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STEM pattern

STEM pattern

Scientific Phenomena

September Phenomenon: Fairy Rings

September Puzzling Phenomenon:  Fairy Ring

Developed by Sarah Lamphier, September 2016

Concept

Ecosystem interactions and/or symbiosis

Introduction & Phenomenon

I had been stuck inside for a solid two days due to record-breaking rains and local flooding.  When the rain stopped and I finally ventured out, I observed something perplexing in two separate yards in my neighborhood:

SP Picture 1

SP Picture 2

What could possibly cause mushrooms to grow in this neatly formed circle?  One of the
 neighbors was out walking her dog, and I asked her about the strange ring of mushrooms in her yard—she said the lawn was clear the day before, that they popped up overnight, and she did not “plant” anything there on purpose.  In fact, she suspected that the ring had been left behind by fairies who had danced in a circle in her yard during the night.  I nearly laughed out loud, but she insisted and explained that she had a family heirloom painting of this phenomenon hanging in her house:

Do you buy her fairy explanation?  If not, what do you think caused these rings of mushrooms?

SP Picture 3 

Explanation of Science Involved

Fairy rings are formed by certain varieties of fungus that flourish in wet, rainy conditions.  The body of the fungus (called the mycelium) lives underground, and it grows outward in a circle in search of more and more nutrients.  The mushrooms spring up from the edge of the mycelium, especially in wet weather, and therefore form a ring.  The organism itself is actually a full circle, which is not at all a curious shape for an organism—but it appears as a ring because the only visible part is the perimeter that shoots up mushrooms above ground. 

SP Picture 4

Additionally, fairy rings that form under the canopy of a tree and appear to neatly circle a tree trunk are typically evidence of a symbiotic relationship between mycorrhizal fungi that partner with tree roots (mutualism).  The tree roots gain fixed nitrogen from the mycelium of the fungi and the fungi depend on the tree roots for structure and space for growth. 

Other, less dramatic and more common instances of this same organismal interaction with the environment are circles of differently colored grass in a lawn—deep green at first, then dry and brown.  As the fungus grows, it breaks down the dead organic material beneath the grass, which at first acts like a fertilizer and enables the grass to grow more richly than the rest of the lawn. But then the fungi uses up all of the organic material for its own growth, and in its absence, the grass at the perimeter of the mycelium dies for lack of nutrients. 

Further ideas for classroom use

-Could be used to begin a unit on ecosystem interactions.  After establishing context and showing the photos (fairy part obviously optional!), students could draw explanatory models of what they think is causing the growth of mushrooms in a ring.  If used as a full-blown modeling exercise like we did with the broken wine glass during the summer, some gotta-haves for the later model iterations could include: 

            1.  What exists beneath the grass to support fungi growth in this location? 

            2.  What role does the rainy weather play, if any?

            3.  How are the mushrooms interacting with the tree (in the 2nd photo)?

            4.  (After showing non-mushroom circle photos, perhaps later in the unit), why does the grass first turn a rich green, followed by brown?

-Later in a unit on ecosystems, you could use just the tree photo and grass ring photos as a way to introduce symbiosis.  After providing some basic information about what’s going on beneath the surface, possibly even showing or drawing a picture of the mycelium and tree roots, some key questions to elicit student thinking and help with sensemaking could include:

            1.  How are the mushrooms interacting with the tree? 

            2.  What might the mushrooms “get” from the tree root system?

            3.  What might the tree roots “get” from the fungus?

            4.  Which organisms benefit from this interaction? 

            5.  How does this interaction compare to _______? (Bring in another symbiotic interaction, but one that is parasitism or commensalism, such as ticks and deer or barnacles and whales.)   

Download this resource as a Word Document here.

November Phenomenon: A Curious Case of Puppies

November Puzzling Phenomenon: 

Developed by Nicole Gerardo, November 2016

Title:  A Curious Case of Puppies

Concept:  Heredity/Genetics (dominant/recessive alleles, monohybrid cross, di-hybrid cross)

Introduction and Phenomenon: 

Some friends of ours just welcomed a brand new litter of Labrador puppies similar to the ones seen in photo below.  Who doesn’t love going to see some brand new adorable puppies?   Of course we had to go for a visit!  I knew from past experience being educated by a sister in love with dogs of all breeds, that Labradors came in three colors: black, chocolate, and yellow.  I did find it a bit curious to see that some of the puppies nestled in with the mother were of a different color than she was.  Most were black labs like mom, but there were some that were yellow as well.  So what would a logical explanation be for some puppies that look nothing like mom? 

