1. Chapter 8
Population Ecology

2. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?
They were over-hunted to the brink of extinction by the early 1900’s and are now making a comeback.
Figure 8-1

3. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?
Sea otters are an important keystone species for sea urchins and other kelp-eating organisms.
Figure 8-1

4. Southern Sea Otter
Figure 5.1 An endangered southern sea otter in Monterey Bay, California (USA) uses a stone to crack the shells of clams that it feeds on (left). It lives in a giant bed of seaweed called kelp (right).
Fig. 5-1, p. 102

5. Core Case Study: Southern Sea Otters - A Species in Recovery
Live in giant kelp forests
By the early 1900s they had been hunted almost to extinction
Partial recovery since 1977
Why care about sea otters?
Ethics
Tourism dollars
Keystone species

6. Chapter Objectives What are the major characteristics of populations?
How do populations regulate their size?
How do species differ in their reproductive patterns?

7. POPULATION DYNAMICS AND CARRYING CAPACITY
Most populations live in clumps although other patterns occur based on resource distribution.
Figure 8-2

8. What are some advantages to living in clumps? Disadvantages?
Figure 5.14 Three general habitat dispersion patterns for a population’s individuals.
a. Clumped (elephants)
Fig. 5-14a, p. 112

9. b. Uniform (creosote bush)
Figure 5.14 Three general habitat dispersion patterns for a population’s individuals.
b. Uniform (creosote bush)
Fig. 5-14b, p. 112

10. Figure 5.14 Three general habitat dispersion patterns for a population’s individuals.
c. Random (dandelions)
Fig. 5-14c, p. 112

11. Changes in Population Size: Entrances and Exits
Populations increase through births and immigration
Populations decrease through deaths and emigration

12. Age Structure: Young Populations Can Grow Fast
How fast a population grows or declines depends on its age structure.
Prereproductive age: not mature enough to reproduce.
Reproductive age: those capable of reproduction.
Postreproductive age: those too old to reproduce.

13. Exponential and Logistic Population Growth: J-Curves and S-Curves
The intrinsic rate of increase (r)
Slope
Rise over run.
Figure 8-4

14. Exponential and Logistic Population Growth: J-Curves and S-Curves
Europeans landed in Tasmania 1642.
Guns, Germs, and Steel.
Tasmania isolated 10,000 years ago.
Figure 8-4

15. Reindeer introduced to small Bering Sea island of St. Paul.
1910.
Lichens, mosses,and other food sources plentiful.
Easter Island
Figure 8-6

16. Exceeding Carrying Capacity: Move, Switch Habits, or Decline in Size
So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for humans.

17. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Can we continue to expand the earth's carrying capacity for humans?
a. No. Unless humans voluntarily control their population and conserve resources, nature will do it for us.
b. Yes. New technologies and strategies will allow us to further delay exceeding the earth's carrying capacity.

18. Population Density and Population Change: Effects of Crowding
Population density: the number of individuals in a population found in a particular area or volume.
e.g. biotic factors like disease
e.g. abiotic factors like weather

19. Types of Population Change Curves in Nature
Population sizes may stay the same, increase, decrease, vary in regular cycles, or change erratically.
Stable: fluctuates slightly above and below carrying capacity.
Irruptive: populations explode and then crash to a more stable level.
Cyclic: populations fluctuate and regular cyclic or boom-and-bust cycles.
Irregular: erratic changes possibly due to chaos or drastic change.

20. Types of Population Change Curves in Nature
Population sizes often vary in regular cycles when the predator and prey populations are controlled by the scarcity of resources.
Figure 8-7

21. Density-Dependent Factors
Wolf and Moose Populations on Isle Royale
The relationship between moose and wolves on Isle Royale illustrates how predation can affect population growth. In this example, the moose population was also affected by changes in food supply, and the wolf population was also affected by disease.
Moose Wolves
Copyright Pearson Prentice Hall

22. White-Tailed Deer Populations What should we do?
Figure 5-17: White-tailed deer populations in the United States have been growing.
Fig. 5-17, p. 115

23. Case Study: Exploding White-Tailed Deer Populations in the United States
Nearly extinct prior to their protection in 1920’s.
Lack of predators (wolf, cougar, bear)
Today million white-tailed deer in U.S. pose human interaction problems.
Deer-vehicle collisions (1.5 million per year).
Injure 14,000 and kills 200
$1.1 billion in damages
Transmit disease (Lyme disease in deer ticks).
Eat native vegetation
Suburbs in Forest expansion and habitat loss

24. More than nine out of 10 of the species recently caught were too young to have reproduced, meaning they may have been the last generation of the bluefin tuna.

