BISC120L midterm exam

09 Jun BISC120L midterm exam

Question
Practice for Midterm 1, BISC120L, Fall 2015

Sample Questions From Previous Exams*

*Note: Material covered in Fall 2010 is not identical to that covered in previous years

Multiple Choice

Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of the progeny of the cross BbTt x BBtt will have black fur and long tails?

A. 1/16

B. 3/16

C. 3/8

D. 1/2

E. 9/16

In humans, males are more often affected by sex-linked traits because

A. males have only one copy of the X chromosome.

B. male hormones such as testosterone often alter the effects of mutations on the X chromosome.

C. female hormones such as estrogen often compensate for the effects of mutations on the X.

D. X chromosomes in males often have more mutations than X chromosomes in females.

E. mutations on the Y chromosome often worsen the effects of X-linked mutation.

Natural selection is based on all of the following except

A. genetic variation exists within populations.

B. the best adapted individuals tend to leave the most offspring.

C. individuals who survive longer tend to leave more offspring than those who die young.

D. populations tend to produce more offspring than the environment can support.

E. individuals adapt to their environments and, thereby, evolve.

1

Which of the following statements about Darwin’s finches is false?

A. They are a classic example of an adaptive radiation.

B. They were critical to the development of Darwin’s theory of natural selection.

C. They are believed to descend from a single, mainland species.

D. Their beaks have been selected to become deeper during dry years.

E. They include a species of ‘vampire finch’ that feeds on blood.

Which of the following indicates a population is not in Hardy-Weinberg equilibrium?

A. p+ q! 1.

B. p2 + 2pq+ q2 !1.

C. The allele frequencies are not 50:50.

D. The observed allele numbers match the expected allele numbers.

E. The observed genotype numbers do not match the expected genotype numbers.

In a certain group of African people, 9% are born with sickle-cell disease (homozygous recessive). If this group is in Hardy-Weinberg equilibrium, what percentage of the group has the selective advantage of being more resistant to malaria (heterozygous) than those individuals who are homozygous for normal hemoglobin or for sickle-cell disease?

A. 18%

B. 21%

C. 30%

D. 42%

E. 81%

The prevalence of sympatric speciation in nature is hotly contested because

A.some examples of sympatric speciation may actually be microallopatric speciation.

B. reproductive isolation in sympatry is vulnerable to gene flow.

C. there are no known cases of sympatric speciation by polyploidy.

D. A and B only.

E. A, B and C.

2

It has been found that certain proteins of the complex motor that drives bacterial flagella are modified versions of proteins that had previously belonged to plasma membrane pumps. This is evidence in support of the claim that

A. some structures are so complex that natural selection cannot, and will not, explain their origins.

B. the power of natural selection allows it to act in an almost predictive fashion, producing organs that will be needed in future environments.

C. the motors of bacterial flagella were originally synthesized abiotically.

D. natural selection can produce new structures by cobbling together parts of other structures.

E. bacteria that possess flagella must have lost the ability to pump certain chemicals across their plasma membranes.

Nucleic acid sequences that undergo few changes over the course of evolutionary time are said to be conserved. Conserved nucleic acid sequences

A. include all mitochondrial DNA.

B. are useful for comparing recently diverged taxa.

C. are abundant in ribosomes.

D. are proportionally more common in eukaryotic introns than in eukaryotic exons.

E. are more prone to homoplasy than less conserved sequences.

Matching

Thomas Malthus A. Structure of hereditary material

Rosalind Franklin B. Sociobiology

Alfred Hershey C. Human population growth

E.O. Wilson D. Natural selection

Alfred Russel Wallace E. Composition of hereditary material

3

Problem solving

Consider the following 3 species and their associated characters, with derived characters determined by comparison with their known ancestor (0=ancestral, 1=derived).

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A. Draw the 3 possible phylogenies for this set of 3 species. (2 points)

B. Using the principle of maximum parsimony, write in the changes necessary to explain differences between ancestor and descendants. That is, for each tree draw a hatchmark and write 1 to indicate each location where character 1 changed from 0 to 1. Next, for each tree draw a hatchmark and write 2 to indicate each location where character 2 changed from 0 to 1. (4 points)

C. Circle the most parsimonious of the 3 trees and label it ‘Pars’ (2 points)

D. Draw an outline around one example of a paraphyletic group on one of the trees and label it ‘Para’ (2 points)

4

True or False

Linnaeus was an early proponent of the idea that species change gradually over time.

Populations are expected to return to Hardy Weinberg after a single generation if all of the Hardy Weinberg assumptions are met.

Convergent evolution can only occur when two species share a recent common ancestor.

A dihybrid cross is expected to result in a 9:3:3:1 phenotypic ratio if both loci are codominant.

The taxonomic hierarchy, from most inclusive to least inclusive, is Domain, Kingdom, Phylum, Class, Family, Order, Genus, Species.

Definitions

Irreducible complexity.

Scientific theory.

Autopolyploid.

Hybrid breakdown.

Ultimate causation.

5

Essay Question (20 points). Please write in complete sentences with no bullet points.

(17pts) Supportive concepts: Maximal points will be given for essays that answer the question thoroughly, get the facts correct, and do not include additional irrelevant or incorrect information.

(2 pts) Presentation and organization: Maximal points will be given for essays with good organization, well-structured sentences and paragraphs, logical flow and high readability.

(1 pts) Original content: We are looking for evidence of understanding that goes beyond the material present in lecture by including ideas or examples from the textbook or other sources.

While natural selection increases the frequency of traits favorable to survival and reproduction, it does not produce perfect organisms. Describe three examples of apparent organismal imperfection. For each example, explain why natural selection could allow this to happen. Select one of the three examples that you believe could most easily be ‘corrected’ by natural selection, and very briefly explain how it could be corrected.