Dog Picture 1

Well dad must have been a yellow lab, right?    

Come to find out, I was quite wrong.  I later learned that the daddy dog was also a black lab!

Dog Picture 2Dog Picture 3

This had me a bit stumped and quite curious to uncover more about what lies hidden in the genes of Labrador dogs.

Explanation of the science involved:

It turns out that the genes behind the coat color of Labrador retrievers provide quite a few opportunities to explore different levels of concepts important to the topic of genetics. 

At the most basic level, surprising litters of Labrador puppies can be used to help students understand the difference between dominant and recessive genes.  Certain Labrador coat colors can be “masked” in some generations, but can reappear in later generations.  Students may be able to generalize that yellow and also chocolate coat colors have a recessive nature after examining multiple examples of litters.  But how can there be two colors that would be recessive?!  The explanation becomes quite interesting when you look at the actual genotypes of the labs in question.

The next level would be to use Labrador coat color to help students understand the possibilities of offspring in a monohybrid cross.  In the case of Labradors, the black and chocolate colors are determined by dominant and recessive alleles at one gene locus.  The black coat color (B) is dominant to chocolate (b). Therefore, a puppy will only be chocolate if each parent contributes a chocolate allele (b) giving the puppy a genotype of “bb”. If one or both parents contribute a black allele (B), the puppy will be black in color, with a genotype of “BB” or “Bb.”  It will be a carrier of the chocolate allele for future generations if the pup has the heterozygous genotype “Bb”.

Here is just one example of a monohybrid cross showing the relationship between black and chocolate lab coat colors. 

Dog Picture 4

Now you might still be wondering where the yellow coat color comes into play.  The explanation behind the third coat color allows for an even deeper look into the complex nature of genetics.  The gene that determines if a Labrador puppy will be yellow or not is actually at a different location (gene locus) than the gene that influences the black and chocolate coat colors.  This second gene locus can carry a dominant allele (Y) or a recessive allele (y).  In order to have a yellow coat, a Labrador must inherit two recessive copies of the yellow allele to have the homozygous genotype “yy”.  This genotype inactivates the black or brown genes, and the resulting puppy has a yellow coat.   However, if only one or no recessive alleles are contributed, as in the genotypes “Yy” or “YY,” the deactivation does not occur.  The resulting puppy will remain either black or chocolate, as determined by the alleles of the puppy’s black/chocolate gene.  Considering the genotypes of black, chocolate, and yellow labs allows for the study of the resulting offspring in dihybrid crosses. 

Here is an example below of a dihybrid cross that shows how two black Labradors can actually produce offspring of all three coat colors.

Dog Picture 5 

 Further Ideas for Classroom Use:

A:  This puzzling phenomenon could be used to begin a unit about Heredity/Genetics.  By showing a picture of a puppy litter with only one parent dog present, students could be asked to develop hypotheses for why the puppies look the way they do. 

Potential Questions after the first picture

            -  What do you observe about the dogs in the picture? 

            -  What is a possible explanation for your observations?

After sharing their ideas, students can then be given the additional information that both parents are black labs. 

Potential Questions after new parent information

- Has this new information changed your initial thinking?  Why or why not?

- What new explanation can account for both parent dogs and the puppies you 

   observe in the pictures?

- Can you think of a similar situation from your own life or from someone close to you?  

   What was the explanation in this situation?

Along with these last questions, student groups could be asked to create explanatory models of how the different looking puppies came about.  By the end of the unit, these are some gotta-haves that students should be able to include in the final examples of their models:

            1.  What can be observed about the dogs?  Describe their relationships. 

                (Students should be able to identify generations of organisms and phenotypes.)

            2.  What information is hidden within the dogs that affects their appearance? 

(Students should be able to predict possible genotypes of organisms and understand that this information lies in the genes of the organism’s chromosomes.)

            3.  What interactions occur with the parent information in order to produce the puppies

                 that are observed? 

