Population DynamicsPopulation Dynamics

EcologyEcology

Chapter 4.1Chapter 4.1

Principles of Population GrowthPrinciples of Population Growth

A population is a group of organisms of the A population is a group of organisms of the same species that live in a specific area.same species that live in a specific area.

Healthy populations will grow and die at a Healthy populations will grow and die at a relatively steady rate unless resources run out relatively steady rate unless resources run out or disease.or disease.

Population GrowthPopulation Growth

Populations grow on a J-curve or exponential Populations grow on a J-curve or exponential curve. curve.

Rates start slow and then rapidly increase.Rates start slow and then rapidly increase.

Limits on GrowthLimits on Growth

Can populations grow forever? NO.Can populations grow forever? NO. Populations reach limiting factors like food, Populations reach limiting factors like food,

disease, predators, lack of space.disease, predators, lack of space. This is depicted in a graph of population #’s This is depicted in a graph of population #’s

as a S-curve.as a S-curve.

Carrying CapacityCarrying Capacity

The number of organisms of one species that an The number of organisms of one species that an environment can support indefinitely is its environment can support indefinitely is its carrying capacity.carrying capacity.

What is human’s carrying capacity?What is human’s carrying capacity?

Reproduction PatternsReproduction Patterns

In nature, animals and plant populations In nature, animals and plant populations change in size- even at different times of the change in size- even at different times of the year.year.

Reproductive patterns are known as life-Reproductive patterns are known as life-history patterns.history patterns.

There are two patterns- slow (humans) and There are two patterns- slow (humans) and rapid (mosquitoes).rapid (mosquitoes).

Slow and Fast life-historySlow and Fast life-history

Rapid- usually small organisms in unpredictable Rapid- usually small organisms in unpredictable environments that rapidly mature and have a environments that rapidly mature and have a short life.short life.

Slow- live in stable environments and have a Slow- live in stable environments and have a long life span and mature slowly. They usually long life span and mature slowly. They usually live around the carrying capacity.live around the carrying capacity.

Density factorsDensity factors

Density-dependent factors- factors that have Density-dependent factors- factors that have an increasing effect on a large, growing an increasing effect on a large, growing population. Diseases, predators, food, population. Diseases, predators, food, parasites.parasites.

Density-independent factors- factors that affect Density-independent factors- factors that affect populations regardless of size or density. populations regardless of size or density. Abiotic factors like fires, floods, drought…Abiotic factors like fires, floods, drought…

Populations are either randomly spread, Populations are either randomly spread, clumped, or uniform.clumped, or uniform.

Dependent or Independent?Dependent or Independent?

Dependent or Independent?Dependent or Independent?

Uniform/Random/ClumpedUniform/Random/Clumped

Predation and Population SizePredation and Population Size

Populations of predators and their prey Populations of predators and their prey experience cycles or changes in their numbers experience cycles or changes in their numbers over periods of time.over periods of time.

Crowding and StressCrowding and Stress

When populations are crowded, organisms When populations are crowded, organisms exhibit symptoms of stress.exhibit symptoms of stress.

Populations exhibit aggression, decrease in Populations exhibit aggression, decrease in parental care and decreased resistance to parental care and decreased resistance to disease.disease.