Population Dynamics Video online: invasive species Chapter 36 Population Dynamics Video online: invasive species

The Spread of Shakespeare’s Starlings European Starling Now: abundant, destructive pest in North America European starling

Starling populations very successful Starling populations very successful spread throughout NA since introduction in 1890 Current 1955 1945 1935 1925 1915 1905 The spread of starlings across North America

What is Population Ecology? changes in population size factors that regulate populations over time

36.1 Population ecology: study of how and why populations change A population... group of individuals of a single species that occupy the same general area

36.4 Idealized models help us understand population growth Who remembers them?!?!

The Exponential Growth Model The Exponential Growth Model Exponential growth accelerating increase that occurs when growth is unlimited

The equation G  rN describes this J-shaped curve The equation G  rN describes this J-shaped curve G  the population growth rate r  an organism’s inherent capacity to reproduce N  the population size Time Number of Cells 0 minutes 20 40 60 80 100 120 (= 2 hours) 3 hours 4 hours 8 hours 12 hours 1 2 4 8 16 32 64 512 4,096 16,777,216 68,719,476,736 = 20 = 21 = 22 = 23 = 24 = 25 = 26 = 29 = 212 = 224 = 236 Number of bacterial cells (N) 70 50 30 10 140 G = r N Time (min) Figure 36.4A

Breeding male fur seals Limiting Factors and the Logistic Growth Model Limiting factors environmental factors that restrict population growth Breeding male fur seals (thousands) 10 8 6 4 2 1915 1925 1935 1945 Year Figure 36.4B

Levels off @ carrying capacity, # individuals envt can support Logistic growth Model, represents slowing of population growth as a result of limiting factors Levels off @ carrying capacity, # individuals envt can support Number of individuals (N) K Time G = r N (K – N) Figure 36.4C

The equation G  rN(K – N)/K describes a logistic growth curve Where K  carrying capacity and (K – N)/K accounts for the leveling off of the curve

36.5 Multiple factors may limit population growth 36.5 Multiple factors may limit population growth As population’s density increases Factors such as limited food supply & increased disease or predation may increase death rate, decrease birth rate, or both 4.0 3.6 3.8 3.4 3.2 3.0 2.8 10 20 30 40 50 60 70 80 Density of females Clutch size Figure 36.5A

Abiotic factors such as weather May limit many natural populations Abiotic factors such as weather May limit many natural populations Exponential growth Sudden decline Number of aphids Apr May Jun Jul Aug Sep Oct Nov Dec Figure 36.5B

Most populations???? probably regulated by a mixture of factors, fluctuations in #s are common Time (years) 1975 1980 1985 1990 1995 2000 20 40 80 60 Number of females Figure 36.5C

36.6 Some pops have “boom-and-bust” cycles regular cycles of growth & decline 160 120 80 40 1850 1875 1900 1925 9 6 3 Snowshoe hare Lynx Hare population size (thousands) Lynx population size Year Figure 36.6

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POPULATION STRUCTURE AND DYNAMICS 36. 2 Density and dispersion patterns are important population variables Population density Is the number of individuals of a species per unit of area or volume

Environmental and social factors Environmental and social factors Influence the spacing of individuals in various dispersion patterns: clumped, uniform, or random Figure 36.2A Figure 36.2B

36.3 Life tables track mortality and survivorship in populations 36.3 Life tables track mortality and survivorship in populations Life tables and survivorship curves Predict an individual’s statistical chance of dying or surviving during each interval of the individual’s lifetime Table 36.3

The three types of survivorship curves The three types of survivorship curves Reflect species’ differences in reproduction and mortality Percentage of survivors (log scale) 100 10 1 0.1 50 III II I Percentage of maximum life span Figure 36.3

LIFE HISTORIES AND THEIR EVOLUTION 36.7 Evolution shapes life histories An organism’s life history Is the series of events from birth through reproduction to death

Populations with so-called r-selection life history traits Populations with so-called r-selection life history traits Produce many offspring and grow rapidly in unpredictable environments Figure 36.7A

Populations with K-selected traits Raise few offspring and maintain relatively stable populations

Are shaped by natural selection Life history traits Are shaped by natural selection Experimental transplant of guppies Predator: Killifish; preys mainly on small, immature guppies Guppies: Larger at sexual maturity than those in pike-cichlid pools Predator: Pike-cichlid; preys mainly on large, mature guppies Guppies: Smaller at those in killifish pools Figure 36.7B

Yield (thousands of metric tons) CONNECTION 36.8 Principles of population ecology have practical applications Principles of population ecology Are useful in managing natural resources 900 800 700 600 500 400 300 200 100 1960 1970 1980 1990 2000 Yield (thousands of metric tons) Figure 36.8

THE HUMAN POPULATION CONNECTION 36.9 Human population growth has started to slow after centuries of exponential increase The human population Has been growing almost exponentially for centuries, standing now at about 6.4 billion The Plague 6 5 4 3 2 1 8000 B.C. 4000 3000 2000 1000 A.D. Human population size (billions) Figure 36.9A

The ecological footprint The ecological footprint Represents the amount of land per person needed to support a nation’s resource needs 16 14 12 10 8 6 4 2 Available ecological capacity (ha per person) Ecological footprint (ha per person) Japan UK Spain Germany Netherlands Norway USA World China India Sweden Canada Australia New Zealand Figure 36.9B

The ecological capacity of the world The ecological capacity of the world May already be smaller than the population’s ecological footprint Traffic in downtown Cairo, Egypt Manhattan, New York City Refugee camp in Zaire Figure 36.9C

Birth or death rate per 1,000 population 36.10 Birth and death rates and age structure affect population growth The demographic transition Is the shift from high birth rates and death rates to low birth rates and death rates 50 40 30 20 10 1900 1925 1950 1975 2000 2025 2050 Year Birth rate Death rate Birth or death rate per 1,000 population Figure 36.10A

The age structure of a population The age structure of a population Is the proportion of individuals in different age-groups Affects its future growth Age 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 8 4 6 2 Percent of population Primary reproductive ages Rapid growth Slow growth Decrease Afghanistan United States Italy Male Female Figure 36.10B

Increasing the status of women May help to reduce family size