chapter 42 self assessment questions

Which features are common to bony fishes, amphibians, amniotes, and mammals?

all have jointed and mineralized skeleton, a cranium encased brain, jaws and vertebral column.

Which synapomorphies unite sponges and eumetazoans as sister groups?

animals in both groups have multicellular bodies with distinct cell types that develop from an embryo that include the blastula phase.

Which features underpin the ecological success of tetrapods on land?

animals living on land- able to move without swimming, obtain oxygen from air, avoid desiccation. modification of the gut sac results in lungs that enable tetrapods to breath air. amniote egg enables egg to survive dry environments. modification of the lobed fins enabled tetrapods to move across the land.

Why do bird feet have scales like those found on snakes and lizards?

because they were present in a common ancestor. even feathers are modified scales.

The hypothesis that ctenophores are sister to all other animals runs counter to the traditional view that sponges and a group containing all other animals diverged from the earliest node on the animal tree. What are the two possible ways of reconciling this new phylogenetic hypothesis with anatomical and morphological observations?

in the new hypothesis, the anatomical and morphological complexity of ctenophores can be explained in terms of two idependent origins of anatomical complexity: one in ctenophores and the other leading to eumetazoans. alternatively the last common ancestor of living animals may have been anatomically complex, requiring that we consider the distinct body plan of adult sponges as having been secondarily simplified.

The protostomes form one major branch of bilaterian animals. Which features do they share with other bilaterians, and which features distinguish them as a separate group within the bilaterians?

like other bilaterians, protostome animals develop from three embryologic germ tissues and have complex organs. in protostomes, the blastopore usually develops into the anus. in contrast, in deuterostomes, the blastopore usually gives rise to the mouth.

Name two features that are unique to mammals and suggest their importance for mammal evolution.

mammals have hair and produce mil to feed the youth. hair- insulation, warm-bloodedness. milk- reliable source of nutritions, develop social bonds between mom and offspring.

How do muscle cells enable cnidarians to function in ways that sponges cannot?

muscle cells permit movement, which enables cnidarians to seek and capture prey.

You do not have a notochord, a long tail, or pharyngeal slits. How do you know that you are a chordate?

our first baby teeth are an example. molecular sequence comparisons firmly place humans within the chordates.

Of the morphological traits of present-day snails, squids, and clams, which features do you think were present in the common ancestor of all three?

the shared features among present day snails, squids and clams suggest that all mollusks descended from a common ancestor that had a head, radula, for, mantle, and well differentiated organ systems.

Which four adaptations account at least in part for the success of insects? Why?

wings, desiccation, metamorphosis, respiratory system.