limiting factors & adaptations changing population sizes
TRANSCRIPT
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Limiting Factors & Adaptations
Changing Population Sizes
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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
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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.
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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.
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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.
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Observations
• What factors changed in between the three scenarios?
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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.
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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.
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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?
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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.
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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”
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Peppered Moth
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Find the camouflaged moth in the picture
• www.bio.georgiasouthern.edu
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Peppered Moths
• www.news.harvard.edu
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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.
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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?