Variables and controls
Do now
Students will define independent, dependent, and controlled variables using teacher notes and the PLTW online task.
- Hand in
- Labeled sample experiment with independent, dependent, and controlled variables identified, plus a written confounding-variable example.
- Where
- Turn this in at the drop folder with your district Microsoft sign-in, or hand it to Mr. Mendoza in class. Both count as submitted. Doing the activity in myPLTW does not.
You get two school days for every day you were absent, so this deadline moves with you.
If worms fed a high-sugar diet live shorter lives, how do we know it was the sugar and not the temperature, the crowding, or the batch of worms?
Students will define independent, dependent, and controlled variables using teacher notes and the PLTW online task.
- • All three variable types are correctly identified in the sample.
- • PLTW online task is submitted complete.
- In an experiment testing whether caffeine speeds up worm movement, what is the one thing the scientist changes on purpose?
- Why would testing only three worms be weaker evidence than testing three hundred?
- 1Take notes on variable types and experimental controls.
- 2Define and explain why it matters.
- 3Complete the PLTW online variables-identification activity.
- 4Label variables in a sample experiment description.
- 5Write one example of a confounding variable.
What did this day actually feel like?
Variables and controls
Independent, dependent, controlled, labeled on a sample experiment. I have half known this since middle school and never had to be precise about it.
The controlled variables are the ones I keep underestimating. They are not the boring leftovers, they are the entire reason the result means anything.
Turned in: labeled variables diagram → Lab Notebooks folder
Fiction. There is no such student. The lessons, labs and dates are the real planned course; the student, the classmates and the conversations are invented.
The same day, drawn.
Independent, dependent, controlled, labeled on a sample experiment. I have half known this since middle school and never had to be precise about it.
Fiction. There is no such student. The lessons, labs and dates are the real planned course; the student, the classmates and the conversations are invented.
🛠 Get unstuck · pick your level
🔑 Today's words · 5
Tap a word in the lesson for a plain meaning and one example. Recycled into next week's Do-Now.
Do the work · 80-minute blockfirst 5 min = hook▸
💡 Big idea: A controlled experiment changes one variable and holds the rest constant, so that any change in the result can be attributed to that single cause.
- 0-10Warm-up: identify what is wrong with a poorly designed experiment (projected example)
- 10-28Guided notes: independent, dependent, controlled variables, , confounding variables
- 28-45PLTW online variables-identification activity
- 45-60Label variables in a provided sample experiment description
- 60-72Write one confounding variable scenario and share with a partner
- 72-80Submit labeled experiment and PLTW activity confirmation
- • Every valid scientific experiment is built on the same logical structure: change one thing, measure one thing, control everything else.
- • Today you will master that structure using real and sample experiment descriptions.
- • Understanding variables is foundational for designing your own C. elegans investigation later this week.
- • The PLTW online activity will let you practice identifying variables in multiple scenarios.
- • The is deliberately changed; the is measured; controlled variables are held constant.
- • affects the reliability and generalizability of experimental results.
- • Confounding variables introduce alternative explanations and weaken causal conclusions.
Unit 2.2 Research Model: Model organisms, C. elegans, neurotransmitters/hormones, scientific literature, research poster. · Variables and controls
Day 2 of this lesson. Open this exact section in myPLTW (find it in Clever, Microsoft sign-in), then do the work below.
Do this: Complete the variables-identification online activity in myPLTW; work through all independent, dependent, and scenarios during the 28-45 minute window.
Mark the variables activity complete in myPLTW after submitting your labeled sample experiment.
Monday's task is done; today the variables task should show complete in your progress bar.
Screenshot or note of completion status for your tracker.
The official PLTW activity stays inside myPLTW. If myPLTW will not open, use F1 and E1-E3 on this page to complete today's local evidence decision, then make up the official activity when access returns. Turn this in at the drop folder with your district Microsoft sign-in, or hand it to Mr. Mendoza in class. Both count as submitted. Doing the activity in myPLTW does not.
Check things off as you work, then submit. This tells Mr. Mendoza how you're doing so he can help the class. It does not replace turning in your producible through the submission route shown below.
