Macroevolution and Speciation

Comprehensive vocabulary flashcards covering the key terms, reproductive barriers, modes of speciation, species concepts, and evolutionary mechanisms presented in the lecture.

Gene pool

All the alleles present within a species.

Gene flow

The spread of an allele through a species' gene pool.

Biological species concept

A species concept that defines a species as a group of individuals that can interbreed; its primary test is reproductive isolation.

Pre-fertilization (prezygotic) barriers

Reproductive barriers that prevent fertilization from ever occurring between different groups.

Post-fertilization (postzygotic) barriers

Reproductive barriers that act after fertilization occurs, resulting in a hybrid that either does not survive or cannot reproduce.

Spatial / habitat isolation

A prezygotic barrier in which groups cannot reach each other and therefore never meet to breed.

Behavioral isolation

A prezygotic barrier where courtship signals or mating behaviors do not match, preventing mating from taking place.

Gametic incompatibility

A prezygotic barrier where sperm and egg cannot complete the molecular steps required to bind and penetrate, causing fertilization to fail.

Temporal isolation

A prezygotic barrier in which reproductive timing does not line up, such as breeding at different times of day or flowering in different months.

Mechanical isolation

A prezygotic barrier where reproductive structures are physically incompatible, even between species that appear very similar.

Hybrid inviability

A postzygotic barrier where the fertilized embryo begins to divide, but developmental errors prevent it from surviving.

Hybrid sterility

A postzygotic barrier where viable offspring are born, but they are sterile and cannot reproduce themselves, such as a mule.

Speciation

The evolution of one or more new species from an ancestral form.

Allopatric speciation

Speciation that occurs when a physical or geographic barrier separates subpopulations from one another.

Adaptive radiation

An evolutionary process where one species enters a habitat with many available ways of life and natural selection shapes it into multiple new species.

Sympatric speciation

Speciation that occurs within the same geographic area without any physical barrier separating populations.

Polyploidy

The condition of having extra copies of genes or chromosomes; it causes instant reproductive isolation in plants but is lethal in animals.

Gradualism

An evolutionary pattern derived from Darwinism proposing that species change gradually over time and branch into new species.

Punctuated equilibrium

An evolutionary pattern shown in the fossil record where species appear stable for long periods, disappear, and new forms appear in sudden bursts.

Morphological species concept

A practical classification concept where organisms that look the same are categorized as the same species, useful for sorting large collections of species.

Genealogical species concept

A species concept that defines species by incorporating both reproductive compatibility and evolutionary ancestry.

Heterozygote advantage

A survival advantage found in individuals carrying one normal allele and one sickle allele, which provides malaria resistance without causing full sickle cell disease.

Convergent evolution

The process where unrelated organisms independently evolve similar physical characteristics because they are shaped by similar environments.

Genetic drift

A change in allele frequencies within a population caused by chance rather than natural selection, having its strongest effect in small populations.

Founder effect

A form of genetic drift that occurs when a small group of individuals colonizes a new location, establishing a gene pool based on the chance alleles of those founders.

Sexual selection

A form of selection driven by mate choice that can favor exaggerated traits that enhance reproductive success even if they hinder survival.