Population Review for Test – ANSWER KEY
1) What are the 4 factors that affect the population growth of the United States?
2) Calculate the population density of the following areas:
a) Area: 2000 km2, Population Size = 1000 individuals
b) Area: 6000 km2, Population Size = 2000 individuals
c) Area: 12000 km2, Population Size = 2000 individuals
Birth, death, immigration, emigration
Density = tot people/area
1000/2000 = 0.5 person per sq km
2000/6000 = 0.33 person per sq km
2000/12000 = 0.17 person per sq km
3) What is the difference between density dependent and density independent factors?
Density dependent factors affect a population (limit population growth) that is more dense (more individuals, closer
together). Examples include; resources like food, water and shelter.
Density independent factors affect all populations similarly, regardless of individuals proximity to one another. Examples:
fire, drought, natural distasters.
4) How do you calculate doubling time? Solve:
a) Rate of growth = 2 %, Doubling time = ?
b) Doubling time = 40 years, Rate of growth = ?
Rule of 70
70/2 = 35 years
70/x = 40
x = 70/40 = 1.75%
5) How do you calculate birth rate? Death rate? Both per 1000? Solve:
birth rate = # of births per year/total population
a) r = 1.6%, deaths = 600, birth = ?, Size of pop = 1000
r = (b – d)/ tot pop
0.016 = (b – 600) / 1000
0.016 * 1000 = b – 600
16 = b – 600 so b = 616
birth rate = 616 per 1000 = 61.6%
b)
r = ? births = 4/1000, deaths = 2/1000
(4 – 2)/1000 = 0.002 x 100 = 0.2%
6) What are the differences between k selected and r selected species?
K-selected species live at densities close to carrying capacity, they have fewer (larger) offspring, but invest more energy into
them so each offspring has a relatively high probability of surviving to adulthood. They have type I survivorship curves. rselected species produce many offspring, each of which has a relatively low probability of surviving to adulthood. They are
usually smaller, and reproduce more quickly. They have Type III survivorship curves.
7) What are the major differences between a developed country, a moderately developed, and a less developed country?
Developed countries create more waste, have higher per capita income, and have stable or shrinking population sizes.
Less-developed countries create less waste, have lower per capita income/women’s empowerment, and increasing
population sizes (exponential growth in most cases)
8) What are the 3 age structure pyramids? Describe the major differences between each of them.
9) How do you determine future population size with the rate and the total population size? Solve:
a) Pop. Size = 2000, r = 0.5 %, t = 10 yrs from now.
2000 x (1.005)10 = 2102
10) Know the demographic transition curve. What are the 4 stages? How are they different from each other?
Pre-industrial: High birth/death rates, small population
Early transitional: High birth rates (agriculture), death rates start to lower with improved sanitation/education
Late transitional: Birth rates start to lower, low death rates (women empowerment)
Industrial: Low birth/death rates, slow to no to decreasing population growth)
11) Know the survivorship curves? What is Type I, Type II, and Type III?
12) How did China and India slow their population growth down? What are the advantages and disadvantages of these policies?
Government mandates and increased education. Slowing population growth so they don’t strain their resources, aging
population because fewer young people entering the work force. Who will care for the young and keep their economies
running?
13) Why have death rates decreased in the last one hundred years? Increased sanitation, modern medicine
Use this scenario to answer questions 14-17: The
country of Transylvania contains 2.3 million people (vampires
not included) and covers 800,000 square miles. In the year after the last census, there were 109,000 new
children born and 111,000 people died.
14) What is the current population density?
15) What are the birth and death rates?
2.3 million = 2,300,000/800,000
2.3/0.8 = 2.88 people per sq mile
109,000/2,300,000 = 0.109/2.3 = 4.7% birth rate
.111/2.3 = 4.8 % death rate
16) What is the population growth rate (r)?
0.109 - .111 = -0.002/2.3 = -0.087%
17) In how many years will the population of Transylvania double? It won’t, it is decreasing in size.
18) Given a 2010 world population growth rate of about 1.3% per year, how long would it take the world’s population to double?
70/1.3 = 53.8 so 54 years
19) If a country doubles its population in 56 years, what has its population growth rate during that time? 70/56 = 1.25%
20) In April of 2010 the U.S. population was 308,745,538 and it is growing by about .97%. Assuming a constant growth rate,
what will the population be in 2020?
308,745,538 x (1.0097)10 = 340 million
…in 2050?
308,745,538 x (1.0097)40 = 454 million
…in 2100?
308,745,538 x (1.0097)90 = 736 million