Model Photosynthesis and Respiration with Berries

 

Students can model photosynthesis and respiration by making molecules out of strawberries, blueberries, grapes, and toothpicks. I wanted to create a healthier option to the gumdrops that are often used to model molecules, so I experimented with berries, and it worked nicely! 

You can use this activity when teaching Next Generation Science Standard (NGSS) MS-LS1-6: Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms. It can also be used to teach MS-LS2-3: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.

Students should prepare for this activity by first creating structural formulas for the reactants and products of photosynthesis and respiration. In a previous class, I provided a handout for students to draw structural formulas of all reactants and products of each process, referring students to this video (start at 6:10 for photosynthesis and 5:33 for respiration):

Chemistry Tutorial: Chemical Equations & Photosynthesis

As students draw their structural formulas, they begin to see that photosynthesis and respiration are opposite processes. 

On the day of the activity, students get directions for creating their berry models. Because carbon atoms are the largest of these atoms, I asked students to represent them using strawberries, the largest berries. The smallest atom, hydrogen, is represented by the smallest berry. Toothpicks are used as bonds.

Strawberries = Carbon Atoms

Grapes = Oxygen Atoms

Blueberries = Hydrogen Atoms

With the structural formulas they created previously in hand, students begin by creating molecules of water and carbon dioxide, the reactants of photosynthesis. You could allow students to work with a partner though you may want students to handle their own berries to prevent the spread of germs. The photo below shows students who successfully completed this first step (one water molecule not shown in the frame).

After building the reactants of photosynthesis, the next step is to model photosynthesis by breaking the bonds in water and carbon dioxide molecules and rearranging the atoms to form glucose, the product of photosynthesis.

The last step is to model respiration by breaking apart the glucose molecule to form the products of respiration, carbon dioxide and water. Students end with the same molecules they started with.

Once students have their hands-on work checked by a teacher and write about the relationship between photosynthesis and respiration, they can eat all the berries. One student told me afterward that she had never really “gotten photosynthesis and respiration” before but understood it now!

If you are interested in another activity that involves playing around with food in the name of science, follow this link to my previous blogpost on making models of cells using pasta and toppings:

Edible Cell Model Made of Pasta

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Edible Cell Model Made of Pasta

Students have fun learning about cell organelles with a buffet-style cell biology lesson! After studying the functions of different cell parts, students create an edible model of a cell using different kinds of pasta and toppings. You can use the activity when teaching Next Generation Science Standard (NGSS) MS-LS-1-2. Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

This activity is best done after students have learned the basics about cell parts and their functions. In my classes, students first completed a cell model on paper and did some written work describing what each cell organelle does. They also studied how different cell parts work together. Before eating their model, students needed to be prepared to tell me some of this information using the model. It was my experience that making pasta cell models was something they looked forward to and served as a nice reward.

If you are leading this activity with a class, requesting parent donations of items needed for making the cell models, if possible, can save you some time and money. I emailed parents a Google doc where they could sign up to donate ingredients. 

Below is a list of items I have used for classes of about 25-28 students. This list seemed to serve the requirements of many different students I had, but you may want to adjust this according to the dietary needs and preferences of your particular group.

2 packages spaghetti

1 package spaghetti- gluten free

2 packages regular lasagna noodles

1 package lasagna noodles- gluten free 

1 package mini wheels pasta

4 jars red pasta sauce- no meat or dairy and gluten free

3 cans black olives

Dried oregano and/or basil

1 package frozen peas

1 can cannellini beans

1 can kidney beans

7 small, thin zucchini (slice into circles and fry)

2 packages cherry/grape tomatoes

4 boxes toothpicks

Be prepared with small bowls and/or plates for students to use when creating their models as well as forks for eating it. We always had leftover items, so having empty food containers on hand is useful.

If you plan to do this activity, it is best to have some extra hands to help you. I always had an assistant and/or a parent volunteer or two help with food preparation before the lesson and clean-up afterward. They helped prepare for the activity by boiling the pasta, cutting and frying the zucchini, warming the frozen peas, and putting ingredients into bowls with spoons to serve. 

If you are unable to arrange an extended class period to make the cell models, it’s a good idea to have students make little toothpick flags as labels for the cell parts the day before. 

