What is Happening to Polar Bears? Real Data, Claims, and Evidence

Looking for a way to incorporate real data into your science class? Or maybe you want to work on evidence-based claims and reasoning. Perhaps you need an engaging way to tackle the subject of climate change. This lesson uses polar bears and sea ice data to promote critical thinking within the context of an important current event.

Lesson Objectives

  1. Students will be able to visually represent data by creating meaningful graphs.
  2. Students will make claims based on graphical evidence and support those claims with evidence-based reasoning.

National Science Education Standards

This lesson closely aligns with three of the Science Content Standards of the National Science Education Standards (NSES): Science as Inquiry, Life Science, and Science in Personal and Social Perspectives.

Science as Inquiry: Abilities Necessary to do Scientific Inquiry (Grades 5-8)

  • Use appropriate tools and techniques to gather, analyze, and interpret data.
  • Develop descriptions, explanations, predictions, and models using evidence.
  • Think critically and logically to make the relationships between evidence and explanations.
  • Recognize and analyze alternative explanations and predictions.
  • Communicate scientific procedures and explanations.

Life Science: Populations and Ecosystems (Grades 5-8)

  • Lack of resources and other factors, such as predation and climate, limit the growth of populations in specific niches in the ecosystem.

Science in Personal and Social Perspectives: Natural Hazards (Grades 5-8)

  • Human activities also can induce hazards…Such activities can accelerate many natural changes.

Engage

Begin the lesson by showing footage of polar bears in Hudson Bay with wildlifeHD’s Polar Bear Cam. Conduct a brief class discussion to elicit prior knowledge about the bears. Next, share some facts about polar bears with students, such as:

  • So far this fall, tour operators and scientists have reported at least four and perhaps up to eight cases of mature males eating cubs and other bears in the population around Churchill, Manitoba. (From Hungry polar bears resorting to cannibalism, December 3, 2009)
  • There are increased bear-human interactions, increased numbers of bears on shore, and bears staying on shore for longer periods of time in the Canadian Arctic. (From Can You Bear It? Churchill a Polar Pioneer, November 18, 2009)
  • The IUCN Polar Bear Specialist Group has listed eight of 19 polar bear subpopulations as currently decreasing, three as stable, and one as increasing. For seven, data were insufficient to assign a trend. (From Polar Bear Status Report, July 6, 2009)

You may wish to share the facts orally, list them on the board or on a PowerPoint slide, or create mock headlines for students to read. Ask students to discuss the facts in small groups, and come up with explanations for the facts (or headlines). Conduct a class discussion to share students’ explanations, and record and post them in a central location.

Explore

Next, group students into teams of 4 or 5 for an Idea Circle about polar bears. In an idea circle, each student reads a nonfiction (informational) text of their own choosing on a particular subject (in this case, polar bears). As each student selects his own text, a variety of reading levels and formats are represented within each small group and within the class. Ideally, no two students read the same text. Idea circles are an excellent strategy for differentiated instruction and a wonderful opportunity to incorporate children’s literature into a middle school classroom.

For an idea circle on polar bears, we’ve suggested titles from the Beyond Penguins and Polar Bears virtual bookshelves, including:

  • Ice Bear: In the Steps of the Polar Bear. Nicola Davies. 2005.
  • Life Cycle of a Polar Bear. Rebecca Sjonger and Bobbie Kalman. 2006.
  • Baby Polar Bear. Aubrey Lang. 2008.
  • Why Don’t Polar Bears Have Stripes? Katherine Smith. 2004.
  • A Polar Bear Journey. Debbie S. Miller. 2005.
  • Polar Bears: Arctic Hunters. Norman Pearl. 2009.
  • Ice Bears. Brenda Z. Guiberson. 2008.
  • Polar Bear Alert! Debora Pearson. 2007.
  • Polar Bears. Amazing Animals Series. Gail Gibbons. 2009.
  • 101 Facts About Polar Bears. Julia Barnes. 2004.

Your librarian or media specialist will be able to recommend other nonfiction titles as well.

After students read their individual texts, they share what they’ve learned with their small group, completing a graphic organizer in the process. Next, conduct another whole-class discussion and record information on a large chart displayed in a central location. Ask students to revisit their explanations from the “Engage” phase, clarifying and revising as needed.

Explain

In this phase of the lesson, students will work with real data to better understand the role of sea ice loss in changing polar bear populations. The Windows to the Universe lesson Graphing Sea Ice Extent in the Arctic and Antarctic provides up-to-date sea ice data and clear procedures for the lesson. You may wish to deal only with the Arctic data if your focus is on polar bear populations.

