Next Generation Science Standards

What do you do when NGSS gets the science wrong?

I was a scientist for about 20 years, but now work for a science education company.  I was shocked to find that NGSS contains quite few misconceptions and that led me here to ask what do teachers do when the standards get the science wrong? Probably the two most important biochemical processes on earth are photosynthesis and cell respiration, yet NGSS get these flat-out, 100% wrong. These are the statements in NGSS that are incorrect:

Cell Respiration:

NGSS DCI PS3.D "The chemical reaction of these molecules with oxygen releases energy." [by the end of grade 8]: "Both the burning of fuel and cellular digestion in plants and animals involve chemical reactions with oxygen that release stored energy."

NGSS DCI LS1.C. [by the end of grade 8]: " In most animals and plants, oxygen reacts with carbon-containing molecules (sugars) to provide energy and produce carbon dioxide."

NGSS DCI LS2.B. [by the end of grade 8]: "for example, when molecules from food react with oxygen captured from the environment, the carbon dioxide and water thus produced"

Photosynthesis:

NGSS DCI PS3. D. "By the end of grade 8. The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen. "

How do you, as a teacher, tackle this problem – teach to the standard, or try to explain that the standard is incorrect and teach the science?

Thanks!

Tom

Tom Robertson
Tom Robertson
20 Activity Points

Hi, Tom.  

First, I strongly suggest that you post this in the NSTA biology listserv.  You'll get a lot more (and better) responses. Second, can you please explain (a) which parts of these statements are incorrect and (b) how you would suggest they should be stated differently?

Thanks,

Matt

Matt Bobrowsky
Matthew Bobrowsky
4280 Activity Points

Tom,

It's great to have pushback from teachers who want to challenge students and that you are passionate about getting the science right. I’m wholeheartedly on the same team, but I think what we’ve bumped into here is not about the science being “wrong,” but rather grade level appropriate descriptions of the science. Here are a couple of points of clarification:

  1. The standards represent what all students should know and be able to do by a particular grade level across all science domains. There are many things that we think that kids should know or are capable of knowing, but to ensure that students are prepared for their lives beyond high school, there are trade-offs about the level of detail that it is possible to delve into with each core idea. In this particular case, the details of the Krebs cycle and the electron transport chain (though as a bio guy, I personally find them fascinating and would love for all students to understand them the way I do) don’t rise to this level. They don’t need to be ignored and certainly shouldn’t be misrepresented, but ensuring that all students learn the details of these cycles is not expected.

  2. Though I can certainly see how one might interpret the text this way, the standards do not intend to claim that oxygen and sugars react directly with each other. This phrase is used in this case to represent the fact that the standards are intentionally not going to the detailed level that you discussed. So, at this point, we really are talking about the summary equations for both photosynthesis and respiration and not the details of the process. I’m sure that you already do this as is indicated by your use of Framework language in your post, but when I bump into issues like this, I check out Appendix E: Disciplinary Core Idea Progressions that lays out how each core idea builds over time in the NGSS using the key ideas from the Framework, NSTA’s DCI Matrix that links together the elements of the standards and/or the Framework itself by clicking on the links embedded in the standards to verify what is really intended.

For example, for PS3.D which is mentioned twice above, here’s the full text from this section of the Framework:

By the end of grade 8. The chemical reaction by which plants produce complex food molecules (sugars) requires an energy input (i.e., from sunlight) to occur. In this reaction, carbon dioxide and water combine to form carbon-based organic molecules and release oxygen. (Boundary: Further details of the photosynthesis process are not taught at this grade level.)

Both the burning of fuel and cellular digestion in plants and animals involve chemical reactions with oxygen that release stored energy. In these processes, complex molecules containing carbon react with oxygen to produce carbon dioxide and other materials.

Machines can be made more efficient, that is, require less fuel input to perform a given task, by reducing friction between their moving parts and through aerodynamic design. Friction increases energy transfer to the surrounding environment by heating the affected materials.

In NSTA’s matrix of the elements used in the standards for PS3.D, you can see the following progression:

As you can see across both of these sources, the focus of the core idea for PS3.D is on energy within these reactions and not the details of the reaction. In fact, you can also see a clear boundary provided by the Framework document that the details of photosynthesis are not what students are held accountable for at this grade level.

