species live in different habitats within the same area and rarely meet (garter snakes in water/land)
habitat isolation
breeding occurs at different times of the day or different seasons (west/east spotted skunk breed at differ times of year)
temporal isolation
different courtship rituals or other behaviors prevent mate recognition between species (blue-footed booties)
behavioral isolation
differences in physical structures prevent successful mating (snails)
mechanical isolation
male and female gametes of different species fail to unite (sea urchins)
gametic isolation
prevent development of viable offspring (capable of reproducing)
postzygotic barriers
development or survival of hybrids is impaired (species of salamanders)
reduced hybrid viability
hybrids fail to produce functional gametes (horse + donkey=mule-sterile)
reduced hybrid fertility
offspring of hybrids are feeble or infertile
hybrid breakdown
occurs when a geographic barrier isolates a population which then follows its own independent evolutionary course
allopatric speciation
mountain range emerges, splitting a population of organisms
one example of a geologic process that divides a population
large lake dries, have two smaller lakes, breaks population into two smaller separate populations
one example of a geologic process that divides a population
few individuals of species colonize a remote area
one example of a geologic process that divides a population
geographic barrier separating south rim squirrel and north rim squirrel
one evidence of allopatric speciation
snapping shrimp, two of 15 pairs separated by the Isthmus of Panama
one evidence of allopatric speciation
occurs when a new species arises within the same geographic area as its parent species
sympatric speciation
the evolution of many diverse species from a common ancestor (variety of birds called galapagos/darwins finches with a variety of beak shapes and sizes for eating a diverse array of food)
adaptive radiation
evolution occurs gradually, relatively small steps
gradualist model of evolution
long periods of little change, equilibrium, punctuated by abrupt episodes of speciation, bursts of rapid, sudden evolutionary change