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Chapter 52: Population Ecology. What is a population? Individuals of a single species that occupy the same general area What is the difference between density & dispersion? Density – number of individuals per unit area or volume

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slide1

Chapter 52: Population Ecology

  • What is a population?
    • Individuals of a single species that occupy the same general area
  • What is the difference between density & dispersion?
    • Density – number of individuals per unit area or volume
    • Dispersion – pattern of spacing within the boundaries of population
figure 52 2 population dynamics

Births and immigration add individuals to a population.

Immigration

Births

PopuIationsize

Emigration

Deaths

Deaths and emigration remove individuals from a population.

Figure 52.2 Population dynamics

Factors that influence density…..

Increase

Decrease

fig 52 3 patterns of dispersion within a population s geographic range

(a) Clumped. For many animals, such as thesewolves, living in groups increases theeffectiveness of hunting, spreads the workof protecting and caring for young, and helpsexclude other individuals from their territory.

(c) Random. Dandelions grow from windblown seeds that land at random and later germinate.

Fig. 52.3 Patterns of dispersion within a population’s geographic range

(b) Uniform. Birds nesting on small islands, suchas these king penguins on South Georgia Islandin the South Atlantic Ocean, often exhibit uniformspacing, maintained by aggressive interactionsbetween neighbors.

slide4

Chapter 52: Population Ecology

  • What is a population?
    • Individuals of a single species that occupy the same general area
  • What is the difference between density & dispersion?
    • Density – number of individuals per unit area or volume
    • Dispersion – pattern of spacing within the boundaries of population
  • What factors influence population size?
    • Birth rate – fecundity
    • Death rate
    • Generation time
    • Sex ratio
  • 4. What do the survivorship curves mean?
figure 52 5 idealized survivorship curves types i ii and iii

1,000

I

100

II

Number of survivors (log scale)

10

III

1

100

50

0

Percentage of maximum life span

Figure 52.5 Idealized survivorship curves: Types I, II, and III

Type I – most born survive & live to their maximum life span – us – k-selected

Type II – constant death rate – each day has an equal opportunity for life or death

Type III – high early death rate but survivors live to maximum life span – r-selected

slide6

Chapter 52: Population Ecology

  • What is a population?
  • What is the difference between density & dispersion?
  • What factors influence population size?
  • What do the survivorship curves mean?
  • What are the 2 main populations growth curves?
    • - Exponential – “J”-curve
figure 52 9 population growth predicted by the exponential model

2,000

dN

1.0N

dt

1,500

dN

0.5N

dt

Population size (N)

1,000

500

0

0

10

15

5

Number of generations

Figure 52.9 Population growth predicted by the exponential model

dN = Δ population size

dt = Δ time

rmax = Births – deaths

(intrinsic rate of increase)

N = population size

Species whose population size is primarily determined by birth rate = r-selected species

self quiz
Self-Quiz
  • A uniform dispersion pattern for a population may indicate that
    • A. the population is spreading out and increasing its range.
    • B. resources are heterogeneously distributed.
    • C. individuals of the population are competing for some resource, such as water and minerals for plants or nesting sites for animals.
    • D. there is an absence of strong attractions or repulsions among individuals.
self quiz1
Self-Quiz
  • I would expect the potential for social interactions among individuals to be maximized when individuals
    • A. are randomly distributed in their environment.
    • B. are uniformly distributed in their environment.
    • C. have a clumped distribution in their environment.
    • D. are non-randomly distributed in their environment.
self quiz2
Self-Quiz
  • Humans are an example of an organism with a type I survivorship curve. This means
    • A. mortality rates are highest for younger individuals.
    • B. mortality rates are highest for older individuals.
    • C. mortality rates are constant over the life span of individuals.
    • D. the population growth rate is high.
slide12

Chapter 52: Population Ecology

  • What is a population?
  • What is the difference between density & dispersion?
  • What factors influence population size?
  • What do the survivorship curves mean?
  • What are the 2 main populations growth curves?
    • Exponential
    • Logistic
figure 52 12 population growth predicted by the logistic model

