Population and Demographics:
• Pop density: number of organisms per unit of land.
• Pop ecology: number of individuals in an area and how/why those numbers are as
• Birth rate: number of live births per 1000 people per year
• Death rate: number of deaths per 1000 per year
• Growth rate (r): (b-d) + (i-e). Natural increase in pop.
• Doubling time: amount of time for pop to double td = 70/r where r is a percent.
• Immigration: people enter a local pop
• Emigration: people leave a local pop
• biotic potential: maximum rate at which pop could increase. Affected by age you
start having kids, % of lifespan reproduction is possible, number of kids made
during that time.
• Exponential growth: way pop behaves under ideal circumstances
• Environmental resistance: restraints put on biotic potential by environment.
• Carrying capacity: largest pop that can be sustained for indefinite period of time,
for a particular enviro. Makes J curve into an S.
• Population crash: like moose of isle royale. When pop is peak 90% starves
because theres not enough food. Then they recover and starve again and recover,
• Density dependent factor: environmental factor whose effect will be affected by
density. EX: predation, disease, and competition.
• Density independent factor: environmental factor that is unaffected by pop
density. EX: severe weather.
• R selection: (r-strategists, r-selected species) focus energy on high growth rate.
Small body size and large broods. In variable/unpredictable environments where
long-term survival is unlikely. EX: dandelions.
• K selection: species that exist at or near carrying capacity. Therefore priority is to
individual survival, not reproduction. Long life spans, slow maturation, late
reprod, large body size. Found in stable environments. EX: humans.
• Survivorship: the proportion of individuals of a given species that survive to
some certain age. Type I is humans, die later in life. Type III is oysters, die early.
Type II is linear. Death is not age-biased.
• Thomas Malthus (1766 to 1834): said human pop would expand more quickly
than food resources. Consequences are famine, disease, war.
• r is declining as of 1965 and will hopefully stabilize by end of 21 century at btwn
7.8 billion and 12.5 bil in 2050 (UN). IIASA says pop will reach 10 bil in 2050
and peak at 11 bil in 2075.
• Zero population growth: when birth rate = death rate
• Demographics: the applied science that deals with population studies.
• Developed countries: low r and high industrialization, low infant mortality, high
life expectancy, and high GNP. • Developing countries: moderately developed have mid-range values. Less
developed countries have highest birth rates, highest infant mortality, lowest life
expectancy and lowest GNPs.
• Infant Mortality Rates: number of babies that die out of 1000 lives births.
• Replacement-Level Fertility: the number of children a couple must have to
replace themselves.2.1 in developed and 2.7 in developing.
• Total Fertility Rate: the avg number of children a woman will have during
fertile years. Currently about 3.0, well above replacement rate.
1. preindustrial: birth and death rates are high so pop growth is modest.
2. transitional: lowered death rate from improved water and healthcare.
Finland in mid 1800’s.