Use the code Mr. Mendoza gave you, not your name. Saved on this device.
Unit 2.2 Research Model: Model organisms, C. elegans, neurotransmitters/hormones, scientific literature, research poster. · Variables and controls
Complete the variables-identification online activity in myPLTW; work through all independent, dependent, and scenarios during the 28-45 minute window.
Monday's task is done; today the variables task should show complete in your progress bar.
This is how Mr. Mendoza sees the class keeping pace with PLTW. Be honest, it only helps if it is accurate.
🎯 Students will define independent, dependent, and controlled variables using teacher notes and the PLTW online task.
- Take notes on variable types and experimental controls.
- Define and explain why it matters.
- Complete the PLTW online variables-identification activity.
- Label variables in a sample experiment description.
- Write one example of a confounding variable.
Notebook check: Labeled sample experiment with independent, dependent, and controlled variables identified, plus a written confounding-variable example.
Turn this in at the drop folder with your district Microsoft sign-in, or hand it to Mr. Mendoza in class. Both count as submitted. Doing the activity in myPLTW does not. Use the checklist just below and upload by 11:29 PM for full credit. Absent with an excused absence? You get two school days for every day you were absent, so this deadline moves with you.
| Task | Who |
|---|---|
| Take notes on variable types and experimental controls. | _______ |
| Define and explain why it matters. | _______ |
| Complete the PLTW online variables-identification activity. | _______ |
| Label variables in a sample experiment description. | _______ |
| Write one example of a confounding variable. | _______ |
Working solo? Put your own name in "Who" for every row.
- All three variable types are correctly identified in the sample.
- PLTW online task is submitted complete.
- 1Do thisStudents will define independent, dependent, and controlled variables using teacher notes and the PLTW online task.
- 2Use this resource
- 3Submit thisNotebook check: Labeled sample experiment with independent, dependent, and controlled variables identified, plus a written confounding-variable example.
- 4Submit it here
- 1Open the drop folder.
- 2Sign in with your district Microsoft account, not a personal one.
- 3Upload the file, named Lastname_Firstname__Assignment Title.
- 4Your own upload panel says Uploaded with a green check: that is your receipt.
Turn this in at the drop folder with your district Microsoft sign-in, or hand it to Mr. Mendoza in class. Both count as submitted. Doing the activity in myPLTW does not. Human Anatomy & Physiology (Human Body Systems) › Unit 2.2 Research Model: Model organisms, C. elegans, neurotransmitters/hormones, scientific literature, research poster. › Notebook checkOpen the drop folder
Learn it · deck, reading, and vocabulary▸
The deck carries the prior idea forward, lets you inspect an analogy, maps the rule to biology, and ends with the same evidence decision and exit ticket used on this page.
Generated from this lesson's canonical data with a red-team citation check.
Scientists use model organisms because they share conserved biology with humans, so their use always carries an ethical cost that must be weighed against the knowledge gained.
A controlled experiment changes one variable and holds the rest constant, so that any change in the result can be attributed to that single cause.
A mechanic studies a tool whose shape allows one job but limits another.
- Which feature makes the tool work?
- What changes if that feature bends or breaks?
- Which observation shows function rather than appearance?
Structure creates possibilities and limits for function.
Living tissues adapt and interact with other systems; a metal tool does not.
- • Tool shape maps to .
- • The job maps to physiological function.
- • Damage maps to a predicted functional change.
Driving question: If worms fed a high-sugar diet live shorter lives, how do we know it was the sugar and not the temperature, the crowding, or the batch of worms?
What you already know: Scientists use model organisms because they share conserved biology with humans, so their use always carries an ethical cost that must be weighed against the knowledge gained.
New idea: A controlled experiment changes one variable and holds the rest constant, so that any change in the result can be attributed to that single cause.
Visual or model: F1. F1. A lesson illustration or teaching diagram for Variables and controls. Use it with E1-E3; it is a model or context image, not experimental or patient data. What to notice: Trace the labeled structure, movement, or system relationship that connects form to function.
- Observe or measure the relevant feature in Variables and controls.
- Organize the observation with a stable evidence ID.
