APBio: Unit 7 Vocab’26

Evolution

Defined by Darwin’s phrase descent with modification: explain’s life’s unity and diversity

Natural Selection

individuals with advantageous heritable traits survive and reproduce more, cause of adaptive evolution

Adaptive Evolution

process where natural selection increases frequency of beneficial traits→ improves pop. fitness and survival in environment over generations

Artificial Selection

human-guided process of selecting plants or animals with desirable traits to breed the next generation

Do individuals evolve?

No, populations do

Adaptations

rely/depend on the environment

Homologous Structures

Structures in different species that are similar because of common ancestry

Vestigial Structures

remnants of features that served a function in the organism’s ancestors (but no longer useful)

Pseudogenes

segments of DNA that resemble functional genes, but are nonfunctional

Evolutionary Trees

a diagram that reflects evolutionary relationships among groups of organism

Analogous Structures/Convergent Evolution

distantly related organisms can resemble one another, similar features in different lineages (similar function, but no common ancestry)

Continental Drift

movements like this united all Earth’s landmasses into a single large continent called Pangaea (continents move apart later on, 200 mil yrs ago)

Vertebrates

organisms with backbones, excludes species like insects, mollusks, arthropods, etc.

Evidence to support Evolution

Direct observations, the fossil record, homology, biogeography

Microevolution

change in allele frequencies in a population over generations

Mutation and Sexual Reproduction

produces the variation in gene pools that contribute to differences among individuals

Mutations

changes in the nucleotide sequences of DNA, cause new genes and alleles to arise (rates are low in animals and plants)

Sexual Reproduction

can shuffle existing alleles into new combinations (crossing-over, independent assortment, fertilization), → recombinations of alleles more important than mutation in producing genetic differences

Heterozygote Protection

maintains a huge pool of alleles that may be harmful under present conditions, but be beneficial in environmental changes

Neutral Variation

genetic differences in DNA that do not give a selective advantage or disadvantage

Population

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

Gene Pool

consists of all copies of every type of allele at every locus in all members of pop.

Conditions for Hardy-Weinberg Equilibirum

no mutations, random mating, no natural selection, extremely large pop., no gene flow (not likely all 5 conditions will occur) → principle used to describe pop NOT evolving

Genetic drift (chance evolution)

describes how allele frequencies fluctuate unpredictably from one generation to the next→ tends to reduce genetic variation through losses of allele (smaller the sample, greater chance of deviation from predicted result)

The bottleneck effect

sudden reduction in pop. size due to a change in the environment

The founder effect

occurs when a few individuals become isolated from a larger population

Gene flow

consists of the movement of alleles among populations (ex. pollen) → tends to reduce differences between populations over time

Inbreeding

mating between closely related partners (causes frequencies of genotypes to deviate from what is expected)

Assortative mating

individuals select mates that are like themselves in certain phenotypic characters

Relative fitness

contribution an individual makes to the gene pool of the next gen, relative to the contributions of other individuals

Directional selection

favors individuals at one end of the phenotypic range

Disruptive selection

favors individuals at both extremes of the phenotypic range

Stabilizing selection

favors intermediate variants and acts against extreme phenotypes

Sexual selection

natural selection for mating success, can result in sexual dimorphism

Intrasexual selection

competition among individuals of one sex (often males) for mates of the opposite sex

Speciation

the origin of new species, is at the focal point of evolutionary theory

Macroevolution

refers to evolutionary change above the species level

Reproductive isolation

existence of biological factors (barriers) that impede two species from producing viable, fertile offsprine

Hybrid

the offspring of crosses between different species

Habitat isolation

two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers

Temporal isolation

species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Behavioral isolation

courtship rituals and other behaviors unique to a species are effective barriers

Mechanical isolation

morphological differences can prevent sucessful mating

Gametic isolation

sperm of one species may not be able to fertilize eggs of another species

Reduced hybrid viabilty

genes of the different parent species may interact and impair the hybrid’s development

Reduced hybrid fertility

even if hybrids are vigorous, they may be sterile

Hybrid breakdown

some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of next generation are feeble or sterile

Allopatric speciation

geographically isolated, reduces gene flow

Sympatric speciation

not geographically isolated, speciation takes place in geographically overlapping populations

Habitat differentiation

appearance of new ecological niches

Sexual selection

females (typically) choose males based on appearance

Punctuated equilibrium

species often show long periods of little change (stasis) punctuated by rapid speciation; contrasts with gradual change

Stages of origin of life

1. abiotic synthesis

2. joining of these small molecules into macromolecules

3. packaging of molecules into “protobionts”

4. origin of self-replicating molecules (likely RNA)

protobionts

membranes, metabolism, simple reproduction

3 Eons

1. archean eon

2. proterozoic eon

3. phanerozoic eon

cyanobacteria

do oxygenic photosynthesis

Endosymbiotic theory

eukaryotes evolved from prokaryotes living inside host cells

Cambrian explosion

sudden appearance of modern body plants, predatory-prey interactions drive diversification

stromatolites

layered rocks that form when certain prokaryotes bind thin films of sediment together

mass extinctions

1. permian → volcanoes

2. cretaceous → asteroid impact

adaptive radiation

rapid evolution of many species from one ancestor → mass extinctions free up niches, survivors diversify, reduce predatory life

EVO-DEVO

study of evolution and development interact

heterochrony

evolutionary change in rate or timing of developmental events

Hox genes

a key class of homeotic genes, clusters that form along body axis→ control body layout (head, thorax, abdomen, limbs)

developmental gene regulation

can alter body form more than gene sequence changes

phylogeny

evolutionary history of a species or group of related species

systematics

systematists use fossil, molecular, and genetic data to infer evolutionary relationships

taxonomy

ordered division and naming of organisms

taxonomic groups

domain→kingdom→phylum→class→order→family→genus→and species

sister taxa

groups that share an immediate common ancestor

molecular systematics

uses DNA and other molecular data to determine evolutionary relationships

claditics

groups organisms by common descent

clade

a group of species that includes an ancestral species and all its descendants

monophyletic grouping

consists of ancestor species and all its descendants

polyphyletic grouping

consists of various species that lack a common ancestor

paraphyletic grouping

consists of an ancestral species and some, but not all, of the descendants

shared ancestral character

character that originated in an ancestor of the taxon

shared derived character

an evolutionary novelty unique to a particular clade

outgroup

species or group of species closely related to the species studied, but not entirely together

maximum parsimony

assumes that the tree requires the fewest evolutionary events, investigate the simplest explanation that is consistent with the facts

maximum likelihood

approach identifies the three most likely to have produced a given set of DNA based on certain probability rules about DNA sequences over time