A similar process for LS1.C shows that the focus for photosynthesis from the 8th grade endpoint from the Framework is on the fact that “Plants, algae (including phytoplankton), and many microorganisms use the energy from light to make sugars (food) from carbon dioxide from the atmosphere and water through the process of photosynthesis, which also releases oxygen. These sugars can be used immediately or stored for growth or later use.” And for respiration, the focus is on the idea that, “…food moves through a series of chemical reactions in which it is broken down and rearranged to form new molecule

Matt Krehbiel
Matthew Krehbiel
215 Activity Points

Hi Matt,

Apologies for the tardy reply!

1. Can you tell me how to send to the NSTA biology listserv please?

2. NGSS state that oxygen and sugars react directly with each other to produce carbon dioxide and water.  This is incorrect.  Sugars are split by glycolysis and move into the mitochondria and enter the krebs cycle.  This produces electron carriers (and CO2 as a side product) that deliver electrons to the electron transport chain that then move down the chain to create a hydrogen ion (proton) gradient that drives ATP synthase.  Oxygen accepts the electrons, which forms water (with hydrogen ions).

3. Photosynthesis: NGSS states that in the presence of light enery carbon dioxide and water react with each other to produce sugars and oxygen.  Light energy is used to excite electrons that move down a transport chain to create a hydrogen ion gradient to drive ATP synthase (similar to cellular respiration). Electrons are provided to the chain by the splitting of water.  The electrons are used to make NADPH.  Carbon dioxide is fixed in the Calvin cycle that uses the ATP and NADPH to create sugars.

If we expect our students to progress to be scientists, I think the standards should get these processes correct.

Thanks,

Tom

 

 

Tom Robertson
Tom Robertson
20 Activity Points

I believe that the intent was that you share your post with the Biology forum in the Learning Center.

Also, you are referring to the middle school standards in your original post. The intent of the NGSS is to help students develop conceptual understandings. Even at the high school level, assessment of the standards on energy for life does not include the steps of the biochemical pathways involved. I do touch on these even though they are not assessed, especially when students show some interest - and explain that there is so much more that they will learn about the details of the pathways involved should they choose to pursue those interests at the university level. 

 

 

Cris DeWolf
Cris DeWolf
11695 Activity Points

I was waiting to see your post in the Life Science forum to see how these teachers responded and didn't see this post. 

The detailed pathways for both cellular respiration and photosynthesis are not spelled out specifically in the statements you provided. That is where the curricula fills in. These are standards, that is guidelines for what students should understand. While the information you provided in your second post is not in the standards, textbooks and instructional materials will include more content information. 

As middle school standards, I do not believe that students will be taught incorrect information but grade-level appropriate information. From my experience, high school instructors will go into the pathways, knowing that the content is not spelled out in the standards, but the expectation of knowing cellular respiration and photosynthesis. When they teach, the details will be provided. Middle School instructors will go in the depth appropriate for their students. 

Bev DeVore-Wedding
Bev Bev DeVore-Wedding
3928 Activity Points

Tom,

On the Forums & Community page, there is a menu on the left with all of the forums; select the Life Science Forum and post your question there. 

Although, the answers provided above may be adequate. The standards are not detailed with the biochemical pathways specifications, but instead what the students should understand overall. At the HS level, most biology teachers I know do go over the details of all of the pathways, even though not all assess them for those details. NGSS doesn't expect students to know the details at all at the middle school (8th grade) level. 

For the NGSS listservs go to this address: http://www.nsta.org/membership/listserver.aspx

Bev

Bev DeVore-Wedding
Bev Bev DeVore-Wedding
3928 Activity Points

Tom,

 I have also noticed that the oversimplification of various  multistep processes results in statements that are technically incorrect. I can usually figure out what was intended. However, I always teach the actual hard core truth at a grade appropriate level.

I once reviewed potential science textbooks for the state in which I live as prospects for purchase by hundreds of public schools. There were lots of competing publishers that sent hundreds of books. Wow, talk about mistakes! There was an entire booklet devoted to the study of brown kelp that was decribed as a "plant"- at the time it was classified as a protist. One that really stands out was the picture of a bowling ball and ping pong ball both dropping to earth in a chapter on gravity. The photo clearly showed the heavier ball dropping more quickly than the lighter ball. I had to pull out my old college physics book to find the calculation of movement and determining speed of fall to convince the teachers I worked with that this was incorrect. I also showed them a few vacation pix of the time I visited Pisa, Italy.

PS

I was also a PhD research scientist for about 20 years! 

 

Susan Lenz
Susan Lenz
640 Activity Points

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