Making Connections
7.
Student answers will vary considerably but should include some of the following:
(a) North Atlantic right whale
Rationale for research:
• This is the world’s most rare large whale; only 350 are estimated to be alive today. It is considered an endangered
species.
• Reduced by commercial whaling but protected since 1935,the population has not shown significant signs of recovery.
• Many continue to die from collisions with ships and are injured by entanglements with fishing gear.
• Serious threats to the population require that its health and current status be examined. Much has yet to be understood
about this species of whale, thus monitoring and research are needed to provide an information base for an effective
recovery plan.
(b) Techniques and technology may include the following, which have been used to research this whale:
• Satellite tracking for their migration pattern
• Photo identification for population census
• Radio tracking, tagging with small implanted transmitter
• Genetic analysis of tissue samples for various forms of information (regarding population compositon, reproduction,
etc.); samples may be obtained using arrow designed to stop when it hits the whale’s skin and takes only a small
sample, often without the whale seeming to notice
• Skin biopsies
• Example of noninvasive technique: Passive acoustics monitoring systems
(c) Potential long and short-term effects from using techniques/technology:
Several of the monitoring techniques used are noninvasive, and even those that are invasive, appear not to cause the
animal distress when are applied by trained people within the research crews.
(d) Consistent with CCAC’s three Rs philosophy:
• Replacement: Not applicable; this category applies more in the case where an animal is used in medical or other
scientific research and the proposal is for a study that may provide alternatives to using the animal, thus replacing it
in research, or replacing painful or distressing methods with milder ones.
• Reduction: Researching the North Atlantic right whale and raising awareness through findings, may reduce mortality
and injury related to vessel strikes, lead to a greater reduction of disturbance by human activities, and help to reduce
exposure to various forms of habitat degradation by influencing policymaking.
• Refinement: Research will monitor the population to better understand the animal and address ongoing threats.
Helpful Web sites
http://www.pirweb.org/ccac.htm (for CCAC guidelines)
http://www.ccac.ca
http://biology.usgs.gov/s+t/SNT/noframe/mr183.htm
http://whale.wheelock.edu/rightwhale/
http://www.mar.dfo-mpo.gc.ca/communications/community/e/FinalEnglishMarch2001.html
14.2 MEASURING AND MODELLING POPULATION CHANGE
PRACTICE
(Page 664)
Understanding Concepts
1. (a)
N (t + 1)
N(t)
50 000 + 32 000 − 29 000
=
50 000
λ=
=
53 000
50 000
= 1.06
300 Unit 5
Population Dynamics
Copyright © 2003 Nelson
(b)
N (2) = N (0) t
N (2) = (50 000)(1.06)2
N (2) = 56 180
N (10) = N (0) t
N (10) = (50 000)(1.06)10
N (10) = 89 540
PRACTICE
(Page 665)
Understanding Concepts
2. (a)
dN
= rN
dt
dN
= (0.345 / day)980
dt
dN
= 338 / day
dt
(b)
0.69
r
0.69
=
0.345 / day
= 2 days
td =
(c)
final population
initial population
2 000 000
2 td =
980
= 2040
2 td =
2 td =2040, so td = 11 and each td = 2 days, so 22 days are needed.
PRACTICE
(Page 668)
Understanding Concepts
3.
r-max
Population size (N)
1.00
20
1.00
200
Copyright © 2003 Nelson
(K − N )
]
K
1000 − 20
1000
1000 − 200
1000
[
Population growth rate
19.6
160
Chapter 14 Population Ecology 301
4.
1.00
500
1.00
900
1.00
990
1.00
1000
1000 − 500
1000
1000 − 900
1000
1000 − 990
1000
1000 − 1000
1000
250
90
9.9
0
No. Carrying capacity is determined mostly by the amount of food that is present. As the population approaches the
carrying capacity, the growth rate should decrease. Otherwise, the population will exceed carrying capacity, food
resources will be depleted, and organisms will starve.
Section 14.2 Questions
(Pages 669–670)
Understanding Concepts
1.
population increase = 20 + 4 = 24
population decrease = 9 + 11 + 8 = 28
N (t + 1)
λ=
N (t )
(24 − 28) + 34
=
34
= 0.88
2.
(b + i) − ( d + e)
n
(342 + i) − ( 43 + 0)
429 =
90
i = 87
population change =
3.
