The critical factor leading to speciation is reduced ________ between two ________ of the same species.

The mule provides an example of the intrinsic isolating mechanism of hybrid ________.

Two factors always play a part in allopatric speciation: first, the development of ________ and second, the development of one or more ________.

Sympatric speciation is speciation that does not involve ________.

Living things are classified into a set of hierarchical categories. Why is this more useful to biologists than simply giving everything a one-word name (or a number) and eliminating some of the categories?

In the biological species concept, the factor that defines a species is:

a. geographical separation.

b. reproductive isolation.

c. hybridization.

d. cladogenesis.

e. its behavior.

Populations of some kinds of organisms may be isolated by a barrier as small as a roadway, while other organisms require a much larger physical barrier to block gene flow. What features of organisms might determine how readily they become geographically isolated? What impact might these features have on how often or how rapidly speciation is likely to occur in these groups?

In allopatric spéciation (select all that apply):

a. allele frequency changes are shared between populations of the same species.

b. populations are geographically isolated.

c. gene flow between populations is greatly reduced because of geographic separation

d. populations accumulate genetic changes over time that result in physical or behavioral changes that eventually block successful interbreeding.

e. populations are directly adjacent.

In an adaptive radiation, one species may colonize a previously empty environment, such as an island, and diversify evolutionarily into a set of closely related species that occupy a very wide range of habitats. For example, with Darwin’s finches on the Galapagos Islands, one species fills the role of woodpecker by using a stick to tap on trees and dig out insects. Do you think that such a species would have been likely to evolve in an area that already had woodpeckers? Why or why not?

Possible intrinsic reproductive isolating mechanisms include (select all that apply):

a. mating at different times of year or times of day.

b. geographical isolation.

c. incompatibility between eggs and sperm that prevent fertilization.

d. singing a different mating song than another species.

e. producing fertile hybrids.