Once students have made their flags and all the food is prepared and set out, students can get into the buffet line and use the ingredients as they like to create their cell model. Giving suggestions can help get them started. Students should decide whether they will create an animal or a plant cell, and this will determine whether they will need to create a border of one layer- just a cell membrane- or two- a cell membrane and a cell wall. These parts could be made using lasagna noodles or spaghetti. The green peas work well as chloroplasts for those students making plant cells. Zucchini slices are a nice size for the cell nucleus. Because ribosomes are very tiny, sprinkling dried herbs on the top works well as a model for ribosomes. Spaghetti with red sauce works well as a model of cytosol.

After creating and labeling the cell model, students show it to the teacher or assistant, naming and explaining the jobs of a few cell parts, and giving an example of how two cell parts work together. Then they can eat it!

If you would like to see other blogposts related to cell biology, follow these links:

Personality Quiz with Plant Cell Parts

Cell City: Cell Organelles Project

Illustrating Science Vocabulary: Plant Cell Organelles

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Illustrating Science Vocabulary: Plant Cell Organelles

Understanding science vocabulary can be very challenging for students. When they create simple drawings for new terms, students get familiar with the vocabulary in an enjoyable, low-stress way. I found that this activity works especially well when teaching about chloroplasts, chromoplasts, and leucoplasts, all organelles found in plant cells. Students are engaged when illustrating the words and have the chance to express their individual style. The result is an informative and colorful display of your students’ work in the classroom.

Before starting the activity, you can show students photos of the three types of plastids- chloroplasts, chromoplasts, and leucoplasts, discussing their function and where they are likely to be found in plants. 

Juan Carlos Fonseca Mata, CC BY-SA 4.0

<https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons

Chloroplasts are where photosynthesis happens, and they are found in the leaves and other parts of the plant that are green. Chromoplasts give flowers and fruits their color. Students are interested to know that leucoplasts help provide some of their favorite foods as storage places for starch, fat, and protein. They are commonly found in potatoes and seeds, including beans and corn kernels. Thank leucoplasts for french fries, chips, and burritos!

Brainstorm with students how they might illustrate the words chloroplast, chromoplast, and leucoplast, writing ideas on the board for reference. 

Chloroplasts - green leaves, sunshine, water, and CO2

Chromoplasts - flowers, fruits

Leucoplasts - potatoes, french fries, beans, corn, burritos

Groups of three students get three strips of paper made by cutting 8 ½” by 11” printer paper into three parts lengthwise. 

Each student illustrates one of the three plastids so that all three plastids are completed by the group. I enjoy seeing the different styles students use in their work.

As students finish their work, they can help arrange the illustrations as a display on the wall. I found that putting each type of plastid illustration in a single column helps students more easily use them as a reference.

If you would like to learn about playing simple vocabulary-building games that draw on students' creativity, follow this link:

Low-Prep Games for Teaching Vocabulary

Here are links to other blogposts related to cell biology:

Personality Quiz with Plant Cell Parts

Cell City: Cell Organelles Project

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Valentine's Day Special: Sexual Selection and Widowbirds

 Photo by David Howard on Unsplash

Are you looking for a way to get the attention of your middle school science students? The funny topic of sexual selection can make for an entertaining lesson on Charles Darwin’s theory of natural selection. It certainly drives home the message that natural selection is all about reproductive fitness! 

You can use the concept of sexual selection to help teach Next Generation Science Standard (NGSS) MS-LS4-4: Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals’ probability of surviving and reproducing in a specific environment. Although you can cover sexual selection whenever you are learning about natural selection, it’s a fitting topic to teach right around Valentine’s Day.

Sometimes we see traits in nature that at first seem difficult to explain using the theory of natural selection and the concept of “survival of the fittest”. The traits don’t seem to serve any obvious purpose for helping the individual to survive. One example is the widowbird- aptly named, as you will see. The female looks normal enough, with brown, camouflaged coloring. The male widowbird, on the other hand, has an extraordinarily long tail. 

Photo by David Howard on Unsplash

How did that happen? Why would nature “select” a long, seemingly cumbersome tail like that? When I ask students what potential problems a long tail like that could cause, they have several ideas. The long tail might be heavy and make it hard for the bird to fly. A predator trying to catch the bird could grab it by the tail when it is trying to fly away. One student said that the tail looked “ugly”, but I guess that beauty is in the eye of the beholder…

One researcher who had a hunch about how natural selection could result in such extraordinarily long tail feathers decided to do a little experiment test his hypothesis. You and your students might question the ethics of this experiment, and it might seem like a bit of a mean trick, but what the researchers did was to clip tail feathers short on some birds and add them to the tails of other birds, making their tails ridiculously long. The male widowbirds were then followed to see how successful they were at winning over the females. Would you like to guess which male birds were most successful at attracting females? You've got it- the ones with the absurdly long tails! So, it was the ladies' fault- the females were selecting the tails!

