biology - chapter 18 & 19

how was the modern theory of evolution developed?

darwin’s idea of natural selection combined with modern genetics

what is an adaptation?

a heritable trait shaped by natural selection that improves survival or reproductive success in a specific environment.

what is convergent evolution?

when unrelated species independently evolve similar traits due to similar environmental pressures

what is divergent evolution?

when related species diverge and become increasingly different due to different environments or selective pressures

what are homologous structures?

structures in different species that share a common ancestral origin but may serve different functions

what are vestigial structures?

reduced or unused structures inherited from ancestors

what are common misconceptions about evolution?

individuals don’t evolve, populations do

evolution doesn’t happen because individuals want to change

evolution doesn’t explain the origin of life

evolution is a scientific theory, meaning it’s well-supported

how do scientists define a species (biological species concept)?

a group of organisms that can interbreed and produce fertile offspring.

how do scientists determine whether species are different?

by reproductive isolation, genetics, morphology, ecological roles, and evolutionary history.

what genetic factors cause speciation?

mutation, genetic drift, natural selection, changes in allele frequencies, and reproductive isolation.

what are prezygotic reproductive barriers?

barriers that prevent mating or fertilization; habitat, temporal, behavioral, mechanical, gametic isolation

what are postzygotic reproductive barriers?

barriers after fertilization; reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

what is allopatric speciation?

speciation that occurs when populations are geographically separated.

what is sympatric speciation?

speciation within the same geographic area, often caused by polyploidy in plants or ecological niche differences.

what is adaptive radiation?

rapid evolution of many species from a single ancestor when new ecological opportunities appear.

what are the positive outcomes in hybrid zones?

reinforcement, fusion, stability

what are the two main models of speciation rate?

gradualism, punctuated equilibrium

what is population genetics?

the study of allele frequency patterns and changes within populations over time

why are population genetics important?

it helps scientists understand how evolution occurs at the population level

what is the hardy-weinberg principle?

allele frequencies remain stable in a non-evolving population

why is the hardy-weinberg principle important?

it provides a baseline to compare real populations to see if evolution is occuring

what kinds of variation exist within populations?

genetic variation, phenotypic variation, continuous variation, discrete variation

why can natural selection act only on heritable variation?

only genetic traits can be passed to offspring; non-genetic changes cannot

what is genetic drift?

random changes in allele frequencies, especially in small populations

what is the bottleneck effect?

a major reduction in population size that decreases genetic diversity and increases drift.

what forces cause allele frequencies to change?

mutation, genetic drift, gene flow, natural selection, nonrandom mating

what are the patterns of natural selection?

directional selection, stabilizing selection, disruptive selection

how can evolutionary forces change population variation?

increase variation, decrease variation, split populations into new species, shift average traits, reduce extremes