Populatin Ecology and the effects of density

Population

a group of individuals of the same species living in an ares

population ecology

analyzes the factors affect population size and how and why it changes over time

Density

the number of individuals per unit area

• counting the number of individuals in the population

• Sampling techniques

Dispersion

the pattern of spacing among individuals within a population

clumped

individuals gather in patches

Uniform

evenly spaced individuals in a population

Random

unpredictable spacing; not common

Demography

the study of the vital statistics of populations and how they change over time

Life table

an age specific summary of the survival pattern of a population

Type I curve

low death rate during early/middle life and high death rate later in life

Type II curve

constant death rate over the lifespan of the organism

Type lll curve

high death rate early in life and

lower death rate for those that survive early life

exponential growth

A population growing exponentially grows at a

constant rate

○ J shaped curve

○ Calculated using the formula

Logistic growth model

the per capita rate of increase approaches zero as the population size

nears its carrying capacity

○ The density of individuals exceeds the system’s

resource availability

Life history

the traits that affect an organism’s schedule of reproduction and survival

K-selection (density-dependent selection)

selection for life history traits that are sensitive to

population density

R-selection (density independent selection)

selection for life history traits that maximize

reproductive success

Density-dependent regulation

as a population increases, factors can slow or stop growth by

decreasing birth rate and increasing death rate

Density-independent regulation

factors that exert their influence on population size, but the birth/death rate of a population does not change