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Why Is Cancer So Rare in Elephants?

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Why Is Cancer So Rare in Elephants?

Biology Crosscutting Concepts Disciplinary Core Ideas Is Lesson Plan Life Science NGSS Phenomena Science and Engineering Practices Three-Dimensional Learning High School Grades 9-12

Welcome to NSTA's Daily Do!

Teachers and families across the country are facing a new reality of providing opportunities for students to do science through distance and home learning. The Daily Do is one of the ways NSTA is supporting teachers and families with this endeavor. Each weekday, NSTA will share a sensemaking task teachers and families can use to engage their students in authentic, relevant science learning. We encourage families to make time for family science learning (science is a social process!) and are dedicated to helping students and their families find balance between learning science and the day-to-day responsibilities they have to stay healthy and safe.

Interested in learning about other ways NSTA is supporting teachers and families? Visit the NSTA homepage.

What Is Sensemaking?

Sensemaking is actively trying to figure out how the world works (science) or how to design solutions to problems (engineering). Students do science and engineering through the science and engineering practices. Engaging in these practices necessitates that students be part of a learning community to be able to share ideas, evaluate competing ideas, give and receive critique, and reach consensus. Whether this community of learners is made up of classmates or family members, students and adults build and refine science and engineering knowledge together.


Cancer Risk Among Different Species

Presentation of Phenomena (What Am I Exploring Today?)

Cancer is a topic that is often covered in high school biology class when teaching about cells. Often it is used at the end of a unit as an example of what happens when cells do not divide properly, or divide uncontrollably without regulatory mechanisms. As many, if not all, students are familiar with cancer in some way, it is often a topic that is disused at a surface level of understanding. However, when used as a phenomenon, it can enable students to use cancer as a vehicle for understanding. For today's Daily Do, we use the table (pictured above) to prompt students to think about cancer differently than they have in the past.

Many traditional class discussions focus on cause, treatment, and prevention of cancer. Today, we examine cancer from a new perspective: why some animals rarely develop cancer. Although several species of animals have a very low incidence of cancer, today students will figure out Why is cancer so rare in elephants? What is happening with the elephants? Let's investigate!

Guidance. The goal is to get students thinking about why elephants and humans have such different rates of incidence of cancer. Presenting a phenomenon and asking students to generate questions about it creates a need to figure out the answer to those questions. This is authentic engagement and a powerful learning process (unlike "learning about" cancer as an example of what happens when cell division goes wrong).

Presenting the Phenomenon

Have students observe the table on slide 2 and write down what they notice about the data presented. This step is critical in eliciting further questions about why some organisms seem more susceptible to developing cancer and other organisms are not. Our goal is to promote student thinking about questions they have related to this. All student questions are acceptable at this point. We want to motivate curiosity and not distinguish between "good questions" and "bad questions" or "right questions" and "wrong questions." Common questions will arise for most students, which is what this task builds upon.

Investigative Questions (What Questions Do I Have About What I Just Saw?)

Investigative questions are common questions kids may ask after they are introduced to the phenomenon. Although questions may vary, many students are curious about what causes cancer and why it presents in so many different ways.

Guidance. It is important to allow time for thinking. Many students have ideas and questions, but need time to formulate their idea or question into words. Some students may also benefit from writing their thoughts first before they share. As adults, we may be tempted to give them questions we feel might be important to explore; however, we need to refrain from this and allow our students to practice asking their own questions. Our goal here is for students to consider all of the data they are seeing in the graph and to develop questions around this data.

Common Questions (slide 3)

  • Why do some humans have a risk of 90%?
  • What is Li-Fraumeni Syndrome?
  • Why is the elephants' risk so low?
  • Why wouldn't the elephants' risk be higher because they are bigger than other things listed, so they have more cells?
  • What is the TP53 gene?
  • Does having more of the TP53 gene give elephants a lower risk?
  • Why do dogs have a higher mortality rate than humans when they get cancer?
  • Do elephants have more TP53 genes because they are bigger?

We want to focus on one question in particular at this point. (slide 4)

  • Why do some humans have a risk of 90%?
  • What is Li-Fraumeni Syndrome?
  • Why is the elephants' risk so low?
  • Why wouldn't the elephants' risk be higher because they are bigger than other things listed, so they have more cells?
  • What is the TP53 gene?
  • Does having more of the TP53 gene give elephants a lower risk?
  • Why do dogs have a higher mortality rate than humans when they get cancer?
  • Do elephants have more TP53 genes because they are bigger?

Connection Guidance. Students may make connections to previous concepts in other grade levels. For example, students may mention that when cells divide incorrectly, they can cause a tumor. They may also bring up ideas of how to "kill" cancerous cells through a variety of different treatment options. We know that many students have been affected by cancer and want to ensure we are sensitive to their past experiences. It will be important for us to acknowledge and validate what each student brings to the discussion, but also move the discussion forward.

Narrowing the Scope

Tell students, "Now that we have identified the first question we want to figure out, it would be helpful to gain some additional background information about what you know about cancer and genes." Create a table like the one on slide 5 to elicit prior knowledge. In addition, document any new questions and ideas for what we need to figure out next.

Discuss the ideas that surfaced from creating the table. "We think there is a link between the TP53 gene and the risk of cancer, but we are not sure. From the data, we can see that elephants, dogs, and humans all have the gene, but all present different rates of risk. We are not sure if elephants have more just because they are bigger, but also notice that dogs and humans have the same amount. We need to find out more about elephants and this gene."

