Ch 27: The Rise of Animal Diversity Flashcards
_______ is an ancestral protist, which is the most recent common ancestor for Kingdom Animalia.
Metazoa
Eumetazoa represents the origin of tissues.
Most animals are invertebrates.
Most groups on the cladogram are invertebrates.
The Cambrian Explosion
jj
Before the Cambrian Explosion,
most animals were scavengers, grazers, or filter feeders.
*** Predator-prey interactions led to “evolutionary arms race”.
Increase in oxygen –> higher metabolism, larger size triggered diversification.
Evolution of genes that regulate development (Hox genes)
**
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.
Read about Hox genes
Chapter 16, pp. 333-335
Chapter 18, pp. 380-381
Chapter 23, pp. 474-475
The Cambrian explosion occurred in _____, and happened about ___ million years ago.
water
535
In contrast, the evidence of vertebrates on land does not appear in the fossil record until about ___ million years ago.
365
Animals required fewer _____ adaptations for land than plants did.
novel
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:
- ) a notochord
- ) a dorsal, hollow nerve cord
- ) pharyngeal slits (or pharyngeal clefts)
- ) a muscular, post-anal tail
What is the only novel adaptation that insects had to develop in order to survive on land?
adaptation for gas exchange (tracheal system)
According to Figure 27.21, what adaptations did terrestrial vertebrates have to develop in order to survive on land?
Support structure – already had a skeletal system, but needed limbs
Protection against dessication (amniotic egg/scales)
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.
*
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.
neck
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.
wrist, ribs
What important adaptations do amniotes share?
amniotic eggs
rib cage
Which of the following are amniotes?
amphibians
reptiles
egg-laying mammals
fish
reptiles (which includes birds btw)
egg-laying mammals
Why is the amniotic egg considered to be such an important evolutionary innovation?
It allowed eggs to be laid in terrestrial environments.
