03.18.24 Populations and Carrying Capacity

03.18.24 Populations and Carrying Capacity Review

Do Now: What is carrying capacity? In what ways can it be increased/raised? In what ways can it be decreased/lowered?

Open Ended

Do Now: What is carrying capacity? In what ways can it be increased/raised? In what ways can it be decreased/lowered?

Multiple Choice

Occurs when organisms MOVE in from another environment.

• Immigration

• Emmigration

Multiple Choice

Occurs when part of the population LEAVES the environment

• Immigration

• Emmigration

Multiple Choice

Carrying capacity is...

• The maximum number of individuals that can fit into an area

• The greatest # of individuals an area can support over time.

• Ability of an area to accommodate a growing population

• The maximum number of species that can co-exist in an area

On a population graph, the carrying capacity is represented by a flat line

• May also be a small "wave"

• Follows a period of exponential growth; a J-shaped curve where the population keeps increasing

• The line represents population size, so it decreases in response to a limiting factor

Multiple Choice

A population always stays exactly at its carrying capacity.

• True

• False

Multiple Choice

What happens if a population grows past its carrying capacity?

• The population keeps growing

• The population starts to die off

• The entire species will go extinct

• The carrying capacity just increases

Multiple Choice

Which graph depicts exponential growth in a population?

Multiple Choice

What is the carrying capacity of the graph?

• around 500

• more than 800

• less than 300

• around 700

Limiting factors are any factor that reduces or the size of a population or keeps it from increasing

• May be a resource, another species, the environment, etc.

• Example: food is a limiting factor because you can't have more individuals than food to feed them

Limiting factors that DO NOT depend on population size are called density-independent

• Include climate, weather, natural disasters, and pollution

• Affect all populations the same, whether they are large or small

Limiting factors whose effect depends on the size of the population are called density-dependent

• Includes natural resources (food, water, space), diseases, and predators

• Tend to have a greater effect on large, dense populations because of increased competition and more opportunity to attract predators and disease

Multiple Choice

An environmental factor such as storms and extreme heat or cold that decrease a population are considered to be -

• density-dependent factor

• population density

• dispersion

• density-independent factor

Multiple Choice

This may cause a population to increase

• increase of food supply

• removal of predators

• removal of disease

• all of these

Multiple Choice

Something that regulates the size of a population is called...

• a limiting measure

• a limiting factor

• carrying capacity

• biodiversity

Multiple Choice

If a disease destroying barley plants in a field swept through an ecosystem, what would happen to the barley eating bird population in the the field ?

• The bird population would stay the same
• The bird population would infinitely increase
• The bird population would decrease

Keystone Species

A keystone species is an organism that helps define an entire ecosystem. 

Without its keystone species, the ecosystem would be dramatically different or cease to exist altogether.

The removal of a keystone species REDUCES the BIODIVERSITY of the ecosystem.

Keystone Examples

The keystone species in this habitat is the sea otter.

The sea otter eat urchins and therefore keep the population of sea urchins low. Sea otters also build dams which create wetlands for other organisms to live in.

Without sea otters, sea urchins over populate and eat all of the kelp. Wetlands are destroyed and biodiversity decreases.

Open Ended

Exit Ticket: Describe the importance of keystone species in helping an ecosystem function normally.