A Sticky Situation!

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SWBAT state how plants depend on animals to move their seeds around.

Big Idea

Why do burrs stick to animals and people? Burrs might be annoying to us, but they depend on this effective method for seed dispersal.

Teacher Notes

Activity Description:

First I read a book on how animals move seeds around.  Then the children look at a burr close up to see if they can figure out why they stick to things.  They discuss their ideas with their "turn and talk" partner.  Then a child volunteer will put on a pair of sweatpants and sweatshirt and walk through the edge of the school grounds.  The class will check out the pants to see the burrs/seeds that stuck on the clothing.  They will look at a burr photo close up and discuss why the burrs/seeds stuck to the clothes.  To further explain, a short story about the invention of velcro will be read.  To elaborate on the concept, the students do a mini experiment.  They will predict which type of skin or fur will have the most burrs/seeds stick to it.  Then the very simple investigation will be conducted and the results will be discussed. 

NGSS Connection:

As an overarching goal of the NGSS the children need to understand how plants and animals depend on one another.  At the second grade level, they need to know specifically that animals can help move the seeds around.  The students will use a cross-cutting concept of understanding the shape and design of a seed relates to its function.  They will also be using different models of animal fur to design a simple investigation.  They will be comparing the models to represent objects in the natural world.







15 minutes

To engage the students, I tell the students a true story.  The children love when I tell stories about my life and it highly engages them.  Plus it does involve them, which is a double-bonus!

I was going out in the back to pick some milkweed for our monarch caterpillars.  I was already dressed for work and I walked into the back of my yard.  When I came out, my sweater was covered with hundreds of tiny burrs.  I had to pick them out one by one.  Besides being highly frustrated, I was also intrigued.  It really made me wonder about the shape and design of the burrs.  How are they shaped that makes them stick to people's clothing?  Have any of you ever had burrs stuck to yourself or perhaps to a pet, like a dog?

I elicit their answers.  Asking them a question that somehow pertains to their life puts them in the framework of the task at hand.  It also plants a seed that the shape of the seed/burr might have something to do with why it is sticking to things like animal fur and clothing.

I read the book titled How and Why Seeds Travel.  It is a fairly simple book with good, relevant information which is a springboard for a great discussion.  It talks about how animals help distribute seeds through their waste, by burying them, hitch-hiking to a place that they can grow, by wind, and by a function of themselves.  But since the science standard relates to how animals and plants help each other, we are just going to focus on how animals can help in seed dispersal.

We begin by looking at the cover of the book.  Since part of the NGSS wants the children to learn how to ask and answer their own questions, I start off by showing the children the cover of the book.  I ask the children to read the title along with me.  I invite them to look at the cover photograph.  

Okay my scientists, take a look at the cover of this book and think about the title.  Can you think of a great question that you have about this book?  

I elicit their questions.  I am looking for them to ask some questions that relate to the title and the photo, or the main concept of how or why seeds travel.  If someone does just that, I make sure to point it out.  Then I continue on by reading the book, stopping and talking about the great photos on each of the pages.  There is a great close-up photo of a burr.  It shows the many hooks that a burr actually possesses. 

Look at this close-up photo of a burr.  What do you notice about how the burr is shaped?  Why do you think that shape helps it stick to other things?  Can you think of anything else shaped like this?  Do you think other things that are shaped like this also stick to things? 

The kids are fascinated by the photo.  Who would have thought burrs could be so fascinating? We continue on to read the rest of the short book stopping and discussing the photos.

We have just read a story about how animals help move seeds around.  What did we discover about the shape of some seeds that make them stick to an animal?  I would like you to discuss your answer with your turn and talk partner.  Remember when you are discussing your ideas with a partner, you should be a good listener.  You should listen and then summarize their idea to show that you are listening and understand what they are saying. Look at your "Partner Power" sheets for reminders on how to be a good listener.

Since children in my classroom have trouble with engaging in rich scientific discourse about their ideas with peers, we use a Purposeful Conversations (Partner Power) Student Desk Sheet when they are discussing ideas.  This sheet is actually placed right on their desk tops and is adhered with thick clear tape (see reflection).

As they are discussing their answer with their turn and talk partner, I listen to their conversations.  I am specifically looking for their ideas to center around the hooked shape of a burr and how that can help it to stick onto things.  If they have trouble, I remind them about our discussion about the shape of the seed and the great photograph.




15 minutes

For the next part of the lesson, I want to have the children actually experience the stickiness of burrs for themselves.  I take the class out by the edge of the baseball field on the school grounds, where there is a tree line and a bit of weeds.  

Most schools probably have a zone like this, but if you don't, you will have to bring some burrs in and put them into a tray.  Then have the children set the clothing into a tray of burrs to simulate this experiment.

I would love for all of the children to experience how burrs and seeds stick to clothing.  However,  having all of the children walk through a "Burr zone" would not be appropriate since their parents would never forgive me, so I ask for one volunteer.  I have the volunteer put on a pair of sweatpants and a sweatshirt.  Then I have them walk through just a small section of the weedy area.  

