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Homework answers / question archive / Understanding Concepts 8
Understanding Concepts 8. What conditions are necessary for a population to
experience prolonged exponential growth?
1. Define and give examples of populations that exhibit > clearly what happens once a lat the following dispersion patterns: 9, Explain clearly w th 7 population
(a) clumped reaches a dynamic equilibrium.
(b) random 10. Classify each of the following as density dependent o;
(c) uniform density independent limiting factors:
2. Students sampled aquatic insect larvae living on a (a) fertilizer run-off resulting in the eutrophication small section of river bottom measuring 2.0 m by of a freshwater body. .
0.8 m. They found approximately 45 000 black fly (b) the impact of predators on a population of snow larvae in their sample. geese. | | | | |
(a) What was the population density of this species? (c) the spread of an infectious disease in a wild
(b) Estimate the number of black fly larvae living in population. , . .
a similar habitat of river bottom measuring 50 m (d) affects of habitat loss on wild populations,
by 10 m. 11. Explain, using an example for each, the differences
3. According to the 2001 census, the population of between intraspecific and interspecific interactions.
Canada had reached 30 007 094 people. 12. Explain briefly the differences between passive and
(a) What is the population density of Canadians if aggressive defense mechanisms.
Canada’s land area is 9 976 000 km? 13. What obvious defense mechanism is utilized by the
(b) Using our population as an example, explain why sea urchin, Strongleocentrotus franciacanus, shown in
the ecological density of a species is usually Figure 1. Of what possible adaptive benefit(s) is its
greater than its crude density. bright colouration?
4, Natality, mortality, immigration, and emigration are = EEE
all terms related to any population. ar ee
(a) Describe briefly what each term means. ay Pea ys
(b) Explain briefly how each process affects a es : i PR fore?
population. ANC,
(c) Which of the terms do not relate to a closed - eral Gy
population? Explain why not. eee ee
(d) Brainstorm several examples of closed popula- 7 a yt
tions that occur naturally. Contrast these with re. \S cee
examples of closed populations produced by se i wat human intervention or other activities. - / A fo > SS
5. Calculate the absolute growth of the Ontario popula- ; | on, tion between July 21, 2000 and June 30, 2001, given Fj , 7 ~
the following data from Statistics Canada. During Sen un ' . ae
rchin =
that year there were:
(i) 130672 births 14. Describe and give two examples of each of the
(ii) 87 565 deaths following:
(iii) 149 868 immigrants (a) commensalism
(iv) 32 156 emigrants (b) mutalism
6. List five environmental resources for which there (c) parasitism
might be intraspecific competition. Provide examples 15. Explain why some examples of mutualism are obliga
of such competition. tory and others are not.
7. Explain why small populations often experience rela- 16. Parasites are often classified according to where they
tively slow growth for several generations. On a sig- live. What two terms are involved? Explain each.
moidal curve, what name is given to this region of
17. Desc ich of the following factors influenced
| human population growth patterns on a g] ce Table 1) Monthly Growth for a Population of Meadow
| (a) the distribution of native large seeded ran vaste
Ls: ed grasses
(b) the availability of large mammal species and the; Month Meadow vole population
ease of domestication ne their December 3 990
(c) the scientific and industrial revolutions January 5 488
18. In the past . years a decrease in death rates has had February 7 683
. a far more ramatic 'mpact on population growth March 10 756
: than an Increase in birth rates. What key technolog- April 15 058
| ical innovations account for much of the drop in
| death rates? May 21 081
! ; June 29 513
19. Why do medical advances that extend the lives of eld- ul 41318
! erly individuals not have a significant impact on pop- y
1 ulation growth rates? August 57 845
20. Suggest five or more reasons why high density September see
| housing developments put less strain on the environ- October 118 378
| ment than low density housing developments.
| 21. Some argue that water filtration systems which pre- (a) Make a graph of the data.
| 1 (b) Based on your graph, is the meadow vole popula-
| pare drinking water must be designed to remove all . ies =
; tion exhibiting logistic, geometric, or exponential
types of contaminants. Others argue that contami- growth? Explain
vice eke ° prevent’ nom h ching water SuP- b (c) Based on your answer to (b), use the appropriate
P les in the first place. Explain why the best approac formula to estimate the size of the vole popula-
involves both of these concepts. tion for the next three months.