Graphing Sea Ice Extent in the Arctic and Antarctic
Students graph sea ice extent (area) in both polar regions (Arctic and Antarctica) over a three-year period to learn about seasonal variations and over a 25-year period to learn about longer-term trends.

Once students have completed their graphs, they will analyze the data and make evidence-based claims that explain why polar bear populations are changing. You may wish to use a graphic organizer to scaffold students’ work with claims, evidence, and reasoning. You may also wish to model this process if students are unfamiliar or unpracticed with these concepts.

At this time, you may choose to conduct another whole-class discussion to share claims, evidence, and reasoning. Student graphs and claims/evidence/reasoning graphic organizers serve as assessment for this lesson (see “Assess,” below).

Assess (Evaluate)

Class discussion during the “Engage” phase of the lesson can serve as a source of formative assessment. Additionally, observation of student behavior during the lessons’ activities can be used as an assessment tool.

Formal (summative) assessment for this lesson includes evaluating student graphs and claims, evidence, and reasoning using rubrics. In addition, you may also choose to assess student understanding of polar bear characteristics and populations.

Expand

Extend this lesson by introducing global climate change and albedo. The following resources may be helpful as you plan extension activities.

Graphing Thermal Expansion of Water and Greenhouse Gases
Two activities have students create graphs of concentrations of greenhouse gases and observe the thermal expansion of water. You may choose to have students also plot global temperatures as well as greenhouse gas concentrations to help them see the correlation between the two.

The Shiniest Moon
This nonfiction article is written for use with students in grades 4 and up. Students learn about two of Saturn’s moons, albedo, the relationship between heat absorption and temperature, and how decreasing sea ice in the Arctic actually contributes to further melting. The article is offered in various formats and reading levels, and related activities are suggested.

Other Related Resources

Create a Graph
Students will learn how to create area, bar, pie, and line graphs. They are provided with information about what each type of graph shows and what it can be used for. Students are given an example of each type of graph, but they can create graphs using their own data in the interactive tool.

WWF-Canon Polar Bear Tracker
For the last 5 years or so, the WWF-Canon Polar Bear Tracker has followed polar bears in the Arctic. Their positions are beamed from collars on the bears’ necks, via satellite to scientists, and then to this website. It allows us to get regular updates about how the polar bears behave in their arctic environment and how they may be affected by climate change. The site also includes multimedia and a kid’s zone.

Dot Earth
Follow climate-related news (including the latest from the climate talks in Copenhagen) with this New York Times blog.

We Want Your Feedback

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org.

This post was originally written by Jessica Fries-Gaither and published December 16, 2009 in the Connecting News to the National Science Education Standards blog. The post was updated 3/27/12 by Jessica Fries-Gaither.

What Can Batting Averages Tell Us?

It’s the bottom of the 9th, 2 outs, bases loaded in the 7th game of the World Series. On the mound is the opposing team’s left-handed pitcher trying to close out the game. As the Head Coach you have a decision to make: let your left-handed 9th batter hitting .270 for the season go up and take his hacks, or pinch hit with your young, recently called-up rookie batting .350?

The first question we need to answer before making a decision is: What do the batting average numbers mean?

Batting averages are a simple decimal that approximates the number of hits per at-bat, or more simply the probability that a batter reached first base on a hit during his previous at-bats. The equation used to calculate batting average is simple: # Hits/# At-Bats.

A batting average is written in decimal form using 3 digits after the decimal point. Avid baseball readers read these as large numbers, so .400 would be read as “four-hundred” and .283 would be read as “two eighty-three.” Each individual thousandth is called a “point,” so .400 would be considered 117 points higher than .283.

But not all batting averages can be read equally. Two players can have the same batting average, take .300 for example, and have very different statistics. Player 1 could have 3 hits in 10 at-bats while player 2 may have 120 hits in 400 at-bats.

So which is a more accurate description of a player’s ability? Let’s take a look at what happens to the players after their next at-bat.

If they were to both get a hit in the next at-bat, their averages would indicate that Player 1 is much more likely to get a hit, yet if they both made an out the numbers would swing heavily in favor of Player 2.

The key to this discrepancy lies in the number of total at-bats. With more at-bats, the denominator for the fraction becomes larger and is less affected by adding 0 or 1 to the numerator. Referring to the chart, the next at-bat for Player 1 will either increase his average by 64 points or decrease it by 27. Player 2 will see either a 2 point increase or a 1 point decrease. So batting averages are less affected with larger numbers of at-bats, and can more accurately describe a hitter’s tendency over a period of time.

