Limiting Factors & Adaptations

Changing Population Sizes

Imagine

• For the next few minutes I want you guys to imagine that you are a lion who lives in the African safari.

• You’ve recently decided to move from your current habitat.

• There’s two areas in the safari that you could live. • Image courtesy of kids.nationalgeographic.com

Compare

Habitat #1• Is one mile long by one mile

wide.• There is a pack of gazelles

that live in this habitat.• There are 20 gazelles in the

pack.• There is no river in this

habitat.

Habitat #2• Is one mile long by one mile

wide.• There is a pack of 15

gazelles in this habitat.• There are also 5 wild boars

in this area.• There is a fresh water

stream in this habitat.

Compare

Habitat #1• This habitat is one mile long

by one mile wide.• A pack of 20 gazelles lives in

this area.• There is a river in this area.

Habitat #2• This habitat is 2 miles wide

by 2 miles long.• The larger area has

increased the gazelle population to 30 and the boar population to 10.

• However, now two more lions live in this area.

• There is a river in this area.

Compare

Habitat #1• This habitat is one mile long

by one mile wide.• A pack of 20 gazelles lives in

this area.• There is a river in this area.

Habitat #2• This habitat is 2 miles wide by 2

miles long.• There was a long dry summer in

this area that caused a lot of plant life to die.

• This drought caused the gazelle population to decrease to 10 and the boar population stayed the same at ten.

• However, now two more lions live in this area.

• There is a river in this area.

Observations

• What factors changed in between the three scenarios?

Limiting Factors

• You should have seen that the factors that changed were:– Space– Water– Food– Weather

• These factors are referred to as limiting factors.• Limiting factors are environmental factors that

cause populations to decrease.

Limiting Factors

• Organisms need food and water to survive for energy and other chemical processes.

• Space is important because organisms need a place to sleep, eat and reproduce. Plants need space so they can grow their roots towards a water source and gain sunlight.

• Weather can cause populations to decrease think of the effect a draught can have on plants.

Limiting Factors

• How do you think organisms react to these changes?

• How would a plant respond to a draught?• How would a lion react to a decrease in food

populations or extinction of one of their food sources completely?

Adaptations

• To deal with these changes in the environment organisms will adapt.

• Adaptations: The behaviors and physical characteristics that allow organisms to live successfully in their environments.

• In the case of our lion we would see a change in behavior.

• Changes in physical characteristics occur over long periods of time.

Natural Selection

• Natural selection occurs when individuals whose unique characteristics are best suited for their environment tend to survive and reproduce.

• Mutations occur for the unique characteristics to form in a species (We will see an example shortly)

• Their offspring will in turn inherit these characteristics.

• “Survival of the fittest”

Peppered Moth

Find the camouflaged moth in the picture

• www.bio.georgiasouthern.edu

Peppered Moths

• www.news.harvard.edu

Peppered Moths

• The peppered moth is a classic example of how animals adapt through natural selection.

• Go to the following link: http://www.techapps.net/interactives/pepperMoths.swf

• Start with the peppered moth life cycle, then impact of pollution, Kethwell’s experiment, then finish with a bird’s eye view.

Purpose of Adaptations

• The combination of adaptations that occur in an organism are based on the organisms specific living conditions.

• The role of an organism in its habitat is called a niche.

• What is the niche of our lion?• What is the niche of a human?• What is the niche of a plant?