Claire GuzinskiPrior Knowledge Investigation – Photosynthesis

NSTA Standards:

NSTA Assessment #5: Candidate's Effect on Student Learning-

8.a Use multiple assessment tools and strategies to achieve important goals for instruction that are aligned with methods of instruction and the needs of students.

8.b Use the results of multiple assessments to guide and modify instruction, the classroom environment, or the assessment process.

The lesson was designed to help meet the following Standards:

BIO.3 The student will investigate and understand the chemical and biochemical principles essential for life. Key concepts included) The capture, storage, transformation, and flow of energy through the processes of photosynthesis and respiration.

BIO.9 The student will investigate and understand dynamic equilibria within populations, communities, and ecosystems. Key concepts includeb) Nutrient cycling with energy flow through ecosystems;

WIDA Standard 4: English language learners communicate information, ideas and concepts necessary for academic success in the are of Science.

Understanding photosynthesis and the role that it plays in energy flow is essential to the study

of Biology for any student. In order to understand how ecosystems function, they must first understand

that plants are the root source of all energy within a system and why. I selected this topic both because

of the pacing at my High School and because of the importance of the topic to understanding later

units. Before planning any lesson, it is important to uncover any misconceptions that might be present

in the students' “big-picture” view of the topic that could prevent them from being able to accept new

information. Once those misconceptions were uncovered, a big part of my lesson planning was making

sure that I included activities that helped students confront and overcome any already existent flaws in

their ideas.

Once I had chosen the topic, it was time to do some research. During this research I read a

scholarly article about secondary students' misconceptions of the process of photosynthesis. I found

that many students hold misconceptions about plants needing Oxygen instead of Carbon Dioxide, and

not knowing how the gas was used in plants. In addition I found that many students were unsure of

why plants needed sunlight, or how they used that sunlight. Once I had finished with my research, it

was time to talk to students and see if I could uncover any misconceptions that they might hold. This

was done verbally as an individual, informal interview with 3 different students. I asked open ended

questions about what plants need to make food, why it is said that all energy starts with the sun, why

plants are green, what organelle plant cells used to make food and what happens to the food that is

made by plants.

Students knew that plants need water and sunlight to make food, but did not seem to know how

the plants used that sunlight. They also seemed pretty sure that plants took in Oxygen and let out

Carbon Dioxide as a by-product. This was a pretty big misconception since students needed to

understand this in order to understand the impact that plants have on humans and animals. When

asked, students seemed convinced that plants were green because they had green cytoplasm and that

plant cells actually carried out photosynthesis in the cytoplasm or the mitochondria. This

misconception needed to be reversed in the lesson in order for students to avoid confusing the process

of photosynthesis with that of cellular respiration.

One of the misconceptions that I focused on the strongest when coming up with my lesson plan

was the view students held that once the food is produced by the plant, it is then released. I was hoping

that logic would guide the students to answer that the plant stores and uses the food. The next

misconception was one that I would expect on the middle school level, but I have to admit that I was

surprised to hear that it was still present in high school students. When asked where in the plant

photosynthesis occurred, the students answered that it occurred in the roots and the flowers. Students

often focus on the flower and think that because it is so prominent, it is involved in all of the major

processes of the plant. The fact that students still held this viewpoint meant that it was not fully

corrected in middle school and that I would need to stress that flowers were not involved in

photosynthesis, and find some way to show that through a discrepant event or examples. Finally,

students knew that plants needed sunlight and that it played a part in photosynthesis, but when asked

about where the plant got the “energy” to carry out photosynthesis, they mentioned nutrient absorbtion

through the roots. Here, even though students had memorized what a plant needed, they had a hard

time placing the role of the sun in the process and found it easier to think of a more visual, tactile

explanation. Because sunlight is not concrete, students seemed to have a hard time visualizing exactly

how it was used to energize the plant.

Once I finished discussing students' prior knowledge about the topic that I planned to cover, it

was time to take a look at all of my notes, as well as the schools pacing guide, and decide what to

include in my lesson. The pacing guide allowed 1 day for photosynthesis and the school had periods

that lasted 1 hour and 30 minutes each, so the length of my lesson was decided for me. I decided to use

the 5-E model while planning (Engage, Explore, Explain, Elaborate, Evaluate) in order to ensure that I

used multiple methods and activities to deliver the material that I needed to cover.

