Download Investigation 25 How Do Species Adapt to Environments

Investigation 25
How Do Species Adapt to Environments?
Introduction
Points:
|310
Organisms have characteristics that enable them to live in particular habitats. Fish, for example, can live in
water because they have gills and fins. Birds have wings and lightweight bones, so they can fly through the air.
Some plants have tiny “claws” that enable them to cling to such surfaces as rocks and walls. Everywhere you
look, organisms seem to be well suited to their particular set of environmental factors. How are these helpful
characteristics acquired? Suppose the environment changes. Can populations of organisms acquire new
characteristics to enable them to be successful under the new conditions, or must they move elsewhere to avoid
extinction?
Objectives
1. To discover ways in which species change over time to become suited to particular environments
2. To propose a mechanism for those changes.
Materials
patterned fabric
paper chips
graph paper
Procedure
1. Select a partner or two to work with. In this investigation, you will attempt to discover what happens to the
characteristics of organisms within a population that is subjected to predation over a number of generations.
Ideas generated from this activity my help you answer the question How do species adapt to environments?
2. To do the activity, you will play the role of a hawk. The colorful paper chips will play the role of the mouse.
As such, you will need to “capture” the first mouse you see, only “capturing” one mouse at a time.
3. Begin by spreading a piece of fabric over your table. The fabric represents a natural habitat (such as a pond,
meadow, forest or desert)
4. Place 10 “mice” of each color onto the habitat. This will yield a total of 100 paper chips in the habitat.
5. Once instructed to begin, start “capturing” one “mouse” at a time, resulting in the group removing a total of
75 paper chips from the habitat- leaving 25 behind.
6. Remove the 25 “survivors” by lifting and gently shaking the habitat.
7. To have the 25 survivors “reproduce”, add three paper chips of the same color for each of the survivors.
This new population should consist of 25 first-generation “mice”, and 75 second-generation “mice”, yielding a
total of 100 “mice”. You may wish to make a table to help you keep track of your populations. The table
should include the number of survivors and offspring of each color after each round of predation.
8. Repeat steps 5-8 at least two more times.
9. When you have completed your last round of predation and reproduction, formulate a bar graph in order to
display the resulting numbers of “mice” of each color- with the number of “mice” on the vertical axis, and the
color of the “mice” on the horizontal axis. If the activity went as planned, your total population should still
contain 100 “mice”. (50 points)
10. What colors of prey were eaten in the greatest numbers in your habitat? (10 points)
11. How does their color compare to that of their habitat? (10 points)
12. Why did you not allow those individuals that you picked to reproduce? (10 points)
13. Did each color of mouse do equally well in each habitat? Why or why not? (10 points)
14. What might happen if the mice were all the same color at the start? (10 points)
15. What might happen if the mice were unable to reproduce at such a high rate? (10 points)
16. What might happen to the mice population if predation stopped? (10 points)
17. What might happen if mouse color was not passed from parent to offspring? What would happen if the trait
was determined environmentally? (10 points)
Study Questions
1. During the 1920’s, a population of spotted crabs was known to inhabit the white sandy beaches near a
volcano on one of the Hawaiian Islands. The spotted crabs were observed to feed off plants that were cast upon
the beaches by the ocean’s waves. Occasionally, seagulls were observed to capture and eat some of the crabs.
When first observed, about 90% of the crabs were nearly completely white with only a few small black spots on
their claws. About 8% of them were white with many black spots, while 2% of the crabs had so many black
spots that they appeared almost completely black.
In 1930, the volcano erupted, sending a lava flow across the beach an out into the water. The lava cooled and
deflected the ocean currents that had deposited the white sands on the beach. Black sands from other currents
began to accumulate on the beach until with a few years the beach had become completely covered with black
sand.
By the 1950’s, nearly 95% of the spotted crab population was composed of crabs that were completely black.
About 4% of the crabs were white with many black spots, while 1% of the crabs were white with only a few
black spots.
Use the theory of natural selection to explain the change of the most frequent color of the spotted crabs from
white to black. Discuss the roles of biotic potential, limiting factors, variation, and heredity. (50 points)
2. Would natural selection occur more rapidly, less rapidly, or not occur at all if… (Explain each) (60 points)
-No variation existed in a species…
-No changes occurred in environments…
-Conditions of life were unlimited…
-Characteristics were not transmitted from parent to offspring…
-Mutations did not occur…
-Biotic potential of a species was relatively low?
3. How is the process of natural selection similar or different from artificial selection? What about the
inheritance of acquired characteristics? (10 points)
4. Does the existence of such intermediate species as ligers and beefalos support or refute the theory of
evolution? Explain. (10 points)
5. Look at the Walking Stick below. Explain how it came to be. (50 points)