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A problem to solve:
A brown mink crossed with a silverblue mink produced all brown offspring. When these F1 mink were crossed among
themselves they produced 47 brown animals and 15 silverblue animals (F2 generation). Determine all the genotypes and
phenotypes, and their relative ratios, in the F1 and F2 generations.
P
PxP
a
a
F1
F1 x F1
F2
A
A
Aa
Aa
Aa
Aa F1
F1 A
A AA
a Aa
a
Aa
aa
F2
A field on which corn was grown for many years is abandoned. How will the species
diversity of the field most likely change over time as a result of ecological succession?
A. Species diversity will increase.
B. Species diversity will decrease.
C. Species diversity will remain the same.
D. Species will increase and then decrease in a ten-year cycle.
The correct answer is A. On a field where only corn plants grow, species diversity is very low.
When the field is abandoned, new species of plants will colonize the field, and new animals
and other organisms will follow. Choices B, C, and D are incorrect.
Cytochrome c is a small protein involved in cellular respiration, consisting of 104 amino
acids. Based on the cytochrome c data, which pair of these organisms probably shares the
most recent common ancestry?
A. Dog and penguin
B. Moth and yeast
C. Chimpanzee and dog
D. Chimpanzee and penguin
The correct answer is C. In this example, cytochrome c is being used as a molecular clock. The
more differences there are between DNA sequences (and thus amino acid sequences), the
more time has elapsed since the species being compared shared a common ancestor. Of the
organisms listed, dog cytochrome c sequence has the fewest differences from chimpanzee
cytochrome c sequence. Choices A and B are incorrect because the data focus only on
differences from chimpanzee sequence. Choice D is incorrect because penguin cytochrome c
has 11 amino acids that are different, while dog cytochrome c has one fewer, 10 amino acids.
A scientist compared the sequence of bases in a region of the same gene, Hoxc8, in a mouse, a
baleen whale, and a chicken. Look at the base sequences in the table above. Which of the
following statements is probably true?
A. The mouse is more closely related to the baleen whale than to the chicken.
B. The chicken is more closely related to the mouse than the baleen whale is.
C. The Hoxc8 genes of the three animals are very different from one another.
D. Hoxc8 genes are not suitable for determining molecular homologies.
The correct answer is A. Choice B is incorrect because the whale and the mouse have more
bases in common than do the chicken and the mouse. Choice C is incorrect because the Hox
genes are quite similar in the three animals. Choice D is incorrect because the Hox genes are
used by scientist to determine molecular homologies.
The graph shows the relationship between beak size and survival for the medium ground finch,
Geospiza fortis, during a drought on one of the Galapagos Islands. The graph shows thatA. when conditions are not dry, Geospiza fortis prefers small seeds Bird Survival Based on Beak Size
B. all finches with beak sizes greater than 11 mm survived
C. heritable variation accounts for the difference in beak size
D. during a drought, large beak size is an adaptive advantage in Geospiza fortis
The correct answer is D. choice A is incorrect because the
graph does not indicate seed preference. Since not all
finches with beak size greater than 11 mm survived,
choice B is incorrect. The graph does not show what caused
the difference in beak size, so choice C is incorrect.
A student designs an experiment to demonstrate the presence of openings in the walls of xylem
cells in plants. He takes a long-stemmed, white chrysanthemum and carefully cuts the stalk
halfway up. He places each half of the stalk in a glass cylinder filled with water. Red dye is added
to one cylinder; blue dye is added to the other. What observations would you expect to make
over the next few days?
A .The flower remains white.
B. The flower turns blue, then changes to red.
C. The flower turns red, then changes to blue.
D. Initially part of the flower will be blue and part will be red, but eventually both colors will
appear in all parts of the flower.
The correct answer is D. Initially, blue colored water will travel up one half of the stem, and redcolored water will travel up the other half. Half the flower will be red, and half will be blue.
Because xylem cells have openings in their walls that allow water to move between adjacent
cells, both colors will eventually appear in all parts of the flower. Choice A is incorrect because
water will travel up the xylem to the flower via transpiration and capillary action. Choices B and
C are incorrect because both colors would be transported up the xylem from the start.