Bio 2 Exam 3 - Mastering Biology with
complete solutions
A group of small fish live in a lake with a uniformly light-brown sandy bottom. Most of the fish
are light brown, but about 10% are mottled. This fish species is often prey for large birds that
live on the shore. A construction company dumps a load of gravel in the bottom of the lake,
giving it a mottled appearance. Which of these statements presents the most accurate
prediction of what will happen to this fish population?
a) There is no way to predict the result.
b) In two generations, all the fish will be mottled.
c) The proportion of mottled fish will increase over time.
d) As the mottled fish are eaten, more will be produced to fill the gap.
e) The ratios will not change. - correct answer ✔✔ c) The proportion of mottled fish will
increase over time.
A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the
triazine works well and almost all the pigweed dies; but after several years, the farmer sees
more and more pigweed. Which of these explanations best explains what happened?
a) Natural selection caused the pigweed to mutate, creating a new triazine-resistant species.
b) Triazine-resistant pigweed has less-efficient photosynthesis metabolism.
c) Triazine-resistant weeds were more likely to survive and reproduce.
d) The herbicide company lost its triazine formula and started selling poor-quality triazine -
correct answer ✔✔ c) Triazine-resistant weeds were more likely to survive and reproduce.
After the drought of 1977, researchers on the island of Daphne Major hypothesized that
medium ground finches that had large, deep beaks, survived better than those with smaller
,beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. If this
hypothesis is correct, what would you expect to observe if a population of these medium
ground finches colonizes a nearby island where Tribulus cistoides is the most abundant food for
the next 1000 years? Assume that (1) even the survivors of the 1977 drought sometimes had
difficulty cracking the tough T. cistoides fruits and would eat other seeds when offered a choice;
and (2) food availability is the primary limit on finch fitness on this new island.
a) evolution of yet larger, deeper beaks over time
b) evolution of smaller, pointier beaks over time
c) random fluctuations in beak size and shape
d) no change in beak size and shape - correct answer ✔✔ a) evolution of yet larger, deeper
beaks over time
Darwin and Wallace's theory of evolution by natural selection was revolutionary because it
_____.
a) dismissed the idea that species are constant and emphasized the importance of variation and
change in populations
b) proved that individuals acclimated to their environment over time
c) was the first time a biologist had proposed that species changed through time
d) was the first theory to refute the ideas of special creation - correct answer ✔✔ a) dismissed
the idea that species are constant and emphasized the importance of variation and change in
populations
From his observations of organisms in the Galapagos islands, Darwin reasoned that _____.
a) organisms had adapted to new environments, giving rise to new species
b) all island species should be similar to each other
c) the organisms in the Galapagos had been specially created to thrive in that environment
, d) the shape of a bird's beak does not affect its ability to survive and reproduce
e) none of the above - correct answer ✔✔ a) organisms had adapted to new environments,
giving rise to new species
The theory of evolution through natural selection is considered a scientific theory because
_____.
a) it is broad enough in scope to explain many observations
b) it is supported by a massive body of evidence from many disciplines
c) it is general enough to provide many testable hypotheses
d) All of the above are correct.
e) None of the above is correct. - correct answer ✔✔ d) All of the above are correct
Prior to the work of Lyell and Darwin, the prevailing belief was that Earth is _____.
a) millions of years old, and populations are unchanging
b) millions of years old, and populations rapidly change
c) a few thousand years old, and populations gradually change
d) a few thousand years old, and populations are unchanging - correct answer ✔✔ d) a few
thousand years old, and populations are unchanging
A challenge to traditional (pre-1860) ideas about species came from embryology, when it was
discovered that _____.
a) embryos of dissimilar organisms, such as sharks and humans, resemble each other
b) the more advanced the animal, the more slowly it develops
c) all animals develop similar embryonic gills
complete solutions
A group of small fish live in a lake with a uniformly light-brown sandy bottom. Most of the fish
are light brown, but about 10% are mottled. This fish species is often prey for large birds that
live on the shore. A construction company dumps a load of gravel in the bottom of the lake,
giving it a mottled appearance. Which of these statements presents the most accurate
prediction of what will happen to this fish population?
a) There is no way to predict the result.
b) In two generations, all the fish will be mottled.
c) The proportion of mottled fish will increase over time.
d) As the mottled fish are eaten, more will be produced to fill the gap.
e) The ratios will not change. - correct answer ✔✔ c) The proportion of mottled fish will
increase over time.
A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the
triazine works well and almost all the pigweed dies; but after several years, the farmer sees
more and more pigweed. Which of these explanations best explains what happened?
a) Natural selection caused the pigweed to mutate, creating a new triazine-resistant species.
b) Triazine-resistant pigweed has less-efficient photosynthesis metabolism.
c) Triazine-resistant weeds were more likely to survive and reproduce.
d) The herbicide company lost its triazine formula and started selling poor-quality triazine -
correct answer ✔✔ c) Triazine-resistant weeds were more likely to survive and reproduce.
After the drought of 1977, researchers on the island of Daphne Major hypothesized that
medium ground finches that had large, deep beaks, survived better than those with smaller
,beaks because they could more easily crack and eat the tough Tribulus cistoides fruits. If this
hypothesis is correct, what would you expect to observe if a population of these medium
ground finches colonizes a nearby island where Tribulus cistoides is the most abundant food for
the next 1000 years? Assume that (1) even the survivors of the 1977 drought sometimes had
difficulty cracking the tough T. cistoides fruits and would eat other seeds when offered a choice;
and (2) food availability is the primary limit on finch fitness on this new island.
a) evolution of yet larger, deeper beaks over time
b) evolution of smaller, pointier beaks over time
c) random fluctuations in beak size and shape
d) no change in beak size and shape - correct answer ✔✔ a) evolution of yet larger, deeper
beaks over time
Darwin and Wallace's theory of evolution by natural selection was revolutionary because it
_____.
a) dismissed the idea that species are constant and emphasized the importance of variation and
change in populations
b) proved that individuals acclimated to their environment over time
c) was the first time a biologist had proposed that species changed through time
d) was the first theory to refute the ideas of special creation - correct answer ✔✔ a) dismissed
the idea that species are constant and emphasized the importance of variation and change in
populations
From his observations of organisms in the Galapagos islands, Darwin reasoned that _____.
a) organisms had adapted to new environments, giving rise to new species
b) all island species should be similar to each other
c) the organisms in the Galapagos had been specially created to thrive in that environment
, d) the shape of a bird's beak does not affect its ability to survive and reproduce
e) none of the above - correct answer ✔✔ a) organisms had adapted to new environments,
giving rise to new species
The theory of evolution through natural selection is considered a scientific theory because
_____.
a) it is broad enough in scope to explain many observations
b) it is supported by a massive body of evidence from many disciplines
c) it is general enough to provide many testable hypotheses
d) All of the above are correct.
e) None of the above is correct. - correct answer ✔✔ d) All of the above are correct
Prior to the work of Lyell and Darwin, the prevailing belief was that Earth is _____.
a) millions of years old, and populations are unchanging
b) millions of years old, and populations rapidly change
c) a few thousand years old, and populations gradually change
d) a few thousand years old, and populations are unchanging - correct answer ✔✔ d) a few
thousand years old, and populations are unchanging
A challenge to traditional (pre-1860) ideas about species came from embryology, when it was
discovered that _____.
a) embryos of dissimilar organisms, such as sharks and humans, resemble each other
b) the more advanced the animal, the more slowly it develops
c) all animals develop similar embryonic gills
