Spines increase a cell's surface area, so the spiniest diatoms should be the most buoyant. Which selective force below might explain the observed shift in spine number?
a. More predators were present during the ice age, favoring diatoms with more spines
b. Endothermic animals in colder climates tend to have smaller surface area to volume ratios to conserve heat
c. Diatoms with more spines could swim better allowing them to stay afloat in colder water
d. As Yellowstone Lake warmed up the water density decreased, favoring less buoyant diatoms
e. During the ice age Yellowstone Lake would have received more light from reflection off of the snow, allowing diatoms to live at greater depths
Answer: d. As Yellowstone Lake warmed up the water density decreased, favoring less buoyant diatoms
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Natural selection has favored the dark form of the peppered moth in areas subject to severe air pollution, perhaps because on darkened trees, moth-eating birds see them less easily. As pollution abated, the light forms increased in the population because
A. light moths had lower fitness than dark moths. B. light moths were able to produce more offspring than dark moths. C. light moths were more genetically variable than dark moths. D. birds ate more light moths.
Which of the following is not true of transposons?
A. They are always part of plasmids. B. They can replace damaged DNA. C. They can change pigmentation. D. They can change the genome. E. They can transfer drug resistance.
How much larger do eukaryotic cells tend to be than prokaryotic cells?
a. 150–1000 times larger b. 10–100 times larger c. 5–10 times larger d. 1000 times larger or more
What is a nerve?
A) a bundle of neurons B) a chain of neurons C) a sensory synapse D) a series of impulses