                 (Students should be able to describe the interactions between dominant and

                  recessive alleles and predict the outcomes of these interactions.)

B:  This phenomenon could also be used later on in a unit on Heredity/Genetics to help provide options for differentiation of student work with Punnett Squares.  If students need more practice with monohybrid crosses, they could work on making predictions about the offspring of only chocolate and black Labrador parents with varying genotypes.  Students could also work up to the challenge of being able to figure out an unknown parent genotype by trying to puzzle out the method that we know as a test cross.     

If students have mastered the use of basic Punnett Squares, they could be given the additional challenge of making predictions of dihybrid crosses between black, chocolate, or yellow lab parents with varying genotypes.  In this case, there are enough options of genotypes that students could even make up their own crosses and see what offspring would be predicted. 

Later in the unit, students could also be given a real-life challenge as if they were in the role of a dog breeder.  Here is an example scenario:

“You get to choose what color coat you believe best suits Labrador retrievers!  Once you have chosen which coat color you prefer, please explain how over the course of at least 3 generations you could maximize the number of puppies born with your favorite coat color.”

Download this month's phenonemon as a Word Document here

October Phenomenon: Which is faster?

Title:  Which is faster? Straight vs. Curved Downward Paths
Concept:  Energy transfers, (potentially forces and motion)

Introduction and Phenomenon:

On a recent family outing to the Kalamazoo Valley Museum, my son and I were playing at the science level where we found this puzzling phenomenon.  Two disks are placed on two separate paths, one is on a straight slope, the other’s path is curving up and down to the end.  The straight slope is about 6 inches shorter than the slope with lots of little hills.  

Watch Youtube video here: https://www.youtube.com/watch?v=Tpkq_GYIxRk  

The disks are identical and have the same starting height.   I suggest you stop the video at 20 seconds into the video, before the disks are let go. I’ve always been told that the shortest path between two points is a straight line.  However, this phenomenon seemed to contradict this rule of thumb.  But why?

Explanation of the science involved:

From the Kalamazoo Valley Museum exhibit…

“The experiment shows how energy can be converted from one form to another.  The disk on the wavy track converts potential energy into kinetic energy at a faster rate, allowing it to reach the end first.

Before the disks are released, they have potential energy.  They may be sitting still, but they have the potential to do something, such as fall.  Once they begin rolling down the track, their potential energy is converted into kinetic energy.  Kinetic energy is the energy of motion.  

On the straight track, the conversion of potential energy to kinetic energy occurs at a constant rate.  

On the wavy track, potential energy is converted more quickly into kinetic energy on the first steep drop.  However, as the disk travels up the first hump, some of the kinetic energy is changed back to potential energy, slowing the disk down.  When it travels downward again, the potential energy is converted back into kinetic energy.

Both disks start the race with the same amount of potential energy. The disk on the wavy track accelerates quickly, changing its potential energy into kinetic energy faster, allowing it to win the race even though its descent is interrupted by the humps, and its path is 6 inches longer than the straight track.

A roller coaster converts potential energy to kinetic energy as it dips, twists, rolls, and zips through the ride.  Did you know that after the first hill, no motors, cables, or chains are needed to move the car along the track? (However, many roller coasters do use chains to boost the ride.)”

Further ideas for classroom use:

Could be used at the start of a unit on energy.  By pausing at 20 seconds into the video, this can be an opportunity to elicit student ideas and language around this phenomenon.

When pausing at 20 seconds into the video (potential questions):

-What do you think is going to happen? Why?

-Who agrees with _______ about their prediction? Why?  

-What other ideas are out there about what is going to happen?  

-Who thinks it will end in a tie? Why? Why not?

-Have you ever seen this before? Where?  How does that relate? Does that impact your prediction?

 

After watching the entire video (potential questions)…

-What happened? What did you notice?

-Compare what happened with your initial ideas.  How would you revise your initial ideas?  

-If the tracks were much much longer, would the straight line path eventually catch up?

-Have you ever seen a situation like this before?  Where? How is it similar or different to this situation?

 

Engineering connections:

-How do the results of this situation apply to designing roads vs. roller coasters?

-How is this situation similar or different from a curving road vs. a straight road on a flat surface?

