AP Biology Unit 7

evolution

the change in the genetic makeup of a population over time

natural selection

process by which organisms with adaptations better suited to an environment have a greater chance of survival and reproduction, thereby passing the adaptations to subsequent generations

competition

organisms struggle with other organisms for limited resources

variation

genetic differences among organisms within a population

adaptations

traits that provide an advantage in a particular environment

fitness

the ability of an organism to survive and produce fertile offspring

reproductive success

component of evolutionary fitness; refers to the production of offspring

heritability

the ability to pass on adaptations

genetic variation

the genotypic and phenotypic differences between individuals in a population; increases the probability that a population will survive when environmental conditions change

selective pressure

biotic or abiotic factors that influence survivability; ex. disease, predation, climate change, food availability

artificial selection

process by which humans select desirable traits in other species and selectively breed individuals with the desired traits

fossils

preserved remains, traces, or impressions of once living organisms

morphological homologies

modified traits shared among different species

homologous structures

variation in a structure derived from a common ancestor

vestigial structures

reduced/obsolete features that serve little to no purpose for the organism

analogous structures

structures that evolved independently in different species due to environmental conditions or selective pressures

genetic drift

random change in the frequency of a particular allele within a population

bottleneck events

when a large, diverse population is suddenly reduced to a small population

founder effect

random process that reduces genetic variation within a small population due to separation from a larger population

gene flow/migration

movement of individuals between populations causing an exchange of alleles between populations

Hardy-Weinberg

a model for describing and predicting allele frequencies in a nonevolving population

pathogen

infectious agent that can produce a disease; evolve and cause emergent diseases; chemically compatible with the host and coevolves

phylogenetic tree

branched diagram showing the evolutionary relationships amongst species

cladogram

simplified diagram used to show evolutionary relationships amongst species

out-group

lineage on a evolutionary diagram that is least closely related to the other organisms on it

derived character

trait in a recent species that has evolved from an ancestral trait

species

a group capable of interbreeding and exchanging genetic information to produce viable and fertile offspring

speciation

the creation of new species; needs reproductive isolation

prezygotic barriers

prevent production of a fertilized egg

temporal isolation

species breed during different times of day, seasons, or times of year

behavioral isolation

species have different courtship behaviors or mate preferences

mechanical isolation

species have differences in their reproductive structures

gamete isolation

sperm of one species is unable to fertilize another species’ eggs

postzygotic barriers

prevent a zygote from developing into a viable, fertile offspring

hybrid inviability

a zygote is produced but is not compatible, so doesn’t develop

hybrid sterility

offspring is produced that survives but is sterile

hybrid breakdown

first-generation hybrids are viable and fertile, but subsequent generations are feeble or sterile

allopatric speciation

evolution of new species due to a population being geographically separated for a long period of time

sympatric speciation

evolution of a new species due to individuals being reproductively isolated from a surviving ancestral population

punctuated equilibrium

evolution occurs rapidly after a long stasis period; caused by changing ecological conditions

gradualism

evolution occurs slowly over hundreds of thousands or millions of years; slow change in ecological conditions

adaptive radiation

evolution of new species that allows empty ecological roles to be filled; can make speciation rates particularly rapid

convergent evolution

process by which similar environmental conditions select for similar traits in different populations/species over time

analogous structures

similar traits in distantly-related or unrelated species

deletrious traits

traits that reduce the chance of survival

adaptive traits

traits that increase the chance of survival

extinction

the disappearance of a species such that no future generations will naturally populate the earth

niche

the role an organism plays within its environment

RNA world hypothesis

proposes that RNA could’ve been the earliest genetic molecule

directional selection

populations shift towards a new phenotype when the environment changes

disruptive/diversifying selection

extreme phenotypes are selected for; intermediate phenotypes are selected against

stabilizing selection

phenotypes that increase survival become more common, decreasing genetic diversity

frequency dependent selection

phenotypes that are either common or rare are favored through natural selection

kin selection

group behavior genes that help relatives survive (even when an individual dies) are favored

sexual selection

mate choice and competition drive which members of a population reproduce

divergent evolution

species with a common ancestor evolve to have different traits

monophyletic

cladogram/phylogenetic tree group that includes the most recent common ancestor of a group of organisms and all of its descendants

paraphyletic

cladogram/phylogenetic tree group that includes the most recent common ancestor and some of its descendants

polyphyletic

cladogram/phylogenetic tree group doesn’t include the common ancestor

maximum parsimony

character-based approach that infers a phylogenetic tree by minimizing the total number of evolutionary steps required to explain a given set of data assigned on the leaves