Unit: Ecology
Lesson: Interactions Among Living Things
Time: 40 Minutes
Grouping: 4 Students per group

National Science Education Standards:
As a result of their activities all students should develop understanding of the interdependence of organisms.

Pennsylvania Environment and Ecology Standards:
4.3.7 c. Explain Biological Diversity
Explain the complex interactive relationships among members of an ecosystem.

4.7.7 a. Describe diversity of plants and animals in an ecosystem.
Understand levels of ecosystem organization (e.g., individuals, populations, species)
 

Student Objectives:

· Classify organisms as predator or prey
· Describe factors that affect population growth and size.

Material:

• Meter Stick
• Masking Tape
• Marked Playing Cards (Hawk/Fieldmouse)
• Data Table/Worksheet

Prior Knowledge:

• Population
• Predator
• Prey
• Predator/Prey Relationship
• Generation

Request that four students take the parts of birds. Offer three of the four students a Gummi Worm each. Repeat two times, offering the same three students the Gummi Worms. Ask the students what will eventually happen to the fourth bird. (It will die from lack of food)

Activity

"Let’s Play Pretend"

Pretend that you are looking at an area with two populations. They are the hawk and field mouse populations. The hawk is the predator and the field mouse is the prey. You will be given hawk cards and field mouse cards.

1. Mark an area sixty (60) centimeter square on the floor. This is where the hawks and field mice live.
2. Drop five (5) field mice in the area.
3. Stand back from the area 1 ½ meters.
4. Throw a hawk into the area. Try to make it land on as many field mice as possible. If a field mouse is touched, the hawk has caught it.
5. Pick up the hawk card. Also remove any field mice caught.
6. You will play this game for twenty (20) generations. Keep a record of each new generation in Table 1. Follow these rules:

1. The field mice left will double each generation. If you have three (3) field mice left after Generation One, throw in three more field mice. You will then have six (6) field mice for Generation Two.
2. In order to live, a hawk has to land four field mice. For each four field mice caught, the hawk will reproduce another hawk. If your hawk catches four to seven field mice, add another hawk for the next generation. If it catches eight field mice, add two more hawks.
3. If a hawk does not catch four field mice, it dies from lack of food. Do not let the hawk population drop below one. Pretend that a new one flies into the area looking for food. Start with one again in the next generation.

Predators and their prey do not simply interact with one another on an individual basis. They also affect one another on the level of populations. In fact, the size of a prey population may have a strong effect on the size of a predator population, and vice versa. Create a graph that shows how the size of the hawk and fieldmouse populations changed over time.
 

Procedure:

1. Enter the data in L1, L2, and L3. (L1 is a list that holds data to be processed.)

 

 
 
 

Process: Press STAT, you will see many choices. Use the blue arrow keys to find Edit and hit ENTER.

You will see the columns where the data is supposed to be. If there is data there use the blue arrow keys to highlight the L1, hit CLEAR then ENTER. Then enter your data.

L1 = Generation (This will work for both Fieldmouse and Hawk)

L2 = Number of hawks

L3 = Number of fieldmice

2. Next plot the points on the x and y axis. Hit 2^nd then Y=. This will take you to STAT PLOTS. Hit ENTER on the highlighted 1. Using the blue arrow keys highlight ON, the scatter-plot graph, Xlist: L1, Ylist L2 and the fist mark.
3. Next find the linear regression. Hit 2^nd the MODE. This will take you back to the main screen. To find the linear regression hit STAT, then arrow over to CALC, then scroll down to number 4, LinReg(ax + b), hit ENTER. This will show LinReg(ax + B) on the main screen. After that hit L1, L2 (Keys: 2^nd, 1, ‘,’, 2^nd, L2).
4. Next graph the points and the regression line. Hit GRAPH. You may not see your points or graph so, hit ZOOM, then the number 9. This will change your view screen.
5. For the other data repeat steps 2 thru 4 with L3 instead of L2.

        1.  Which population reaches higher numbers?    Why is this?

        2.  As the field mouse population gets bigger, what happens to the population of hawks?

        3.  Notice that as the hawk population rises, the fieldmouse population falls. Why?

        4.  Why do populations rise and fall?

        5.  What do predators do to the size of a population?

        6.  What is a predator?

        7.  What is a prey?

        8.  What is a predator-prey relationship?
 

EXTENSION:

Neighboring Stackhouse Park has been set aside as a park preserve, and no hunting is allowed in the park. There are plenty of plants to serve as food for the deer population.  The herd is healthy and has begun to multiply faster than expected.  Predict what will happen if the deer population continues in the park area.
 

Assessment:

Data generated graph
Completion of summary worksheet

Adaptations:

· Input: -provide students with prior knowledge learned during the ecosystem unit.

    -give students a chance to practice ‘Let’t Play Pretend’ before large group activity.

· Output: -allow students to orally explain data sample results.

    -allow students to complete prepared worksheet to graph data samples.

    -use a computer program to generate the graphs.

· Level of Support: -students work in smaller group during ‘Let’s Play Pretend’ activity.

    -students work together to graph sample data, check each other’s work for accuracy and understanding of activity

· Participation: -participates in ‘Let’s Play Pretend’ sampling activity but not required to complete mathematical calculations of sample data.
 

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