As my Engage in the lesson I decided to begin by using some visuals. I brought in 2 different

plants from my house; 1 that had been deprived of water, and 1 that had been moved a few feet away

from a direct light source. I asked the class to raise their hands and make some observations about the

plants. After a few other observations, students eventually pointed out that one was browning and that

the other plant was leaning hard in one direction.

As my Explore I continued to use the same plants and I asked the children to tell me what the

plants were missing that might cause this behavior. They immediately replied water and sunlight. I

asked them to draw a conclusion about what plants need to make food and be healthy and they replied

that they needed water and sunlight.

As my Explain we went through a set of Powerpoint notes, making sure to allow time for

questions and discussion. I used as many examples and cool, memorable facts as possible and made

sure to pull in a few more plants that I had brought from home to illustrate pigment differences and that

photosynthesis takes place in the leaves. Towards the end the notes we discussed that in addition to

water and sunlight, plants need Carbon Dioxide for photosynthesis. Because this was one of the

students' misconceptions I asked students to tell me what humans inhaled and exhaled. Next, while

showing the students the equation for photosynthesis, I asked them to tell me what plants “inhaled” and

“exhaled”. Finally, I asked them to make some observations about the relationship between the two.

Once they noted that our breathing patterns were opposite those of plants, we spent a few minutes

talking about why we need plants to photosynthesize and renew our Oxygen supply. One of the other

points that we spent some time discussing was how the energy produced by photosynthesis is the same

energy that is recycled up the food chain. This helped to drive the point home that the sun is the root

source of all energy for living things.

Finally, I combined the Elaborate and Evaluate sections by giving the students the following assignment:

On a sheet of paper draw a picture of a leafy plant.

Label the products and reactants of photosynthesis using both their common and chemical name. (EX: Glucose-C6H12O6)

Label Sunlight (energy), Water (H20), Carbon Dioxide (CO2), Glucose (C6H12O6) and Oxygen (O2)

Include and label at least one autotroph and one heterotroph in your picture.

Draw arrows to show whether the products are going in, going out or staying inside of the plant.

Title and color your drawing.

The following is one example of the assignment that was turned in.

In looking at the work that was turned in it became obvious that students now understood that

photosynthesis too place in the leaves of the plant, which absorbed sunlight and CO2, while the roots

absorbed water. One of the most important things that I wanted students to show was that they

understood that Glucose does not leave the plant, and through the lack of an arrow I feel comfortable

that this point made it across. I included this assignment because I wanted to make sure that students

were not just repeating the information but that they really understood what they were saying. There

was no template for this picture in the book and every students' looked different. The drawing allowed

them to practice both the chemical and common names for the compounds in the equation and forced

them to confront any misunderstandings. If they didn't know where the arrow needed to go they were

forced to ask and it gave me a chance to catch any errors in comprehension. The final benefit of using

a picture as an assessment was that it forced the students to contextualize what we had just learned. By

completing the assignment I could be sure that they were not just repeating vocabulary, but that they

actually understood how the process worked in action.

Overall this lesson was a very big success. In addition to interviewing my 3 students again at

the end of the lesson I received diagrams from every student, including those with IEPs. The students

with IEPs responded very well to the hands-on assessment. Some of them take longer to write and

have a hard time with reading, so I feel as though the discussion during the notes and the pictorial

assessment were key. It allowed these students to learn the vocabulary without getting lost in a lot of

copying out of the book or long sections of text. The three students who I interviewed were spot-on

during the post-lesson interview, with only one of the three students getting confused for a moment

between the term “chlorophyll” and the term “chloroplasts”, which she promptly corrected on her own.

The other students in the class demonstrated their understanding though the diagram and with the

exception of 4 students who had trouble visualizing that the Glucose stayed inside of the plant once it

was produced, everyone seemed to really grasp what photosynthesis involved and looked like in action.

Article on Student Misconceptions

Ozay, E., & Oztas, H. (2003). Secondary students' interpretation of photosynthesis and plant nutrition.

Journal Of Biological Education, 37(2), 68.