Population DynamicsHow populations change in any given area

How Populations Grow

Geographic distribution – the area in which a population lives (its range)

• Population Density: the number of individuals in an area

Population Growth• Measures how populations grow over time

• Affected by 4 factors:• Number of births for a species• Number of deaths for a species• Emigration (out) # of individuals who leave an

area• Immigration (in) # of individuals who come into

an area

In the city of East Bumble, if 45 babies are born in the year 2008 and 15 people died that same year, what was the growth rate for the city?

Give answer in units of: _____ babies per year.

Positive Growth rate = population increaseNegative Growth rate = decrease

Is the growth positive or negative?

Exponential Growth: organisms

reproduce at a constant rate.

Occurs under ideal conditions (no

limits)

J-shaped curve

This shows that as time goes on, the

population just continues to get larger

This RARELY happens because of

competition for resources like food.

Types of growthTypes of growth

Types of growthTypes of growth

•Logistic growth: as resources become less available, growth slows or stops.

•S-shaped curve•Carrying capacity: The number of organisms an environment can support.

•no growth occurs beyond this because of limited resources in the habitat.•Where population growth equals zero.

Types of growthTypes of growth

•Limiting factor: any factor in an organism’s environment that causes population growth to decrease

•The following factors are dependent on current population density:

o amount of foodo amount of watero amount of space (for living/home building)o predatorso diseaseo competition

Some limiting factors are not dependent on population density:

(density-independent factors)

- Unusual weather- Natural disasters- Some human activities

Types of growthTypes of growth