Energy and Human Ambitions on a Finite Planet, 2021a

3 Population 50
think that is (hint: what changed so that we invalidated a single,
continuous mathematical function)?
8. Using the logistic model presented in Problem 7, what would the
population be in the year 2100? How does this compare to the
exponential result at 1% growth as in Problem 6?
Comparison of this problem <strong>and</strong> Problem
6 highlights the difference the choice of
mathematical model can make.
9. Which of the following are examples of positive feedback, <strong>and</strong>
which are examples of negative feedback?
a) a warming arctic melts ice, making it darker, absorbing more
solar energy
b) if the earth’s temperature rises, its infrared radiation to space
increases, providing additional cooling
c) a car sits in a dip; pushing it forward results in a backward
force, while pushing it backward results in a forward force
d) a car sits on a hill; pushing it either way results in an acceleration
(more force, thanks to gravity) in that direction
e) a child wails loudly <strong>and</strong> throws a tantrum; to calm the child,
parents give it some c<strong>and</strong>y: will this encourage or discourage
similar behaviors going forward?
10. Think up an example from daily life (different from examples
in the text) for how a delay in negative feedback can produce
overshoot, <strong>and</strong> describe the scenario.
[19]: (2016), List of Sovereign States <strong>and</strong> Dependent
Territories by Birth Rate
[20]: (2011), List of Sovereign States <strong>and</strong> Dependent
Territories by Mortality Rate
11. Pick five countries of interest to you not represented in any of the
tables in this chapter <strong>and</strong> look up their birth rate <strong>and</strong> death rate [19,
20] , then find the corresponding dot on Figure 3.11, if possible. 40 40: Numbers may change from when the
At the very least, identify the corresponding region on the plot.
12. A country in the early stages of a demographic transition may
have trimmed its death rate to 15 per 1,000 people per year, but still
have a birth rate of 35 per 1,000 per year. What does this amount
to in terms of net people added to the population each year, per
1,000 people? What rate of growth is this, in percent?
13. If the population of the country in Problem 12 is 20 million this
year, how many people would we expect it to have next year? How
many were born, <strong>and</strong> how many died during the year?
plot was made; population can help settle
based on dot size.
14. Figure 3.11 shows Egypt st<strong>and</strong>ing well above China in terms of
excess birth rate compared to death rate. 41 Yet Table 3.3 indicates
that China contributes a much larger annual addition to global
population than does Egypt. Explain why. Then, using the first
four columns in Table 3.3, replicate the math that produced the
final column’s entries for these two countries to reinforce your
underst<strong>and</strong>ing of the interaction between birth <strong>and</strong> death rates
<strong>and</strong> population in terms of absolute effect.
41: . . . much farther from dashed line
Show work <strong>and</strong> add one more decimal place
to the answer as a way to validate that you
did more than copy the table result.
15. In a few clear sentences, explain why the maps in Figure 3.13
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.