Populations in Balance

Initiate a class discussion prior to beginning the activity. The terms "backfire" and "unintended consequences" are included in the title of the comic.

Paraphrase:

We're about to read a comic called "Barnyard Backfire: a tale of unintended consequences." You may not know what the word "backfire" means. Maybe you aren't sure about "unintended" or "consequences" either.

Have you ever tried to make something better and it actually got worse because you tried to help?

Display and discuss slide. The words in green, "backfire," "unintended," and "consequences" are individually defined if you click on them.

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Comic

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Show the slide with the "First panel" tab selected.

Paraphrase:

This is based on a true story
 somewhere in the United States
 …except for the talking cow part.

Select 1, 7, or 15 students to read the
 roles in the comic out loud.

• Chickens (1, 3, or 7)
• Farmer with the Hat
• Farmer in Overalls
• Optional: Gun 1 and 2
• Cow 1
• Cow 2
• Rat 1
• Rat 2

Listen as students read the first comic panel to the class. Ask:

What do you think will happen next?

Show the slide with the "Second panel" tab selected. Listen as students read the second comic panel to the class. Ask:

What do you think will happen next?

Show the slide with the "Third panel" tab selected. Listen as students read the third comic panel to the class. Ask:

What do you think will happen next?

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Idiomatic expressions in the comic

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For English Language Learners

Review the several idiomatic expressions in this cartoon. Students can find the idioms in the text as you review, underlining or circling where they are used if you distributed printouts. See Teacher Tips for more details.

The idiomatic expressions are highlighted in yellow in the image at right.

Display and discuss the slides by clicking on the black "See all panels" button. As a class, discuss the comic. Ask the students:

Consider the events of this cartoon from a scientific perspective. What were the unintended consequences in Barnyard Backfire?

If they need prompts, ask them to think about how many of each type of animal there were.

Demonstrate how to make a simple graph that shows the relationship between number of rodents and number of hawks. (You may want to skip this step if you plan to proceed to the next step, "Explore human impact" to explore the predator-prey relationship using data.)

Step 1

• Draw the x-axis and y-axis, forming an L-shape.
• Label the y-axis “number of rodents."
• Label the x-axis “number of hawks."

Step 2

• Wave your hand over the origin (where the two axes meet).
• Ask, “When there are fewer hawks, will there be more or fewer rodents?”
• Students should answer that there will be more rodents.
• Draw a dot near the top of the y-axis.

Step 3

• Wave your hand over the arrow end of the x-axis.
• Ask: When there are more hawks, will there be more or fewer rodents?
• Draw a dot near the end of the x-axis.

Step 4

• Tell the students:

The relationship between hawks and rodents is an inverse relationship.

We can draw a line or a curve between these two points to model how many predators and prey the farmers will see.

Step 5 (optional deeper dive for more advanced students): Make a third graph to combine the two graphs on one graph to look for correlations.

Graphing Hawks vs. Rodents

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This activity shows how someone might use data to try to figure out what is happening in the situation presented in the cartoon. The data table shows the number of sightings of both the hawks and the mice over a year’s time.

Show Slide #1. Paraphrase:

Could there be a connection between the hawk problem and the rodent problem? Hmmm....

The farmer’s daughter, Maria, decided to investigate. She knew that when her father got out the shotgun to kill the hawks, she saw a lot fewer hawks around. But she wasn’t sure about the mice. So for one year, she spent two hours each month observing for hawks and two hours observing for mice.

Look at the spreadsheet of her data.

Show Slide #2. Paraphrase:

Maria was still having trouble making sense of her data. So she graphed it. The data from the hawk sightings have been graphed. Let's graph the mice sightings.

In studying her graphs, Maria started to think she had some scientific evidence. But of what? Discuss with a partner what you think can be concluded from Maria’s data.

Ask students to write down their conclusions. Discuss with the students.

Possible answers:

• When there were more hawks, there were fewer mice and when there were fewer hawks, there were more mice.
• As the hawk population declines, the mouse population explodes.
• There is an inverse relationship between the hawk and mice sightings.

For English Language Learners: About "Fewer" or "Less"

Students might get confused whether to say “fewer” or “less.” They probably learned that we say “less” when the item is a non-count item, like milk or sugar. When the item is a count item, like hawks, we say fewer.

Since non-count items frequently don’t have an “s” at the end to indicate plural, some students might get confused with an irregular plural word like “mice.” Even though mice doesn’t end with an “s,” mice is still a count item. You can count mice. Therefore, we say “There are fewer mice when there are many hawks around.”

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What’s going on here?

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Survival of the Fittest Paper Catchers is a hands-on predator-prey activity developed by Project GUTS at MIT and Code.org. In it, students toss and catch crumpled paper to collect data. For it, you need a stack of scratch paper to crumple and a sheet or two of newspaper (or a similar way to mark an area on the floor, like a hula hoop).

In the activity, students learn about population growth and its limits.

In Round 1, one student throws the paper ball two feet up and attempts to catch it. If they do, they stay in the population and reproduce; if they drop their paper ball, they die and must sit down. They reproduce by selecting another student to join in the population. Repeat these steps for several generations while recording the population size and generation number after each throw. When all students are standing, ask them to look for patterns and predict what could happen if the game could be played with an unlimited number of people.

In Round 2, students follow the same rules with an added constraint. To survive, they must throw and catch their paper ball while keeping one foot on the piece of newspaper. Ask students to predict any changes in the data pattern they anticipate. Ask students what the piece of newspaper might represent. One answer is similarly limited resources in nature, such as food supply. The maximum number of paper catchers the piece of newspaper can support is its “carrying capacity.”

In Round 3, replace the piece of newspaper with a sheet of 8.5"x 11" / A4 printer paper. Ask, “What will happen when we play again?” and “What will the shape of the population growth curve be?”

For a lot more detail on this activity, see Survival of the Fittest Paper Catchers at Project GUTS.

Paper catchers!