- Apply this rule: Structure creates possibilities and limits for function.
- Choose the option the evidence supports and state the limit of the conclusion.
Real biomedical example: If worms fed a high-sugar diet live shorter lives, how do we know it was the sugar and not the temperature, the crowding, or the batch of worms?
What the evidence supports: E1-E3 and F1 support the daily take-home when the response meets the stated success criteria.
What it cannot prove: The package does not support claims beyond this lesson's or any real patient diagnosis.
- • : A species, such as zebrafish or mouse, studied because its biology is similar enough to ours to teach us about human development and disease.
- • C. elegans: Use the lesson context and glossary entry to explain C. elegans in your own words.
- • : A that measures the presence, amount, or activity of a target substance such as a , , or chemical in a sample.
- • literature: The body of published research articles and reports on a topic that scientists read to learn what is already known before doing new work.
- • variable: Any factor in an experiment that can change or be changed, including what you test, what you measure, and what you hold steady.
- • control: The comparison condition that isolates the effect of the variable being tested by keeping everything else the same.
- • : The number of subjects or observations in a study; larger samples give more reliable results and reduce the role of chance.
Use it now: Choose one decision option. Cite E1 and E3, then explain how the rule connects the evidence to your choice.
Go further, optional: The source links below are optional enrichment. Every fact required for today's local evidence decision appears in this lesson package.
The is deliberately changed; the is measured; controlled variables are held constant.
Limit: E1 supplies context or an observation; it does not by itself establish the explanation.
A controlled experiment changes one variable and holds the rest constant, so that any change in the result can be attributed to that single cause.
Limit: E2 is a teaching statement or comparison and must be checked against the task evidence.
All three variable types are correctly identified in the sample.
Limit: E3 supports only the result or product criterion named here; it cannot justify a broader clinical or causal claim.
PLTW-HAP-2027-04-07 · Simulated classroom evidence scenario
Your role: anatomy and physiology consultant
Decision: Your team must decide what the evidence from Variables and controls supports before submitting the notebook record named on the lesson page.
- • Select the option best supported by E1-E3.
- • Select a reasonable alternative and name the evidence it would require.
- • Delay the claim because the evidence does not distinguish the options.
Response: State one choice, cite at least two evidence IDs, explain the rule that connects them, and add one limitation. Submit it as the notebook record.
Claim ceiling: The supplied lesson evidence can support an observation, pattern, classroom mechanism, or next-step decision about Variables and controls. It cannot by itself prove causation, establish a real clinical diagnosis, or justify action outside this classroom task.
- • The solution must address the stated need in Variables and controls.
- • The decision must be supported by E1-E3.
- • The final product must make the success criteria visible.
- • Complete the work inside the 80-minute block.
- • Use only supplied or teacher-approved materials and evidence.
- • Do not trade , accessibility, or privacy for speed.
- • and evidence quality: must pass before scoring other criteria.
- • User need and effectiveness: highest scored criterion.
- • Time, cost, and ease of use: compare only after and effectiveness pass.
Test evidence: For each option, record the E1-E3 result that supports or fails each criterion. Do not assign a score without a named observation.
- Version or option tested
- Criterion met or missed
- Evidence ID and result
- Revision made
- Reason for the revision
- Need and user
- Criteria and constraints
- Chosen option and evidence
- Test result
- Revision and reason
Students often think Students often think the is "the thing you control" and mix it up with the .. The trap: Flip it and your whole experiment reads backward. The is what you change on purpose; the is what you measure in response. A quick fix: the dependent variable depends on what you did to the independent one.
Sample experiment: Testing whether a low dose of copper in the water changes how fast C. elegans worms move.
- Independent variable (what I change): the amount of copper added to the water (0, low, medium).
- Dependent variable (what I measure): the worms' movement speed (body bends per minute).
- Controlled variables (held constant): temperature, food amount, age of the worms, dish size, observation time.
Confounding variable example: if the copper dishes were also kept warmer than the control dishes, then temperature would be confounded with copper, and I could not tell whether slower movement came from the copper or the heat.
This model shows the level of evidence and organization needed to complete: A sample experiment with the independent, dependent, and controlled variables correctly identified, plus a written example of a confounding variable.
