Campbell Biology Twelfth Edition: The Origin of Species

A set of vocabulary flashcards covering the processes of speciation, reproductive isolation, species concepts, and patterns of evolutionary change based on Chapter 24 of Campbell Biology.

Speciation

The process by which one species splits into two species, explaining both the diversity and unity of life.

Microevolution

Consists of changes in allele frequency in a population over time.

Macroevolution

Refers to broad patterns of evolutionary change above the species level.

Operational Taxonomic Units (OTUs)

Pragmatic, sequence-based clusters (usually $97\%$ similarity) used as flexible placeholders for taxa when exact species identification is impossible.

Biological species concept

The definition of a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups.

Hybrids

Offspring that result from interspecific mating between members of different species.

Prezygotic barriers

Reproductive barriers that block fertilization from occurring by impeding mating attempts, preventing successful completion of mating, or hindering fertilization.

Habitat isolation

A prezygotic barrier where two species occupy different habitats within the same area and encounter each other rarely, if at all.

Temporal isolation

A prezygotic barrier where species breed at different times of the day, in different seasons, or in different years.

Behavioral isolation

A prezygotic barrier where courtship rituals and other behaviors unique to a species prevent individuals of different species from mating.

Mechanical isolation

A prezygotic barrier where mating is attempted but morphological differences prevent its successful completion.

Gametic isolation

A prezygotic barrier where the sperm of one species is unable to fertilize the eggs of another species.

Postzygotic barriers

Factors that prevent hybrid zygotes from developing into viable, fertile adults through reduced viability, sterility, or breakdown in later generations.

Reduced hybrid viability

A postzygotic barrier where genes of different parent species interact in ways that impair the hybrid's development or survival.

Reduced hybrid fertility

A postzygotic barrier where hybrids fail to produce normal gametes during meiosis, resulting in sterility, often due to differences in chromosome number or structure.

Hybrid breakdown

A postzygotic barrier where first-generation hybrids are viable and fertile, but the offspring of the next generation are feeble or sterile.

Morphological species concept

A definition of species that distinguishes organisms based on structural features.

Ecological species concept

A definition of species based on their ecological niche, which is the sum of their interactions with the nonliving and living parts of the environment.

Allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

Sympatric speciation

The formation of new species in populations that live in the same geographic area.

Polyploidy

A condition resulting from accidents during cell division that produces extra sets of chromosomes, common in plants but rare in animals.

Autopolyploid

An individual that has more than two sets of chromosomes, all of which are derived from a single species.

Allopolyploid

A fertile individual that has more than two sets of chromosomes as a result of interbreeding between different species and subsequent chromosome doubling.

Hybrid zone

A region in which members of different species mate and produce hybrid offspring.

Reinforcement

A process in which natural selection strengthens prezygotic barriers to reproduction, reducing the formation of hybrids that are less fit than parent species.

Fusion

The process by which reproductive barriers weaken due to substantial gene flow, causing two parent species to merge into a single species.

Stability

An outcome in a hybrid zone where there is continued formation of hybrid individuals because of extensive gene flow from outside the zone.

Punctuated equilibria

Periods of apparent stasis in the fossil record punctuated by sudden change, rather than gradual change over time.