Chapter 23: 7.4 Microevolution

This set of vocabulary flashcards covers key concepts of microevolution, genetic drift, species concepts, and mechanisms of speciation as presented in the Chapter 23 lecture notes.

Allelomorph

Derived from the Greek words al- and allel-, meaning 'alternative form of a gene'.

Population

A group of organisms of the same species that live in the same area and interact (interbreed) with one another.

Convergent

Derived from the Latin root -verge, meaning 'to bend with or towards'.

Divergent

Derived from the Latin root -verge, meaning 'to bend into 2 (away)'.

Radiation

The act of beaming or shining in all directions; derived from the Latin radi-, meaning 'a staff', 'a root', or 'a beam'.

Gene pool

The total sum of all the genes, including their different alleles, within a population or species.

Alleles

Different versions of a gene that are found at the same location.

Homozygous

Having two identical alleles for a specific gene.

Heterozygous

Having two different alleles for a specific gene.

Genotype

The genetic makeup of an organism, including all of the alleles present.

Phenotype

The observable traits or characteristics of an organism.

Microevolution

The change of allele frequencies in the gene pool of a population over time.

Relative frequency

A measure of how often a specific biological variant occurs, divided by the total number of instances.

Hardy-Weinberg Principle

A principle that describes an ideal population that is not evolving, stating that frequencies of alleles and genotypes remain constant from generation to generation.

$$p$$

In the Hardy-Weinberg formula, the variable conventionally assigned to represent the frequency of the dominant allele.

$$q$$

In the Hardy-Weinberg formula, the variable conventionally assigned to represent the frequency of the recessive allele.

$$p^2$$

The frequency of the homozygous dominant genotype in the Hardy-Weinberg equation.

$$q^2$$

The frequency of the homozygous recessive genotype in the Hardy-Weinberg equation.

$$2pq$$

The frequency of the heterozygous genotype in the Hardy-Weinberg equation.

Genetic drift

Random fluctuations in the frequency of alleles within a small population due to chance events.

Founder effect

A type of genetic drift that occurs when a small group of individuals leaves a larger population and starts a new one with reduced genetic diversity.

Bottleneck effect

A type of genetic drift that occurs when a population’s size drastically decreases due to events like natural disasters, leading to a loss of genetic diversity.

Gene flow

The movement of individuals between populations, bringing new genetic material and potentially changing the genetic diversity.

Mutations

Random changes in DNA that create genetic variation and can introduce new traits into a population.

Somatic mutations

Mutations that occur in nonreproductive cells and are passed to new cells through mitosis but not to offspring.

Germ-line mutations

Mutations that occur in cells that give rise to gametes and can be passed to approximately half of the next generation.

Natural selection

The process where individuals with traits best suited to their environment are more likely to survive and reproduce.

Sexual dimorphism

Marked differences between the sexes in secondary sexual characteristics.

Sexual selection

A type of natural selection where certain traits evolve because they help attract a mate, even if they don’t directly contribute to survival.

Intrasexual selection

Selection within the same sex, where individuals of the same sex compete directly for mates (e.g., combat or displays).

Intersexual selection

Also known as mate choice, where individuals of one sex (usually females) are choosy in selecting their mates from the other sex.

Polygenic trait

A characteristic influenced by multiple genes, often resulting in a continuous range of phenotypes following a normal distribution.

Directional selection

Selection where individuals at one extreme of the phenotypic curve have higher fitness than individuals in the middle or at the other extreme.

Stabilization selection

Selection that acts upon the intermediate phenotype, where individuals near the center of the curve have higher fitness than those at either end.

Disruptive selection

Selection where individuals at both the upper and lower ends of the curve have higher fitness than individuals near the middle.

Speciation

The process through which new, distinct species evolve, often due to genetic differences or geographical separation.

Biological Species Concept

Defines a species as a group of populations whose members have the potential to interbreed and produce viable, fertile offspring.

Morphological Species Concept

Defines a species based on physical characteristics, structure, and appearance.

Ecological Species Concept

Defines a species based on its ecological niche, habitat, and role within the environment.

Reproductive isolation

Occurs when different populations of a species are unable to interbreed, leading to the development of separate species over time.

Geographic isolation

Speciation mechanism involving physical barriers like mountains or rivers that separate populations and prevent gene flow.

Temporal isolation

Speciation mechanism where species breed at different times or seasons, reducing the likelihood of interbreeding.

Behavioral isolation

Speciation mechanism where differences in mating rituals or behaviors prevent successful mating between populations.

Mechanical isolation

Speciation mechanism where anatomical differences prevent successful mating or the transfer of sperm between species.

Ecological isolation

Speciation mechanism where species occupy different habitats or niches, minimizing interactions and breeding opportunities in the wild.