- Date and label the entry.
- Record the procedure, observation, or design decision clearly.
- End with what the evidence means and the next step.
Keep the structure. Replace the question, facts, measurements, and evidence. Then recheck units, vocabulary, and whether the conclusion goes beyond the evidence.
Also due today: Submit your labeled experiment on the class site, or hand it to Mr. Mendoza in class.
- CER:
- Claim, Evidence, Reasoning: make a claim, back it with evidence, explain your reasoning.
- SOP:
- Standard Operating Procedure, the exact steps to follow (especially in a lab).
- Tracker:
- Your PLTW progress log where you record completed evidence.
- myPLTW:
- The PLTW course site where you do the online activities. Find it in Clever with your Microsoft sign-in, right next to Schoology.
Tap the speaker to hear a term. Add two of these to your notebook glossary with a definition and an example in your own words.
Pick just 2 or 3 words from today and make them yours: write what each one means in your own words, name the context clue or evidence that helped, then give one example from what you actually did in Variables and controls. Try your own words first; the glossary is there if you get stuck. This is voluntary and counts as extra credit, so keep it short.
Saved on this device. Show Mr. Mendoza or add these to your notebook glossary to claim the extra credit.
Hand-picked readings, videos, and interactives for this lesson, all free and from authoritative open organizations (NIH, CDC, OpenStax, Khan Academy, PhET, HHMI, and more).
A fillable, Cornell-style notebook for Unit 2: Research Ready. Type your notes, cues, and summaries right in the PDF, or print it and write by hand. Each lesson page has a cue column, a notes column, and a summary box, plus dated lab-record pages you can turn in.
HBS Unit 2 notebook: Research Ready Fillable PDFCornell notes + lab recordsOpenVetted readings and references for this unit. Use them to prepare, to catch up if you were absent, or to go deeper on today's target.
This site may ask you to verify you are human. If it blocks you on a school device, ask for the class copy.
Check yourself · commit, then reveal▸
Claim ceiling for this check: The supplied lesson evidence can support an observation, pattern, classroom mechanism, or next-step decision about Variables and controls. It cannot by itself prove causation, establish a real clinical diagnosis, or justify action outside this classroom task.
A student tests whether louder music makes worms move faster. They change the volume, measure worm speed, and run the test on 4 worms in a warm room and 4 in a cold room. Name the independent variable, the dependent variable, and the confounding variable.
Write an answer and pick a confidence to unlock the key.
Fast retrieval with instant answers, not the commit-then-reveal check above. Try each from memory first: write what you remember about the earlier units, then check yourself here.
Go further and get help▸
What today's skills lead to. These are real health-science careers this course builds toward. Tap one to see, on the US Department of Labor's O*NET site, what the job actually involves, what it pays, and how fast it is growing.
Why zebrafish and mice model human development, and the Atit lab's work.
Goes with: Why zebrafish and mice: animal models and the Atit lab
Use to see how IRF6's 3D shape lets it do its job.
Goes with: AlphaFold and UniProt: structure tells function
Today is individual work you can do from home: complete the same target above, then submit your Notebook check.
Open the drop folderTurn this in at the drop folder with your district Microsoft sign-in, or hand it to Mr. Mendoza in class. Both count as submitted. Doing the activity in myPLTW does not.
Class still runs. Complete the online activity above (it's self-guided). Need the concept taught without a teacher? Use this authoritative explainer:
Khan Academy: The science of biology (experimental design)You've passed Unit 2, so the optional extra-credit track is open. Complete reserved-unit work from home, including virtual labs, for extra credit. Each item shows its correct submission route.
Open the extra-credit track- CompleteEvery required part of the artifact is present, nothing left blank.
- AccurateThe science and the data are correct and match the evidence.
- Scientific reasoningYou explain your claim with evidence and reasoning (CER), not just an answer.
- Professional communicationClear, organized, labeled, and written the way a clinician or scientist would.
- SubmittedTurned in the right way, on the class site or handed to Mr. Mendoza in class, and confirmed. Not in Schoology: that is where the report-card grade appears later.