final - population ecology

population ecology

study of the dynamics of species abundance

how biotic and abiotic factors influence density, size, and age structures of populations

population

group of individuals of the same species living in the same general area

denisty

number of individuals per unit area or volume

dispersion

pattern of spacing among individuals within the boundaries of the population

clumped dispersion

individuals aggregate in patches - influences by resource availability and behavior

ex: flock of birds

uniform dispersion

individuals are evenly distributed

may be influenced by territoriality

random dispersion

position of each individuals is independent of others

mark-recapture method

-Scientists capture, tag, and release a random sample of individuals (s) in a population
– Marked individuals are given time to mix back into the population
– Scientists capture a second sample of individuals (n), and note how many of them are marked (x)
– Population size (N) is estimated by N = sn/x

demography

study of the vital stats of a population and how they chnage over time

birth/death/reproduction rate

sometimes stats are only collected for females

Life table

specific summary of the survival pattern of a population

survivorship curve

graphic way of representing the data in a life table

type 1 survivorship curve

low death rates during early and middle life, then an increase in death rates among older age groups

ex: humans

Type 2 survivorship curve

the death rate is constant over the organism’s life span

type 3 survivorship curve

high death rates for the young, then a slower death rate for survivor

iteroparity

repeated reproductions - produce offspringe repeatedly

semelparity / big-bang reproductoons

reproduce once and die

trade-offs

Organisms have finite resources, which may lead to trade-offs between survival and reproduction

immigration

influx of new individuals from other areas

emigration

movement of individuals out of a population

exponential model

describes population growth in an idealized unlimited environment - help understand the capacity of species

population growth rate

if immigration and emigration ar eignored - a populations growth rate equals birth rate

population growth rate equality

birth rate

B = bN

where b is the annual per capita birth rate

death rate

D= mN

where m is per capita death rate

difference between birth and drath rate

r = b-m

population growth rate expression

dN/dT = rN

if r>0 then population size increases

if r<0 then population declines

exponential population growth

population increase under idealized conditions

dN/dt - rmaxN

j shaped curve

logistic model

limits growth by incorporating carrying capacity

s shape curve

carrying capacity (K)

maximum population size the environment can support

logistic growth model

per capita rate of increase declines as carrying cappacity is reach

dN/dt = rmax N(K-N)/K

allee effect

individuals have a more difficult time surviving or preprodcuing if the population is too small

density-dependant

brith rates fall and death rates rise with population density - negtaive feedback

competition for resources

in crowded population, increasing population density intenses competition and results in lower birth rate

disease

in dense populations, pathogens spread more rapidly

territorailty

competition for territory may limit density

predation

as prey population builds, predators may feed preferentially on that species

toxic wastes

accumulation of toxic wastes can attribute to desnity-dependent regulation of population size