APES unit 3

Demographics

the study of human populations (ic)

11

how many years to add another 1 billion humans modern

2%

Exponential growth of humans per year (modern)

doubling time

estimation of how long for a population to double in size

exponential, logistical growth

different types of growth

developing countries

poor, young, or rapidly growing countries (china, india, boliva, congo)

Developed countires

wealthy, old, and mostly shrinking population (US, japan, france)

fertility rate

number of births per 1000 women per year; developing countries ~10, developed countries ~5

replacement level

when you have 2.1 children per couple (replacing parents)

migration

the movement of individuals between areas

life expectancy

average age a newborn can expect to attain in any given society

• mostly affect by infant mortality rates

• strongly correlated with income up to about 4,000 US per person

pronatalist forces

factors that increase desire for children

• source of pleasure, pride, comfort

• support for elderly parents

• social status

antinatalists forces

Against having children; women less likely to have children when

• higher education and freedom

• salary opportunites

preindustrial

• food shortages, malnutrition, lack of sanitation/medicion

• Birth rates tend to match death rates

transitional

• hygiene, nutrition, and education improve

• death rates drop, birth rates remain high (INITIALLY)

• population increases quickly

industrial

• birth rates begin to fall

• population may have increased 2x or 4x by this time

Post industrial

• transition is complete

• birth and death rates low

• population is at equailibrium

higher birth rate

more younger people

Type I survivorship

shows high survival rates during early and middle life, followed by a steep drop-off in death rates as organisms reach old age. (usually k strategists)

type II survivorship

intermediate survivorship curve; population experiences a roughly constant mortality rate or survival probability throughout its entire lifespan

type III survivorship

high mortality early in life, followed by a much lower death rate for the small percentage of individuals that survive to adulthood (usually r strategists)

population

all of the individuals of a species that live together in one place at a time

demography

the statistical study of populations. Used to predict how the size of a population will change

population size, population density, dispersion

key features of populations

population size

number of individuals in population, has important effect on the ability of the population to survive; a small pop. is more likely to become extinct

inbreeding

genetic diversity decreases —> leading to recessive traits

population density

number of organisms in a given area

disease, competition, predators, parasites, food, crowding

density dependent factors

natural disasters, abiotic factors

density independent factors

dispersion

the way in which the individuals are arranged

logistic model (s curve)

accounts for the declining resources available to populations as they grow.

exponential (j curve)

no limit to population size

r strategists

an organism that prioritizes high growth rates, rapid reproduction, and large numbers of offspring over individual survival and parental care. Can live in unpredictable and rapidly changing enviornments

k strategist

an organism that lives in a stable environment and maintains a population size close to the maximum limit that the local habitat can support. Reproduce late and life and few offspring

generalist species

Species with a broad ecological niche that can survive in many different environments and use a variety of resources.

specialist species

Species with a narrow ecological niche that depend on specific habitats or food sources.

type I

what type is the blue line

type II

what type is the red line

type III

what type is the yellow line

carrying capacity

The maximum population size an environment can sustainably support with its available resources, such as food, water, and space.

biotic potential

The maximum rate at which a population can reproduce under ideal environmental conditions with unlimited resources and no limiting factors.

population overshoot

When a population exceeds the carrying capacity of its environment; can lead to resource depletion, competition, loss of resources, increased mortality/disease, and population dieback

predator

is red predator or prey

prey

is blue predator or prey

resource limiting factors

Essential resources that limit the growth, size, or distribution of a population.

food, water, space, nutrients

resource limiting factors examples

density dependent factors

Factors whose effects on a population increase as population density increases.

density independent factors

TYPE of Factors that affect a population regardless of its density, often due to environmental events.

crude birth rate

Number of live births per 1,000 people per year.

crude death rate

Number of deaths per 1,000 people per year.

life expectancy

Average number of years a newborn is expected to live under current mortality conditions.

total fertility rate

The average number of children a woman would have if current age-specific fertility rates continued throughout her reproductive years.

replacement level fertility

Average number of children per woman needed to replace the parents' generation.

infant mortality rate

Number of deaths of children under age 1 per 1,000 live births per year.

intrinsic rate of increase

the maximum per capita growth rate of a population under ideal, unlimited conditions (no food, space, or resource limits, and no predators or disease). similar to biotic potential

Actual growth rate

• The real-world per capita growth rate observed in nature.

• It is constrained by density-dependent and density-independent factors (like limited food, competition, disease, and weather)

stage 1

Preindustrial: High birth rate + high death rate → little population growth.

stage 2

Transitional: Death rate decreases, birth rate remains high → rapid population growth.

stage 3

Industrial: Birth rate decreases, death rate remains low → population growth slows.

stage 4

Postindustrial: Low birth rate + low death rate → stable population.

native species

species that are indigenous to a particular ecosystem

non native species

living outside its native distributional range, which has arrived there by human activity, either deliberate or accidental; not necessarily invasive.

high reproductive rates, long-lived, few natural predators, generalists

common characteristics of invasive species

displace/kill native species, reduce ecosystem health

impact of invasive species