Answers ■ A27Q3: Are individual species more closely related within the same
order or within the same family?
A3: Family.
Figure 14.14
Q1: Is Xiaotingia an earlier or later bird than Archaeopteryx in
this tree?
A1: Xiaotingia is later than Archaeopteryx.
Q2: If a future study, based on more fossils or new measurements,
placed Archaeopteryx back with dinosaurs, would this suggest that
birds are not related to dinosaurs? Why or why not?
A2: No. What is in question is not whether birds are related to
dinosaurs, but when exactly they split off from related dinosaur
species and which species is the first example of that split.
Q3: If you were to create an evolutionary tree of modern birds,
where would you expect to place the roadrunner (judging by its
appearance in this figure) as compared to a house sparrow or
pigeon?
A3: The roadrunner looks more like a dinosaur, so it might be
argued that it belongs closer to the base of the tree.
Figure 14.15
Q1: What extinction event occurred about 200 mya? What animal
groups were most affected by this event?
A1: Triassic; reptiles.
Q2: Which of the mass extinctions appears to have removed the
most animal groups? How long ago did this extinction occur?
A2: Permian; about 250 mya.
Q3: The best studied of the mass extinctions is the Cretaceous
extinction. Why do you think it has been better studied than the
other extinctions?
A3: Because it is more recent, more fossils may be available from
this extinction than from earlier ones.
CHAPTER 15
END-OF-CHAPTER ANSWERS
- d
- e
- c
- b
- Archaea, Bacteria, Prokaryotes, eukaryotes
- b
- e
- (a) 1, (b) 5, (e) 3, (d) 2, (c) 4
- a
- Each individual eukaryote weighs much more than an
individual prokaryote.- Prokaryotes are smaller and have simpler cellular structures,
so they take less time to divide into two. Because they
replicate so much more quickly, it is hard for our immune
systems to respond to them in a timely way.
ANSWERS TO FIGURE QUESTIONS
Figure 15.3
Q1: If an individual prokaryote divides every 20 minutes, how
many individuals will there be after an hour?A1: 8.Q2: If the generation time is 20 minutes, how much time will have
gone by when the final generation shown has doubled?A2: 20 minutes.Q3: Many bacteria are able to reproduce more quickly in warmer
conditions. What does this suggest to you about the importance of
refrigerating foods?A3: Refrigerating food slows generation time, so dangerous
bacteria like E. coli have less of a chance to increase to threatening
levels.Figure 15.4
Q1: In which of the three ways did the navel microbiome
participants contribute?A1: They were experimental subjects.Q2: Which of the advantages listed above do you think the navel
microbiome citizen scientists received?A2: They may have felt a sense of contribution and purpose.Q3: Would you be willing to contribute to the navel microbiome
project? Why or why not?A3: Various answers possible; some might express privacy
concerns.Figure 15.5
Q1: The figure (and thus the study) demonstrates that Archaea and
Eukarya are more closely related to each other than to Bacteria.
How is that illustrated?A1: The first split seen is Bacteria, apart from the other groups.Q2: Where in the figure would you place the first life found on
Earth?A2: At the base of the tree.Q3: Where in the figure is the earliest split between Archaea and
Eukarya? When did that occur?A3: The earliest split occurred where the cluster identified as
Eukarya begins. This would have been about 2.7 million years ago.Figure 15.7
Q1: Which of these shapes do you think Streptococcus would take?A1: Sphere, or coccus.