Biology Now, 2e

A26fiffAnswers

12. (See figure below)

Common ancestor

of the Eukarya

Domain

Bacteria

Domain

Archaea

Kingdom

Plantae

Kingdom

Protista

Kingdom

Fungi

Kingdom

Animalia

The history of

life begins with

the common

ancestor of all

living organisms

at the root of

the tree.

Common

ancestral cell

or universal

ancestor

Domain

Eukarya

Domains

Kingdoms

13. (a) Bacteria, Archaea, Protista; (b) Bacteria, Archaea;

(c) Bacteria, Archaea; (d) Animalia; (e) Plantae, Bacteria

14. Xu: We hypothesize that Archaeopteryx and Xiaotingia are

dinosaurs, closely related to the deinonychosaurs.

Godefroit: We hypothesize that Archaeopteryx and

Xiaotingia are early birds, and Aurornis is an earlier bird.

ANSWERS TO FIGURE QUESTIONS

Figure 14.2

Q1: Why is there a shared line from the universal ancestor for

Archaea and Eukarya?

A1: Archaea and Eukarya share a common ancestor with each

other more recently than either one does with Bacteria.

Q2: Where would birds be found within this figure? What about

humans?

A2: Birds and humans would both be found as branches of

Eukarya.

Q3: To which domain would you expect a disease-causing

organism to belong? What if the organism was multicellular?

A3: Disease-causing organisms could be found within Bacteria,

but also within Eukarya (kingdom Fungi). Multicellular organisms

would be within Eukarya only.

Figure 14.3

Q1: During what geologic period did life on Earth begin?

A1: The Precambrian.

Q2: How long ago did species begin to move from water to land?

What period was this?

A2: About 480 mya, in the Ordovician.

Q3: In what period would Archaeopteryx have been alive?

A3: The Jurassic.

Figure 14.5

Q1: In what ways were theropods the same as modern birds?

Give at least two similarities.

A1: They ran on two legs and had hollow, thin-walled bones.

Q2: In what ways did theropods differ from modern birds? Give at

least two differences.

A2: They were more variable in size and in skin covering.

Q3: Birds are often referred to as “living dinosaurs.” Is this

accurate? Why or why not?

A3: Birds are direct descendants of dinosaurs, so they could be

argued to be dinosaurs.

Figure 14.6

Q1: In the traditional tree, identify the node showing the common

ancestor for early birds and dinosaurs.

A1: The common ancestor came after the split from the theropods.

Q2: What do both the traditional tree and Xu’s tree suggest about

troodontids and dromaeosaurids?

A2: Both trees suggest that these two groups were closely related.

Q3: In both trees, identify the node for the common ancestor of

Archaeopteryx and other birds. In what way are the nodes different

in the two trees?

A3: The traditional tree shows Archaeopteryx on the bird side of

the split between birds and dinosaurs; the common-ancestor node

is the point where the birds split into two groups. Xu’s tree shows

Archaeopteryx on the dinosaur side of the split; the common-

ancestor node is the theropods.

Figure 14.9

Q1: What group of organisms shares the most recent common

ancestor with plants?

A1: Green algae.

Q2: Are fungi more closely related to plants or to animals? Does

the answer surprise you? Why or why not?

A2: Fungi are more closely related to animals.

Q3: If you were to create an evolutionary tree in which amoebas

were included within the kingdom of organisms to which they

were the most closely related (rather than with protists, where they

are currently placed), where would you put them?

A3: Either with Animalia or with Fungi.

Figure 14.10

Q1: Within which category are individuals most closely related to

one another?

A1: Species.

Q2: Within which category are individual species most distantly

related?

A2: Kingdom.