Bio 1114; Unit 12 - Population Ecology

Ecology

the study of the interactions between organisms and their biotic and abiotic environments

population ecology

studied population sizes and how and why they change over time

community ecology

investigates species interactions and how they effect species assemblages and organization

ecosystem ecology

studies energy flow and ecosystem structure as a result of the interaction between organisms and their abiotic and biotic environment

global ecology

examines how local/regional interactions affect global changes in energy flow and species dynamics

population

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

mark-recapture method

capture and mark an initial set of individuals, release to population, use proportion of re-caught individuals in second capture to estimate total population

What does it mean if there are no individuals marked in capture 2?

the population is way bigger than originally assumed OR marking affects individuals capture probability

mark-recapture equation

X/n = S/N

X

marked capture in second sample

n

total caught in 2nd sample

s

number of marked in first sampleN

N

size of whole population

change in population size

number of individuals added to a population over time (births - deaths)

B

births

D

deaths

B-D = ?

change in population size/ change in time

per capita birth rate

b; number of offspring produced per individual member of population per unit of time

b=?

B/N

per capita death rate

d; number of deaths per individual member of population per unit timeThe rate at which individuals in a population die, typically expressed as a fraction or percentage per time unit.

d=?

D/N

net effect

sum effect of both additions through birth and losses through death

per capita population growth rate

r; number of individuals added per pre-existing individuals in pop. accounting for both deaths and births

r=?

b-d

exponential growth model

number of individuals added each time interval increases as N increases in absence of factors limiting population growth

Why is exponential growth rate uncommon?

resource limitations

exponential growth model equation

change in N/change in time = rN

logistic pop. growth

pop. growth slows as it approaches carrying capacityc

carrying capacity

K; the max pop. size that a given environment can sustain - where line flattens out as pop. growth slows

limiting resources

shelter from predators, nesting sites, food, water, etc,

Survivorship

percent of pop. that survives to a given age

survivorship curves

plots of the prop. of individuals still alive in each age

Type 1 survivorship curve

high survival rate until later age - these species have few offspring with high parental care

Type 2 survivorship curve

roughly equal proportions die in each age class

Type 3 survivorship curve

high mortality rate in early life, but lower for old age - large number of offspring with little to no parental care