Bio 1100 Mechanisms of Microevolution Vocab

Gene Flow

Movement of individuals between populations, migration, mixes alleles between separate populations

Genetic Drift

random chance of which individuals survive and reproduce which changes allele frequency

How does mutation change allele frequency?

Introduces new alleles into the population gene pool, which shifts the percent difference of organisms with each allele

Why are natural selection and sexual selection NOT random events?

Because they are both driven by survival and reproduction

Why does natural selection lead to adaptations?

Because natural selection involves individuals who live and reproduce, so those who are fit to survive live on and pass their traits to their offspring

What is fitness and how do we measure it?

an organism’s reproductive success, we can calculate it by taking the average number of offspring produced by a specific genotype or phenotype compared to the average of the population

What is relative fitness?

the measure of an individual of genotype’s reproductive success compared to others in a population

What are the three types of natural selection?

Directional, Stabilizing, and Disruptive

Directional Selection is …

when the average phenotype shifts, the whole thing

Which part of the bell-shaped curve does directional selection act?

Directional selection acts on one of the extreme ends

Stabilizing Selection is …

removes extreme phenotypes, maintains the status quo of a trait, the center remains the same

Which part of the bell-shaped curve does Stabilizing selection act?

Stabilizing selection acts on the central part of the curve

Disruptive selection is …

favors extreme phenotypes, get two or more contrasting phenotypes

Which part of the bell-shaped curve does Disruptive selection act?

Disruptive selection acts on the middle part of the curve

Does natural selection act directly on genotype or phenotype

Acts on phenotype because it is the observable traits that interact with the environment

How is genetic variation maintained in populations?

Through mechanisms they introduce new variation and prevent its loss

Why is having a variety of alleles in a population a good thing?

Having a variety of alleles is a good thing because it increases their ability to adapt to a changing environment

What is balancing selection?

Type of selection that maintains genetic diversity within a population rather than favoring a single trait, happens through frequency-dependent selection and heterozygote advantage

What is heterozygote advantage?

situation where the heterozygote has a higher fitness than either homozygous genotype, happens when the heterozygote has a beneficial trait that the homozygous lack, also preserves both alleles in the population

What impact do all three natural selections have? Are they the same?

Yes, they all increase population fitness

Why aren’t less adaptive alleles eliminated from the gene pool?

because of Heterozygote advantage

What is hidden on diploidy individuals?

Recessive alleles, but they are still there and can still be passed down if the individual survives

What is frequency-dependent selection

there is an advantage to having the less common phenotype

Example of frequency-dependent selection

left mouthed vs. right mouthed parasitic fish that attaches to other fish. If left mouthed fish are more common then other fish will be on the lookout on their left side to avoid these parasites, but they won’t for right-mouthed

Why does natural selection not make perfect organisms?

Because natural selection only occurs with existing alleles, they cannot make whatever trait they need

Historical constraints

What features/genes can be co-opted for a new function

Environments change …

change is the only constant, natural disasters, pandemics are big ones

Explain artificial selection

When humans provide the selective pressure causing evolution

Examples of artificial selection

Dogs, pesticides on bugs, industrial melanism (moths becoming darkly colored to blend in when the lichens were killed), bacterial resistance

What is non-random mating?

when individuals select partners based on specific traits or preferences

What is Sexual Selection?

Individuals with certain traits are more likely to get mates and reproduce, may lead to phenotypic differences between males and females

What is sexual dimorphism?

differences between male and female appearance or behavior or the same species

Which sex usually has more decorative or showy morphologies or behavior in sexual selection?

Males

Why do males usually have the exaggerated morphologies or behaviors?

Because the females pick

Main impact of artificial selection

can make dramatic changes in a short time period, because we are making strong quick affecting pressures and in situations where we are raising them we make sure the ones we want to survive do and reproduce

Pesticide Resistance

This is why we should rotate pesticide treatments so that they don’t give the bugs an opportunity for the resistant gene in the bugs to grow, we don’t want this but we did create this pressure

Industrial melanism

bring darker color to local environments causing the reproduction of darker colored species

What are secondary sexual traits?

not directly related to reproduction and survival, they can also be a hindrance

Display vs Ritual

Display = showy features (peacock feathers, dances) Ritual = males fighting to show strength

Why are confrontations not fatal?

There is not natural selection advantage to killing the other, they aren’t your alleles being passed on but alleles are being passed on if both survive

What is intersexual selection?

Members of the same sex compete for mates, usually males through display or ritual

Why do the showy traits that would seem to be a disadvantage persist in populations?

because females are drawn to showy traits, so those who do survive with those traits are more likely to pass on their traits

What is intrasexual selection?

mate choice, usually the female choses

What effect does gene flow have on the genetic variation between two populations?

reduces the variation between the populations, when organisms move they bring their genetic information with them making the two populations more similar to each other

Why do allele frequencies change during genetic drift?

By random chance, alleles are eliminated from the population

What happens to genetic diversity because of genetic drift?

Genetic variation decreases as a result, has a more significant impact on smaller populations

Two types of genetic drift?

bottleneck effect & Founder effect

If 1 individual migrates from population 1 to population 2, what allele frequencies change?

The allele frequencies of both population 1 and 2 change

Chance events …

cause allele frequency to fluctuate unpredictably from one generation to another, harmful alleles can become fixed in a population

Bottleneck effect is …

when only a select few of the population survive and reproduce, so results in a decrease in the population, so not all alleles are represented in the new generation, habitat destruction is a common cause

Founder effect is …

when a new environment with no similar species inhabit a new area, small number of founders and less likely to have high diversity, and they often evolve to be nothing like the species they originated form once separated, like one way migration

How do you know if a population is evolving?

Use Hardy-Weinberg Equilibrium to see what they allele frequency would be which produces the alleles of the next generation assuming no evolution

What is HWE?

Relates allele frequencies of a gene in a pop. to genotype frequencies in a pop. under certain conditions

Null hypothesis is …

assuming no change in allele frequency, no evolution

The five HWE assumptions

No mutations, mating is random, there is no natural selection, large population size, no migration (all of this is very unlikely)