22. Describe what aspects of your life would need to be 27. A fisheries biologist studied a population of cichlids
assessed in order to establish your personal ecological in a 120-ha section of Lake Tanganyika in central
footprint. Africa. She found that the fish lived only in scattered
| 23. Use a triple Venn diagram to compare and contrast reed beds that accounted for 15% of the study area.
the three models of population growth: logistic Data were collected using the mark-recapture method
growth, geometric growth, and exponential growth. and summarized in the table below.
i j ulations show more Irreg-
3 24. Explain how regional pop | lations Table 2 Mark-Recapture Analysis of Cichlids
2 ular changes in size than large global populations. a
25. Discuss the observation that a small population may Number of cichlids marked 185
have greater effects on the local and the global envi- Number of cichlids captured in second sample 208
ronment than a large population. Support your Number of marked cichlids recaptured 13
answer with specific examples of human patterns of 00 oo
consumption. (a) How many cichlids would you estimate to be in
the study area?
| . “ . b) What is the density of the cichlid population per
f= Applying Inquiry Skills Geld mice ") hectare? ‘ en
J . e ml > . . .
| 26. Meadow voles, sometimes referred to ° s xeed (c) What is the dispersion pattern of the fish’
are extremely common small rodents 1 : becoming (d) How might the dispersion pattern affect your
' actively throughout the year with fema ‘i tain interpretation of their density?
fertile at under two months of age. aa , a (e) How might the interpretation of the mark-
r ] . . .
Table 1 represents the growth ove small grassland. recapture data be affected if behavioural studies
population of these voles living 1n 4 determined that this species of cichlid is highly
, territorial?
| a Population Dynamics 757
28. Analyze the graph of the growth curve representing the that are carrying the bacteria Bornes mrad | |
human population of Ireland before 1900 (Figure 2). Today, the only area in Ontario eT in risk 0 Lyme dis- :
(a) Label the different phases of this growth curve. ease is Long Point on the shore o Le Ene Research 2
(b) Suggest possible reasons for the decline in car- Lyme disease and answer the following: a
rying capacity at time D. (a) Is Lyme disease a serious health concern? Justify
(c) Research the events that actually occurred in your answet.
Ireland before 1900 that led to this decline in car- (b) Is there a natural balance between predators and
rying capacity. the deer population of Long Point? |
(c) What strategies in both wildlife management and |
ch [wwweciencenelsoncom human behaviour might reduce the risk of
acquiring this disease?
wn | sce: oo
>
z | 31. Some suggest that lakes without fish populations due to
6 new carrying acid deposition can simply be stocked with young fish.
§ capacity (a) Who might be satisfied with this solution? Explain.
E (b) Explain why this action does not solve the problem.
< 32. Great gray owls, Strix nebulosa, are very vulnerable to
A B C D F human disturbance such as clearing of forests for
Time timber or farmland. Their population dispersion and
Figure 2 geographic range are most affected by the availability
of nest sites. Other factors such as food supply, influ-
29. Examine the data in the table below which compares ence the carrying capacity of the local environment.
Canadian population statistics for the periods These birds are top predators and feed heavily of mice |
1861-1871 and 1991-1996. and voles.
Table 3 Canadian Population Statistics (a) How might use of pesticides influence the health
Population | Births Deaths Immigrants} Emigrants of gray owl populations: —
(1000's) (b) How could forestry practices be altered to limit
period negative impacts on the range and dispersion
(1000's) patterns of these owls?
1861-1871 410 (c) Many environmental organizations advocate
1991-1996 229 taking action to ensure this and similar wildlife
populations are given adequate protection. What
(a) What was Canada’s annual per capita birth and reasons do you think these groups would offer in 2
death rates in the period from 1861-1871? support of their position? Explain.
(b) How did these values change during the next 130 33. As water becomes scarce, the competition for water
years? Suggest reasons for these changes. between cities and countryside intensifies. In this |
(c) Calculate the annual percent growth rate for competition, farmers almost always lose. The
these two time intervals. demands for water use by people in cities must by
balanced by the needs for water used for irrigation.
Making Connections (a) What water uses would you consider essential for
30. Healthy, natural ecosystems play an important role in (b) Oa meters! ch 8 7
controlling the emergence and spread of infectious dis- log; th, eral changes in lifestyle and/or tec
eases by maintaining a balance between predators and ie Seles at could be used to : educe water
prey, and parasites and their hosts. The deer tick, Ixodes emand in homes and industries. ,
dammini, feeds on white-tailed deer and occasionally (c) How m ight farmers reduce their water demands:
bites people. Lyme disease is spread by the bite of ticks Consider alternative irrigation technologies as
well as crop selection.
758 Unit 5 va ;