-What are switchbacks?  Why are they used?

 

Modeling Connection:

-Students could also draw explanatory models before the video of what they think is going to happen.  They could then revise their initial model of the situation after watching the rest of the video. They could also revise their model of this situation later in a unit on energy transfers or forces and motion.    

Download this resource as a Word Document here.

December Phenomenon: Mysterious M&Ms

December Puzzling Phenomenon: Mysterious M&Ms

Developed by Sarah Lamphier, December 2016

Concept

Properties/interactions of matter, specifically solubility and possibly density

 

Introduction & Phenomenon

I was snacking on some M&Ms and accidentally dropped a few into my cup of water.  Before I could fish them out and get a fresh cup of water, my mom called and I talked to her on the phone for about 25 minutes.  When I returned to my ruined water, I was perplexed by what I saw.  Instead of describing it, I think it would be more fun to show you what I found in my cup. 

View the following video, or do a demo of what you see in the video:  https://www.youtube.com/watch?v=z664hPVeBVA

Show with mute on, to avoid hearing the explanation; best to play from about 25 seconds to 1:30.  The video is less dramatic than watching it happen in real life, but it is quicker because of the time lapse. 

What you see essentially happens in two steps.  First, the color on the outside of the M&Ms gradually comes off the candies and flows into the water directly under and around them, mainly on the bottom of the cup.  (Some mesmerizing videos of this phase can be found here:  https://www.youtube.com/watch?v=031Xr1zqbJ0 )  Then if you wait long enough, you’ll see the white M (which remains, and doesn’t come off with the color) detach from the candy and float up to the surface of the water.

Explanation of Science Involved

The dye on the candy coating of M&Ms is soluble in water.  So as the M&Ms sit in the water, the polar water molecules gradually dissolve the polar dye molecules.  Here’s a helpful animation of this in action:  https://www.youtube.com/watch?v=umJmRaG6v80 (watch 1:26 to 1:50).  This dye is also more dense than water, so it stays on the bottom of the cup, rather than mixing freely around the cup or floating to the top.  In contrast, the M is actually made of an edible paper that is not water soluble, so it does not dissolve in water.  But once all the dye (which essentially acts like a glue for the M to stick to the candy) has dissolved, the M detaches from the candy and floats up to the surface of the water.  It floats because the edible paper is less dense than the water. 

Further Ideas for Classroom Use

This puzzling phenomenon could be used during a physical science unit on matter and interactions (or properties of matter).  Some physical properties are highly accessible for students, such as color, state, texture and odor, and therefore provide a nice place to begin an interactions of matter unit.  But others, such as solubility, polarity and density, are less obvious and require some manipulations or careful measurements to “see.”  Watching the M&M dye dissolve in water, and then the white M float to the top could be a rich jumping off point for this more difficult tier of physical properties before moving onto chemical properties and changes.  After showing the video or allowing pairs or groups to place and carefully observe M&Ms in water themselves, some discussion questions might include:

  1. How are the dye molecules interacting with the water molecules as the color moves off the candy and into the water? (Drawing could be a useful way to elicit thinking on this one.)
  2. Why does the white M initially stay on the candies unlike the bright colors?  When it eventually comes off, why does is float to the top instead of sinking to the bottom?
  3. How might the substance that makes up the dye be different from the substance that makes up the M?  How might these two substances be similar to or different from water?

A robust class discussion could elicit student thinking about what might explain the phenomena that we observed, and then the teacher can move toward sense-making by introducing the terms solubility, polarity and density as properties of matter that precisely name what has already been described during the discussion. 

To then push students further to apply these new concepts, the procedure could be repeated in different liquids, such as isopropyl alcohol (also polar, but less so than water) and oil (non-polar) to observe how the rate of dissolving changes.  A POE (predict-observe-explain) framework would be a nice way to approach this, pushing students to explain what they observe using one or more of the new physical properties.  To explore density, try it with hot water; you’ll observe a quicker dissolving process (which can be explained by the added thermal energy), and then when the M detaches, watch it fall to the bottom of the cup rather than float to the top (because the water is now less dense at a higher temperature, so the static density of the M is now greater than the water surrounding it).

Download this month's phenonemon as a Word Document here. 

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