Evolution: Microevolution, Macroevolution, and Speciation

Vocabulary flashcards covering key terms from the lecture notes on evolution.

Microevolution

small-scale evolution → changes in allele frequencies in a population over generations.

Macroevolution

large-scale evolution above the species level, including mass extinctions and origin of new groups.

Speciation

process by which one lineage splits into two or more distinct species.

Darwin's Theory of Evolution

Evolution is change over time; natural selection is the main mechanism; favorable traits accumulate.

Natural selection

differential survival and reproduction of individuals due to heritable traits.

Variation

differences in traits among individuals in a population.

Heritable traits

traits that can be passed from parents to offspring.

Differential reproduction

some individuals leave more offspring than others.

Fossils

preserved remnants showing evolutionary history, e.g., prokaryotes to eukaryotes to multicellular.

Homology

similar structures in different organisms due to shared ancestry; often with different functions.

Analogy

similarities due to convergent evolution, not shared ancestry.

Comparative embryology

similar stages in embryos, e.g., tails and pouches in embryos.

Molecular biology

DNA/protein similarities among organisms.

Population

group of the same species living in one area.

Gene pool

the total collection of genes/alleles in a population.

Mutation

new alleles; rare but essential for variation.

Sexual reproduction

shuffles alleles through crossing over, independent assortment, and random fertilization.

Crossing over

exchange of genetic material during meiosis, creating new allele combinations.

Independent assortment

random orientation of chromosome pairs during meiosis.

Random fertilization

random combination of egg and sperm producing diverse offspring.

Hardy-Weinberg Principle

allele frequencies remain constant in large populations with no mutations, migration, selection, or nonrandom mating.

p

frequency of the dominant allele in a population.

q

frequency of the recessive allele in a population.

p^2

expected frequency of homozygous dominant individuals under Hardy-Weinberg equilibrium.

2pq

expected frequency of heterozygotes under Hardy-Weinberg equilibrium.

q^2

expected frequency of homozygous recessive individuals under Hardy-Weinberg equilibrium.

Stabilizing selection

selection that favors intermediate phenotypes.

Directional selection

selection that favors one extreme phenotype.

Disruptive selection

selection that favors both extremes.

Sexual selection

selection arising from mate choice (e.g., colorful peacocks, antlers).

Diploidy

two sets of chromosomes; hides recessive alleles in heterozygotes.

Heterozygote advantage

heterozygotes have higher fitness (e.g., sickle-cell carriers resist malaria).

Frequency-dependent selection

fitness depends on how common a trait is in the population.

Origin of life

hypotheses about how life began; steps include small molecules → polymers → protocells → self-replicating molecules (RNA world).

Miller-Urey

experiment showing organic molecules can form from nonliving chemicals under early-Earth conditions.

Protocells

simple membrane-bound units representing early cell-like structures.

RNA world

hypothesis that self-replicating RNA preceded DNA/protein world.

Prokaryotes

first life forms, around 3.5 billion years ago.

Eukaryotes

cellular organisms with a nucleus, around 2.1 billion years ago.

Multicellular eukaryotes

first appeared around 1.2 billion years ago.

Plants & fungi colonize land

plants and fungi moved onto land around 500 million years ago.

Phanerozoic

eon of Earth’s history last 542 million years, subdivided into Paleozoic, Mesozoic, and Cenozoic.

Paleozoic

earliest of the Phanerozoic eras; early animal diversification.

Mesozoic

era of dinosaurs; ends with mass extinction ~65 million years ago.

Cenozoic

era of mammals and humans today.

Permian extinction

251 million years ago; ~96% of marine species died; linked to Pangaea formation.

Cretaceous extinction

65 million years ago; asteroid impact; dinosaurs extinct except birds.

Plate tectonics

continents move due to convection in the mantle.

Pangaea

supercontinent that existed before breaking apart; isolated marsupials in Australia.

Adaptive radiation

rapid diversification after extinctions or new habitats.

Evolutionary novelties

gradual refinements and new features; exaptation can repurpose structures.

Exaptation

a structure evolves for one function, later used for another (feathers → insulation → flight).

Feathers

example of exaptation in which features initially for insulation or display later aided flight.

Phylogeny

evolutionary history of species or groups.

Tree of Life

diagram depicting relationships among all organisms.

Horizontal gene transfer

movement of genes across species or domains (via plasmids, viruses).

Three Domains

the highest taxonomic rank: Bacteria, Archaea, Eukarya.

Plasmids

small DNA circles used in horizontal gene transfer among bacteria.

Viruses

infectious agents that can transfer genes between hosts.