This graph shows the success of the male widowbirds with and without altered tails:

Widowbird Graph

Using the graph, I ask students to answer these questions:

1. Approximately, what is the average number of active nests of widowbirds that had their tail shortened? 

2. Approximately, what is the average number of active nests for the birds that had their tails lengthened?

3. Approximately, what are the averages for the normal and control groups?

4. Do you see a correlation between tail length and the number of nests a male bird has?

5. Can you think of another explanation for this finding, aside from sexual selection, for longer tail feathers?

6. What might you conclude is a possible explanation for why the widowbird has evolved such long tail feathers?

This short BBC video clip from Planet Earth II, narrated by David Attenborogh, shows male widowbirds in action as they strut their stuff for females:

BBC Earth: Male Widowbird Display

The video gives a clue about the purpose that long tail serves: showing off for the females. Natural selection is about survival of the fittest, but fitness is really a measure of an individual's reproductive success. An individual with lots of offspring will pass on its traits to all of its babies. This is how a trait becomes more common in a population. In the case of sexual selection, there can be a snowball effect as females that prefer a certain trait, such as a longer tail, pass on this preference to female offspring, and male offspring inherit the trait. Over time, the trait can become more and more pronounced. Was there originally some benefit to having a slightly longer tail? Students often say that maybe it helped with balance in flying. There are different theories about how the whole thing got started.

The story of the long-tailed widowbird (aptly named?) can make for an entertaining Valentine's Day story to share with students.

For more information on the study of the widowbird's long tail, follow this link:

https://static.nsta.org/case_study_docs/case_studies/widowbirds.pdf

Sexual selection is not limited to birds. Here's a video that students like showing the display of a male peacock spider:

Peacock Spider Courtship Video

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Low-Prep Games for Teaching Vocabulary

 

Many science topics contain lots of new terms that students need to learn. Students can benefit from engaging in activities that reinforce this vocabulary, and games are a fun approach. I started using games to teach vocabulary in language arts class with grades three to five, and I continued playing these games with students when I began teaching middle school science.

There are two simple games I have used that require little preparation and tap into students’ creativity. One is to play variations on charades. The other is to have a volunteer draw a vocabulary word on the board as the rest of the class guesses what it is. 

After distributing and reviewing a list of new vocabulary words, I introduce students to a game. I might have the class vote on either playing charades or drawing words on the board, but sometimes I simply use my best judgment knowing the interests and strengths of students in the class. 

If the class is playing some form of charades, I ask for a volunteer to act out a word of their choice. It has been my experience that the students with the best participation are frequently ones who exhibit attention-getting behaviors that may be distracting at other times. In a game like charades, this kind of energy is just what is needed! Other “stars” of charades are students who have strengths related to the performing arts or who have a great sense of humor.

The student volunteer silently points to a word of their choice on the vocabulary list. It must be one that has not been chosen before. As the volunteer silently acts out the word, I ask the rest of the class to hold off on guessing until the volunteer is done. The class can then raise their hands, and the volunteer acting out the word calls on students until the right answer is chosen. The student who answered correctly may either take a turn or choose the next volunteer to take a turn. One variation is to allow a student to take a buddy or two along to act out a word. Students often enjoy this!

If students are drawing the vocabulary words on the board, the steps are the same. A volunteer comes to the front of the class, chooses a word, and illustrates it on the board. Then the class guesses what it is. 
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A helpful addition I have made to both games happens at the end of the game once the word is guessed. I ask the student volunteers to explain how their actions or drawings illustrate the meaning of their chosen word. Before beginning the game, I also ask students to draw or act out the meaning of the vocabulary word rather than breaking the word into smaller parts as a strategy to help their peers guess it.

When students illustrate and dramatize vocabulary words, it engages strengths and intelligences that are not always apparent with other science assignments and activities. The games tap into students' creativity and encourage them to be playful in class. The fun spills over into other science activities and can lead to greater student buy-in when tackling more challenging assignments. Allowing students to play a little helps us all get to know each other better, too.

