Session 7
T or F Alfred Russel Wallace developed his theory of natural selection about 20 years after Darwin
True
T or F Genetic drift has a much more significant effect on small populations than on large populations
True
T or F Speciation can occur without dramatic anatomical or genetic change
True
allopatric speciation
a population evolves into separate species when separated by a geographic barrier
homology
common structure in different species that result from a shared ancestry
behavioral isolation
courtship and mating displays keep organisms breeding within their own species
intrinsic isolating mechanisms
difference in anatomy, physiology, or behavior prevent interbreeding of closely related species
population bottleneck
dramatically reduces the size of a population
a small number of individuals from one area establish a new isolated population in another area. The gene frequencies of the new population differ from those of the original population
founder effect
alleles migrate into or out of a population from neighboring populations
gene flow
new individuals move into a population
gene flow
ecological isolation
gene flow between species is restricted because their habitats are separate
by chance, some wildflowers in this population reproduce, while others do not
genetic drift
chance events change allele frequencies in populations
genetic drift
the evolution of populations due to chance is
genetic drift
extrinsic isolating mechanisms
geographic separation prevents interbreeding
hybrid infertility
horses and donkeys can interbreed, but the mules that result are sterile
Where would a researcher most likely find find examples of allopatric speciation?
in forests on the east and west sides of Lake Michigan
natural selection is regarded as a theory because:
it is a general principle, supported by a wide variety of evidence
what is true about reinforcement?
it is a type of natural selection
temporal isolation
members of one species mate at dusk, while members of a closely related species mate at dawn
the ultimate source of genetic differences among species is
mutation
reproductive isolating mechanisms
natural factors prevent interbreeding between closely related species
a prominent tail helps the peacock attract a mate
natural selection
came enables the insect to evade predators
natural selection
the bird's beak is well suited for cracking seeds
natural selection
Many commercial pesticides become less effective after two to three years because:
pests with resistant genes will survive and reproduce
females tend to mate with brightly colored males
sexual selection
individuals with average phenotypes are favored over those with extreme phenotypes
stabilizing selection
disruptive selection operates whenever:
the extremes in a distribution of phenotypes are more fit than the average
speciation
the process by which new species form
gametic isolation
the sperm of one bird species cannot reach or fertilize the egg of a related bird species