N (t + 1)
N (t )
42 + 263 − 26 − 8 − 12
=
42
= 6. 2
λ=
4. (a) exponential
(b) N(t) = N(0) λ t
N(t) = (2)4.58
= 336 000 ( assuming that the species mature in one year)
5. (a) Exponential
(b) Large food supply, enough space to minimize disease spread by overcrowding, little predation, especially by man.
(c) Decreasing food supply leads to starvation, increasing disease; overcrowding leading to increased competition for
resources.
6. Student answers will vary. Some possible reasons include the following:
• lack of new surfaces for attachment
• exhaustion of food resources
• spread of disease in crowded habitat
• introduction of predators
302 Unit 5
Population Dynamics
Copyright © 2003 Nelson
Applying Inquiry Skills
7. (a) population change = (34 + 12) – (86 + 0) =
N(t+1) = 198
= 158
í N (t + 1)
N
158
=
198
= 0.8
í
λ=
í
The population has a growth rate of
(b) The population decrease represents about 25% of the population. This is a considerable change in a small population.
Because frogs are an indicator species, one would be concerned about the quality of the environment that the frogs are
in. A study of any changes in the marsh itself would be needed, such as water temperature, depth, quality, and cold
periods during egg laying or tadpole growth periods.
(c) This study is not adequate to make conclusions about the environment. Too many accidental factors can affect small,
isolated populations like this one. Larger studies over larger areas and longer periods are needed to show the impact of
environmental factors.
8. (a)
N (t + 1)
N (t )
8
λ=
2
λ=4
N (t ) = N (0)λt
λ=
N (5) = 2(4) 5
N (5) = 2048
(b)
N(t) = N(0) λ t
2
8
32
128
512
2048
generation
0
1
2
3
4
5
snake population
2500
2000
1500
population
1000
500
0
0
1
2
3
4
5
generation
Copyright © 2003 Nelson
Chapter 14 Population Ecology 303
(c) The population growth would still be exponential, although not at as fast as with a growth rate of six offspring per pair
per year. As the chart below shows, the growth rate is still exponential and the curve will be identical to the one above,
although the numbers along the y-axis will be lower.
generation
0
1
2
3
4
5
N(t) =N(0) λ t
2
5
13
31
78
195
Making Connections
9. (a) Student answers will vary considerably but should include some of the following:
Potential action plans:
(i) Reactive control methods (i.e. to control already established population). These may include mechanical cleaning;
desiccation; thermal treatment; high-pressure water jetting; scraping; oxygen deprivation; freezing; or chemical
treatment
(ii) Acoustic energy (AE) has been shown to be very effective in preventing attachment of juvenile mussels to pipes; a
range of 3 kHz to 8 kHz, with acceleration of about 150 m/sec2 to 200 m/sec2 have yielded 75% to 100% mussel
detachment and mortality. These are within limits that allow for normal operation of piping equipment and are
especially promising, because the technique does not require the use of chemicals and is financially feasible.
(iii) Extremely low frequency electromagnetism (ELF EM); it is similar to AE (above), does not require chemical use, can
be installed in water intake systems, and is a low-maintenance form of control.
(iv) Low pressure; it can be used where flow is of raw, untreated water. Vacuum pressure in pipe segments will decrease
the O2 supply in water to near 0, suffocating the mussels, which can then be removed by back flushing (the process
takes about 2 to 3 days per section).
(v) Raising public awareness and sense of individual responsibility: teach boaters the importance of examining and how
to examine their vessels for zebra mussels, and how to prevent infestation.
(b) Student PMI charts will vary. A summary of PMI charts and what they should include is found in Appendix A4 of the
Student Text, page 768.
14.3 FACTORS AFFECTING POPULATION CHANGE
Section 14.3 Questions
(Page 675)
Understanding Concepts
1. Natality is the number of births in the population and therefore increases population size. This increases population
density, which in turn can increase intraspecific competition.
Mortality is the number of deaths in the population and therefore decreases population size. This decreases
population size.
Immigration is the number of individuals that enter the population. Like natality, this can increase population density
and can therefore increase intraspecific competition.
Emigration is the number of individuals that leave the population. This is like death, which decreases population size.
2. Density-dependent factors are those that influence population regulation, having a greater impact as population density
increases or decreases. Density-independent factors are those that influence population regulation regardless of population
density.
3. (a) density dependent
(b) density independent
(c) density independent
4. Density independent: rainfall will affect plant growth, which affects herbivore populations as well.
Density dependent: fire spreads quickly through dense vegetation, especially if the vegetation is the same age and height.
Applying Inquiry Skills
5. (a) density dependent
304 Unit 5
Population Dynamics
Copyright © 2003 Nelson