Population Ecology What is a Population? An interbreeding

Population Ecology What is a Population? An interbreeding

Population Ecology What is a Population? An interbreeding group of the same species living in the same general area may be distinguished by natural or arbitrary boundaries

Population Density vs Dispersion the number of individuals per unit area or volume the pattern of

distribution of individuals Patterns of Dispersion What is the pattern for the population on the

previous slide? On the title slide? Population Dynamics Demographics Life table: age-specific summary

of survival pattern of a population Survivorship Curve Survivorship Curves I Fewer offspring and low mortality

until old age due to parental care. II Death rate is relatively constant throughout the life span.

III Many offspring & high mortality in young due to lack of parental care. Reproductive Rates

focus on females reproductive tables: age-specific summary Semelparity vs Iteroparity

reproduce once reproduce repeatedly MANY offspring FEW offspring

most offspring die most offspring survive offspring are on their own

Offspring are cared for Population Growth Rate Change in Births (B) Deaths (D) = population size per unit time (DN/Dt)

Per capita birth rate (b): average # offspring produced by individual

Per capita death rate (m): used for expected # of deaths Per capita rate of increase (r) rN = bN mN = DN/Dt

Simplifying the Population Growth Rate rN = bN mN = DN/Dt r=bm r > 0 : population is growing r < 0 : population is shrinking r = 0 : zero population growth (ZPG)

Exponential Growth J-Curve Growth r is steady & positive Maximal growth rate Abundance of resources

Logistic Growth Model carrying capacity (K): Max population size habitat can sustain

Logistic Model & Real Populations Growth rate decreases approaching K or Population size overshoots K, then decreases as a result

Trade-offs in life history Trade-off between reproduction and survival Invest in numbers of offspring or in provisions to offspring? Kselected competitive species r-selected opportunistic species

Regulation of Population Growth Density-independent factors: unrelated to population density Density Dependent Factors: change in response to population density

decrease birth rates and/or increase death rates closer to the carrying capacity Density Independent vs Density Dependent Growth Population Dynamics

Fluctuate due to changes in weather & climate, resources, predator population size, pathogens Human Population Growth Why the Population Explosion? Industrial Revolution

Medical & Biotechnology Revolution Human Growth Rate is Decreasing The Demographic Transition high birth & death

rates high birth, low death rates (population expansion)

low birth & death rates Key: education of women! Age Structures

useful for predicting future population growth Ecological Footprint surface area required to sustain each person (at current levels of consumption) Worldwide Energy Use

One person in the U.S. consumes more than 20 times the resources of a person living in an LDC.

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