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7 Favorite Blogposts of 2022

Happy New Year! I surveyed folks on my email list about the blogposts from 2022 that they enjoyed most. Here are seven of their favorites.

1. Caga Tió- the Catalan Christmas Pooping Log!

Readers seemed to like my first blogpost about Caga Tió, a pooping Christmas log from Catalunya (pictured above). I can't believe this tradition hasn't caught on in the U.S. yet! If you started reading this blog recently, you may be wondering what this has to do with science, and the answer is absolutely nothing! I started writing about my experiences teaching in general and have more recently focused on science. 

2. Trashion Show: Weaving Art into Lessons on Human Impact and Sustainability

The Trashion Show blogpost describes an event in which my science students created outfits- some functional and some for show- out of used items. This project was part of a larger unit on sustainability. The entire school community was invited to attend the annual show, and it was always a favorite with students and families.  

3. Cell City: Cell Organelles Project

The Cell City project was inspired by a CrashCourse video in which a eukaryotic cell is compared to a tiny city. The project helps students make connections between city functions and the activity inside cells.

4. Why Do Leaves Change Color in the Fall?

Many readers enjoyed a piece I posted that was written by my daughter as a school assignment. While we were spending time in Maine, she researched why the leaves of deciduous trees change color in the fall. I was impressed with her work and thought others could learn from it, so we decided to publish it as a blogpost.

5. Personality Quiz with Plant Cell Parts

I created a plant cell personality quiz as a fun way to ease my students back into academics after spring break last year. I was surprised by how well the assignment worked in the classroom. Students enjoyed comparing their quiz results with friends as they reviewed plant cell parts and their functions.

6. Teaching Resources from the California Academy of Sciences

I have used many online resources from the California Academy of Sciences in the classroom, and recently my family visited the museum in San Francisco. In addition to the online resources, they offer field trips, and it was a great experience for our family!

7. Snow Science: Freezing and Melting Points the Same?!

This blogpost about snow science came from a conversation with my daughter about the best snow texture for making "snow women".  It's strange but true that the melting and freezing points are the same!

I hope that you enjoyed this blogpost and looking back at some favorites from 2022. If you are interested in joining my email list, please follow this link:

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Teaching Resources from the California Academy of Sciences

The online resources offered by the California Academy of Sciences have been valuable to me as a science teacher. Recently I took a trip to San Francisco and visited the museum with my family. We really enjoyed the exhibits, and it seemed like a wonderful place to bring students on a field trip. If you live in the Bay Area or are ever visiting, it's worth a trip!

The California Academy of Sciences is a sizable science museum that houses impressive exhibits on four floors. It's topped with a living roof covered in native plants that attract and feed local pollinators.

There were many exhibits in the museum that we enjoyed. Some of the highlights were the aquarium, the planetarium show, and a living rainforest exhibit. 

The aquarium presented marine ecosystems from around the world though we especially enjoyed viewing the large tank with kelp, sea anemones, and fish found on the California coast.

As we entered the rainforest exhibit, we immediately felt the increase in temperature and humidity. The exhibit is filled with tropical plants, and you can see butterflies fluttering close by.

I have a love of rocks and minerals and was impressed by their collection, which was beautiful to view. 

Tickets to the California Academy of Sciences can be a little pricey, but as of the writing of this blogpost, San Francisco school groups get free admission, and the ticket price is reduced for other school groups.

Before ever visiting the museum itself, I used multiple online teaching resources from the California Academy of Sciences with my middle school students. I always found the  resources, which include video simulations and short films, to be of a very high quality. 

One of my favorite resources is a short video simulation depicting a kelp forest food web that teaches students how sea otters, sea urchins, kelp, and other ocean life are connected to one another and to the sun. This video could be used to help teach standards related to ecology, particularly NGSS standard MS-LS2-3: Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem. Guiding questions to ask students are provided. Here is a link to the video:

Take a Virtual Dive in a Kelp Forest

Another video I like is a simulation of photosynthesis viewed from inside a leaf. This video is a good resource for teaching NGSS standard MS-LS1-6: Construct a scientific explanation based on evidence for the role of photosynthesis in the cycling of matter and flow of energy into and out of organisms. Here's a link to the video:

Travel Deep Inside a Leaf

The California Academy of Sciences has multiple teacher resources that include lesson plans, videos, and short films available online at no cost. These resources along with information on field trips and professional development can be found here:

California Academy of Sciences Educator Resources

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