Are your biology students struggling with writing scientific explanations using the claim evidence reasoning format? These seven simple steps will help break down the CER and guide students through answering questions using the claim evidence reasoning format. Follow along as I take you through the process using an ecosystem example.

Claim evidence reasoning is a way for students to give a scientific explanation to a question. In the claim, the students will state their answer. They then use evidence from the data, graphs, and diagrams to support their claim. The reasoning combines scientific knowledge to explain why and how the evidence supports the claim. Many students struggle with writing a claim evidence reasoning; however, these simple steps will take them from feeling frustrated to confident as they master a claim evidence reasoning paragraph.

STEP 1: IDENTIFY THE QUESTION.

Now, this might seem like an obvious first step that doesn’t even need to be addressed. But, I have found that some students have trouble looking at an experiment and figuring out what they are being asked to do. This is why, whether you think they need it or not, it is essential to model and guide students through identifying the question they will be answering. I have the students highlight or mark the question so that it stands out and helps focus their investigation. The example below asks: Which human interaction, hunting or logging, creates a more significant impact on the forest ecosystem?

STEP 2: LOOK AT THE DATA TABLE, GRAPH, AND DIAGRAM AND RECORD OBSERVATIONS.

I like to have my students fill out a graphic organizer that allows them to fill out their observations or evidence on one side and what they know about the topic or why they recorded the evidence, in other words, the reasoning on the other side. I take them through how to read a data table or graph. I lead them through looking at diagrams to pull out the critical information it shows. Using a graphic organizer to record the observations will help the students later when they start to write their CER.

In this example, I have the students:

• Identify what the graph shows by looking at the title, x-axis label, and y-axis label.
• Give a summary of each graph, including some key numbers.
• Write the key details from each graph into their graphic organizer, including the numbers.
• Explain why the key details are important on their graphic organizer.

STEP 3: LOOK OVER THE EVIDENCE AND REASONING AND WRITE THE CLAIM.

Now that they have looked through the information about an experiment or study, they can use their observations to write their claim. First, have them re-read the question. Next, have them look at the observations they recorded in their graphic organizer. Before they write their claim, have them discuss what it would be with a partner or group. When they write their claim, they need to use the keywords from the question.

In the example, the question asks Which human interaction, hunting or logging, creates a more significant impact on the forest ecosystem? We discussed the three graphs and what they are showing and then decided on the claim. The claim for this one is that logging significantly impacts the forest ecosystem more than hunting. Notice how the keywords in the question are “human interaction,” “significant impact,” and “forest ecosystem.” Those words are also in the claim.

STEP 4: USE THE EVIDENCE TO SUPPORT THE CLAIM.

Now that they have stated the answer to the question in the form of a claim, they need to provide evidence that supports their claim. To make it easier, students can use what they recorded in their graphic organizer to help write their evidence sentences. Students need to ensure that their evidence sentences include numbers from the data tables and graphs. It’s not enough to say that the population decreased. They need to explain how they knew it decreased by stating the beginning and ending population numbers.

In the example, the evidence would need to include the populations of the ecosystem when there is no hunting or logging, the populations of the ecosystem when hunting is introduced, and the populations of the ecosystem when logging is introduced. It should also include the source of information.

STEP 5: WRITE THE REASONING TO EXPLAIN HOW THE EVIDENCE SUPPORTS THE CLAIM.

Many students get confused with evidence and reasoning. Reasoning explains why and how the evidence supports the claim. The reasoning uses the scientific principles we already know. It explains why the evidence is essential and what it is showing. One thing that I have found that has helped students to differentiate between evidence and reasoning is by using a quick little check. If the information comes directly from the data table, graph, or diagram; in other words, the actual population numbers, then it is evidence. If the information is an explanation, definition, or scientific principle, then it is reasoning.

In the example, the reasoning should explain how organisms in an ecosystem interact with each other and how a change in one could affect a change in other organisms in the ecosystem.

STEP 6: PUT IT ALL TOGETHER IN A PARAGRAPH.

When my students write their claim evidence reasoning, I usually have them write each part as a separate piece first. This way, they focus on only one part at a time. This also allows students to discuss each part with a partner or group and for us to go over the information together as a class. Then I have them join all of the pieces together into one paragraph. After they create their paragraph, it is crucial to have them read out loud the paragraph. This is best done by having students read their paragraphs to their partners. Reading the paragraph aloud helps students identify mistakes and see if it flows smoothly.

STEP 7: CHECK THAT YOU HAVE THE KEY PARTS.

The last thing I have my students do is to complete a self-check list. This helps them to identify that they have all the key parts. Including the claim evidence reasoning, that the evidence includes numbers given in the graph, that the reasoning explains why and how the evidence supports the claim, and that there are no spelling or grammar errors.

Repeating these seven steps every time they write a scientific explanation will help students gain the confidence they need to master the claim evidence reasoning paragraph. As students go through the process over and over again, you will notice that the time it takes them to go through an experiment or study and write their scientific explanation will decrease as they start to become more confident. Writing a CER does take time; sometimes, a CER can take a whole class period.

The CER practice activity in the example above includes four different ecosystem experiments. Grab it below and use the steps to help your students conquer writing CER paragraphs.