Evolution Concepts: Darwin, Population Genetics, and Speciation (Campbell Biology, 9th Ed.)

Vocabulary flashcards covering key terms and definitions from the evolution-focused lecture notes.

Descent with modification

Darwin's idea that current species are descendants of ancestral species with heritable changes over time.

Evolution

Descent with modification; the process by which allele frequencies change over time, leading to new species.

Darwinian revolution

Shift from viewing Earth as young and species as unchanging to understanding evolution by natural selection.

Fossil

Remains or traces of past organisms preserved in sedimentary rock layers.

Sedimentary rock

Rock formed in layers that often contain fossils and reflect historical deposition.

Catastrophism

Boundaries between sedimentary strata reflect catastrophic events; proposed by Cuvier.

Uniformitarianism

Earth's features result from slow, ongoing processes—principle popularized by Lyell.

Hutton

Geologist who proposed gradualism, emphasizing deep time and slow geological change.

Lyell

Geologist who advocated uniformitarianism, influencing Darwin's view of Earth’s history.

Lamarck

Early evolutionist who proposed use/disuse and inheritance of acquired characteristics.

Use and disuse

Structures change in response to use; traits can be passed to offspring (Lamarckism).

Inheritance of acquired characteristics

Idea that acquired traits can be inherited by offspring (Lamarckian)).

Natural selection

Differential survival and reproduction of individuals due to heritable variation.

Artificial selection

Humans breed organisms for desirable traits; a model for natural selection.

Malthus

Economist who argued populations can outstrip resources, driving competition.

On the Origin of Species

Darwin's 1859 book proposing natural selection and the unity/diversity of life.

Homology

Similarity due to shared ancestry; variations on a common structural theme.

Vestigial structures

Remnants of features that served important functions in ancestors but are reduced now.

Comparative embryology

Study of embryos revealing anatomical homologies not evident in adults.

Tree thinking

Viewing evolution as branching lineages; relationships inferred from data.

Convergent evolution

Unrelated groups evolve similar traits due to similar environments; analogous traits.

Biogeography

Geographic distribution of species; supports evolution and continental drift.

Pangaea

Ancient supercontinent that split into today’s continents.

Endemic species

Species found nowhere else in the world.

Allopatric speciation

Speciation due to geographic isolation that reduces gene flow.

Sympatric speciation

Speciation without geographic separation; occurs in overlapping populations.

Polyploidy

Extra sets of chromosomes; common in plants; includes auto- and allopolyploidy.

Autopolyploid

Polyploid with multiple chromosome sets from a single species.

Allopolyploid

Polyploid with chromosome sets from different species.

Habitat differentiation

Speciation due to divergence in habitat use or ecological niches.

Hybrid zone

Region where two species meet and produce hybrids.

Reinforcement

Strengthening of reproductive barriers when hybrids have lower fitness.

Fusion

Merging of species when hybrids are as fit as parents and gene flow occurs.

Stability

Hybrid zones maintain gene flow and continuous hybridization without complete isolation.

Punctuated equilibrium

Speciation with long periods of little change interrupted by rapid changes.

Gradual pattern

Slow, steady evolution over time.

Speciation

Origin of new species through reproductive isolation and divergence.

Microevolution

Change in allele frequencies within a population over generations.

Macroevolution

Broad evolutionary changes above the species level (patterns across taxa).

Reproductive isolation

Barriers that prevent gene flow between species.

Prezygotic barriers

Barriers that block fertilization before a zygote forms.

Habitat isolation

Species rarely meet due to occupying different habitats.

Temporal isolation

Different breeding times prevent interbreeding.

Behavioral isolation

Different courtship or mating behaviors prevent mating.

Mechanical isolation

Incompatible genitalia or body structures prevent mating.

Gametic isolation

Sperm and egg incompatible; fertilization fails.

Postzygotic barriers

Barriers after zygote formation that reduce hybrid viability or fertility.

Reduced hybrid viability

Hybrids fail to develop or survive well.

Reduced hybrid fertility

Hybrids are infertile.

Hybrid breakdown

First-generation hybrids are viable; later generations are weak or sterile.

Biological species concept

Species defined by reproductive isolation and gene flow barriers.

Morphological species concept

Species defined by structural features and form.

Ecological species concept

Species defined by ecological niche and role.

Phylogenetic species concept

Smallest group of individuals that share a common ancestor.

Mutation

A change in nucleotide sequence; source of new genetic variation.

Gene duplication

Duplication events create new genetic material for evolution.

Gene pool

All the alleles for all loci in a population.

Locus

Position on a chromosome where a given gene occurs.

Allele frequency

Proportion of a given allele in a population.

p and q

Frequencies of the two alleles at a locus; p + q = 1.

Hardy-Weinberg equilibrium

Allele and genotype frequencies remain constant in a non-evolving population.

p^2, 2pq, q^2

Expected genotype frequencies under Hardy-Weinberg for a two-allele locus.

PKU example

Phenylketonuria; q^2 equals disease incidence; carriers are 2pq.

Natural selection, genetic drift, gene flow

Three main mechanisms driving evolution: differential reproduction, random allele changes, and migration between populations.

Genetic drift

Random fluctuations in allele frequencies, especially in small populations.

Founder effect

A few individuals start a new population with different allele frequencies.

Bottleneck effect

Sudden population size reduction changing allele frequencies.

Relative fitness

An individual's contribution to the next generation's gene pool.

Sexual selection

Natural selection for mating success; includes intra- and intersexual forms.

Intrasexual selection

Competition within one sex for mates.

Intersexual selection

Mate choice by the opposite sex.

Directional selection

Favors one extreme phenotype, shifting the population mean.

Disruptive selection

Favors extreme phenotypes at both ends, reducing intermediates.

Stabilizing selection

Favors intermediate phenotypes, reducing variation.

Heterozygote advantage

Heterozygotes have higher fitness than either homozygote, maintaining variation.

Sickle-cell malaria example

In malaria regions, heterozygotes are resistant to malaria, preserving the sickle-cell allele.

Limits of natural selection

Cannot produce perfect organisms; bound by history, constraints, and trade-offs.

MRSA resistance

Methicillin-resistant Staphylococcus aureus evolves resistance via natural selection.

Mutation and gene duplication

Source of new genetic variation and raw material for evolution.

Gene pool

All alleles in a population available for reproduction.

Allele frequency

Relative frequency of a specific allele in a population.

Locus

Specific location of a gene on a chromosome.

Punnett square

Tool to predict genotype frequencies in offspring.

Euhadra snail (single gene)

Example where shell spiral direction is controlled by one gene, illustrating simple genetic control of behavior.

Mimulus (flower color)

Example where two loci affect flower color, influencing pollinator preference.