It is valuable for learners to stop periodically and gain consensus about what they currently understand to be true. Teachers do this often in the classroom, periodically pausing instruction to be sure students have achieved the learning milestones necessary to move forward.

"Let's look back at what we've figured out up to this point."

After gathering information from the video, students will have figured out the following (slide 9):

  • p53 is a gene that "guards our genome." This means its job is to protect our cells.
  • Elephants have many copies of this gene (40), while other animals, like humans, have a lot less (2).
  • Some organisms only have one copy of the p53 gene (some humans) and are at a greater risk for developing cancer.
  • The p53 gene destroys mutated cells in the body so they cannot reproduce.
  • Studying elephants could lead to helping humans who have cancer.

Next, we revisit the questions we had after the first reading and decide what question(s) need to be figured out next. (Slide 10)

  • Are other animals at a low risk of developing cancer like elephants are?
  • How can animals help with human treatments?
  • Are other animals being studied?
  • Why don't all cells react the same when subjected to stressors?
  • How can things than seem so similar react so differently? For example, why wouldn't all blood react the same?

We engage in a discussion and decide we need to figure out if other animals  present at low risk or if elephants the only ones. If other animals are at low risk of developing cancer, are they also being studied? We feel that these new questions warrant investigation, so we engage in additional research.

Additional Investigative Research

We did some investigation through readings and discussion and discovered that

  • Several other animals also have a very low incidence of cancer.
  • The naked mole rat produces hyaluronic acid, which helps kill mutated cells, and they also have a gene, p16, which also helps prevent cancer cells from growing.
  • The bowhead whale can live for up to 200 years (Wow!) and has a better ability to repair mutated cells.
  • Dogs, mice, and cheetah have a high risk of cancer.
  • Many animals of both high and low risk are being studied to help figure out treatments for different cancers that affect humans.
  • Scientists hope that this research will lead to treatments, including gene therapy, genetic engineering, or pharmacology.

So, let's return to our original questions:

  • Why do some humans have a risk of 90%?
  • What is Li-Fraumeni Syndrome?
  • Why is the elephants' risk so low?
  • Why wouldn't the elephants' risk be higher because they are bigger than other animals listed, so they have more cells?
  • What is the TP53 gene?
  • Does having more of the TP53 gene give elephants a lower risk?
  • Why do dogs have a higher mortality rate than humans when they get cancer?
  • Do elephants have more TP53 genes because they are bigger?

Do we have enough information to create an argument from evidence for this question? What data have we gathered that we could use for evidence in defending a claim that either supports or refutes the idea that having more copies of the p53 gene gives an organism a lower risk of developing cancer?

Teacher Guidance. At this point, students may want to engage in more research, or you could have them do a claim, evidence, reasoning (CER) activity. Traditionally, the CER activity is presented as a written task; however, there are several ways for students to engage in a CER that allows for differentiation. Consider offering students a choice, including oral arguments, presentations, and informational posters, or creating a public service announcement. For more information on other uses of the CER, see STEM Teaching Tool #17.

What Did We Figure Out?

To answer our phenomenon question—Why is cancer so rare in elephants?—we need to look back at all of the evidence we have gathered through our research. (slide 15)

Looking back, it didn't make sense that an animal that is so big and has so many cells developed cancer at such a low rate. We figured out the following:

  • Even though elephants live a long life and have a very large number of cells, their cancer rate is less than 5%.
  • Many animals have a gene, p53, that helps guard against cancer. The p53 gene codes for a protein that regulates the cell cycle and apoptosis (cell death).
  • Humans have two copies of the p53 gene, but some humans only have one. Humans with one copy have a 90% risk of developing cancer.
  • Elephants have 40 copies of the p53 gene.
  • Researchers are studying p53 in elephants to figure out how p53 might be used in human cancer treatments including gene therapy, genetic engineering, and drug therapies.
  • Elephants are not the only animal with a very low risk of developing cancer. Scientists are also studying axolotls, naked mole rats, blind mole rats, bats, and some whales.
  • Some of the animals being studied have other cancer-fighting properties along with the p53 gene.
  • Scientists are also studying animals with a high incidence of developing cancer, including dogs and mice.

"Based on what we have figured out and our current understanding about elephants and cancer, can we answer our phenomenon question?" Here students have the opportunity to develop an explanation based on all of the connections they have made among cancer, genes, and elephants.

Connection Guidance. Almost everyone has been impacted by cancer in some way by the time they reach high school. As this can be a stressful topic for some students, be cautious about asking students to make personal connections about this topic.

NSTA Collection of Resources for Today's Daily Do

NSTA has created a Why is cancer so rare in elephants? resource collection to support teachers and families using this task. If you're an NSTA member, you can add this collection to your library by clicking Add to My Library, located near the top of the page (at right in the blue box).

Check Out Previous Daily Dos From NSTA

This Daily Do is inspired by and uses materials from the The Disease storyline developed by the Illinois Science Teaching Association-supported NGSS Biology Storyline Working Group and HHMI Biointeractive. These are an open-source resources that can be used by parents and teachers to implement student driven learning and can be found on the Illinois Science Teaching Association (ISTA) website.

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