Example

Dress Rehearsal

Your textbook offers up an explanation to account for the rising of water in the stems of plants. Water tends to move up from the root to the stem, but why? Many theories have been developed, and your textbook traces how those theories evolved into the current belief. Let’s follow along.

First, it was believed that water enters the root cells at a greater rate than they leave the cell. So, pressure in those root cells increase, forcing the water up the stem. This is known as root pressure. Mmmm…. that sounds right.

Second, it was believed that narrow passages inside the plant’s stem cause the water to rise by capillary action. This action is a result of adhesion (the attraction between water and plant stem walls) and cohesion (like molecules sticking together). Think of them holding hands. Sweet. That could be right, too.

Third, it was believed that, since water evaporates, lowering pressure in the cells at the top of the plant (due to evaporation), allows atmospheric pressures to push water upward. Yep, definitely the answer.

Wait! There’s more….Fourth, it was believed that cohesion keeps the water column intact. Between the pull of water due to evaporation and the root pressure, the water moves upward. That complicates things.

Which of these four theories do scientists today believe explain water movement in plants? Scientists reasoned that root pressure and evaporation can each account for SOME movement, but, acting alone, neither can get the job done. Capillary action is impossibly s-l-o-w. Simple experiments helped scientists determine the solution to the problem. Today, scientists believe that ALL conditions added together account for the rise of water in plant stems. Theory number four is our lucky winner! It is now known as the cohesion-adhesion-tension theory.
It all adds up.

Source:

Morrison, Earl, et al. Science Plus: Technology and Society. Texas: Holt, Rinehart and Winston, 1993.

That’s a Wrap

When you teach this standard, be sure to give your students some examples of faulty reasoning or questionable evidence. By tracing the structure of an argument, students can better understand how researchers arrive at solutions to scientific problems. Students need to analyze the evidence and reasoning in order to evaluate how convincing the solution or claim is. Well, at least until the next better theory comes along.

Drill

Using the following passage, complete the sentences below in order to show the reasoning and evidence used in supporting the author’s claim.

How Your Voice Works 

Although you may not realize it, the production of voice involves a complex set of tasks requiring the coordination of many muscles and sensory nerves. Simply producing a syllable such as \a\ involves the use of rib and stomach muscles in coordination with the diaphragm to control airflow combined with muscles in the neck, voice box, upper throat, and mouth to modulate that air into sound. Sensory feedback from nerves in the throat and voice box, as well as sensory cues from the nerves of hearing also are involved in the processing of that sound to form the proper syllable. All of this complex coordination is performed instantly, subconsciously, and continuously during speech.

As the system is complex, there are many things that can go wrong with it. Anything from scarring of the vocal cords to lung problems can produce hoarseness. Below is a conceptual framework for how the human voice is created.

The human voice can be looked at as if it were a set of tunes played from a complex musical instrument. The basic setup for the production of voice involves three components. The first is the power generator. This consists of the lungs, which produce a column of air with a certain force. The force or pressure produced depends on the capacity of the lungs to store air prior to exhalation, and the strength of the muscles used to exhale that air. 

The second component in voice production is a vibrating structure. This consists of the vocal cords. To produce voice, the vocal cords are brought together. As the column of air generated in the lungs rushes through the windpipe, the vocal cords vibrate to produce a tone. Different tones can be produced by varying the tension on the vocal cords. 

Once a tone is created, it needs to be modified to produce a proper voice. This involves the third component, the resonance chamber. The resonance chamber consists of the upper part of the throat, the nose, and the mouth. Modifications of the configuration of these areas alter the voice to produce speech. 

Source:
“How Your Voice Works.” NYU Voice Center. 2010. NYU Medical Center/School of Medicine. 21 April 2012. http://www.med.nyu.edu/voicecenter/patient/speech/howvoice.html. Web.

Complete the following sentence for these three components: the lungs, the vocal cords, and the throat, nose and mouth

Sentence:

This component, _________________, also known as the_______________, produce(s)_________ , resulting in _____________________.

ANSWERS:

1. This component, the lungs, also known as the power generator, produces a column of air, resulting in pressure.

2. This component, the vocal cords, also known as the vibrating structure, produces a vibration, resulting in the production of tone.

3. These components, the upper part of the throat, the nose, and the mouth, also known as the resonance chamber, produce changes in configuration, resulting in speech.