Homeostasis and the Characteristics of Life Teaching Box

Start the school year with a bang: this dissection helps students practice their lab and safety skills, make detailed observations (qualitative and quantitative), practice group work, and begin to think about the characteristics of life.

Resource Link

Resource Attribution
Woodside High School

Resource Type
Classroom Activity

Teaching Notes

• Introduce observations vs. inferences and qualitative vs. quantitative observations before you begin the lab.
• Because this is one of our first labs of the year, I spend a lot of time discussing safety and expectations and group roles before we start, as well as respect for the materials being used, including the frog.
• If students are uncomfortable with dissections, I first ask whether they are OK with being in the room and recording observations while their group members touch the frogs and do the cutting. If that doesn’t work for them, they can go to another room with computer access to do a virtual frog dissection instead. They can return to work with their groups to create the list of characteristics of life.
• Pre-lab discussion questions (Think-Pair-Share)
  • What do you know about frogs?
  • What can you measure about your frog? What can you infer about your frog based on those measurements?
  • What other senses can you use to describe your frog? What can you infer about your frog based on observations using these senses?
• There are diagrams provided in the links above, but I try not to distribute them until after they have attempted their own drawings. Otherwise, I would end up with a bunch of traced images of the diagrams that look nothing like the frog that they are actually dissecting.
• To assess their work, I often have student groups circle what they think is their strongest observation-inference link (you could also have them jot down why they chose it). I give detailed feedback based on their choices.
• The Characteristics of Life lists created by the student groups are a good place to start a class discussion the next day and practice consensus-building. Here are some possible discussion questions, with sentence starters:
  • Compare and contrast each group’s list of the characteristics of life.
    • “I see that many groups think that all living things…”
    • “One group thinks that all living things… while another group thinks…”
  • If we were to pick our top five from all these ideas and come up with a class list, which would you recommend? Why?
    • “I think all living things… because…”
    • “I disagree because…”
• It’s important to explain at this point that it is OK to disagree; even scientists still disagree on what is considered living and nonliving.

Review the characteristics of life: give students cards relating to the characteristics of life and allow them to group themselves together or look for their “matches.”

Resource Link

Resource Attribution
Woodside High School

Resource Type
Classroom Activity

Teaching Notes

• This is intended to be an interactive method of direct instruction, but it could also be used as a formative assessment to gauge students’ prior knowledge.
• Print these onto cardstock or plain paper and glue them onto individual index cards.
• One option is NOT to hand out the first eight cards to students, have them match up with at least one other person, then post the eight characteristics around the room and have students walk to the characteristic they think they best fit with.
• Discussion questions:
  • Share why you think you and your partner are a good match.
  • Share why you think you and your partner may not be a good match.
  • Who thinks they need more information before they make their final decision?

Using a comparison chart and claim-evidence-reasoning (CER) writing and argumentation, students work in groups to consider the characteristics of life and decide whether viruses are living or not.

Resource Link 1

Resource Attribution
Woodside High School
Scientific Argumentation in Biology: 30 Classroom Activities (NSTA)

Resource Type
Classroom Activity

Teaching Notes

• Here are some video clips that could be used as part of this activity:
  • Clip 1 (Advanced and longer)
  • Clip 2 (Simple and shorter)
• The chart used in the NSTA publication is not available online, and the charts that are available don’t offer the same rich evidence and argument support. I suggest buying a copy of the book.
• Students may need some modeling from the teacher before beginning the task.
• Because I use this at the beginning of the school year, I often pair this activity with a gallery walk so that students can look at each other’s work and practice giving effective and appropriate feedback.
• Again, this activity can demonstrate that there are still disagreements among scientists, and that there is no right or wrong answer. What is considered true in science is the claim backed up by the best and strongest evidence.

Students observe examples of negative feedback when oxygen levels decrease in their bodies. While this lab focuses on the interactions between the circulatory and respiratory systems, students do not need much background knowledge about each system in order to understand how they relate to homeostasis and feedback loops.

Resource Link

Resource Attribution
Woodside High School
Drs. Ingrid Waldron, Lori Spindler, and Jennifer Doherty
Department of Biology, University of Pennsylvania

Resource Type
Classroom Activity

Teaching Notes

• If on a block schedule, Days 1 and 2 can be combined into a 90-minute period.
• There are multiple data-collection options, especially for heart rate. If your school has access to heart rate monitors, the easiest to use are those that are placed on the finger rather than across the chest. If students are collecting heart rate by checking for a pulse, it’s best to take a reading before and after the lab rather than attempting to monitor heart rate throughout the experiment.
• Each student will need a new plastic garbage bag, since the condensation from the students’ breath makes it awkward to share.
• There are Web-based alternatives to this activity, including Keep an Athlete Running (free) and Gizmo (paid).
• If breathing into a bag is not ideal for your students (due to health conditions or asthma, or because you’re worried about plastic waste), you can collect the same data with a different condition, like running up a flight of stairs if those are available at your school.

Students describe an analogy for homeostasis from their everyday lives using their choice of drawing, flowchart, or diagram.

Resource Link

Resource Attribution
Woodside High School

Resource Type
Assessment

Teaching Notes

• If time is tight, this could be shortened to a kick-off question or Do Now-type entry task for a more informal assessment.
• It may be helpful to revisit the thermostat example that was presented earlier in the unit.
• Sometimes, the “set point” may not be very clear, which is a good place to start discussing the limitations of their examples and how they may not translate to the importance of homeostasis to living things.
• Sometimes I help students get started by showing some images (i.e. mixing colors of paint, a hole at the top of a sink that prevents water overflow, a person that is being offered food when they’re already full); they’re included at the bottom of the student handout.

Science and Engineering Practices

Developing and Using Models

• Develop a model based on evidence to illustrate the relationships between systems or components of a system. (HS-LS1-2)

Planning and Carrying Out Investigations

• Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly. (HS-LS1-3)

Constructing Explanations and Designing Solutions

• Construct an explanation based on valid and reliable evidence obtained from a variety of sources (including students’ own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future. (HS-LS1-1)

Disciplinary Core Ideas

LS1.A Structure and Function

• Systems of specialized cells within organisms help them perform the essential functions of life. (HS-LS1-1)
• Multicellular organisms have a hierarchical structural organization, in which any one system is made up of numerous parts and is itself a component of the next level. (HS-LS1-2)
• Feedback mechanisms maintain a living system’s internal conditions within certain limits and mediate behaviors, allowing it to remain alive and functional even as external conditions change within some range. Feedback mechanisms can encourage (through positive feedback) or discourage (negative feedback) what is going on inside the living system. (HS-LS1-3)

Crosscutting Concepts

Systems and System Models

• Models (e.g., physical, mathematical, computer models) can be used to simulate systems and interactions—including energy, matter, and information flows—within and between systems at different scales. (HS-LS1-2)

Structure and Function

• Investigating or designing new systems or structures requires a detailed examination of the properties of different materials, the structures of different components, and connections of components to reveal its function and/or solve a problem. (HS-LS1-1)

Stability and Change

• Feedback (negative or positive) can stabilize or destabilize a system. (HS-LS1-3)