2,000

dN

1.0N

Exponential growth

dt

1,500

K  1,500

Logistic growth

Population size (N)

1,000

dN

1,500  N

1.0N

dt

1,500

500

0

0

5

10

15

Number of generations

Figure 52.12 Population growth predicted by the logistic model

K = carrying capacity

Species whose population size is primarily determined by carrying capacity

= k-selected species

slide14

Chapter 52: Population Ecology

  • What is a population?
  • What is the difference between density & dispersion?
  • What factors influence population size?
  • What do the survivorship curves mean?
  • What are the 2 main populations growth curves?
  • What is the difference between r-selected & k-selected species?
    • r-selected (generalists) k-selected (equilibrial)
    • Maturation time: short long
    • Lifespan: short long
    • Death rate high low
    • Offspring/episode: many few
    • Size of offspring/eggs: small large
    • Parental care: none extensive
    • Timing of 1st reproduction: early late in life
    • Reproductions/lifetime: usually 1 several
    • Examples: insects, fish, frogs mammals, birds
  • 7. What factors limit a population?
slide15

Chapter 52: Population Ecology

  • What is a population?
  • What is the difference between density & dispersion?
  • What factors influence population size?
  • What do the survivorship curves mean?
  • What are the 2 main populations growth curves?
  • What is the difference between r-selected & k-selected species?
  • 7. What factors limit a population?
    • Density – dependent factors – intensify as population size increases
      • Resource limitation
      • Health
      • Predation
      • Waste accumulation
    • Density – independent factors – effect population regardless of density
      • Weather
      • Climate
      • Environmental disasters
figure 52 21 population cycles in the snowshoe hare and lynx

Snowshoe hare

160

120

Lynx

9

Lynx population size (thousands)

Hare population size (thousands)

80

6

40

3

0

0

1850

1875

1900

1925

Year

Figure 52.21 Population cycles in the snowshoe hare and lynx
slide17

Chapter 52: Population Ecology

  • What is a population?
  • What is the difference between density & dispersion?
  • What factors influence population size?
  • What do the survivorship curves mean?
  • What are the 2 main populations growth curves?
  • What is the difference between r-selected & k-selected species?
  • What factors limit a population?
  • How has the human population changed & how is it shown?
figure 52 22 human population growth data as of 2003

6

5

4

Human population (billions)

3

2

The Plague

1

0

8000 B.C.

4000 B.C.

3000 B.C.

2000 B.C.

1000 B.C.

0

1000 A.D.

2000 A.D.

Figure 52.22 Human population growth (data as of 2003)
figure 52 25 age structure pyramids for the human population of three countries data as of 2003

Rapid growth Afghanistan

Decrease Italy

Slow growth United States

Male

Female

Female

Male

Male

Age

Age

Female

85

85

80–84

80–84

75–79

75–79

70–74

70–74

65–69

65–69

60–64

60–64

55–59

55–59

50–54

50–54

45–49

45–49

40–44

40–44

35–39

35–39

30–34

30–34

25–29

25–29

20–24

20–24

15–19

15–19

10–14

10–14

5–9

5–9

0–4

0–4

8

8

8

6

6

6

4

4

4

2

2

2

0

0

0

2

2

2

4

4

4

6

6

6

8

8

8

Percent of population

Percent of population

Percent of population

Figure 52.25 Age-structure pyramids for the human population of three countries (data as of 2003)

Group

NOT

making

babies

Group

making

babies

Babies

Wide base = rapid growth

Same width = slow growth

Narrow base = decreasing

self quiz3
Self-Quiz
  • A population’s carrying capacity is
    • A. the number of individuals in that population.
    • B. a constant that can be estimated for all populations.
    • C. inversely related to r.
    • D. The population size that can be supported by available resources for that species within the habitat.