA• DNA contains genes• Genes code for proteins, usually enzymes• Genes that differ slightly are called alleles• Different alleles make different forms of the same

enzyme• These enzymes determine an organisms phenotype• Alleles can be inherited

Population Genetics• Gene pool: all the alleles of all the genes in all

the individuals in a population• Each organism will have a unique combination

of alleles and, therefore, a unique phenotype • Unique combination of alleles

– Mutation– Crossing-over– Independent assortment– Fertilization– Change in chromosome number or structure

Population Genetics

• Allele frequency: relative proportion of one allele for one gene

• Evolution: change in the allele frequency within a population

How does Evolution Occur?

• Describe how evolution can occur– Mutation – No gene flow – Small population size– Non-random mating– Natural selection

• Disruptive• Directional• Stabilizing

Violation of equilibrium: mutation• Mutations are rare (1/100,000 gametes)

• Mutations can be:– Helpful

• Depends on

environment

– Neutral– Harmful

• Lethal mutation

Gene Flow

• Individuals, and their alleles, move into and out of populations

• The physical flow counters the effects of:– mutation

– natural selection

– genetic drift

Small Population Size• Hypothesis: how often will you get tails?• Flip a coin ten times:

– # heads– # tails

• Everyone flip a coin ten times:– # heads– # tails

• Discuss the difference between 10 and 200 events: sampling error

Small Population

• Random events can have drastic effects on the allele frequencies in a small population: Genetic Drift

• Two examples:– Founder effect– Bottleneck

phenotypes of original population

phenotype of island population

A seabird carries a few seeds, stuck to its feathers, from the mainland to a remote oceanic island.

Founder Effect

Bottleneck Effect: Elephant seal

http://www.aad.gov.au/default.asp?casid=1239

Año Nuevo State Park

Reduction of a population’s gene pool produced when a few members survive the widespread elimination of a species.

Non-random mating

• Do humans mate randomly?

• How do people pick a mate?

Non-random mating: 3 types• Assortive – shifts genotype frequency

– Organisms choose a mate with the same genotype as themselves.

– Organisms choose a mate with a different genotype from themselves.

• Self-fertilization – shifts genotype frequency– Organism mates with itself

• Sexual selection –shifts allele frequency– Some genotypes mate more successfully than

others

Assortive Mating

Self-fertilization

Sexual selection

http://subjunctive.net/photoblog/2003/peacock-wooing-peahen.jpg

Natural Selection

• Evolution due to natural selection results from unequal reproduction of various alleles

• Natural selection acts on phenotypes but affects genotypes

• Adaptations help an individual survive and reproduce

Agents of Natural Selection• Abiotic factors

– Climate– Geology– Other non-living factors

• Biotic factors– Competition

• Food, Shelter, Mating

– Interspecies Interactions• Predation

– Sexual Selection

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3 Modes of Natural Selection:

Directional Selection

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3 Modes of Natural Selection:

Stabilizing Selection

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3 Modes of Natural Selection:

Disruptive Selection