Population Ecology Models Explained

[object Object],[object Object],[object Object]

[object Object],[object Object]

[object Object],[object Object],Figure 52.1

Density and Dispersion ,[object Object],[object Object],[object Object],[object Object]

Density: A Dynamic Perspective ,[object Object],[object Object],[object Object],[object Object]

[object Object],[object Object],Figure 52.2 Births and immigration add individuals to a population. Births Immigration PopuIation size Emigration Deaths Deaths and emigration remove individuals from a population.

Patterns of Dispersion ,[object Object],[object Object]

[object Object],[object Object],[object Object],Figure 52.3a (a) Clumped. For many animals, such as these wolves, living in groups increases the effectiveness of hunting, spreads the work of protecting and caring for young, and helps exclude other individuals from their territory.

[object Object],[object Object],[object Object],Figure 52.3b (b) Uniform. Birds nesting on small islands, such as these king penguins on South Georgia Island in the South Atlantic Ocean, often exhibit uniform spacing, maintained by aggressive interactions between neighbors.

[object Object],[object Object],Figure 52.3c (c) Random. Dandelions grow from windblown seeds that land at random and later germinate.

Demography ,[object Object],[object Object],[object Object],[object Object]

Life Tables ,[object Object],[object Object],[object Object]

[object Object],[object Object],Table 52.1

Survivorship Curves ,[object Object],[object Object]

[object Object],[object Object],Figure 52.4 1000 100 10 1 Number of survivors (log scale) 0 2 4 6 8 10 Age (years) Males Females

[object Object],[object Object],Figure 52.5 I II III 50 100 0 1 10 100 1,000 Percentage of maximum life span Number of survivors (log scale)

Reproductive Rates ,[object Object],[object Object]

[object Object],[object Object],Table 52.2

Life History Diversity ,[object Object]

[object Object],[object Object],Figure 52.6

“Trade-offs” and Life Histories ,[object Object],Figure 52.7 ,[object Object],RESULTS Researchers in the Netherlands studied the effects of parental caregiving in European kestrels over 5 years. The researchers transferred chicks among nests to produce reduced broods (three or four chicks), normal broods (five or six), and enlarged broods (seven or eight). They then measured the percentage of male and female parent birds that survived the following winter. (Both males and females provide care for chicks.) EXPERIMENT The lower survival rates of kestrels with larger broods indicate that caring for more offspring negatively affects survival of the parents. CONCLUSION 100 80 60 40 20 0 Reduced brood size Normal brood size Enlarged brood size Parents surviving the following winter (%) Male Female

[object Object],[object Object],Figure 52.8a (a) Most weedy plants, such as this dandelion, grow quickly and produce a large number of seeds, ensuring that at least some will grow into plants and eventually produce seeds themselves.

[object Object],[object Object],Figure 52.8b (b) Some plants, such as this coconut palm, produce a moderate number of very large seeds. The large endosperm provides nutrients for the embryo, an adaptation that helps ensure the success of a relatively large fraction of offspring.

Per Capita Rate of Increase ,[object Object],[object Object]

[object Object],[object Object],[object Object],dN dt  rN

Exponential Growth ,[object Object],[object Object],[object Object],[object Object]

[object Object],dN dt  r max N

[object Object],[object Object],Figure 52.9 0 5 10 15 0 500 1,000 1,500 2,000 Number of generations Population size ( N ) dN dt  1.0 N dN dt  0.5 N

[object Object],[object Object],Figure 52.10 1900 1920 1940 1960 1980 Year 0 2,000 4,000 6,000 8,000 Elephant population

[object Object],[object Object],[object Object],[object Object],[object Object]

The Logistic Growth Model ,[object Object],[object Object]

[object Object],[object Object],Figure 52.11 Maximum Positive Negative 0 N  K Population size ( N ) Per capita rate of increase ( r )

[object Object],[object Object],dN dt  ( K  N ) K r max N

[object Object],[object Object],Figure 52.12 dN dt  1.0 N Exponential growth Logistic growth dN dt  1.0 N 1,500  N 1,500 K  1,500 0 5 10 15 0 500 1,000 1,500 2,000 Number of generations Population size ( N )

The Logistic Model and Real Populations ,[object Object],[object Object],Figure 52.13a 800 600 400 200 0 Time (days) 0 5 10 15 (a) A Paramecium population in the lab. The growth of Paramecium aurelia in small cultures (black dots) closely approximates logistic growth (red curve) if the experimenter maintains a constant environment. 1,000 Number of Paramecium /ml

[object Object],[object Object],Figure 52.13b 180 150 0 120 90 60 30 Time (days) 0 160 140 120 80 100 60 40 20 Number of Daphnia /50 ml (b) A Daphnia population in the lab. The growth of a population of Daphnia in a small laboratory culture (black dots) does not correspond well to the logistic model (red curve). This population overshoots the carrying capacity of its artificial environment and then settles down to an approximately stable population size.

[object Object],[object Object],Figure 52.13c 0 80 60 40 20 1975 1980 1985 1990 1995 2000 Time (years) Number of females (c) A song sparrow population in its natural habitat. The population of female song sparrows nesting on Mandarte Island, British Columbia, is periodically reduced by severe winter weather, and population growth is not well described by the logistic model.

The Logistic Model and Life Histories ,[object Object],[object Object]

[object Object],[object Object],[object Object],[object Object]

Population Ecology Models Explained

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