9.2 Establishing Phylogenetic Relationships - Answer Key
1. Carolus Linnaeus developed a classification system for organisms based
on similarities in their characteristics.
2. Phylogeny is the evolutionary development
3. A branching diagram that represents the evolutionary relationships among species or
groups is called a phylogenetic tree. A cladogram is a type of phylogenetic tree that
shows the derived characteristics of the organisms illustrated.
4. Molecular data...see pg. 252
5. Taxonomy (the classification of organisms).
6. Each evolutionary branch in a phylogenetic tree is called a clade. The most common
method used today to determine the sequence of branches in a phylogenetic tree is
called cladistics. A phylogenetic diagram that specifies the derived characters of
clades is called a cladogram.
7. A common ancestor from which two species diverged.
8. Leopard closest relative. Turtle least related.
9. Primates are characterized by having grasping hands and feet with opposable first digits.
10. The ancestral primates diverged into two groups: prosimians and anthropoids (Figure
9.19). The prosimian lineage diverged several times and now includes modern lemurs,
lorises, and tarsiers. The anthropoid lineage also diverged several times, starting about
25 to 30 million years ago. First, new-world monkeys and old-world monkeys diverged.
Then hominoids and old-world monkeys diverged. Humans - anthropoids.
11. Hominoids have relatively large brains, lack tails, and have swinging arms.
12. What distinguishes hominids from all other species is their large brain size and
bipedalism. Bipedalism is the ability to walk on two feet.
13. African
SECTION 9.2
Establishing Phylogenetic Relationships, p. 251–
258
Section Answers
Explore More, p. 253
1. The vertebral column is a shared derived character of all organisms in the cladogram. Therefore, it
likely evolved before hair, which is shared by only two of these organisms.
2. It was probably made of cartilage because bone is a shared character of bony fishes, lizards,
monkeys, and kangaroos, but not of sharks. Therefore, cartilage most likely evolved later than bone.
Concept Check, p. 255
1. Phylogenetic relationships are established by comparing homologous structures and looking at
similarities of DNA and/or proteins.
2. Analogous structures show common function but not similarities in structure. They do not show
similarities between organisms due to common descent.
3. A branch point in a cladogram indicates a separation of a clade.
9.2 Check and Reflect, p. 258
Key Concept Review
1. Cladograms are constructed using shared derived characteristics based on homologous structures and
DNA similarities. Species that share a specific derived characteristic are part of the same clade.
2. Primates are subdivided into these two subdivisions:
(a) prosimians, which include modern lemurs, lorises, and tarsiers
(b) anthropoid lineage, which include new-world monkeys, old-world monkeys, and hominoids
3. Hominoids have relatively large brains, lack tails, and have swinging arms.
4. Hominids are humans and all their ancestral species that occurred after the split from ancestral
chimpanzees. This includes australopithecines.
5. The Homo genus differs from australopithecines by the larger brain size and the shape of the jaws
and teeth.
Connect Your Understanding
6. By looking at the rates of evolution of viruses, scientists can determine the relative time of infection
of potential victims from a bioterrorist case. If all the victims have closely related viruses, then they
were infected by a common source. If the common ancestor of the virus existed when these victims
were in contact with the potential suspect, then it is probable that the suspect could have infected the
victims.
7. (a) They are most related to birds.
(b) Birds fly while crocodiles do not. At first, glance they appear different.
(c) Comparing their anatomy, homologous structures can be used to establish relationships. Also,
similarities in DNA and proteins can also be used.
8. (a)
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(b) A backbone most likely evolved first since most species have it.
(c) The salamander is most closely related since they share most of the same derived characteristics.
(d) Since a frog has a backbone and legs but not hair, it would be placed in the same location as the
salamander.
9. (a) Bipedalism evolved first.
(b) Fossil evidence shows that species were bipedal before the evolution of a bigger brain size. For
example, both australopithecines and species in the Homo genus were bipedal, but the Homo
genus had a larger brain size.
10. Previously it was believed that the common ancestor or “missing link” between humans and
chimpanzees must have had features that were common to the two groups. A. ramidus, however,
shows more similarities to early humans and ancestral apes than it does to chimpanzees. This shows
that both humans and chimpanzees have evolved different features and both species now look very
different from their ancestors.
11. Modern human DNA should resemble early Homo sapiens DNA rather than the DNA of Homo
neanderthalis.
12. DNA evidence was used to determine the migration patterns of hominids.
13. You would have to analyze the skeletal features of the skull and compare it to known hominids.
For example, you would look at the shape of the brow ridge, the shape of the jaw, the type of teeth,
and the face projection.
14. Scientists would choose a model that shares similar derived characteristics to humans. Species
that are more related to humans are assumed to react the same way to testing as humans would.
Reflection
15. Students’ answers will vary but may say that they did not know that humanoids developed such a
long time ago. Another possible answer is that they didn’t realize that bipedalism occurred before the
evolution of a larger brain size.