A34fiffAnswers
ANSWERS TO FIGURE QUESTIONS
Figure 19.1
Q1: What parts of the United States are within the range of the
mosquito that carries Zika?
A1: Roughly, the southern United States and the eastern coastline.
Q2: What areas are not within the mosquito’s range? Why do you
think that is?
A2: The northern and northwestern states, probably because it is
too cold for mosquitoes to overwinter there.
Q3: Find your own state, and where you are in the state. Are you at
risk of contracting Zika?
A3: Answers will depend on student location. If you travel to areas
with Zika-infected mosquitoes, your risk increases. If local Zika
infections have not yet been reported in your state, you are at less
risk than, for example, citizens of Florida.
Figure 19.3
Q1: What is the main way by which someone is infected with the
Zika v irus?
A1: By being bitten by a mosquito that is infected.
Q2: Judging by the poster and your knowledge of mosquito
behavior, what can you do to decrease your risk of being infected
with the Zika virus?
A2: Cover up when you’re outside, don’t go out at dusk, wear insect
repellent, and use protection when having sex with someone who
has been exposed.
Q3: Besides the transmission methods shown on the poster, what
are some other ways you could become infected with the Zika
v irus?
A3: From kissing an infected individual, or possibly from sharing a
razor or toothbrush with someone. (Other answers are possible.)
Figure 19.5
Q1: Which form of population growth displays a J-shaped curve?
A1: Exponential growth.
Q2: Which form of population growth displays an S-shaped curve?
A2: Logistic growth.
Q3: Describe a situation in which a population initially shows
exponential growth and later shows logistic growth.
A3: If a population enters a new area—an island, for example—
it will initially grow exponentially as it expands into the
environment. Later, as it reaches the carrying capacity of the new
area, it will begin to display logistic growth.
Figure 19.6
Q1: According to this graph, approximately when did exponential
grow th begin?
A1: Around the year 1800 ce.
Q2: What milestone corresponds to the transition from logistic to
exponential population growth?A2: The onset of the industrial revolution.Q3: What is the UN’s projected carrying capacity of Earth, and
when will we reach it?A3: The UN projects Earth’s carrying capacity to be 9–10 billion
people, which we will reach in about 2050 ce.Figure 19.7
Q1: List all the stages of the mosquito life cycle.A1: Egg, larva, pupa, adult.Q2: Which life cycle stage is vulnerable to the GM treatment?A2: The larvae, which do not survive to become pupae.Q3: Why are only male GM mosquitoes released into the wild,
rather than both males and females?A3: Males do not feed on blood, so they are not able to transmit
Zika virus, whereas females do feed and thus can transmit Zika.Figure 19.8
Q1: What factors may be limiting growth and reproduction in the
plantain’s crowded conditions?A1: Possible factors include availability of nutrients, water,
sunlight, and room for root and shoot growth.Q2: Why are overcrowded conditions considered density-
dependent population changes?A2: Because the more organisms there are in the environment or
the more densely packed they are, the more competition there is
for resources and the less each individual will likely receive.Q3: Relate this example of overcrowded conditions to the human
population growth shown in Figure 19.6. How do you think the
situations are similar? How are they different?A3: Increasing human populations may lead to an increase in
competition for jobs, housing, and food. So far, humans have been
able to increase their carrying capacity through technology, but
that may no longer be possible.Figure 19.9
Q1: In what year did the reindeer’s numbers begin to rise
exponentially?A1: About 1933.Q2: In what years was the reindeer’s population growth logistic?A2: Between about 1911 and 1932.Q3: How do you predict the graph (population size) would change
if someone had begun bringing in supplemental food for the
reindeer in 1940? Draw a sketch of your prediction.A3: Supplemental food would have caused the population decline
to end, and the population would have either remained constant or
again increased, depending on the amount of supplemental food
provided.