Evolution of Populations-(Fall 2024) (1)

How many pairs of each chromosomes do humans have?

2

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA

Gene

The specific Location of a gene on a chromosome

Loci

An alternative version of a gene that may produce distinguishable phenotypic effects

Alleles

The set of two alleles one has for a specific trait/gene

Genotype

a genotype consisting of two different alleles

Heterozygous

Evolution

Change in allele frequencies in a population over time

The 3 mechanisms that cause evolution

Natural selection, Genetic Drift, Gene Flow

What makes evolution possible

The difference among individuals in the composition of their genes and or other DNA Sequences

Gene Variability

The presence or creation of genetic differences within or between populations

How do genetic variability arise from?

Mutations, Genetic recombination, Gene Flow and Polyploidy

Mutation

a permanent change in the DNA sequence of a cell or organism— due to error or environment

What are two requirements for a mutation to impact natural selection?

Occurs more frequently in an organism that reproduce rapidly

Sexual reproduction

A mechanism for evolution that occurs when organisms compete for mating partners or the ability to fertilize their gametes

Population

group of individuals of the same species that are in the same area and interbreed, producing a fertile offspring

Gene Pool

the collection of all genes and their alleles in a population of an organism that reproduce sexually

Allele Frequency

How often a specific variant of a gene/allele appears within a population

Example of allele Frequency

Blood type

What are the useful applications of calculating genotype and allele frequencies

Helps us determine if Evolution is occurring, determine the cause of evolution and is useful fro solving genetic problems

Hardy—Weinberg Equilibrium

describes a population that is not evolving

What are the 5 conditions of Hardy—Weinberg Equilibrium

No mutations, Random mating, No natural selection, Extremely Large population size and no Gene Flow

No mutations

The gene pool is modified if mutations occur or if entire genes are deleted or duplicated

Random Mating

If individuals mate within a subset of the population, such as neighbors or close relatives (interbreeding), random mixing of gametes does not occur and genotype frequencies change

No Natural selection

Allele frequencies change when individuals with different genotypes show consistent differences in their survival or reproductive success

Extremely Large population size

In small populations, allele frequencies fluctuate by chance over time— genetic drift

Genetic drift

A change in the frequency of an existing gene variant in the population due to random chance

No gene flow

By moving alleles into or out of populations Gene Flow can alter frequencies

Two types of Genetic Drift

Founder effect and Bottleneck Effect

Founder effect

occurs when few individuals become isolated from a larger population

Bottleneck Effect

A sharp reduction in a population size that leads to a decrease in genetic variation in subsequent generations — Cheetah

Gene Flow

Any movement of individuals and/or the genetic material they carry from one population to another

Why is Gene Flow important ?

Can increase genetic diversity and make smaller populations more richer

Natural Selection

The process thru which populations of living organisms adapt and change

Relative Fitness

Contribution an individual makes to the gene pool in the next generation In relation to other individuals— depends on the specific environment

What are the 3 main types of natural selection

directional, disruptive, and stabilizing

Directional

Conditions favor one extreme of a phenotypic range

Disruptive

Conditions favor both extremes of a phenotypic range

Stabilizing

Conditions select against extremes of phenotypic range

Balancing selection

A type of natural selection that maintains genetic diversity in a population by preserving multiple alleles of a gene

Heterozygote Advantage

When the heterozygotes have a higher fitness than the homozygotes

What is not a mechanism of evolution

Genetic stabilization

A mountain separates a population of birds from another population in next valley over. Every couple years, a bird finds its way over the mountain and joins the other population. This is an example of

Gene flow

One year, a blue-feathered bird makes it to the second population. It is the target of predators that can see the blue feathers more easily than the other colors. The blue alleles are eliminated from the second population. This is an example of

Natural selection

Frequency- dependent selection

Fitness depends on how common a phenotype is in the population