All posts by David Swart

High school science teacher
Central Dogma

Central Dogma: Nature vs Nurture

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As promised yesterday, students received the first 15 minutes of class to complete their quiz from yesterday.  After the quiz, we transitioned to the final segment of Central Dogma: traits.  We reviewed the key vocabulary concepts associated with Central Dogma and introduced the vocabulary word phenotype (the set of an organism’s observable characteristics).  We discussed how we are born with some traits (nature) while others we acquire during our lifetime (nurture).  Students learned about how scientists study the origin of traits through twin studies, and we watched a short video (below) where twin sisters raised in very different environments were studied after being separated for 35 years.  Students then worked in small groups to debate whether a list of traits provided on a worksheet are inherited via nature, nurture, or both.  The activity was so engaging we will allocated additional time tomorrow to complete the work.

Updated 2/19/16: After meeting in groups of 2-3 yesterday, students were challenged to identify other small groups of people they haven’t worked with recently and who might have different ways of thinking about how traits are inherited.  After 15 minutes of respectful scientific debate, students returned to their seats and took the remaining 30 minutes of class to respond to the following writing prompt:

Identify a trait you marked as being inherited through both nature and nurture.  Write a clear explanation supporting your position.  Include evidence! 

If someone were to disagree with you, what might they argue (counter-argument)?  Explain what evidence you have (or what evidence you might need) to defend your claim.

At the end of class, students turned in both the written response as well as the traits worksheet.

Chemistry

Weather: Charles’s Law

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We formally connected observations about the relationship between temperature and volume by introducing Charles’s Law.  The Lesson 54 PowerPoint includes the definition of Charles’s Law and introduces k, the proportionality constant.  We worked through the ChemCatalyst and watched a few minutes of a YouTube video showing a lava lamp in action:

We sketched out a before/during/after model of how a lava lamp works and the white board notes are shown below.  Students then practiced working through Charles’s Law by completing the Lesson 54 Worksheet.  For homework, students were assigned textbook questions 1 and 7 (or Notes).

 

Central Dogma

Central Dogma: Central Dogma Quiz

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As promised last Friday, students were greeted with a quiz to start the short school week.  With the two copy machines unavailable this morning, we were extremely fortunate to have the Chromebook cart available to us today.  Students accessed the quiz on Google Classroom and answered the questions on a separate sheet of paper.  Students will have an additional 15 minutes of class time tomorrow to complete the quiz.

Chemistry

Weather: Thermometers

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We jumped into the short week with a lab designed to help students understand the relationship between temperature and pressure.  The Lesson 52 Worksheet has two parts, and we conducted the lab for part 2.  We adjusted the lab procedure as follows:

  1. Bring 200 mL of water to 80 degrees Celsius, measuring temperature with a digital thermometer.
  2. Invert a 10 mL graduated cylinder and place in the heated water for 3 minutes.
  3. Quickly and carefully move the graduated cylinder from the heated water into 100 mL of room temperature water (colored blue with 2 drops of food coloring) and quickly add ice to chill the water.
  4. Record observations throughout the experiment.

Several groups had difficulty observing the intended outcome, so I conducted a quick demonstration toward the end of class and we discussed why the results occurred.  The picture below shows cold water entering the graduated cylinder and rising above the water line.IMG_0547

Students successfully reasoned that at the beginning of the experiment, the graduated cylinder contains room temperature air.  When placed in the heated water, the steam (evaporated water molecules) displace the room temperature air in the graduated cylinder, as evidenced by the bubbles observed leaving the graduated cylinder.  When the steam-filled graduated cylinder was transferred to the cold water, the decrease in temperature caused the steam to condense back into liquid form, and the volume of space occupied by the liquid water decreased.  As a result, cold water was drawn into the graduated cylinder.  The concepts of pressure and vacuum were introduced by students looking to explain further, and those concepts will be introduced in upcoming lessons.  For reference, the Lesson 52 PowerPoint is attached.  For homework, students should complete textbook questions 5-9 or take notes on the lesson.

Central Dogma, Uncategorized

Central Dogma: Strawberry DNA Lab Results

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With the short class period, we briefly reviewed the science behind the strawberry DNA extraction solution by watching a segment of the video below (beginning at about the 3:00 mark):

Students then located their DNA samples from yesterday.  Although our microcentrifuge stopped working toward the end of 3rd period, students had the opportunity to observe their samples and use laboratory-grade micropipettes to transfer a small volume of their DNA samples to glass slides.  The samples were visualized using our class digital microscope connected to the projector for all to see.  Students in 2nd and 3rd period were able to compare findings after centrifuging their samples, while students in 4th and 5th periods had more time to prepare and observe samples under the microscope.  Notes from the whiteboard, as well as a selection of microscope pictures (some potentially showing several DNA strand clusters and others showing cellular debris with some possible DNA strand clusters), are shown below:

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Second Period Observations
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Third Period Observations

 

Chemistry

Weather: Kelvin Scale

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Because of the altered class schedule yesterday and the short class period today, we skipped Lesson 52 and moved ahead to Lesson 53.  We will return to Lesson 52, which involves a lab where students make rudimentary thermometers, when we return from the 4-day holiday break on Wednesday (2/17).  Today, class began with a short SciShow video about the Kelvin Scale:

After the video, students worked through the Lesson 53 Worksheet.  The Lesson 53 PowerPoint is available for review by clicking here.  For homework, students should complete textbook questions 6, 9, 11, and 12 or take notes on the lesson.

Central Dogma

Central Dogma: Strawberry DNA Extraction Lab

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With the Curriculum Fair resulting in shortened class periods, students worked incredibly efficiently in small groups to extract DNA from strawberries.  We modified the procedure written the day before such that groups of 4 students worked together to prepare 500 mL of extraction solution using one of the 5 available liquid soap products (450 mL water + 50 mL soap + 1 tsp salt).  Each student then extracted DNA from their strawberry and saved an aliquot of the extracted DNA in an Eppendorf tube labeled with the student’s initials which will be used in class tomorrow for further study and analysis.

Central Dogma

Central Dogma: Strawberry DNA Lab Prep

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In our continued study of Central Dogma, we set our sites on extracting DNA from strawberries.  To prepare for the lab, students watched two videos explaining the DNA extraction procedure (both produced by the North Carolina Community Colleges group NCBioNetwork.org).  The first video, produced 5 years ago, provides students with a straight-forward approach to extracting DNA.  Students watched the video and wrote down as many details as they could.

After watching the video, we assembled one class procedure “crowd-sourced” from the all of the student notes. Missing from the original video are some of the details explaining how the reagents in the extraction solution actually work. NCBioNetwork recently reduced a newer version of the video, complete with dramatic effects and a really awful script. Because the content in the newer video added to student understanding, we elected to watch and then updated the class procedure after.

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At the end of the second video, students learned that human DNA varies by only 0.1% from person to person.  For the final segment of class, students watched a thought-provoking video about a scientist who has combined a variety of tools and technologies to turn DNA from hair into portraits using 3-D printing.

Chemistry

Weather: Measuring Liquids

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A huge thank you to Mr. Frank for overseeing a lab while I was away on a WABS professional development field trip to Renton Technical College.  Students worked in small groups to complete the lab outlined in the Lesson 50 Worksheet.  For future reference, students may also review the Lesson 50 PowerPoint slides that accompany the textbook reading.  For homework, students were assigned textbook questions 5-7 from the end of Lesson 50 (or notes on the reading).