Chapter 17

Question 1

Which method is least useful for dating rock strata, fossils, or events in geologic time?

Answer 1

The written historical record

Question 2

Which feature is universal among organisms, thus implying that all living things derive from a common ancestor?

Answer 2

The genetic code, the machinery of replication and protein synthesis, basic metabolic reactions, and the use of L optical isomers of amino acids as building blocks for proteins

Question 3

If we use molecular clocks to estimate that the most recent common ancestor of a species pair existed 5 million years ago in a specific region, what strata of fossil-bearing rock would be the best choice for finding a fossil most similar to that ancestor?

Answer 3

Strata slightly older than 5 million years old

Question 4

Microevolution involves _______, whereas macroevolution involves _______.

Answer 4

Processes that occur within species; evolution above the species level (i.e., higher taxa)

Question 5

Refer to the figure showing the evolutionary morphology of two different taxa. The figure demonstrates

Answer 5

Evolution of morphological differences between species by gradualism, that the common ancestor of two different forms need not have morphology that is precisely intermediate

Question 6

The eye is such a complex feature that some have difficulty imagining how it could have evolved. Even Darwin wrote, “That the eye, with all of its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection seems, I freely confess, absurd in the highest possible degree.” How has this dilemma been resolved?

Answer 6

Numerous examples of intermediate forms have been found, indicating that complex eyes can evolve via gradual change

Question 7

Why might a species’ “optimal” phenotype remain unchanged for long periods of time, resulting in apparent evolutionary stasis?

Answer 7

Tracking of a single kind of habitat

Question 8

Stephen Jay Gould suggested that if we were to replay the “tape of life,” the course of events that we know as “history” might play themselves out very differently. Which statement supports this idea?

Answer 8

Historical contingency suggests that small differences in random events can result in large downstream differences

Question 9

How can speciation enhance the rate of adaptive evolution?

Answer 9

Reproductive isolation allows new beneficial mutations to become fixed as adaptations to local environments

Question 10

Which data would not affect the likelihood of a particular phylogeny being the best hypothesis when comparing different trees?

Answer 10

The lengths of the branches, the tree topology (i.e., branching patterns), the nucleotide substitution rate, the branching order of the tree are important for finding the most likely tree

Question 11

How do evolutionary biologists view the notion of biological “progress”?

Answer 11

Objective definitions of progress are fraught with difficulty, as the processes that drive evolution have no mechanism for foresight

Question 12

Most of the different _______ first appeared during the Cambrian

Answer 12

Modern animal phyla

Question 13

A group of species has a Gondwanan distribution. Therefore, it is most likely that they first diversified

Answer 13

Between the late Paleozoic and early Mesozoic eras

Question 14

The two main hypotheses for a taxon’s distribution are dispersal and vicariance. Which of the following would be the poorest source of data for testing these hypotheses?

Answer 14

The current geographic distribution of the organism

Question 15

After the breakup of Gondwana, new species evolved in South America, Africa, and Australia. Which speciation model best fits this vicariance event?

Answer 15

Allopatric speciation

Question 16

What should a biologist do if she finds that two different methods of analyzing the same data (say, parsimony and maximum likelihood) provide different estimates of the relationships among certain taxa? What should she do if the different analytical methods give the same estimate, but the estimate differs depending on which of two different genes has been sequenced?

Answer 16

The biologist should greatly consider the method that provides her the most valid results based on the type of data being considered (genes, morphological traits). In most cases, quantitative data (maximum likelihood) have been the most widely used approached in comparison to qualitative data (parsimony). Yet, it depends on the type of data being analyzed. The difficulty of homoplasy associated with parsimony is resolved in maximum likelihood and Bayesian interference thereby making the latter two methods more acceptable in DNA sequencing. Yet, concepts from parismony should not be entirely disregarded if DNA and morphological data were to be compared and analyzed together.

If estimate differs depending on which of two different genes has been sequenced, the biologist may want to consider probability theory to determine the chances that a species with an observed DNA sequence would occur in regards to different branching events, branch lengths, and substitution rates. Degrees of confidence should be calculated directly with maximum likelihood or Bayesian inference or through bootstrapping for parsimony to assess the possibly validity of the phylogenetic methods.

Question 17

Would you expect large numbers of species in a region to have had similar histories of geographic distribution? Why or why not?

Answer 17

Yes, large numbers of species in a particular region are expected to have similar histories of geographic distribution under certain limitations. While geographic range through dispersal or vicariance do have a large influence in geographic distribution history, it should not be the only factor taken into account. Species must be able to withstand survival conditions that are presented before them in their particular habitual region such as obtaining reliable resources and contending with other neighboring species. Phylogeographic analyses could be used to address geographic distribution history in the construction of trees through specific traits that are necessary for organisms in a particular geographic region to survive. Those organisms can then be compared with further phytogeographic analyses of their closest relatives in a neighboring geographic location to illustrate the differences in traits or genes that led to the geographic division between species population.