Population Dynamics

Every organism has a habitat

and a niche.

A habitat differs from a niche. • A habitat is all aspects

of the area in which an organism lives.– biotic factors– abiotic factors

• An ecological niche includes all of the factors that a species needs to survive, stay healthy, and reproduce and the role they play.– food– abiotic conditions– behavior

Organisms interact as

individuals and as populations.

Competition and predation are two important ways in

which organisms interact. • Competition occurs when two organisms fight for the

same limited resource.– Intraspecific

competition

– Interspecificcompetition

Competition and predation are two important ways in

which organisms interact. • Competition occurs when two organisms fight for the

same limited resource.– Intraspecific

competition

– Interspecificcompetition

Where have we seen these

prefixes before?

Predation occurs when one organism captures and eats another.

Think – Pair – Share

Do predators or prey directly control the population size? Be able to defend your

answer.

Mutualism: both organisms benefit

There are three major types of symbiotic relationships. (Symbiosis means you live close to someone you are NOT related to!)

Mutualism

Commensalism: one

organism benefits, the

other is unharmed.

Commensalism

Parasitism: one organism benefits, the other is harmed

– Parasites meet their needs as ectoparasites (such as leeches) and endoparasites (such as hookworms)

Parasitism

Each population has a density, a

dispersion, and a reproductive

strategy.

• Population dispersion refers to how a population is spread in an area.

Geographic dispersion of a population shows how individuals in a population are

spaced.

Clumped

dispersion

Uniform

dispersion

Random

dispersion

clumped

There are three types of dispersion.

uniform

There are three types of dispersion.

random

There are three types of dispersion.

Populations grow in one of 2

ways. Exponentially or

logistically

The size of a population is always changing.

• Four factors affect the size of a population.

– immigration

– births

– emigration

– deaths

Think – Pair – Share

Which two factors make a population grow?

Which two will make a population smaller?

• Exponential growth is a rapid population increase due to an abundance of resources.

Logistic growth is due to a population facing limited resources.

Carrying capacity is the maximum number of individuals in a population that the environment

can support. We represent this with a K

Ecological factors limit population growth.

• A limiting factor is something in the environment that keeps the size of a population down.

• There are 2 types of limiting factors;

• A) Density dependent

• B) Density independent

Think – Pair – Share

What does the word “density” mean?

What do the words dependent and independent mean?

Examples

include:

Predation

competition

parasitism and

disease

Density-dependent limiting factors are affected by the number of individuals in the population.

Density-independent limiting factors limit a population’s growth regardless of

the density.

– Examples

include:

– unusual weather

– natural disasters

– human activities