2. Population Ecology (Measuring Populations)

Intro Evolution and Ecology

population ecology

the study of populations in relation to environment, including environmental influences on density and distribution, age structure, and population size

density

the number of individuals per unit area or volume

dispersion

the pattern of spacing among individuals within the boundaries of the population

clumped dispersion

(pic)

random dispersion

(pic)

spaced dispersion

(pic)

ex of what dispersion: 

• filter-feeding stream-dwelling insects

• tnet catepillars

• wolves (living in group increases hunting effectiveness, work divided up)

clumped/aggregated

ex of what dispersion: 

• penguins in a rookery

• trees in an orchard

• king penguins nesting

regular/spaced

ex of what dispersion: 

• forest trees

poisson/random

demography

the study of the vital statistics of a population and how they change over time

factors where population grows:

• birth

• immigration

factors where population decreases:

• death

• emigration

closed population is when there is no:

immigration or emigration

immigration

moving to an area

emigration

leaving an area

parameters that are important to maximize growth rate in growing populations:

• age at first reproduction

• fecundity

• survivorship

fecundity

average number of offspring per episode (clutch size)

survivorship

how many females of a particular age, x, are reproducing

what is a life table?

age-specific summary of the survival pattern of a population

horizontal life table

single observed cohort: age specific data collected

vertical life table

time-specific data are utilized

l_x is:

age specific survivorship

n₀ is:

the number at the start

n_x / n₀ is:

proportion of individuals alive at the start of age interval x

3 types of survivorship curves

1. Type I: low death rate during early and middle life, then an increase among older age groups

2. Type II: the death rate is constant over the organisms life span

3. Type III: high death rate for the young, then slower death rate for survivors

survivorship curve examples

(pic)

reproductive table

or fertility schedule, an age specific summary of the reproductive rates in a population

m_x is:

age-specific survivorship

• mean number of offspring produced by females of age x

R₀ is:

net reproductive rate

• expected number of female offspring produced per female per generation

if R₀ = 1

population is stable

if R₀ < 1

population is decreasing

if R₀ >1

population is increasing

mean generation time

ex

T= (1.6)/(1.3) = 1.23 time units