bio unit 2

assortive mating

when individuals mate with those who are phenotypically similar to themself

bottleneck effect

- a type of genetic drift that happens when a population is reduced in size
- reduces genetic variation because some that were included in the previous population are not there anymore.

gene flow

the flow of alleles in and out of a population due to the individual or gamete migration

genetic drift

the change in frequency of an existing allele in a population due to chance

genetic variance

Differences in genes or traits between individuals in a population.

Example: Some rabbits have brown fur, while others have white fur.

geographical variation

Differences in traits between populations living in different geographic locations.

Example: Rabbits in colder regions may have thicker fur than rabbits in warmer regions.

heritability

how much genes explain why people are different from each other.
Example: Height
Some people are tall.
Some people are short.
Their genes help explain why they have different heights.

inbreeding

mating of closely related individuals

inbreeding depression

when offspring have lower fitness (such as survival or reproduction) because closely related individuals breed

mutation

a change in the DNA sequence of an organism

nonrandom mating

is when individuals choose mates based on certain traits instead of mating randomly.

Example: Peahens choosing peacocks with bigger, brighter tails.

population variation

the differences in traits among individuals in the same population.

Example: People in a population have different heights, eye colors, and hair colors.

selective pressure

something in the environment that makes individuals more likely to survive and reproduce than others.

Example: Predators eat slower rabbits, so faster rabbits are more likely to survive and have offspring.

allele frequency

how common a specific version of a gene is in a population.

Example: If 60% of the alleles for a trait in a population are the brown-eye allele, its allele frequency is 60%.

founder effect

when a small group starts a new population, causing it to have less genetic variation than the original population.

Example: A few birds start a new island population, and their offspring have only some of the genes found in the original population.

gene pool

all the alleles (versions of genes) in a population.

Example: All the different alleles for fur color in a population of rabbits make up their gene pool.

genetic structure

The types and amounts of genes in a population and how they are distributed among individuals.

Example: A population of rabbits has different frequencies of alleles for brown and white fur.

Hardy-Weinberg equilibrium

when allele frequencies in a population stay the same from generation to generation, meaning the population is not evolving.

NO EVOLUTION

Example: A population of rabbits keeps the same proportions of fur-color alleles over many generations.

macroevolution

large-scale evolutionary change that can lead to new species over long periods of time.

Example: Dinosaurs evolving into modern birds.

microevolution

small changes in allele frequencies within a population over time.

Example: A population of bacteria becomes more resistant to antibiotics.

modern synthesis

The theory that combines Darwin’s evolution by natural selection with genetics to explain how species evolve over time.

Example: A population of insects develops pesticide resistance because insects with helpful genes survive and reproduce more.

population genetics

the study of how genes and allele frequencies change in a population over time.

adaptive evolution

when a population develops traits that help it survive and reproduce better in its environment over time.

Example: Polar bears evolved thick fur to help them survive in cold climates.

Charles Darwin

was a scientist who developed the theory of evolution by natural selection.

decent with modification

when species change over generations and pass inherited traits to their offspring, sometimes leading to new species.

Example: Modern birds evolved from ancient dinosaur ancestors over millions of years.

natural selection

the process where organisms better adapted to their environment tend to survive and produce more offspring, driving evolution

Thomas Malthus

was an economist who argued that populations grow faster than their food supply, leading to competition for resources.

directional selection

when natural selection favors one extreme version of a trait, causing the population to shift in that direction over time.

diversifying selection

favors two or more distinct extreme phenotypes while selecting against intermediate or average traits

evolutionary fitness

how successful an organism is at surviving and reproducing, passing its genes to the next generation.

frequency-dependent selection

when a trait’s advantage depends on how common or rare it is in a population.

Example: Rare-colored fish may avoid predators more easily because predators are used to seeing the more common colors.

relative fitness

individual's ability to survive and reproduce relative to the rest of the population

stabilizing selection

when natural selection favors average traits and selects against extreme traits.

five forces of evolutionary change

mutation, non-random mating, gene flow, genetic drift, natural selection

genetic diversity

the variety of genes within a given species

Increased Homozygosity/Decreased Heterozygosity

Increased homozygosity: Having two identical alleles for a gene (AA or aa).

Decreased heterozygosity: Having fewer pairs of different alleles (Aa).

allopatric speciation

when a population is separated by a geographic barrier and evolves into two different species.

Homologies

similar traits in different species because they inherited them from a common ancestor.

ecological isolation

when two species live in the same area but use different habitats or resources, so they rarely mate with each other.

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

developmental homology

similarities in the development of embryos between different species that share a common ancestor

homeobox (Hox) genes

the genes that tell the body where to grow its parts.
They act like a set of building instructions, making sure your head, arms, and legs all grow in the right places.

regulatory gene

gene that controls when and where other genes are expressed

vestigial structure

physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor

phylogeny

Evolutionary history of a species

analogy

occurs when different species develop structures or traits that perform similar functions, but these structures do not share a common evolutionary origin.

- the result of convergent evolution

altruism

behavior that benefits the recipient at a cost
to the donor

2 major costs of sexual reproduction

1. cost of meiosis - each parent passes half of their DNA to offspring
2. cost of males - in most species females reproduce & males don't.

benefits of sex

- new gene combinations
- genetic variation can help offspring survive better

red queen hypothesis

organisms must keep evolving to keep up with other evolving organisms.

gamete

reproductive cells that combines during sexual reproduction.
egg & sperm

Monogamy

one individual mates with one partner.

polygyny

One male, several females.

polyandry

One female, several males.

promiscuity

Having many sexual partners without commitment

good genes

females choose a male with traits that suggest good genetic quality.

direct benefits

female chooses a male that provides resources and help.

s3xy sons

females choose attractive mates to ensure their male offspring inherit those traits maximizing the reproductive success of future generations.

apparent altruism

behavior that looks altruistic but actually benefits the actor.

Mutualism

both individuals benefit

parasitism

one benefits while the other is harmed

kin selection

natural selection that favors behaviors that increase an individual's fitness.
helps relative's pass on shared genes.

inclusive fitness

direct & indirect fitness (own reproduction & relative reproduction)

indirect fitness

fitness gained by helping relatives reproduce

direct fitness

fitness gained through an individual's own reproduction.

reciprocal altruism

helping someone & expecting future help