Answers ■ A25A3: No, geographic barriers are not universal. A river, for example,
might block gene flow between two lizard populations but not two
bird populations.
Figure 13.7
Q1: What factors must be present for allopatric speciation to
occur?
A1: A geographic barrier.
Q2: If a geographic barrier is removed and the two reunited
populations intermingle and breed, what attributes must the
offspring have in order for the two populations, according to the
biological species concept, to be considered still the same species?
A2: The offspring must be viable (alive) and fertile (be able to
r epr o duc e).
Q3: If the two populations in question 2 are determined to still be
the same species, did allopatric speciation occur?
A3: If they are still the same species, no speciation occurred.
Figure 13.11
Q1: Describe how coevolution, as with the hummingbird bill and
hummingbird-pollinated flowers, is different from the kind of
evolution described in Chapters 11 and 12.
A1: In coevolution, a species evolves directly to interact better
with another species. Coevolution can be both species evolving to
interact better with each other, or it can be just one of the species
adapting to the other species.
Q2: Is coevolution the same thing as convergent evolution,
described in Chapter 12? Why or why not?
A2: No. In convergent evolution, two genetically different species
look more alike over time because they are adapting to similar
environments. In coevolution, two different species adapt to each
other’s adaptations over time.
Q3: Do you think one species’ adapting over time to feed
specifically and extremely successfully on another species is an
example of coevolution? Why or why not?
A3: Yes. Coevolution does not have to be reciprocal.
Figure 13.12
Q1: What is the main difference between allopatric and sympatric
speciation?
A1: Allopatric speciation requires a geographic barrier, and
sympatric speciation cannot include a geographic barrier.
Q2: Name two events that must happen for both allopatric
speciation and sympatric speciation to occur.
A2: The two populations must be reproductively isolated, and
genetic change must occur.
Q3: Do you think all of the 500 species in Lake Victoria arose
through sympatric speciation? Why or why not?
A3: Yes, because there are no geographic barriers to separate the
populations in the lake. There would have to be a human-made
wall or fence for allopatric speciation to occur.
Figure 13.13
Q1: What does “prezygotic” mean?A1: “Prezygotic” means “before a zygote” or “before fertilization of
an egg by a sperm”—in other words, no fusion of egg and sperm.Q2: How is the booby’s ritual dance a prezygotic reproductive
barrier?A2: This dance happens before mating. If the dance is not correct,
no mating happens. No mating means no fusion of egg and sperm.Q3: What are some other prezygotic reproductive barriers besides
a mating dance?A3: Examples include all geographic barriers, inability of egg
and sperm to fuse for genetic reasons (gamete incompatibility
and isolation), inability to mate because the genitalia are
physically incompatible (mechanical incompatibility and
isolation), and ecological isolation in which two species breed
in different portions of their habitat, at different seasons, or at
different times of day.Figure 13.14
Q1: Which species is/are sympatric with Echinometra lucunter?A1: E. viridis, because it is found on the same side of the Panama
landmass as E. lucunter.Q2: Which species is/are allopatric with E. lucunter?A2: E. vanbrunti, because it is found on the opposite side of the
Panama landmass as E. lucunter.Q3: If two individuals have incompatible gametes, what will be the
result of a mating event between them?A3: No zygote will form. Egg and sperm will not fuse.CHAPTER 14
END-OF-CHAPTER ANSWERS
- c
- b
- a
- d
- clade: 2, node: 3, lineage: 5, evolutionary tree: 4, shared
derived trait: 1 - prokaryotes, Eukarya, Plantae, Animalia
- d
- e
- (a) Eukarya, Animalia; (b) Eukarya, Fungi; (c) Eukarya,
Plantae; (d) Eukarya, Plantae; (e) Eukarya, Animalia - (a) kingdom, phylum, class, order, family, genus, species;
(b) domain; (c) answers will vary - (a) 3, (b) 1, (c) 4, (d) 2, (e) 5