Now, looking back to the original question, I will add more context to the problem. In an average 162-game season a player might amass about 450 at-bats, and back-ups could see 100 at-bats. Rookies and recent call-ups (players invited to the major-league team from the minor leagues) will usually be on the team for the final 50 games of the season.

Knowing this information and having seen the chart from above, does this change your original decision for what to do? Why or why not? There is no definitive correct answer to this question, but I do ask that you use numbers to support your reasoning. Please post your decisions in the comments.


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. Post updated 11/27/2011.


This post was originally posted in the Everyday Explanations – Answers to Questions Posed on a Middle School Bus Ride by Sean Mittleman. We have his permission to re-post in the MSP2 blog.

Algebra: Teaching Concepts

When we teach algebra, most teachers find that getting across the manipulation of expressions is far easier than teaching the big ideas that underlie algebra. Lately I’ve run across sites that help middle school students grasp those concepts. I’d like to share them with you in this post and ask for your ideas in return.

First, two excellent ideas on helping students walk the bridge from arithmetic to algebra:

Building Bridges In this lesson, students move from arithmetical to algebraic thinking by exploring problems that are not limited to single-solution responses. These are common, not complex, problems that are developed through questioning to a higher level. Within real-world contexts, students organize values into tables and graphs, then note the patterns, and finally express them symbolically.

Difference of Squares uses a series of related arithmetic experiences to prompt students to generalize into more abstract ideas. In particular, students explore arithmetic statements leading to a result that is the factoring pattern for the difference of two squares. Very well done.

Equivalence is one of those underlying concepts that make algebraic reasoning possible. Everything Balances Out in the End offers a unit in which students use online pan balances to study key aspects of equivalence. The three lessons focus on balancing shapes to study equality, then balancing algebraic statements in order to explore simplifying expressions, order of operations, and determining if algebraic expressions are equal.

The next lesson, Equations of Attack, is a game but developed to uncover the algebra beneath the strategies. The two players each plot points on a coordinate grid to represent their ships and points along the y-axis to represent cannons. Slopes are chosen randomly (from a deck of prepared cards) to determine the line and its equation of attack. Students use their algebraic skills to sink their opponent’s ships and win the game. Afterwards, the algebraic approach to the game is investigated.

Walk the Plank is also a game. You need to place one end of a wooden board on a bathroom scale and the other end on a textbook. Students can “walk the plank” and record the weight measurement as their distance from the scale changes. This investigation leads to a real world occurrence of negative slope.

A final teaching idea develops students’ understanding of algebraic symbols: Extending to Symbols.  As students begin to use symbolic representations, they use variables as unknowns. To help their concept of symbolic representation to grow, they need to explore questions such as: What is an identity? and When are two symbolic representations equal? This activity engages students in work with an online algebraic balance.

Each of these lessons comes from NCTM’s Illuminations site, a rich source for K-12 teaching.


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. Post updated 11/08/2011.

Venn Diagrams

Venn diagrams are one of many tools used in logic and reasoning. Their use is especially helpful in learning foundational notions of definition and set theory. One of the five Process Standards promoted by NCTM, Reasoning and Proof requires middle school students to sharpen such skills as they learn to develop mathematical argument.

Venn Diagram Shape Sorter
A good activity for introducing the concepts of definition and set! Students move various shapes, available in two sizes and three colors, into a circle. By seeing which figures are accepted into the circle, they determine the rule guiding the circle’s selection. In a more complicated example, a Venn diagram of two intersecting circles is used, requiring that two rules be stated.

Factor Tree (Grades 6-8)
Students first find the prime factors for two numbers. These are displayed in tree diagrams from which the student drags the factors to the appropriate areas of a Venn diagram. The Venn diagram offers a useful visual display showing unique factors and common factors for the original pair of numbers. Using the display, the learner must find the pair’s least common multiple (LCM) and greatest common factor (GCF).

Venn Diagrams
This virtual manipulative with an interactive three-circle Venn diagram can be used to model set operations for union, intersection, and subset. For each statement, the student highlights the region that is the solution, then clicks a button to find out if the solution is correct.

Who Played the Raptors?
In this online activity, students analyze predictions made by sportswriters about which basketball teams will win to determine which teams are playing each other. The solution illustrates and explains three different ways to successfully organize information, including using a Venn diagram.


We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. Post updated 10/18/2011.