APES Unit 3: Populations

r strategists

r strategists

reproduce quickly and at an early age with large numbers of offspring and little to no parental care, have short lifespans and aren’t affected much by unstable environments

K strategists

mature slowly and have small amounts of offspring with lots of parental care, live for a long time and tolerate stable environmental conditions

what reproductive strategy do invasive species tend to have?

they tend to be r-selected

type I survivorship curve

most survive until they’re old (late loss) - typically K strategists

type II survivorship curve

relatively constant death rate throughout life (stable loss)

type III survivorship curve

high death rate at the beginning of their life - typically r strategists (early loss)

specialists

can only exist within a certain set of conditions (narrow range of tolerance) and are vulnerable to changing factors

generalists

can live in many different types of environments and have a varied diet, (wide range of tolerance) have an advantage in unstable environments

change in population equation

Change in population = [b(births) + I(immigration)] - [d(deaths) + e(emigration)]

growth rate equation

∆N/∆t = gr

population distribution patterns…

are based on resource availability

random population distribution

abundant and evenly distributed resources

clumped population distribution

scarce/clumped resources

spaced population distribution

resource partitioning, lowering competition

population density

the number of individuals in a definite area or volume

population density equation

D_p = N/A or N/V

density dependent factor

any factor whose effect increases when the population size increases (starvation, parasitism, disease, predation)

density independent factors

natural disasters (storms, floods, earthquakes, volcanoes)

lag phase

when population size primarily increases slowly

exponential phase

after lag phase, number of individuals multiplies rapidly

carrying capacity (K)

the maximum amount of individuals in a population the environment can support

biotic potential (r)

the maximum reproductive rate for a population in ideal conditions (exponential growth)

logistic growth (J and S curve)

exponential growth that levels off around carrying capacity

what happens when a population reaches carrying capacity?

the population will level off or bust

boom, then bust

population grows rapidly and overshoots (boom), and then begin to die rapidly (bust)

overshoot

when a population exceeds carrying capacity

doubling time equation

DT = 70/% growth per unit time (r)

Thomas Malthus

theorized that like the rest of nature, humans would be limited by certain factors

what countries tend to grow the fastest?

less developed countries

how did technological advances lead to a population boom?

they lowered death rates

correlation between high infant mortality and high population growth rate

people have more children to replace those lost

solutions to high infant mortality rate

good healthcare and good nutrition

TFR (Total fertility rate)

the number of children a woman will have in her lifetime

replacement fertility

the number of children a couple must have in order to replace themselves and keep the population stable

why is replacement fertility (typically) 2.1?

not all babies born will survive, so exactly 2.0 will not keep the population stable

as countries develop their economy…

women will want fewer children

what does a high proportion of young people show?

high population momentum: rapid population growth; all those kids will have kids of their own

what does a high proportion of old people show?

declining growth rates with more future deaths than births

when does a population become stable?

when the birth rate is equal to the death rate and there is no net growth

demographic transition: stage 1

pre-transition, high birth and death rates and stable growth

demographic transition: stage 2

transition stage, death rates begin to decline while the birth rate stays high, population boom

demographic transition: stage 3

industrial stage, birth rate begins to decline while the death rate continues to decline, growth slows

demographic transition: stage 4

post-industrial stage, birth and death rates are both low, growth stabilizes

urbanization

the redistribution of people from rural to urban area; occurs as countries industrialize