Populations & Ecology Distribution: geographic and ecological range (i.e. North America) (i.e. desert) Often determined by presence or absence of suitable habitat Does it include migration areas? Yes! Dispersion: spacing of individuals

Populations: individuals of same species at the same place and time Demography: Study of populations

Clumped: in groups Can be social, due to resources, safety

Uniform (spaced): minimum distance from one another not common in animals seen in plants such as oaks, creosote and sages

Random: no pattern, spaced without regard to one another

Survivorship Curves

r vs. k selection life history strategies k-selected r-selected Fewer offspring Slow development Long lived Good competitors Slow dispersers Much parental care Examples?? Trees bears Many small offspring Rapid development Short lived Poor competitors Fast dispersers Little parental care Examples?? Weeds ants r-selected = opportunistic k-selected = equilibrium

Exponential Growth: increases by multiples N = number in population t = time r = rate of increase

Population Growth Rates Exponential growth -increases by multiples starts off slowly than rapid increase J-shaped curve Logistic growth –population slows than stops growing at carrying capacity (K) S-shaped curve Carrying capacity (K): the number of individuals the environment can support

Density: number of individuals per area Density dependent factors: Crowding causes these factors to have more of an influence on population regulation i.e. food, water, shelter, predators, disease Density-independent factors: Crowding has no influence i.e. earthquakes, temperature

Natural Populations all normally reach K

Natural Regulations Territory size mammals/birds resources defendable Physiological impairment White-tailed deer: reabsorption of embryos with poor nutrition

Oscillations: predator/prey cycles

Kaibab Deer Story Kaibab plateau in the grand canyon 200 deer/200 acres In early 1900’s – predator elimination program Between 1900-1911: 781 mountain lions, 556 bobcats, 31 wolves, 5000 coyotes killed By 1911: 500 deer/200 acres Massive starvation due to severe overgrazing By 1950 only 50 deer/200 acres due to environmental degradation

Human Population Growth: r or K selected?

Age-structure diagrams: show proportion of population at each age group Which is stable? Unstable?

Types of overpopulation People Overpopulation: too many people for the area LDCs=lesser developed countries Consumption Overpopulation: a few people use most of the resources MDCs=more developed countries