CHAPTER 14 POPULATION ECOLOGY
Reflect on Your Learning
(Page 648)
1.
Competition for food and water; competition for breeding space; competition for living space and shaded areas;
competition for hiding spaces from predators.
2.
• water hole in a dry area; organisms need the water to drink
• most remaining leaves are on trees and bushes, so only tall animals can feed here
• dry grasses for impala to feed on
3.
Student answers will vary. Possible answers include the following:
• Hunting by lions and man may reduce the numbers.
• Competition between these animals and domestic animals may reduce their numbers.
• Fires and droughts will decrease the populations.
Try This Activity: Interaction
(Page 649)
Figure 1 shows three positions of animal tracks.
(a) One animal ate the other. From the footprints, it is evident that two organisms enter from position 1 into position 2, but
only one leaves, as seen in position 3, so one organism ate the other.
(b) Predation.
(c) Student answers will vary, but most will have similar answers to (a) and (b)
(d) Student answers will vary, but most will realize that there was no observer so no definite answer is known.
14.1 CHARACTERISTICS OF POPULATIONS
PRACTICE
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Understanding Concepts
1.
population
area
34 turtles
density =
200 ha
density = 0.17 turtles/ha
density =
2.
3.
Student answers will vary, but should include some of the following: parking lots, picnic grounds, grasslands, and rocky
areas.
Student answers will vary considerably. The amount of park taken up by the items listed in #2 varies greatly. For instance,
if the amount of unliveable space in the park totals 40 hectares, then the ecological density is,
population
density =
area
34 turtles
density =
(200 ha − 40 ha)
density = 0.21 turtles/ha
296 Unit 5
Population Dynamics
Copyright © 2003 Nelson
PRACTICE
(Page 654)
Understanding Concepts
4.
# individual s
area
4 + 8 + 9 + 5 +1
density =
5 ×1 m 2
density =
density =
27
5 m2
density = 5.4 slugs/m 2
population = density × area
population = 5.4 slugs/m 2 ×100 m 2
population = 540 slugs
PRACTICE
(Page 657)
Understanding Concepts
5. (a)
# marked × size of 2nd sample
# recaptures
Mn
N=
m
430 × 154
N=
15
N = 4415
(b) No deaths, immigration, or emigration.
population =
Try This Activity: Mark–Recapture Analysis
(Page 657)
Student answers will vary throughout this activity:
(a) formula to be used is
# in your first class
# in your second class that are also in the first
=
total grade 12 population
# students in your second class
total grade 12 population =
# in your first class × # students in your second class
# in your second class that are also in the first class
(b) Differences might include relationships between blocks of students and subject choices, differing class sizes, spares.
(c) Yes, the student is both the observer and part of the population.
Copyright © 2003 Nelson
Chapter 14 Population Ecology 297
Section 14.1 Questions
(Page 659)
Understanding Concepts
1. (a) Large amounts of food will be needed, overcrowding may cause an increase in the incidence of disease, and such a
large population may drive other bird populations to dangerously low levels if they use the same food resource.
(b) Allowing hunting, culling, introducing predators.
2. (a)
population size
density =
area
1800 elephants
density =
(40 km × 60 km)
1800
density =
2400 km 2
density = 0.75/km 2
(b)
population
area
population
area =
density
5306 giraffes
area =
1.4 giraffes/km 2
density =
area = 3790 km 2
(c)
population
area
1050 giraffes
density =
3790 km 2
density = 0.277 giraffes/km 2
density =
3.
Student solutions will vary depending on their brainstorming.
(a) Challenges with whales include the fact that they migrate thousands of kilometres and it is hard to follow individuals
over such a great distance. Additionally, the whales are under water for a great deal of time, making finding the whales
difficult. The best method to estimate population size is via direct count from aerial/satellite images.
(b) Algae are so small and have such a huge population size that it is impossible to count every alga in a population. The
best method to estimate population size is random sampling applied to a three-dimensional habitat.
(c) Caribou are large, fast animals, which makes counting them difficult. They also live in very uninviting areas
(mountains, etc.). The best method to estimate population size is direct count from aerial/satellite images or possible
mark and recapture methods.
(d) Amphibians have large population sizes and they are very good at hiding. They are also very fast and can be dangerous
(poisonous). Quadrat sampling or mark and recapture can be used with amphibians.
4. (a) clumped
298 Unit 5
Population Dynamics
Copyright © 2003 Nelson
(b)
# marked × size of second sample
# of recaptures
Mn
N=
m
195 × 210
N=
10
N = 4095
population
density =
area
4095
=
900 ha
= 4.6 / ha
population size =
5.
To determine the size of a prairie dog population, a mark and recapture experiment or quadrat sampling would work the
best. Quadrat sampling is generally used for small, stationary organisms. If quadrat sampling were used, the area occupied
by the prairie dogs would have to be measured and then random quadrats marked out. One would have to watch for a long
time as prairie dogs are burrowers and are not out in the open. Additionally, without a good look at the organisms, it
would be impossible to tell whether that individual had been counted already. Videotape could be used to watch the
prairie dogs. The video could then be used to determine the average quadrat population and from this the total population
could be estimated. Mark and recapture could also be used, but it would be hard to assume that all the conditions for such
an experiment were met.
Applying Inquiry Skills
6. (a) From Table 1,
# marked × size of second sample
# recaptures
Mn
N=
m
280 ×130
N=
8
N = 4550
population
density =
area
4550
density =
2.0 ha
density = 2275/ha
population size =
From Table 2,
# marked × size of second sample
population =
# recaptures
Mn
N=
m
150 × 70
N=
26
N = 404
population
density =
area
404
density =
1.0 ha
density = 404/ha
(b) The oil refinery appears to have reduced the grasshopper population.
Copyright © 2003 Nelson
Chapter 14 Population Ecology 299
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