Chapters 1 and 2

Question 1

Why is evolutionary biology one of the best paradigms in which to study the spread of viruses like Ebola into new populations and species?

Answer 1

Evolutionary biologists work on understanding how populations (the viruses) adapt to new environments (the hosts)

Question 2

Biological evolution is defined as

Answer 2

Inherited change in the properties of groups of organisms over the course of generations

Question 3

What is meant by “the theory of evolution”?

Answer 3

Evolution is well supported by evidence and has survived repeated testing

Question 4

Natural selection is only one of several possible mechanisms of evolution. Another mechanism is

Answer 4

Genetic drift

Question 5

Which of the following had the least influence on Darwin’s work and writing?

Answer 5

Knowledge of the genetic nature of inheritance, as discovered by Gregor Mendel

Question 6

In the 1930s and 1940s the modern evolutionary synthesis occurred. Which of these was not a major outcome of the evolutionary synthesis?

Answer 6

The integration of orthogenesis with evolutionary biology

Question 7

What was the most important immediate outcome of Wallace’s 1858 letter to Darwin, which included Wallace’s ideas of natural selection?

Answer 7

Darwin was prompted to make his own research on the subject public

Question 8

Refer to the figure showing the phylogenetic tree from Charles Darwin’s On the Origin of Species. Based on the figure, which statement is false?

Answer 8

Darwin recognized hybridization as an important means of genetic change

Question 9

A monophyletic group (also called a clade) is defined as

Answer 9

The set of species derived from one common ancestor

Question 10

Which of the following is an example of homologous characters?

Answer 10

Crocodiles and humans both have forelimbs with five digits

Question 11

Once variant DNA sequences are aligned and analyzed, it is possible to

Answer 11

Construct gene trees

Question 12

True/False: The below cladogram implies that the amount of time that has passed in E is equivalent to the amount of time that has passed in F

Answer 12

False

Question 13

HIV is actually composed of five different viral families: HIV-1 groups M, N, and O and HIV-2 groups A and B. All of these families are closely related to SIV (Simian Immunodeficiency Virus), which infects apes and monkeys. Below is a phylogenetic reconstruction of the RNA sequence data from SIV and HIV groups. Based on this phylogeny, human HIV-1 shares a common ancestor with viruses that infected which species of monkey or ape?

Answer 13

Chimpanzee

Question 14

Which of the following would not cause complications in inferring a phylogeny?

Answer 14

Presence of shared, derived homologous traits

Question 15

HIV is actually composed of five different viral families: HIV-1 groups M, N, and O and HIV-2 groups A and B. All of these families are closely related to SIV (Simian Immunodeficiency Virus), which infects apes and monkeys. Below is a phylogenetic reconstruction of the RNA sequence data from SIV and HIV groups. Based on this phylogeny, are HIV strains considered to be monophyletic, paraphyletic, or polyphyletic?

Answer 15

Polyphyletic

Question 16

One of the early examples supporting Darwin’s evolution by natural selection involved changes in the frequencies of color morphs in Biston betularia, the peppered moth. During the nineteenth century, the dark (melanic) form of this moth went from being very rare to very common in the United Kingdom. This change in frequency coincided with the Industrial Revolution and and corresponding increase in air pollution. Presumably, as trees became darker due to soot, the darker form of the moth was less visible to predators (such as birds) than the lighter form. Studies in the middle twentieth century showed that the color difference was due primarily to a single gene, with the melanic allele being dominant to the non-melanic allele.

During the latter part of the twentieth century, clean air laws were passed in both the United Kingdom and the United States. This led to reductions in air pollution. Given that the rise of the melanic form coincided with the increase in air pollution making it less visible to predators, one might expect that a decrease in air pollution would lead to a decrease in the frequency of the melanic form.

Bruce Grant and his colleagues examined changes in the frequency of the melanic form of the moth over time in both the United States and the United Kingdom.

Figure 1 Frequency of melanic moths in Caldy Common, U.K. (solid circles) and in Michigan, U.S. (solid diamonds) between 1959 and 1995. Note that the moths at Caldy Common were sampled annually, but there was a large gap in the Michigan samples. (The open circles denote the theoretical expectations based on a constant selection coefficient of s= 0.153 against the dominant allele.)

Q1 (0.5 pts) Compare the changes in frequency of melanic moths at Caldy Common and in Michigan. Are there any differences?

Q2 (1 pt) The open circles in the figure represent expected values given continual selection against the melanic form at a rate sufficient to explain the decline in frequency of the melanic moths at Caldy Common. How do the expected and observed changes in frequency compare? What are some possible explanations for the discrepancy?

Answer 16

1) There does not appear to be much of a difference between the frequency of melanic moths in Caldy Common, U.K. and Michigan. Both populations in melanic moths is decreasing exponentially with the melanic moths in Michigan decreasing more gradually than Caldy Common, U.K. However, the frequency of melanic months in both locations in both the first and last year of the study (1959 and 1995) are pretty much equivalent.
2) The expected and observed changes in frequency implies differences between the rate of the decline in melanic moths due to reduction in air pollution. Whereas the expected results in frequency would be that there would a steady decline in melanic moths, the principles of evolution states that the frequency is based on chance via adaptations or genetic selection in color made against their environment. Some possible explanations for the discrepancy is the ability for the melanic moths to blend in with their environment to avoid predation initially since it takes time for the trees to darken; but over time, the continuous enforcement of air pollution laws would cause the trees to drastically change possibly at a faster rate. Trees then remaining as a lighter color would give rise for melanic moth predation to occur.

Question 17

When did metazoans (multicellular animals) first arise? The fossil record is spotty before the Cambrian explosion (circa 545 million years ago) and absent prior to 600 million years ago, yet there is substantial diversity of body forms by the middle of the Cambrian period. Did this diversification occur in just tens of millions of years, or had diversified metazoan lineages existed long before the Cambrian?

Figure 1 Chronogram showing estimated times of divergence for lineages of animals, based on the average of the genes used in this study. The Cambrian is indicated on the left (~540-490 million years ago).

Q1 (0.5 pts): Which two of the lineages presented diverged most recently? How long ago did they diverge?

Q2 (0.5 pts):Based on these results, what can you conclude about the origins of animals in relation to the Cambrian?

Answer 17

1) The Agnatha and Gnathostomata lineages of Deuterostomia diverged most recently around 600 million years ago.
2) Based on the chronogram, the Cambrian explosion (circa 545 million years ago) occurred after the divergence of the Agnatha and Gnathostomata lineages. Thus, the Cambrian could not have possibly given rise to theAgnatha and Gnathostomata lineages of Deuterostomia since the time frame of the event does not align with the emergence of the new metazoans lineages. Thus, it supports the idea that diversified metazoan lineages existed long before the Cambrian.