Close Read Your Evidence Statements: Cells and Cell Organelles (MS-LS1-2)

Using evidence statements to help student develop skills and understanding.

When I first started teaching, cells were one of the topics in my curriculum.  My old standards read something like, “Students will know the parts of the cell, including cell wall, cell membrane, mitochondria, chloroplast, lysosomes, Golgi apparatus, ribosomes, nucleus, blah blah blah blah blah.” And so that’s how I taught it.


I expected students to memorize the parts of the cell. We made Jello “models” (they weren’t NGSS models!) of plant and animal cells. They made up little analogies to relate the function of each cell part to a school or city. (Confession: I do still like that activity!). And then they took a test on it, and I asked them to label the blank cell and match each part to its function.




Also, NOT NGSS. Not in the slightest!


The NGSS is all about understanding the BIG IDEAS.  And I didn’t get that when I first started teaching.  Even when I started using the NGSS, I still was missing BIG parts – like the use of phenomena and storylines, driving discovery through the Science and Engineering Practices, and how to incorporate the Crosscutting Concepts.  I was super fixated on the content, AND in reality, I didn’t even have that right!


So what do I do now?


Designing From The Evidence Statement

Well first, when I’m starting any unit, I always print out the Evidence Statements for each of the standards in my unit bundle. (Check out this blog post on breaking down those Evidence Statements, if you need some help here!) Then, I take a look at the BIG ideas – the Performance Expectation and the Disciplinary Core Ideas.


The goal of MS-LS1-1 is for students to “Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.”  And in the clarification statement, it explains that the emphasis is on the functioning of the cell as a whole system. Then, it identifies several key parts that students should know: nucleus, chloroplasts, mitochondria, cell membrane, and cell wall. You’ll notice this is a MUCH smaller list than what I started off with!  And the focus isn’t on just memorizing the function of each, but rather, understanding how the function relates to the functioning of the entire cell.


Without breaking down the Evidence Statement, I wouldn’t necessarily have realized all of the time I could save by simplifying my instruction on cell organelles.  Saving time by cutting content gives me MORE time for student exploration. My students are actually able to discover the different types of cells by examining them themselves. They build models and conduct investigations to understand how parts like the cell wall and cell membrane work. And then they tie it to our larger unit phenomenon – in this case, its flu epidemics caused by body invaders!  This type of learning takes time, and that time is gained by cutting content.


(Because really, do they need to memorize all of the cell parts? Or could they pull it up on Google as fast as their LTE network allows? With the NGSS, our goal is for students to UNDERSTAND – not memorize.  So if a student can understand how several KEY parts of the cell actually WORK to keep your body healthy, that’s a whole lot more beneficial than memorizing the function of random parts without seeing the big picture.)


Now, let me confess – I do introduce my students to the other components.  They are exposed to lysosomes and ribosomes and the Golgi apparatus. I don’t expect them to memorize these parts, and I don’t actually assess them on these parts.  But they walk away knowing – there ARE other parts in the cell, and these other parts DO have jobs.


When it comes to assessment time, my focus returns to those parts of the cell referenced in the Evidence Statement, and as I design my assessment, I keep a close eye on the Evidence Statement breakdown.  I notice that in the first line, it reads: “To make sense of a phenomenon, students develop a model in which they identify the parts of cells relevant for the given phenomenon.” Two things stick out here “to make sense of a phenomenon” and “relevant for the given phenomenon.”  


What does that actually MEAN?

Understanding the evidence statement

Understanding The Evidence Statement

It means that students should only be including the parts of the cell RELEVANT to the phenomenon. So basically, choose your phenomenon carefully.  For my assessment, I utilize two scenarios – or phenomena – to assess students on their understanding. This allows me to address all the organelles I want to assess their understanding of.  In my Cells Assessment, I focus on plant cells.  Later in my Body Invaders unit, the focus shifts to “animal” or human cells as they investigate cells and their relation to body systems (like the circulatory and immune systems).  While my Cells Assessment fully addresses the Performance Expectation MS-LS1-1 and MS-LS1-2, I reiterate some elements of those Performance Expectations in my final unit assessment that ties together cells to body systems (MS-LS1-1, MS-LS1-2, and MS-LS1-3).


The NGSS is all about big ideas and tying those big ideas together to develop strong student understanding.  In order to do that – and to engage students in the kind of discovery-centered, three-dimensional science instruction – we are trimming our content.  We’re sacrificing memorizing facts and figures for developing skills and understanding.


(Side Note: That’s the reason resources and curriculum we’ve used in the past doesn’t automatically align.  Aside from missing the Three Dimensions of the NGSS, oftentimes the CONTENT doesn’t actually match the standard either! I had a unit on cells back in the day, but as you can see, it wasn’t an NGSS unit on cells.  If you’re looking for more tips on avoiding this “NGSS-washing,” check out the Teaching Science In 3D podcast episode “How You Know It’s NOT NGSS.”