25. Chapter Objectives What are the major characteristics of populations?
How do populations regulate their size?
Humans must manage populations in the future.
How do species differ in their reproductive patterns?

26. REPRODUCTIVE PATTERNS
Asexual.
Offspring are exact genetic copies (clones).
Sexual.
Genetic material is mixture of two individuals.
Courtship and mating rituals can be costly.
Because there is variation in a population…………….

27. Sexual Reproduction: Courtship
consume time and energy, transmit disease, inflict injury.
picking the most fit for next generation is worth the risk
Figure 8-8

28. Reproductive Patterns:
Large number of smaller offspring with little parental care (r-selected species).
Fewer, larger offspring with higher invested parental care (K-selected species).
Figure 8-9

29. Little or no parental care and protection of offspring
r-Selected Species
Cockroach
Dandelion
Many small offspring
Little or no parental care and protection of offspring
Early reproductive age
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental conditions
High population growth rate (r)
Population size fluctuates wildly above and below carrying capacity (K)
Generalist niche
Low ability to compete
Early successional species
Figure 8.10
Natural capital: generalized characteristics of r-selected (opportunist) species and K-selected (competitor) species. Many species have characteristics between these two extremes.
Fig. 8-10a, p. 168

30. Fewer, larger offspring High parental care and protection of offspring
K-Selected Species
Elephant
Saguaro
Fewer, larger offspring
High parental care and protection
of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental conditions
Lower population growth rate (r)
Population size fairly stable and usually close to carrying capacity (K)
Specialist niche
High ability to compete
Late successional species
Figure 8.10
Natural capital: generalized characteristics of r-selected (opportunist) species and K-selected (competitor) species. Many species have characteristics between these two extremes.
Fig. 8-10b, p. 168

32. Survivorship Curves: Short to Long Lives
The way to represent the age structure of a population.

33. Percentage surviving (log scale)
Late loss
Constant loss
Percentage surviving (log scale)
Figure 8.11
When does death come? Survivorship curves for populations of different species, show the percentages of the members of a population surviving at different ages. Most members of a late loss population (such as elephants, rhinoceroses, and humans) live to an old age. Members of a constant loss population (such as many songbirds) die at all ages. In an early loss population (such as annual plants and many bony fish species), most members die at a young age. These generalized survivorship curves only approximate the realities of nature.
Early loss
Age
Fig. 8-11, p. 169

34. TYING IT ALL TOGETHER
Southern Sea Otters and Sustainability
p. 117

35. Figure 5.B Changes in the population size of southern sea otters off the coast of the U.S. state of California, 1983–2012.
Changes in the population size of southern sea otters off the coast of the U.S. state of California, 1983–2012. How do we determine delisting threshold?
Fig. 5-B, p. 114

36. What term is used for the maximum population of a given species that a particular habitat can sustain indefinitely?
range of tolerance
carrying capacity
population density
environmental resistance

37. Biotic potential and ______ determine ______.
Environmental resistance; intrinsic rate of increase
Intrinsic rate of increase; carrying capacity
Carrying capacity; environmental resistance
Environmental resistance, carrying capacity

38. A J-shaped curve is characteristic of
Zero population growth
Logistic growth
A population that has overshot its carrying capacity
Exponential growth

39. True or false? Humans throughout history have been exempt from the effects of population overshoots and diebacks.
True
False

40. What term is used for the maximum population of a given species that a particular habitat can sustain indefinitely?
range of tolerance
carrying capacity
population density
environmental resistance

41. Biotic potential and ______ determine ______.
Environmental resistance; intrinsic rate of increase
Intrinsic rate of increase; carrying capacity
Carrying capacity; environmental resistance
Environmental resistance, carrying capacity

42. A J-shaped curve is characteristic of
Zero population growth
Logistic growth
A population that has overshot its carrying capacity
Exponential growth

43. Generally, a species with a high intrinsic rate of increase will
r-selected
K-selected
Be a specialist
Reproduce late in life

44. True or false? Humans throughout history have been exempt from the effects of population overshoots and diebacks.
True
False

45. Chapter Questions
Critical Thinking
Homework
Projects
groups