Lecture Notes: Key Evolution Terms (Ch.1-3)

Vocabulary flashcards covering key terms from Chapters 1–3.

adaptation

A trait that increases an organism’s fitness in a given environment or the process by which populations become better suited to their environment.

blending inheritance

The outdated idea that offspring are simple blends of parental traits.

descent with modification

Darwin’s idea that species descend from common ancestors with gradual changes over time.

diverge

To develop in different directions from a common ancestor.

evolution

Change in heritable traits within a population over generations.

evolutionary synthesis

A framework combining Mendelian genetics with natural selection to explain evolution.

genetic drift

Random fluctuations in allele frequencies in a population, especially in small populations.

genotype

The genetic makeup of an organism; the set of alleles it carries.

taxon (taxa)

A group or category in taxonomy (e.g., species, genus, family).

hypothesis

A testable statement used to explain observations.

inheritance of acquired characteristics

Lamarckian idea that traits acquired during life can be passed to offspring.

Lamarckism

The theory that characteristics acquired during an organism’s life are inherited.

macroevolution

Large-scale evolutionary changes above the species level.

microevolution

Small-scale evolutionary changes within populations.

modern synthesis

See evolutionary synthesis; the integration of genetics with Darwinian evolution.

Mutationist

A theory emphasizing mutation as a primary driver of evolution.

natural selection

Differential survival and reproduction of individuals due to trait differences.

neo-Darwinism

Synthesis of Darwinian natural selection with Mendelian genetics.

neo-Lamarckism

A revival of Lamarckian ideas within a modern context.

neutral theory of molecular evolution

Most genetic variation at the molecular level is due to genetic drift of neutral mutations.

orthogenesis

Directional evolution along a predetermined path.

particulate inheritance

Inheritance of traits via discrete units (genes) rather than blending.

phenotype

Observable traits of an organism resulting from the interaction of genotype and environment.

phylogeny

The evolutionary history and relationships among organisms.

population

A group of interbreeding individuals of the same species in a defined area.

proximate causes

Immediate physiological or mechanistic causes of a trait.

scientific theory

Well-substantiated explanations that integrate many observations and hypotheses.

selection

Differential reproductive success due to trait differences; often refers to natural selection.

speciation

The formation of new and distinct species.

synthetic theory

Another term for the modern synthesis of evolution.

ultimate causes

Evolutionary explanations for why a trait exists (fitness advantages over time).

uniformitarianism

Geological principle that present processes explain past changes; used analogously in biology.

adaptive radiation

Rapid diversification of a lineage into many ecological niches.

anagenesis

Evolution within a single lineage without branching.

character

A heritable trait used in evolutionary analysis (e.g., wing color, temperature tolerance).

character state

The different conditions a character can take (e.g., red vs. blue).

clade

A group consisting of an ancestor and all its descendants.

cladogenesis

Branching evolution that produces new lineages.

common ancestor

The most recent ancestor shared by two or more lineages.

conservative characters

Traits that change slowly over time.

convergent evolution

Independent evolution of similar traits in unrelated lineages.

divergent evolution

Lineages evolving in different directions from a common ancestor.

evolutionary reversal

Return to an ancestral trait after a derived trait has evolved.

extinction

The permanent loss of a lineage or species.

gene duplication

A DNA segment is copied, creating gene copies that can evolve new functions.

gene family

A set of related genes derived from a common ancestral gene.

gene genealogy

The evolutionary history of a gene across species.

gene tree

Phylogenetic tree representing the history of a gene.

higher taxon

A higher-level taxonomic category (e.g., order, class).

homologous

Traits derived from a common ancestor.

homoplasy

Similarity not due to shared ancestry (e.g., due to convergent evolution or reversal).

horizontal gene transfer

Transfer of genetic material between species, common in microbes.

hybridization

Crossing between species to form hybrids.

ingroup

Group of taxa being studied in a phylogenetic analysis.

lineage

A sequence of populations connected through time from a common ancestor.

molecular clock

Idea that genetic mutations accumulate at a relatively constant rate over time.

monophyletic

A group containing an ancestor and all of its descendants.

mosaic evolution

Different parts of an organism evolve at different rates or times.

most recent common ancestor

Most recent individual from which all members of a group are descended.

outgroup

A taxon outside the group of interest used to root a phylogenetic tree.

parallel evolution

Independent evolution of similar traits in related lineages due to similar pressures.

paraphyletic

A group that includes an ancestor and some, but not all, of its descendants.

parsimony

The simplest explanation with the fewest evolutionary changes.

phylogenetic tree

Diagram showing evolutionary relationships among taxa.

phylogeny

The evolutionary history and relationships of organisms.

polyphyletic

A group that does not include the most recent common ancestor of its members.

rooted species tree

A phylogenetic tree with a designated root representing the oldest common ancestor.

taxon (taxa)

A defined group in taxonomy at any rank (e.g., species, genus).

altruistic traits

Traits that benefit others at a cost to the actor’s own fitness.

character displacement

Evolutionary shift in traits to minimize competition between species.

comparative method

Analytical approach comparing species to test evolutionary hypotheses.

exaptation

A trait that evolved for one function but was co-opted for a new use.

fitness

Reproductive success; contribution of an individual’s genes to the next generation.

frequency

The proportion of alleles or phenotypes in a population.

group selection

Natural selection acting on the level of groups rather than individuals.

hypothetico-deductive method

Approach: form hypotheses and test them with experiments or observations.

individual selection

Natural selection acting on individual organisms.

kin selection

Natural selection favoring traits that help relatives share genes.

levels of selection

Different hierarchical levels (gene, individual, group, species) that selection can act upon.

meiotic drive

Non-Mendelian inheritance where certain alleles are transmitted more than 50% of the time.

neutral alleles

Genetic variants with no significant effect on fitness.

preadaptation

An existing trait that becomes useful in a new context (exaptation).

reproductive success

The production of surviving offspring; a measure of fitness.

segregation distortion

Deviation from expected Mendelian inheritance ratios.

selfish genetic elements

Genetic elements that spread themselves in a genome, sometimes at a cost to the host.

sexual selection

Selection arising from variation in mating success, often via traits like courtship or ornaments.

species selection

Selection acting at the species level, affecting lineage persistence.

trade-off

Compromise between two traits due to limited resources or constraints.