ecology slide deck 6 (population ecology part 2)

changes in population over time is the difference in

the arrival (birth and immigration) and loss of individuals (death and emigration)

an open population has

immigrations and emigration

a closed population does not have or has a very low level of

immigration and emigration that doesn't influence population growth

fertility

ability to produce offspring

natality (birthrate)

number of births related to population size

fecundity

number of offspring/female/unit time

potential fecundity

potential reproductive capacity of individual (under optimal conditions)

realized fecundity

actual reproduction of individual

potential longevity

maximum lifespan under optimal conditions

realized longevity

actual life span

disease, predation, natural disasters ->

lower longevity

net reproductive rate (Ro)

average number of female offspirng produced by an average female during lifetime

equation for net reproductive rate

Ro=Σlxbx

lx survivorship

the number of individuals surviving to a given age (x) as a proportion of the original cohort size nx/no)

bx fecundity

the mean number of females born to each female in an age group

a life table is an

age-specific account of mortality

if Ro = 1.0

females on average produce on daughter, replacing themselves; population is stable

if Ro > 1.0

females on average produce more than one daughter; population is growing

if Ro < 1.0

females on average produce less than one daughter; population is declining

discrete

all individuals in a population reproduce in roughly the same time window

overlapping

multiple age classes coexist and reproduce at the same time

intrinsic rate of increase (r)

per capita rate of growth of population with stable age distribution

geometric growth model

predicts changes in population size in discrete intervals where birth and death are not continuous processes

exponential growth model

continuous, unlimited growth, overlapping generations

logistic growth

found where environmental limit exist, growth rate is influenced by population size

K=

maximum population size that the environment can support

the effect of K on population growth is

(1-N/K), where N=population size

geometric growth=

discrete generations (stepwise, j-shaped curve with plotted points)

exponential growth=

overlapping generations (smooth, continuous J-shaped curve)

logistic growth=

overlapping generations (smooth, continuous S-shaped curve)

N=

number of individuals in the population

t=

time

N(t)=

number of individuals in the population at a given time

when r=0, b=d

the population size does not change

when r>0, b>d

the population increases exponentially

when r<0, b

the population decreases exponentially

the exponential growth model assumes

unlimited essential resources, a constant environment

logistic growth describes population growth when resources are ___________ and growth is density dependent

limited

to this point, population growth has been considered to be a

deterministic process

stochasticity

random, unpredictable fluctuations that influencepopulation dynamics

demographic stochasticity

variation in birthrates and death ratesoccurring in populations from year to year

environmental stoachasticity

random variation in environmentthat can influence birthrates and death rates in population

generally ______ populations are more vulnerable to extinction

small

small populations are more vulnerable to extinction because of

loss of genetic variability, increased vulnerability to demographic and environmental stochasticity