We are going to test out what we just learned.  I am going to have a volunteer pretend to be an animal in the woods.  Since I do not have magic powers to turn anyone into an animal, we are going to have to pretend to be an animal.  So I will need an animal volunteer for this demonstration.  The volunteer is going to put on this pair of sweatpants/sweatshirt and then walk through this section of the woods.  Do I have any volunteers?

Most hands shoot up!  Can things get any better?  Somehow the children secretly think about how fun it would be to be turned into an animal, although they know it is just pretend.  I have the volunteer put on the animal garb (sweatpants and sweatshirt) to protect them against the nasty burrs.  

Note:  Unless you want to pick out burrs for the next week, use old clothing, like from a Goodwill store. :)

Let's make a quick prediction.  What do you think will happen when our animal walks through this section of the weeds?  Do you think anything will stick to them?  Do you think a lot of burrs will stick to them?  How many do you think?

Making predictions is part of the NGSS.  The children will be using their past knowledge to help guide their predictions.  In this case, they are taking the knowledge they have learned about burrs sticking to animals from the book and applying it to this new situation.

Then the volunteer "animal" takes a quick walk through what I call the "burr zone," (Walking Through the Burr zone video clip).  It is amazing how many burrs are on the sweatpants.  A few burrs were on the sweatshirt, too.







15 minutes

After this mini trip is over, we return to the classroom. To explain the concept of the stickiness of the burrs, the students watch as I narrate a power point slide presentation Why Do Seeds and Burrs Stick to Animals.  One of my friends made a "burr bunny" made entirely from burrs (here's a photo of it).  It is so adorable and helps get across the idea of how sticky burrs are.  I show the burr bunny to the children to help in our discussion.

Then I read the interesting passage of how velcro was invented-- The History of Velcro Information Sheet.  

Isn't it wonderful that a scientist named Mestral,  asked questions?  Because of his questioning mind, now we have velcro.  How many of you know something that has velcro on it?  What about shoes? Clothing? Tents?  Let's see how many things we can come up with.

I write down their ideas.  Here is a list of the Ways We Use Velcro we came up with.  I'm sure there are many more, but they got the idea.  

Bringing up all of these examples helps them relate their new experience and learning with what they already know.  It helps kids make the connection, which will in turn help them not only understand, but remember.

Burrs are actually seed pods.  Inside of the burr pod is little seeds.  

I show them a burdock photo and the seeds that came from inside of it.

The stickiness of the burrs cause them to stick to animals.  Then the animals move the burrs with the seeds inside to another location without even knowing it.  If the burr is moved to a favorable spot on the ground, then the seeds will grow into a plant.


10 minutes

I would like the children to make some predictions of what type of animal skin would attract the most seeds.  Making predictions is one of the goals of the NGSS.  

I put burrs in three different tubs.  I try to make sure each of the containers have an even amount.  

I would like you to be scientists today.  Take a look at the different types of "animal skin/fur" that I have on my table.  The one covered with fur is like the squirrel from the book, the felt represents deer and the snake skin represents himself.....the snake.

I hold up the snake skin, fur and felt covered cans.  Then I ask the children to make predictions of what type of fur or skin would stick the most to the burrs.  I have them raise their hands for which skin type they think it would be.

We roll one different can in each bin to check their predictions.  We take a look at our results.  

Which type of skin attracted the most burrs?  How would this help the seed move the seed around?

We discuss the results of our simple investigation.  The snake skin did not attract any burrs, so we discuss why that would be so.  The felt attracted the most burrs (see photo), and the fur came in a close second. We discuss why each type of skin attracts or did not attract the burrs.  We talk about plausible reasons why this is so.

Think about the structure of the burrs.  Think about the fuzzy fur and felt. Why do you think that the felt and fur attracted the most burrs?  Why did the snake skin not attract any?   How is the burr shaped that makes it stick to the furry materials the most?  

I want them to come up with the idea that the burrs have hook-like things at the end of them that would allow them to stick to animals, not to a smooth surface like the skin of a snake.  If they are not able to make this connection, you could pull up one of the photos from the Powerpoint to help clarify--sticky, sticky seedsalien burrs, or 3 burrs photo.


5 minutes

The main idea for the children to get out of this lesson was that animals help plants move their seeds around, even though it is not intentional.  The fact that burrs, which are seed pods, are moved around unknowingly be an animal is very important.  

How do you think the structure of the burr then would help the animal move seeds around?  Why is that helpful to the plant?  Do you thinks helps them to survive year after year?

I pass out the Sticky Situation student assessment.  

I would like you to think back on the activities that we did today.  Think about the whole cycle of how a plant seed is carried by an animal, moved to a different location and then develops into a plant.  I would like you to draw a sketch that shows that process on this paper.  I would also like you to label each part or thing that you have drawn, just like scientists do.

I am assessing the students' understanding of the main concept--that animals help move seeds around.  Their drawings should show each of these parts:

  • a plant with a seed 
  • the seed sticking to an animal
  • the animal moving the seed to a new location
  • the seed becoming a new plant

Here is a student sample which shows each of the four main parts.  Here is a sample of a child's paper in which he drew great sticky burrs, but did not make a clear connection of how animals help with seed dispersal.

Any early finishers can turn the paper over and draw (or write) other ways that animals can help move seeds around.  Possible answers would be through by burying them or in their waste (brace yourself for some interesting pictures).