NEW AP Biology Unit 7 Natural Selection

evolution

change in the genetic makeup of a population over time

natural selection

process where individuals with advantageous traits survive and reproduce more

competition

drives selection; because organisms produce more offspring than survived

adaptation

heritable trait that increases fitness

fitness

ability to survive and produce fertile offspring

phenotypic variation

variation in traits; natural selection acts upon phenotypic variations; adaptations -> survival -> reproduction

selective pressure

environmental factor that influences survival and reproduction

impact of phenotypic variation

may be positive or negative, determinted by the environment

molecule variation in cells

variation in the number and types of molecules within cells can increase fitness in different environments.

peppered moths

the soot-filled environment favored the survival of dark-colored months, increasing their fitness

DDT resistance

DDT-resistant insects survive and reproduce

sickle cell anemia

the sickle cell mutation only increases the fitness in malaria-prone regions, despite it causing anemia

artificial selection

human-directed breeding for desired traits; animal & plant domestication; lead to more or less genetic diversity

population

group of interbreeding individuals of the same species in the same area

gene pool

total genetic makeup of a population

allele frequency

proportion of a specific allele in a population; can change over time

microevolution

small-scale changes in allele frequencies; driven by random occurrences

mutation

primary source of genetic variation; can form new alleles

genetic drift

chance events that cause random change in allele frequencies

bottleneck effect

sharp reduction in population size by non-selective disasters, causing loss of variation

founder effect

new population established by a small group of individuals; gene pool differs from the large population

gene flow

movement of alleles between populations; may increase or decrease genetic variation

relative fitness

the number of surviving offspring compared to the number left by others in the population

directional selection

selection favoring one extreme phenotype

stabilizing selection

selection favoring the average phenotype

disruptive selection

selection favoring extreme phenotypes; mostly caused by catastrophic events that change the environment

sexual selection

selection based on mating success; can produce traits that attract the oppositve sex but harm survival

Hardy-Weinberg equilibrium

model describing non-evolving populations

Hardy-Weinberg conditions

no mutation, random mating, no selection, large population, no gene flow

p + q = 1

equation representing allele frequencies (p=dominant, q=recessive)

p² + 2pq + q² = 1

equation representing genotype frequencies (AA,Aa,aa)

fossil record

preserved remains or traces of past life

comparative morphology

the analysis of the structure of living and extinct organisms

homology

shared characteristics in related species, regardless of function

homologous structures

structures with shared ancestry but different functions

analogous structures

structures with similar function but different ancestry

vestigial structures

reduced structures with little or no function

morphological homology

species share similar structures, including vestigial structures

molecular homology

species share similar DNA and amino acid sequences

eukaryote common ancestry

shown by membrane-bound organelles, linear chromosomes, genes that contain introns

biogeography

study of species distribution

genomic change

continuing evolution where DNA changes through gene/chromosomal mutations

cell division and evolution

sexual reproduction; increasing genetic variation through independent assortment and crossing over

environment and evolution

sudden environmental change enforces different selective pressures, changing allelic and genetic frequencies

pathogen evolution

continuing evolution of pathogens that cause emergent diseases

phylogeny

evolutionary history of a species

phylogenic trees

diagram that shows evolution

cladogram

diagram showing evolutionary relationships; consists of nodes, clades, and a root

node

branch point representing a common ancestor

clade

group consisting of a common ancestor and all descendants

synapomorphy

a trait in a recent species, having evolved from an ancestral trait

outgroup

species used for comparison outside the study group; the species with the most differences

speciation

formation of a new species

reproductive isolation

prevention of gene flow between populations

prezygotic barriers

prevent mating or fertilization

types of isolation (prezygotic)

habitat, temporal, behavioral, mechanical, gametic

postzygotic barriers

prevent hybrid viability or fertility

types of isolation (postzygotic)

reduced hybrid viability, reduced hydrid fertility, hybrid breakdown (fertile 1st gen but sterile 2nd gen)

allopatric speciation

speciation caused by geographic isolation

sympatric speciation

speciation without geographic isolation

punctuated equilibrium

rapid evolution following long periods of stasis

gradualism

slow, continuous evolutionary change

convergent evolution

when similar selective pressures result in similar phenotypic adaptations; associated with analogous structures

divergent evolution

when adaptation to new habitat sresults in phenotypic diversification; associated with adaptive radiation and homologous structures

adaptive radiation

a new habitat and/or niche becomes available; speciation rates increase rapidly

genetic diversity and resilience

genetically diverse population are more resilient to environmental perturbation because they are more likely to contain individuals that can withstand the environmental pressure

deleterious

traits that reduce the chance of survival

adaptive

traits that incerase the chance of survival (an adaptive allele may be deleterious in another environment)

4.6 bya

when Earth formed

3.9 bya

when Earth was finally suitable for life

3.5 bya

when organic life starts (roughly); earliest fossil evidence is from cyanobacteria

Oparin and Haldane

hypothesized that early Earth was mostly H2, CH4, NH3, H2O

Miller and Urey experiments

tested the Oparin and Haldane hypothesis; some amino acids formed through exposure to electric spark; but hypothesis has limitation to conditions, environment, and temperature

RNA World Hypothesis

RNA was the most primitive biological compounds that existed; it started to self-replicate and transfer genetic information

extraterrestrial organic molecules

organic molecules came from e.g. meteorites that landed on Earth and survived the meteorite impact

endosymbiotic theory

early eukaryotic cells engulfed prokaryotic cells