A Mini Lesson on Specialized Root Systems

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Objective

Students will be able to identify how roots function to help a plant survive.

Big Idea

Students dig up a dandelion to identify the type of root it is and how it functions. Can we tell why dandelions are so invasive by looking at the root structure?

Root System Introduction

10 minutes

We had studied bulbs, but to help students understand root systems better, I assigned students the task of bringing in a dandelion, with the root in tact. I gave them instructions to dig down, they could use a dandelion digging tool or a screwdriver to help them uproot the plant. I instructed them to place it in a container or plastic bag and bring it to school. You could assign them to bring any common invasive weed with a tap root system. 

My students sat in front of the SB in order to take notes as they watched 2 different short videos that helped them understand root systems better. The first video is short, but very informative and students easily took notes. I stopped the video so they could take notes easily. I emphasized the differences between tap and fibrous roots. The second video gave us more information in a different way. This video allowed me to stop again and discuss the growing radish seed. Students could easily see the root hairs and they were able to grasp how roots grow because of the time lapse part of the video.

I had shown them some photos of root systems of grasses from photos I took while recently visiting the special exhibit at the National Botanical Gardens in Washington, DC. I cannot publish those photos because of copyright. However, to get kids to see just how large fibrous root systems can be in common field grasses and grain, Wikipedia does a good job. I wanted them to really see how huge and complicated roots can be.

We discussed the power that root systems have of holding the plant fast in the ground. I roved around and asked them to show me their notes on root systems to be sure they had both fibrous and tap roots in their science journals. It was time to examine our plant samples!

 

Examining the Roots

30 minutes

Students gathered magnifying glasses as I passed out their Root Data Sheet. This sheet allowed them to enter data and compare it with their notes. They needed to decide what kind of root a dandelion was based on evidence from their videos.  They spent time drawing and looking at the dandelion, discovering root hairs. Suddenly, their metric measurement skills were practiced as  they had to decide what unit to use to measure. They entered this data on their sheets. 

As I roved the classroom and listened to group conversations about the dandelion, I needed to clarify some misconceptions. Some confused roots with bulbs, while others had heard the word "fibrous" and confusing fibrous with a food product. They don't understand where fiber comes from in our food.  We had discussed how carrots are a tap root and are food. But, when they saw the fibrous grass roots, they immediately thought that grass roots were what they added to cereal for fiber or have heard that raw vegetables are a fiber food. 

I brought up a free image of the two root systems we learned about on the SB to clarify the shapes of the root systems for reference because I could see that their sketches from the videos were not enough for them to feel confident in making the decisions because of the misconceptions. 

As we finished up, I asked them to turn in their data sheets so I could assess their understanding and see if they could choose what kind of root the dandelion is. 

Roots Are in What? Homework

10 minutes

 I emailed the article from Today I Found Out, "Why Rootbeer is Called That." to expose them to how roots are engineered into food products. Rootbeer is an upcoming celebration treat when we finish MAPS testing! Everyone gets a glass of rootbeer and if you have mastered your goals, you get a scoop of ice cream for every area; up to three scoops. So, I thought this article fit appropriately and they probably would never experience rootbeer in the same way!

Their assignment was to read the article and then combine all that they learned to write a short paragraph to tell me what they never knew before about roots and root systems. They typed them on Google Docs and emailed me the articles. I could comment and send them back for immediate feedback. I really like Google Docs for this purpose!