View the step-by-step solution to: a. How does the existence of an archipelago promote speciation?

a. How does the existence of an archipe...
a. How does the existence of an archipelago promote speciation? Explain or provide an example.

b. Is the mode of speciation that occurred on these islands more likely to have been allopatric or sympatric? Explain.

c. Is the type of speciation seen on the Galápagos Archipelago more likely to be the result of anagenesis or cladogenesis? Explain.
Activity_24.docx

Activity 24.1 What Factors Affect Speciation?
1. The Galpagos Archipelago consists of a dozen islands all within 64 km of their nearest
neighbor. From 1 to 11 of the 13 species of Darwins finches live on each island. Many
evolutionary biologists believe that if there had been only one island, there would be only one
species of finch. This view is supported by the fact that Cocos Island is isolated (by several
hundred kilometers of open ocean) from the other islands in the archipelago and only one species
of finch is found there.
a. How does the existence of an archipelago promote speciation? Explain or provide an
example.
b. Is the mode of speciation that occurred on these islands more likely to have been allopatric or
sympatric? Explain.
c. Is the type of speciation seen on the Galpagos Archipelago more likely to be the result of
anagenesis or cladogenesis? Explain.
2. Hybrids formed by mating two different species are often incapable of reproducing
successfully with each other or with the members of their parent populations. Explain why this is
the case. (Hint: Consider what you know about chromosome numbers and meiosis.)
3. Because most hybrids cant reproduce, their genes (and the genes of their parents) are removed
from the population. Only the genes of individuals who breed with members of their own species
remain in the population. This implies that there is a strong selective advantage for genes that
enable individual organisms to recognize members of their own species. Today a wide range of
reproductive isolating mechanisms has been identified.
Each of the following scenarios describes a reproductive isolating mechanism. Indicate whether
each is a prezygotic or postzygotic isolating mechanism. Explain your answers.
a. Crickets use species-specific chirp patterns to identify a mate of their own species.
b. Two species of butterfly mate where their ranges overlap and produce fertile offspring, but the
hybrids are less viable than the parental forms.
c. Two species of a plant cannot interbreed because their flowers differ in size and shape and
require pollination by different species of bee.
d. Two species of firefly occupy the same prairie and have similar flash patterns, but one is
active for a half-hour around sunset while the other doesnt become active until an hour after
sunset.
4. Many of our most successful grain crops arose as hybrids; most are also allopolyploids. These
crops can successfully reproduce. Explain.

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