Studied by 10 people
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
Dp = 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
Note
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