Use the fossil evidence shown in Figure 25.6 to determine whether flight evolved earlier in insects or in birds. Is flight an example of homology or convergent evolution? Explain.

You can use a 'one-snip test' to identify monophyletic groups—meaning that if you 'cut' any branch on a tree, everything that 'falls off' is a monophyletic group. Why is this valid?

In terms of structure, how do channel proteins differ from carrier proteins?

VISUAL SKILLS The relative lengths of the frog and mouse branches in the phylogenetic tree in Figure 26.13 indicate that a. frogs evolved before mice. b. mice evolved before frogs.c. the homolog has evolved more rapidly in mice.d. the homolog has evolved more slowly in mice.

If you were using cladistics to build a phylogenetic tree of cats, which would be the best choice for an outgroup?a. kangaroob. leopardc. domestic catd. iguana

Which of the following could provide the best data for determining the phylogeny of very closely related species?a. the fossil recordb. their morphological differences and similaritiesc. a comparison of nucleotide sequences in homologous genes and mitochondrial DNAd. a comparison of their ribosomal DNA sequences

You have discovered an enzyme that appears to function only when a particular sugar accumulates. Which of the following scenarios would you predict to be responsible for activating this enzyme?a. The sugar cleaves the enzyme to form the active conformation.b. The sugar is an allosteric regulatory molecule for the enzyme.c. The sugar is a competitive inhibitor for the enzyme.d. The sugar phosphorylates the enzyme to form the active conformation

Phylogenies are created based on the principle that all species descending from a recent common ancestor .a. should be identical;b. should share characteristics that evolved in that ancestor;c. should be found as fossils;d. should have identical DNA sequences;e. should be no more similar than species that are less closely related

The traditional tree of life (shown above) presents the three domains as distinct, monophyletic lineages. However, other hypotheses propose different views on the relationships among the Archaea, Bacteria, and Eukarya. In particular, the two-domain hypothesis—or eocyte hypothesis—is emerging as a well-supported alternative to the three-domain hypothesis. The eocyte hypothesis, illustrated below, suggests that eukaryotes evolved from eocytes (also known as the Crenarchaeota—a major lineage of the Archaea). Resolving the relationships among these ancient lineages is difficult, but it has profound implications on our understanding of the origin of eukaryotic cells. Why are Archaea considered a monophyletic group according to the three-domain hypothesis?a. Because this group includes all organisms except eukaryotes.b. Because this group includes an ancestral population and all of its descendants.c. Because all members of this group lack membrane-bound organelles.d. Because this group evolved after the origin of bacteria.