Key Terms
- adaptation
- heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment
- adaptive radiation
- speciation when one species radiates to form several other species
- allopatric speciation
- speciation that occurs via geographic separation
- allopolyploid
- polyploidy formed between two related, but separate species
- aneuploidy
- condition of a cell having an extra chromosome or missing a chromosome for its species
- autopolyploid
- polyploidy formed within a single species
- behavioral isolation
- type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place
- convergent evolution
- process by which groups of organisms independently evolve to similar forms
- dispersal
- allopatric speciation that occurs when a few members of a species move to a new geographical area
- divergent evolution
- process by which groups of organisms evolve in diverse directions from a common point
- gametic barrier
- prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs and sperm) prevent fertilization from taking place
- gradual speciation model
- model that shows how species diverge gradually over time in small steps
- habitat isolation
- reproductive isolation resulting when species’ populations move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the same species’ other populations
- homologous structures
- parallel structures in diverse organisms that have a common ancestor
- hybrid
- offspring of two closely related individuals, not of the same species
- hybrid zone
- area where two closely related species continue to interact and reproduce, forming hybrids
- natural selection
- reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change
- postzygotic barrier
- reproductive isolation mechanism that occurs after zygote formation
- prezygotic barrier
- reproductive isolation mechanism that occurs before zygote formation
- punctuated equilibrium
- model for rapid speciation that can occur when an event causes a small portion of a population to be cut off from the rest of the population
- reinforcement
- continued speciation divergence between two related species due to low fitness of hybrids between them
- reproductive isolation
- situation that occurs when a species is reproductively independent from other species; behavior, location, or reproductive barriers may cause this to happen
- speciation
- formation of a new species
- species
- group of populations that interbreed and produce fertile offspring
- sympatric speciation
- speciation that occurs in the same geographic space
- temporal isolation
- differences in breeding schedules that can act as a form of prezygotic barrier leading to reproductive isolation
- variation
- genetic differences among individuals in a population
- vestigial structure
- physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor
- vicariance
- allopatric speciation that occurs when something in the environment separates organisms of the same species into separate groups