23. Speciation

Which of the following describes a postzygotic barrier?

Which of the following pairs correctly matches the postzygotic barrier with its definition?

Giraffes live throughout large regions of Africa. Historically, only one species of giraffe has been recognized, but many scientists argue that giraffe populations actually represent four distinct species. What piece of evidence would best determine whether different giraffe populations should be considered different species according to the biological species concept?

Abalone, a type of sea snail, are broadcast spawners, meaning they release their gametes into open water, where the sperm and egg drift until they meet and fertilization occurs. The sperm of the red abalone does not recognize the eggs of the pink abalone and vice versa due to biochemical incompatibilities. This is an example of what type of reproductive barrier?

“Ring species” are species that are distributed across a habitat in a ring-like distribution. Every population is able to breed with neighboring populations, but where the ring closes, the populations at the two “ends” do not interbreed. One example of a ring species is Ensatina escholtzii, a species

of salamander in California. The species began as a single population in the North, and spread South on either side of the California Central Valley. Each color on the map shows the distribution of different named population of E. escholtzii. Hybrids created by interbreeding of the populations marked

with the circle are sterile. If hybrid sterility is present, why do you think these populations are still considered the same species?