Evolution, Speciation, Phylogeny - Video Notes (Vocabulary Flashcards)

Vocabulary flashcards covering origins of life, early evolution, speciation, phylogeny, evolutionary mechanisms, and key evidence.

Natural selection

Process by which individuals with heritable traits that increase survival and reproduction are more likely to pass those traits to the next generation; acts on phenotypes and leads to differential reproductive success.

Descent with modification

Darwin’s idea that species arise through accumulated heritable changes over generations, leading to new species (evolution).

Evolution

Change in the genetic makeup of a population over time; descent with modification of populations.

Genetic variation

Differences in DNA among individuals in a population; the raw material on which natural selection acts.

Adaptive radiation

Rapid diversification of a lineage into several new species when a new habitat or niche becomes available.

Speciation

Formation of new species through reproductive isolation and genetic divergence.

Allopatric speciation

Speciation that occurs when populations are geographically separated, reducing gene flow.

Sympatric speciation

Speciation that occurs without geographic separation, often via reproductive isolation within the same area.

Polyploidy

Condition of having more than two complete sets of chromosomes; common mechanism of sympatric speciation in plants.

Autopolyploidy

Chromosome duplication within a single species leading to polyploid individuals.

Allopolyploidy

Polyploidy resulting from combining chromosomes from two different species.

Prezygotic barriers

Reproductive barriers that prevent mating or fertilization from occurring between species.

Habitat isolation

Prezygotic barrier where species occupy different habitats within the same area and do not encounter each other.

Temporal isolation

Prezygotic barrier where species breed at different times (days/seasons) and do not interbreed.

Behavioral isolation

Prezygotic barrier where species have different mating behaviors or rituals.

Mechanical isolation

Prezygotic barrier where reproductive structures are incompatible for mating between species.

Gametic isolation

Prezygotic barrier where sperm and egg gametes cannot fertilize even if mating occurs.

Postzygotic barriers

Reproductive barriers that prevent hybrids from developing into viable, fertile adults.

Reduced hybrid viability

Postzygotic barrier where hybrids have lower fitness and may not survive well.

Reduced hybrid fertility

Postzygotic barrier where hybrids are sterile and cannot reproduce.

Hybrid breakdown

Postzygotic barrier where first-generation hybrids are viable/fertile, but their offspring are inviable or sterile.

Bottleneck effect

Genetic drift caused by a drastic reduction in population size, reducing genetic diversity.

Founder effect

Genetic drift occurring when a new population is started by a small number of individuals, reducing genetic variation.

Gene flow

Movement of alleles between populations via migration or interbreeding.

Genetic drift

Random changes in allele frequencies from one generation to the next, especially impactful in small populations.

Mutation

A change in the DNA sequence that can create new alleles and contribute to genetic variation.

Hardy-Weinberg equilibrium

A null model in which allele and genotype frequencies remain constant across generations if no evolution occurs.

Allele frequencies (p and q)

Proportions of the dominant (p) and recessive (q) alleles in a population; p + q = 1.

Genotype frequencies (p^2, 2pq, q^2)

Proportions of homozygous dominant (p^2), heterozygous (2pq), and homozygous recessive (q^2) genotypes in a population.

Five Hardy-Weinberg conditions

No mutations, random mating, no natural selection, very large population size, no gene flow.

Null model of evolution

Assumption that no evolution occurs; Hardy-Weinberg equilibrium represents this model.

Punctuated equilibrium

Evolutionary model with long periods of stasis interrupted by short bursts of rapid change.

Gradualism

Evolutionary model where changes accumulate slowly over long periods of time.

Convergent evolution

Evolution of similar traits in distantly related lineages due to similar environments; analogous structures arise.

Divergent evolution

Descent with modification where related groups evolve different traits, forming separate species.

Homologous structures

Body structures in different species that share a common ancestry, though they may serve different functions.

Analogous structures

Structures with similar function in different species but different evolutionary origins.

Vestigial organs

Organs that have lost or reduced function but are remnants of an ancestor’s structures.

Biogeography

Study of the geographic distribution of species and ecosystems in space and time.

Fossil record

Documentation of past life through fossils, used to infer evolutionary change and dating.

Comparative morphology

Comparison of body structures to infer evolutionary relationships and shared ancestry.

Molecular homology

Similar DNA, RNA, or protein sequences across species reflecting common ancestry.

Comparative embryology

Study of embryonic development across species to reveal conserved developmental patterns.

HOX genes

A family of regulatory genes controlling body plan development in animals.

Phylogeny

Evolutionary history and relationships among organisms, often depicted as trees.

Phylogenetic trees

Diagrams showing evolutionary relationships and the timing of divergence among lineages.

Cladograms

Trees that show relationships among taxa using shared derived characters; emphasize branching order.

Synapomorphy

Derived character shared by members of a clade, used to infer evolutionary relationships.

Outgroup

A lineage outside a group used for comparison to infer ancestral states in cladistics.

Monophyletic group (clade)

Group consisting of a common ancestor and all its descendants.

Paraphyletic group

Group including a common ancestor but not all of its descendants.

Polyphyletic group

Group that does not include the most recent common ancestor of all members.

Parsimony (in phylogenetics)

Principle that the simplest explanation with the fewest evolutionary changes is preferred.

Sister taxa

Two descendants that split from the same node in a phylogenetic tree.

Basal taxon

Lineage that diverges first from a common ancestor and remains relatively unchanged.

Clade

A group consisting of a common ancestor and all its descendants; a single branch on a phylogenetic tree.

Homology vs. Convergence

Homology = shared ancestry; Convergence = similar features from separate ancestors due to similar environments.

Gene pool

All the alleles present in a population; source of genetic variation for evolution.

Genotype vs. Allele frequency

Genotype frequency: proportion of genotypes (AA, Aa, aa); allele frequency: proportion of alleles (A, a) in a population.

Vestigial example (human)

Tailbone and appendix as vestigial structures illustrating evolutionary remnants.

Darwin

English naturalist who proposed natural selection and descent with modification; studied biogeography and Galápagos finches.

RNA World Hypothesis

Hypothesis that RNA may have been the first genetic material and catalyst in early life before DNA/proteins.

Protobionts

Aggregates of prebiotic molecules capable of maintaining an internal environment; potential precursors to cells.

Miller-Urey experiment

Laboratory experiment showing organic molecules, including amino acids, can form from simple inorganic compounds under early Earth-like conditions.

Oparin-Haldane hypothesis

Idea that early Earth’s reducing atmosphere could synthesize organic molecules from inorganic precursors.

Stromatolites

Layered sedimentary formations created by cyanobacteria; among the earliest evidence of life.

Cyanobacteria

Photosynthetic bacteria that played a key role in oxygen accumulation in Earth’s history.

Biogeography of islands (Darwin)

Observation that island species resemble mainland species, informing evolutionary relationships.

Fossil dating (carbon-14)

Method to date fossils by measuring the decay of carbon-14 in organic remains.