Ch 27: The Rise of Animal Diversity

Question 1

_______ is an ancestral protist, which is the most recent common ancestor for Kingdom Animalia.

Answer 1

Metazoa

Question 2

Eumetazoa represents the origin of tissues.

Question 3

Most animals are invertebrates.

Answer 3

Most groups on the cladogram are invertebrates.

Question 4

The Cambrian Explosion

Answer 4

jj

Question 5

Before the Cambrian Explosion,

most animals were scavengers, grazers, or filter feeders.

Answer 5

*** Predator-prey interactions led to “evolutionary arms race”.
Increase in oxygen –> higher metabolism, larger size triggered diversification.

Question 6

Evolution of genes that regulate development (Hox genes)

Answer 6

**

Question 7

A third hypothesis proposes that the origin of Hox genes (see Concept 23.3) and other genetic changes affecting the regulation of developmental genes facilitated the evolution of new body forms. These hypotheses are not mutually exclusive, however; predator-prey relationships, atmospheric changes, and changes in the regulation of development may each have played a role.

Question 8

Read about Hox genes
Chapter 16, pp. 333-335
Chapter 18, pp. 380-381
Chapter 23, pp. 474-475

Question 9

The Cambrian explosion occurred in _____, and happened about ___ million years ago.

Answer 9

water

535

Question 10

In contrast, the evidence of vertebrates on land does not appear in the fossil record until about ___ million years ago.

Answer 10

365

Question 11

Animals required fewer _____ adaptations for land than plants did.

Answer 11

novel

Question 12

All chordates share a set of derived characters, though many species possess some of these traits only during embryonic development. Figure 27.17 illustrates four key characters of chordates:

Answer 12

1. ) a notochord
2. ) a dorsal, hollow nerve cord
3. ) pharyngeal slits (or pharyngeal clefts)
4. ) a muscular, post-anal tail

Question 13

What is the only novel adaptation that insects had to develop in order to survive on land?

Answer 13

adaptation for gas exchange (tracheal system)

Question 14

According to Figure 27.21, what adaptations did terrestrial vertebrates have to develop in order to survive on land?

Answer 14

Support structure – already had a skeletal system, but needed limbs
Protection against dessication (amniotic egg/scales)

Question 15

The recent discovery of a fossil called Tiktaalik provided new details on how this process of modification occurred (Figure 27.25). Like a fish, this species had fins, gills, and lungs, and its body was covered in scales. But unlike a fish, Tiktaalik had a full set of ribs that would have helped it breathe air and support its body.

Answer 15

*

Question 16

Also unlike a fish, Tiktaalik had a ____, allowing it to move its head about. In addition, the bones of Tiktaalik’s front fin had the same basic pattern found in all limbed animals: one bone (the humerus), followed by two bones (the radius and ulna), followed by a group of small bones that comprise the wrist.

Answer 16

neck

Question 17

Finally, Tiktaalik’s pelvis and rear fin were larger and more robust than those of a fish; the pelvis is the bony structure to which hind limbs are attached in tetrapods. Although it is unlikely that Tiktaalik could walk on land, the skeletal structure of its fins and pelvis suggests that it could prop itself up and walk in water on its fins. Since Tiktaalik predates the oldest known tetrapod, its features suggest that key “tetrapod” traits, such as a _____, ____, and a neck, were in fact ancestral to the tetrapod lineage.

Answer 17

wrist, ribs

Question 18

What important adaptations do amniotes share?

Answer 18

amniotic eggs

rib cage

Question 19

Which of the following are amniotes?

amphibians
reptiles
egg-laying mammals
fish

Answer 19

reptiles (which includes birds btw)

egg-laying mammals

Question 20

Why is the amniotic egg considered to be such an important evolutionary innovation?

Answer 20

It allowed eggs to be laid in terrestrial environments.