Populations

Size Difficult to measure as many organisms

are mobile. Sample size

Scientists count how many individuals in a small area and multiplied that by the total area.

Only an estimate. Why?

Density How crowded a population with in a

particular location is. Expressed as a # of individuals per unit

of area or volume Ex: 100 people per square kilometer.

THINK ABOUT IT!!! Which one would be more densely

populated?

a) 50 people per square meter

b) 500 people per square kilometer

Dispersion Spatial Distribution of individuals in a

population Clumped-organisms clustered together

• Resource availability & social behavior (herding) Uniform-fairly evenly distributed

• Some organisms avoid others in the populations Random-location of each individual is

independent of the others in the population• rare

Growth Rates Dependent upon birth rate, death rate,

immigration & emigration Per capita = per 1,000 individuals in the

population Ex: birth rate = 52 births = 52/1,000 =

.052 births per capita per yeardeath rate = 14 deaths = 14/1,000

=.014 deaths per capita per

year

Equation

Birth rate – death rate = growth rate

THINK ABOUT IT!!! What is the per capita growth rate if the

birth rate is 52 and the death rate is 14?

In a population of 50,000, how many INDIVIDUALS will the population increase by?

0.038

1,900

Exponential Growth In a positive per capita growth rate,

each generation produces a larger amount of individuals than the previous generation.

The RATE at which the population grows, increase over time.

J-curve

Limiting Factors Biotic and abiotic factors that limit

population growth. Abiotic factors include water, space,

shelter, weather Biotic factors include predation,

competition, disease

Logistic Growth Population will grow exponentially

until limiting factors regulate it. S-curve Carrying capacity-the number of

individuals the environment can support over a long period of time. When carrying capacity is reached,

birth rate = death rate and no growth is occuring. Fluctuates with changes in the

environment (greater when prey/food is abundant and smaller when prey/food is scarce.