Choose 3 questions to answer within the required 45 minute time frame. Answer the other
3 questions for homework.
1. Explain why cockroach populations will not expand indefinitely and take over the entire
world. Include in your discussion appropriate definitions of population growth terminology such
as: exponential growth, logistic growth, carrying capacity, and resistant factors.
Cockroaches populations exhibit exponential growth, that is accelerating population
growth that occurs when optimal conditions allow a constant reproductive rate over a
period of time. When the cockroach population grows exponentially, the larger the
population gets, the faster it grows (J curve). However, environment resistance factors
limit growth of the population. These factors include such unfavorable environmental
conditions as the limited availability of food, water, shelter, and other essential resources
(resulting in increased competition) as well as limits imposed by disease and predation. As
the number of individuals in a population increases, so does environmental resistance, which
acts to limit population growth. Because the environment sets limits, cockroach population
growth is transformed from exponential growth into logistic growth. In the logistic
growth pattern, the population of roaches would level at the carrying capacity appropriate
for the local environment. The carrying capacity is the maximum number of individual of a
given species that a particular environment can support for an indefinite period, assuming
thee are no changes in the environment.
2
a) Identify the two most extreme types of reproductive strategies and make a distinction
between the traits that would characterize these extremes. Give an example of an
organism that illustrates each strategy.
Populations described by r selection have traits that contribute to a high
population growth rate. Weeds, such as dandelions, and insects, such as mosquitoes, are
examples of “r” strategists. Distinguishing traits typical of r strategists include: small
body size, early maturity, short life spans, large broods and little or no parental care of
offspring. These organisms live in unpredictable environments where the probability of
long-term survival is low. In populations described by K selection, traits maximize the
chance of surviving in an environment where the number of individuals is near the carrying
capacity of the environment. Characteristics of K strategists include: long life spans with
slow development, delayed reproduction, large body size, and a low reproductive rate with
high parental obligations to offspring. Tawny Owls, humans, elephants, and redwood trees
are all examples of the “K” strategists.
b) Compare and contrast density-dependent and density-independent factors that affect
population size. Include two examples of each type of factor.
Certain natural mechanisms influence population size. Factors that affect population
size fall into two categories. A density-dependent factor is an environment factor whose
effects on a population change as the population concentration changes. Predation,
disease, and competition are examples of density-dependent factors. For example, the
more crowded the population, the more likely members of a population encournter one
another frequently transmitting infections diseases. As population density increases, so
does competition for resources such as living space, food, water and sunlight. Densityindependent factors are typically abiotic. These are factors that affects the size of a
population but are not influenced by changes in population density. Random weather events
such as blizzard, hurricane, tsunami, that reduce population size are examples of densityindependent factors.
3. The overall shape of an age structure diagram indicates whether the population is increasing,
stable, or shrinking. Consider this age structure diagram:
a) Describe all aspects of the age structure diagram including distribution of people by
gender, age categories, and the projection size of the population.
This diagram shows a population that is slightly decreasing in size. The diagram
is divided vertically with no significant differences between the percentage of males on
the left and females on the right. The bottom third of the diagram represents prereproductive individuals between 0 and 14 years of age. This population is at about 3.8 –
4.0% for each gender. The middle third, reproductive individuals between 15 – 44 years
indicates the largest %. The top third, post reproductive individuals 45+ years are the
smallest width implying a smaller population in this age category.
b) Identify and discuss factors that contribute to a population with this age structure.
In the declining population model, represented by first world countries, with higher
education, wide-spread birth control and a structure of society that promote careers
and delayed reproduction.
c) Discuss the population growth momentum for this population.
The population growth momentum is positive
4. a) Discuss ways that the total fertility rate (TFR) can be reduced and identify the cultural
values that make this process more complicated. Education for women, delaying marriage until
the age of 25, and family planning services that enable men and women to limit their family
size, safeguard individual health rights, and improve the quality of life for themselves and
their children are ways to reduce the TFR. High fertility rates are traditional in many
cultures, and in some developing countries children play important economic and societal
roles. Also many cultures place a higher value on male children than female children, and
religious values are another aspect of culture that affect TFRs.
b) Identify the major problems anticipated with the increase in the human population in the
21st century and explain why it is difficult to accurately predict the carrying capacity for
humans. Environmental degradation, hunger, persistent poverty, economic stagnation,
urban deterioration, and health issues are the potential problems. It is impossible to
quantify the carrying capacity for humans because our impact on natural resources and
the environment involves more than the number of humans; the sustainable population
size is linked to the quality of life and standard of living for each individual.
c)Discuss the relationship between world hunger and population growth, and explain why the
world food problem is difficult to solve. Countries with the highest total fertility rates also
have the greatest food shortages. However, agriculture currently produces enough food
for everyone to have enough if it were distributed evenly. Economic development, poverty,
and the uneven distribution of resources affect the relationship between world hunger and
population.
5. a) Many people believe that India will quickly surpass China as the world’s most populous
country. Identify the ways that India has tried to control its population, and the reasons why the
TFR still remains at 3.1 in 2004.
In the 1950s India became the first country to establish government
sponsored family planning. Because of diverse cultures, religions, and customs in different
regions of the country, the program was only moderately successful. Indian culture is
biased towards male children, and female infanticide is often practiced Next compulsory
sterilization was used in several states, but it was very unpopular and soon abandoned. The
current approach includes education of young couples, and multimedia advertisements and
education to promote voluntary birth control. Health services to lower infant and child
mortality rates have improved. However, 40% of Indians live below the poverty level and
this further complicates the problem.
b) Compare and contrast the governmental policies designed to control population growth in
China and Mexico. Be sure to identify the specific policies used in each country. Evaluate the
effectiveness of each approach in reducing fertility rates: Which policies have been most
effective, and why?
In 1979 China instituted the one-child policy and provided incentives to
promote later marriages. One-child incentives included medical care and schooling, cash
bonuses, preferential housing, and retirement funds. Penalties were instituted if more
than one child was born. This plan brought about a rapid and drastic reduction from 5.8
births per woman in 1970 to 2.1 in 1981. In 2004 China’s TFR was 1.7 and the government
continues its policy of strict population control. Problems with this include the need for
larger families in agricultural regions, and the bias towards producing a son as the only
child – distorting the balance of males and females in the population.
In 1974 the Mexican government instigated several measures to reduce population
growth: educational reform, family planning and health care. The TFR was reduced from
6.7 births per woman in 1970 to 2.8 births per woman in 2004. Multimedia campaigns,
including popular television and radio shows that carry family planning messages have
recently been used to further promote these ideas. Many Mexican women have been
ignoring the decrees of the Roman Catholic Church and purchase contraceptives on the
black market and this has helped to support the government’s goals to control the
population.