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 Habitat #2 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. 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 Habitat #2 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. 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 Habitat #2 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. 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?