Banana Biology

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SWBAT observe and document the decomposition of bananas.

Big Idea

The Rain Forest is a lush and diverse biome, but the soils are not rich in nutrients because of the high rate of decomposition. This lesson shows the decomposition process and allows for discussions and learning to further from its results.

Setting the Stage

5 minutes

This lesson takes four days to complete.  The first and last day will take the longest days to complete the lesson. 

The design of this lesson is rather complex and addresses many issues. First, the lesson will lay background knowledge for students demonstrating the interdependent relationship within ecosystems. It will lead to the role that decomposition plays in the soil systems of temperate and tropical rain forests.

It will also provide an opportunity for students to clearly see the Cross Cutting Concept of Cause and Effect.  Dialogue will follow that will involve the children making conclusive statements that utilize the variables of the water and yeast combinations to draw conclusions from their observations. 

Another reason, I believe it is important to bring this lesson in to the teaching focuses on the role that decomposition plays in the life of a biome.  The soils of biomes are very important to the life that is sustained in those areas.  The biodiversity of a biome is as dependent upon the soils and their functions within the systems, as the plants and animals them selves.  

Understanding completely the process and scientific concepts of decomposition may be higher level thinking and understanding for Second Grade students.  However, the visualization and demonstration they witness throughout the course of this lesson is powerful and provides strong background knowledge that will come into play in many later lessons in their educational careers. One connection it lays ground work for is understanding how fossils are created.  In Washington State this is a state standard. 

2-3 LS3D Fossils are often similar to parts of plants or animals that live today.

2-3 LS3E Some fossils are very different from plants and animals that live today.  


5 minutes

I hold up a banana and ask the children to look closely at it. The children do not even question why I am holding the banana.  They know that this fruit grows in tropical jungles and know that it will lead us to an investigation dealing with the jungles. 

I ask them to think about when their parents buy bananas at the grocery store.  Then I ask, "How long does that banana last sitting on your kitchen counter at home if no one eats it?" 

Many variations of answers are shared,,,,,one day, two days, three days.  The estimations of time vary and are wide.  Most children at this age do not have a strong sense of estimation in time. Developmentally, it is not expected that Second Grade children can easily deal with elapsed time.  But I still want to see what their concept of the idea leads to.  That is the reason for the question.

After all discussion and ideas are shared, I ask the children to look at the screen.  The Banana Biology power point is ready to go and screen one has the title.  I anticipate that there will be excitement running through the class. The children are well aware of the word biology and know that it leads to something fun. 

Slide two poses a new scientific question about the banana...How long do you think a banana can last out of it’s skin? This question is different than the first because it has eliminated the skin.  

Day One

45 minutes

I explain to the children that this lesson will be similar to the apple lesson, but have a few different twists to it. However, it will be a great idea if they remember back to our previous learning.  Because we just never know when that learning will help us (SP3).

I remind the children that scientists do this all time. They are constantly using what they already know about previous situations to help them in making new learning come to life. This is called making an inference. 

When I move the slide show to Slide three, the children see the materials we will be using in this investigation.  I do not read the list to them. I allow them to read it themselves. I want them to read the list and come to the word, yeast, and make their own connections. 

I move through the next several slides showing the children what the investigation will look like and the expectations of each bag's ingredients.  

Before we begin to set up any of the materials, I pass out the student student documentation.  (I only pass out the first page.  The second page will used at the end of the entire investigation. I like to put all my documents together in one power point for ease of retrieving the pages when I need them in the next time I teach the lesson). 

I tell the children that before we can begin, they will need to document their hypotheses of what they believe will happen to the bananas.  A short conversation ensues describing what a hypotheses is....I explain it like this..

"Your hypotheses is what you believe or think will happen.  You use any prior knowledge you already have to help you to make an educated guess of what you believe will happen in this investigation." 

I allow the children about three to five minutes to formulate and document their ideas.  Most of them are very confident about their predictions. 

After this, I ask the team leaders to come and get a tray with all the materials for their investigation. The children know that the team leader will dispense the materials and lead the investigation.  (Team leaders are determined by the children and they rotate and take charge of this themselves.  Each day a new team leader is in charge, which allows for all the children the opportunity to be in charge). 

When all the bags have been created and set up, the children make their first observations.  I tell them they are allowed to decide how to document their findings on their own.  I am beginning to gradually release the ownership of direction and allowing the children to determine how they will complete the work. They have practiced all year with my guidance, it is now time to see if they are able to do it on their own.

When this stage is complete, we tidy up our work and place the trays in the windowsill and wait to make the next days observation. (Slide nine). 

Day Two

20 minutes

I instruct the days team leaders to gather their team trays and bring them to the tables. The children get out their documenting pages and write all their observations in the box labeled Day Two. 

I am circulating throughout the classroom, observing the children working. There is not much need for me to interject or make suggestions. The children know what to do and are quite anxious to do the work. 

Day Three

20 minutes

On Day Three, we had to wrap our investigation up one day sooner than we had expected.  The next day, our science time was going to be filled with an unexpected school assembly.  After class discussion, the students and I determine that we have enough data to draw conclusions.  

I direct the children to make their final observations of the bananas.  I encourage them to try and find any different observations than they have noticed on the previous two days. They begin to document what their observations.  I allow students to choose their method of documenting. Some students choose to draw, while others document with words.

After all the documenting is done, I ask the children to look at all the observations.  I want them to notice the differences that have occurred.   

I lead a class discussion with the observations. I ask these questions:

  • Do you notice any days that look as though the results are similar?
  • Do you notice any days that look significantly different? 
  • Which bag would say has the most dramatic changes? (Bag D is the answer)
  • Think back to the first day, we did not build each bag the same way.  In each bag we put different combinations of ingredients.  What was the one material that was the same in all four bags? (the banana slices)
  • The other two ingredients were simple ingredients. Do you believe they were the reason for the changes in the bananas? Why do you believe so? 
  • What evidence do you have that leads you to believe this? 

I am trying to lead the children to the yeast and it's effect on the banana (SP6).  The yeast is a fungus that when activated, instantly begins to speed the process of the decomposition of the banana.  I ask the children to look at the screen and Slide ten.  This slide explains the directions for the conclusions to our work. 


Our Conclusions

15 minutes

Second Grade students need multiple opportunities to practice drawing conclusions from their science work.  It is much easier for them to do this verbally.  Combining it with writing can be much more challenging. Teachers need to be actively involved in helping students to construct reasonable explanations to their observations (SP8).

I explain to the children the concept of accurate and inaccurate and how this relates to their hypotheses.  I remind them what their hypothesis is: their best guess or prediction of what would happen.  I remind them that they had written a prediction on their documenting page and they are able to use it to guide their conclusion writing now.    

I ask the children to reread their first prediction on the Banana Biology documenting page and explain that this prediction will guide them to write their conclusion.  I ask them if their prediction was accurate or inaccurate?  When they are able to tell me if they were correct or not correct, I have them write their first sentence. 

I model for them a possible way to structure their writing on the Smart Board with the Power Point on Slide eleven.  When the children have worked through writing their statement, I explain that a scientist needs to back up their work with evidence.  

Finding the evidence is difficult. I have to prompt the children to really pull out for them what evidence they have that proves or disproves their hypotheses. (Mostly, what made the bananas decompose....the yeast).