Evolution & Speciation Vocabulary Flashcards

Vocabulary flashcards covering key terms from the lecture notes on natural selection, adaptation, gene flow, genetic drift, speciation, and phylogenetics.

Adaptation

A trait that has become more common in a population due to natural selection because it increases survival and reproductive success.

Acclimation

Physiological, anatomical, or morphological adjustments within an individual in response to environmental change; not inherited by offspring and limited by the genome.

Natural selection

The differential survival and reproduction of individuals due to heritable variation in traits, leading to changes in allele and phenotype frequencies over generations.

Directional selection

A type of natural selection that shifts the population mean toward one extreme by favoring one phenotype over others.

Stabilizing selection

A form of natural selection that favors intermediate phenotypes, reducing variation around the mean.

Diversifying (disruptive) selection

Selection that favors extreme phenotypes at both ends of the distribution, increasing variation and potentially creating a bimodal distribution.

Fitness

Rates of survival and reproduction of a phenotype/genotype within a population, relative to others, over time.

Allele frequency

The proportion of all copies of a gene in a population that are of a given allele.

Gene flow

Movement of alleles between populations through migration, which can increase diversity and homogenize populations.

Genetic drift

Random fluctuations in allele frequencies from generation to generation, especially strong in small populations, leading to fixation or loss of alleles.

Mutation

A random change in DNA sequence; the ultimate source of genetic variation; can be deleterious, beneficial, or neutral.

Speciation

The process by which one lineage splits into two or more distinct species, often via isolation and divergence.

Allopatric speciation

Speciation caused by geographic isolation that prevents gene flow between populations.

Sympatric speciation

Speciation occurring without geographic isolation, often via reproductive barriers within a shared area.

Prezygotic barriers

Barriers that prevent mating or fertilization (habitat, temporal, behavioral, mechanical, or gametic barriers).

Postzygotic barriers

Barriers that occur after fertilization, reducing viability or fertility of hybrids (hybrid inviability, sterility, or degradation).

Biological species concept

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.

Morphological species concept

Species defined by shared physical characteristics and morphology.

Ecological species concept

Species defined by their unique ecological niche or habitat.

Phylogenetic species concept

Species defined as the smallest monophyletic groups with a shared evolutionary history and distinct traits.

Monophyletic

A group that includes a common ancestor and all of its descendants.

Clade

A monophyletic group; a lineage consisting of an ancestor and all its descendants.

Outgroup

A taxon outside the group used to root a phylogenetic tree and infer ancestral states.

Descent with inheritance (Evolution)

The idea that species descend with modification from ancestors, with traits passed to offspring.

Central Dogma (DNA
\rightarrow RNA
\rightarrow protein)

The flow of genetic information: DNA is transcribed into RNA, which is translated into protein.

Mutations are random

Mutations occur randomly with respect to an organism
eligible(s fitness and can introduce new alleles into a population.

AMELX allele (tusklessness)

X-linked allele identified in Gorongosa elephants; associated with tusklessness in females; lethal to males.

Tuskless phenotype

The observable tusklessness trait in elephants, linked to the AMELX allele and influenced by poaching selection.

Allele

Alternative form of a gene at a given locus.

Genotype

The genetic constitution of an individual at a locus, e.g., X1X1, X1X2.

Phenotype

The observable traits of an organism determined by genotype and environment.

Parsimony (phylogenetics)

The principle that the simplest explanation with the fewest evolutionary changes is preferred when constructing phylogenies.

Descent with inherited modification (Evolution definition)

Evolution: descent with modification, where traits are inherited and can change across generations.

Prezygotic barriers examples

Habitat, temporal, behavioral, mechanical, and gametic barriers that prevent fertilization.

Postzygotic barriers examples

Barriers such as reduced hybrid viability or fertility that occur after fertilization.

Genetic variation

Differences in alleles or genotypes within a population, essential for evolution.

Hardy-Weinberg Principle

A mathematical model describing a non-evolving population where allele and genotype frequencies remain constant over generations in the absence of evolutionary forces.

Convergent evolution

The independent evolution of similar features in species from different lineages, often due to similar environmental pressures.

Sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.