Performance Expectation 

Each standard contains a performance expectation that details how students can perform to show what they’ve learned. It describes what students can do, as opposed to what they understand.

In HS-LS1-2, the first thing we need to consider is that this standard asks students to develop models to illustrate the hierarchical organization of living systems. The clarification statement refine this PE to explain that we’re only look at the level of detail of organ systems, without going into specific cellular mechanisms. For example, how does the salt intake from the digestive system impact circulatory system function. 

The assessment boundary also helps us limit the level of detail to avoiding molecular level characteristics like the ionic nature of substances or valence electrons. This performance expectation is intended to look at systems more holistically to provide students a platform to explain how they interact with each other at a more macroscopic scale.

The Three-Dimensions

1. The SEP for this performance expectation is developing and using models, and more specifically, students are asked to develop a model to illustrate relationships between living systems.
2. There is one element to the DCI in this PE. Students must understand that multicellular organisms have hierarchical organization in their systems. For example, the kidneys are a part of the excretory system that interacts with elements in the circulatory system to extract waste materials.
3. Finally, the Cross-Cutting Concept in this PE is Systems and System Models. Students must make connections in their models that systems can show interactions and flows within the system and between different systems. 

The Goals

By the end of a lesson or unit covering this PE, students should achieve the following milestones: 

1. 1. Understand that living systems are hierarchical, meaning there are cells, tissues, organs and organ systems that make them up, and these systems interact with each other to help the function of the organism. 
   2. Visually modeling how the systems are hierarchical and how they interact with each other, in terms of inputs, outputs, and flows. 
   3. Finally, student need to use their model to explain HOW and WHY the interactions of these systems helps the overall function of the organism.

There are many different ways to provide students with phenomena for them to better understand and demonstrate an understanding of on HS-LS1-2:

1. Students can examine the interactions between the excretory system (pancreas) and Circulatory System in the interaction they have with blood glucose control. If your want to take the opportunity to chat about examples of problematic functioning in type 1 or type 2 diabetes. 
2. Students can also investigate the interplay between salt intake in the digestive system, and blood pressure in the circulatory system.
3. A final phenomena that students can use to examine models of interacting systems in the body would be to look at immune response and fever. How are the circulatory system and immune system work together to make things a little too toasty for virus and bacteria to be comfortable? 

Student Activity

Once students understand the concepts in this standard, they can develop models Show how and why different systems interact to help living things function. For example, we can look at chromatophores in giant squid.

Chromatophores are pigmented cells that are controlled by the octopus’ nervous system. They are located in the skin and can be contracted and expanded to change the octopus’ color and texture. This allows the octopus to blend in with its environment to avoid predators or to communicate with other octopuses.

How can we model the ways the cephalopods’ nervous system interacts with their chromatophores to decide on the color and texture of their skin? 

The key here is that students need to understand the concept that the visual system and integumentary system are work together through smaller parts, ideally through separate instructional phenomena. Once they have that foundation, they should be able to use the given information to explain how inputs and outputs of the visual system, and the integumentary system (and/or nervous system!) are interacting to help the function and survival of a giant squid.

Assessment

There are different ways to assess students on MS-PS1-1:

1. Ask them to model a molecule you’ve already discussed in class. A good formative assessment might be: “Draw a model of a water molecule that has two hydrogens and one oxygen” or “Draw a model of a carbon dioxide molecule that has two carbons or one carbon and two oxygens.”
2. Explain how atoms can form diamonds, graphite, or carbon-only structures. Crystalline structures or structures where a single atom or molecule is repeated would be an excellent example. An assessment question might be: Draw a dry malt model of those repeating subunits.
3. If you want students to make sense of phenomena, we’ll ask them to model something they have never seen before. You can briefly define some of the characteristics or properties of the phenomenon, but we won’t tell them what the model looks like. Students have to develop a model that they have never seen before to explain how simple molecules or extended structures are just different combinations of atoms.