Ch. 53 Population Ecology

Population Density

Number per nit area

Population dispersion

How distributed over an area

Total population

Growth rate ® = (birth rate - death rate)

Immigration

Individuals enter a population and increases its size

Emigration

Individuals leave a population and decrease its size

Rmax

Maximum rate a species (population) could increase under ideal conditions

J-shaped curve

Growth under optimal condition (exponential)

Limiting factors

Availability of food, water, shelter, and essential resources

Carrying capacity (K)

The maximum number of individuals in a population that an environment can support

K

Carrying capacity of a population can change over time

Density dependent factors

Size of population limits population growth

Negative feedback mechanism

Due to increased density there is increase in mortality/decreased birth rate

Competition

Occurs when two or more individuals attempt to use same limited resources

Intraspecific Competition

Between individuals within a population

Interspecific Competition

Between different species

Density-independent factors

Not related to population size/ number of individuals per unit

• randomly affects individuals

• Abiotic factors (weather)

Survivorship curve

Probability of a given individual in a population will survive some age

Type I survivorship curve

Long mortality life (ex. Elephant)

Type II surviorship

Death likely at any age (ex. Bird)

Type III survivorship curve

Very likely die young (ex. Fish)

Replacement level fertility pyramid

Relatively even number in all age groups

Population increase

Pre-reproduction age group larger than upper age group