Photosynthesis - Claim and Evidence

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SWBAT write an essay describing the process of photosynthesis using claims and evidence from variety of sources.

Big Idea

Students use claim and evidence to describe photosynthesis.


10 minutes

This lesson is conducted after students have been exposed to photosynthesis and have been assessed to have a strong background knowledge in the overall process.  This is a performance task completed at the end of  my photosynthesis unit where students have learned about the basics of photosynthesis through readings, demonstrations, experiments, and writing tasks. (See one my previous lessons Photosynthesis - Plant's Greatest Gift).

To engage students each student receives a copy of Concept Map Cards.  Students are required to put cards into a logical flow map, in this case a multi-flow map.  I have provided three different type of cards for differentiation purposes (pictures, text, chemical formula).

After students have created their concept maps students are instructed to explain their concepts maps to their table group specifically discussing their reasoning behind each placement.  The objective of this is to assess student comprehension of photosynthesis process.  This needs to be mastered in order to continue with particular lesson.

The picture below shows a multi-flow map with the addition of starch:

Video below is of concept map card activity described above.  

Guided Practice

10 minutes

Since the proper use of claims, evidence, and reasoning is a skill that must be practiced to be mastered, it is crucial to introduce it to students before any type of writing task that will require its use.  I have students practice this skill by having them complete Claims, Evidence, and Reasoning Practice.  In this exercise, students are required to come up with a claim that will answer the question, "Who do you think took Ms. C's lunch?".  To support their claim students are required to list pieces evidence from the story that gives their claim credibility (W.7.1b).  

Most importantly, students are introduced to the concept of giving reasoning to why a piece of evidence supports their particular claim. I have attached the Case of Missing Meatballs powerpoint which includes sample student responses at different proficiency levels.  

Writing Task

35 minutes

Students are given the following 3 handouts: (SP6 - Constructing Scientific Explanations)

1.  Claims and Evidence

2.  Making a Claim Based on Evidence T Chart

3.  Photosynthesis Performance Task


1. Claims and Evidence includes 4 pieces of evidence that students can use support to fill out their claims, evidence, reasoning table at the bottom of each page.  

  • Evidence 1 has an excerpt from Priestly on his 1775 experiments describing his observations that helped him develop the claim that plants produce oxygen during photosynthesis.  Along with his quotes it includes a data table of his experiment that students can analyze and develop the claim like Priestly that plants produce oxygen during photosynthesis.
  • Evidence 2 has an excerpt from Ingenhousz from his 1779 experiments describing his observations that helped him develop the claim that light is necessary for photosynthesis to occur.  Along with his quotes it includes a data table of his experiments that students can analyze to develop claim like Ingenhousz that plants need light for photosynthesis to occur.
  • Evidence 3 is a diagram that illustrates that carbon dioxide is a required reactant for photosynthesis to occur.  
  • Evidence 4 is a diagram that illustrates that light is needed in order for leaf to produce sugar and store it as starch during photosynthesis.


For each piece of Evidence students are required to come up with at least 1 claim, 1 evidence artifact, and 1 reasoning artifact.  These 4 CER (Claim, Evidence, Reasoning) will be included in students' Photosynthesis Performance Task.

2.  Making a Claim Based on Evidence T Chart ( is a T-chart that allows students to write and organize their claims and evidence for their Photosynthesis Performance Task.  It's a good idea for students to record (write) the source of their evidence (Evidence 1, 2, 3, 4).

3.   Photosynthesis Performance Task (MS-LS1-6)has directions for assignment along with samples of appropriate CER's (Claim, Evidence, Reasoning).  The second page includes general outline for essay with specific instructions on what information should be included in each section.  The final page includes the assignment rubric.