Key Terms

Key Terms

acquired characteristics
modifications caused by an individual’s environment that can be inherited by its offspring
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 out to form several other species
allopatric speciation
speciation that occurs via geographic separation
polyploidy formed between two related, but separate species
condition of a cell having an extra chromosome or missing a chromosome for its species
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
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 populations of a species move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the other populations of the same species
homologous structures
parallel structures in diverse organisms that have a common ancestor
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
gametes with extra chromosomes
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
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; this may be brought about by behavior, location, or reproductive barriers
formation of a new 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
theory of evolution
explains how populations change over time and how life diversifies the origin of species
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
allopatric speciation that occurs when something in the environment separates organisms of the same species into separate groups