🐆 Week 1: The Cheetah-Gazelle Arms Race 🌿
Grade 8 Science | Rosche | Kairos Academies
MS-LS4-4 Natural Selection + Cycle 2 Forces | 100 Points Total | ~75 Minutes
Working on Your Chromebook - Important Tips
- Your work saves automatically in Google Forms every time you click outside a text box. You can close this page and come back anytime—just scroll back to where you left off.
- Complete sections in order (Hook → Station 1 → Station 2 → Station 3 → Exit) — each one builds on the last.
- Keep a calculator handy for force and acceleration calculations (F=ma).
- Take breaks if needed — the brain learns better with short breaks. Try 20 minutes work → 3 minute break.
- If a form won't load: (1) Refresh the page, (2) Check your internet connection, (3) Try a different browser, (4) Email Rosche if still stuck.
- Before submitting each form: Scroll up and review your answers. You cannot change them after clicking Submit!
🦎 NGSS Standards Covered This Week
MS-LS4-4 (This Week's Focus)
What it means: Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individuals' probability of surviving and reproducing in a specific environment.
In student language: I can explain why some animals survive better than others based on their traits.
Spiral Standards from Cycle 2 (You already learned these!)
- MS-PS2-1: Apply Newton's Third Law to design a solution involving two colliding objects
- MS-PS2-2: Plan an investigation showing change in motion depends on forces and mass (F=ma)
How These Connect (3-Dimensional Learning)
| Dimension | What You'll Practice |
|---|---|
| SEP Constructing Explanations | Use F=ma calculations to explain survival advantages |
| DCI LS4.B Natural Selection | Explain how trait variation affects survival probability |
| CCC Cause and Effect | Connect mass differences to acceleration differences to survival |
🎯 Learning Targets
By the end of this week, you will be able to:
Success Criteria – How You'll Know You've Got It
Target 1: Apply Newton's Third Law to predator-prey collisions
Self-check: Can I explain why forces are equal even when animals have different sizes?
Target 2: Use F=ma to explain why smaller prey can escape larger predators
Self-check: Can I calculate acceleration when given force and mass?
Target 3: Describe how trait variation leads to differential survival
Self-check: Can I explain why some traits become more common over generations?
Target 4: Connect physics principles to natural selection mechanisms
Self-check: Can I explain how F=ma creates selection pressure in predator-prey systems?
🐆 The Phenomenon: The Cheetah-Gazelle Mystery
Consider this puzzle:
- Cheetahs can run 70 mph – the fastest land animal!
- Gazelles can only reach about 60 mph
- Cheetahs have been hunting gazelles for millions of years
If cheetahs are faster, why haven't gazelles gone extinct?
🤔 Driving Question: What factors besides top speed determine survival in a predator-prey chase?
📊 Why This Matters:
The physics of predator-prey interactions drives natural selection. Understanding how forces, mass, and acceleration determine survival helps explain why certain traits become more common in populations over time. This is evolution in action!
What You Already Know from Cycle 2 (You'll Need This!)
| Cycle 2 Concept | How You'll Use It Today |
|---|---|
| Newton's Third Law | Forces between predator and prey are always equal and opposite |
| F = ma (Newton's Second Law) | Same force on smaller mass = greater acceleration = escape advantage |
| a = F/m (rearranged) | Calculate how fast an animal accelerates given force and mass |
| Action-Reaction Force Pairs | Identify forces when animals push off ground or collide |
Cognate Strategy: Many science words look similar in English and Spanish — use your Spanish to learn science!
| Term | Spanish | Definition |
|---|---|---|
| natural selection | selección natural | ✓ Process where organisms with better traits survive / Proceso donde organismos con mejores rasgos sobreviven |
| trait | — | A characteristic like speed or size / Una característica como velocidad o tamaño |
| variation | variación | ✓ Differences in traits within a population / Diferencias en rasgos dentro de una población |
| adaptation | adaptación | ✓ Trait that helps survival in an environment / Rasgo que ayuda a sobrevivir en un ambiente |
| population | población | ✓ Group of same species in one area / Grupo de la misma especie en un área |
| predator | — | depredador |
| survival | — | supervivencia |
🎯 Hook – The Cheetah-Gazelle Mystery
12 Points | ~10 Minutes
🔥 The Challenge
What You'll Do (~10 minutes)
- Recall what you know about Newton's Third Law (2 min)
- Make predictions about WHY gazelles survive (3 min)
- Connect to your Cycle 2 physics knowledge (3 min)
- Submit your predictions before moving on (2 min)
Think About This:
- When a cheetah and gazelle collide, what does Newton's Third Law tell us about the forces?
- If forces are equal, why might a smaller animal have an advantage?
- What factors besides top speed might help prey escape?
- How does F=ma relate to survival?
Cycle 2 Connection Question:
If a 50 kg cheetah and a 25 kg gazelle experience the same force during a collision (Newton's Third Law), which animal will accelerate more? Why?
Complete the Form Below:
Your responses save automatically. When you finish all questions, click Submit.
Before Moving to Station 1, Check:
- ☐ I stated Newton's Third Law in my own words
- ☐ I made predictions about why gazelles survive
- ☐ I identified physics-based advantages for prey
- ☐ I clicked "Submit" on the form
⚡ Station 1 – Predator-Prey Force Analysis
20 Points | ~18 Minutes | INTERLEAVED RETRIEVAL
⚡ Your Mission: Use Physics to Explain Survival
Apply Newton's Third Law and F=ma to understand why smaller prey can escape larger predators. You'll calculate actual forces and accelerations!
🐆 Interactive: Predator-Prey Physics Simulator (Click to expand)
Experiment first! Adjust the masses and watch how F=ma determines who wins the chase. Why can smaller prey escape larger predators?
Scenario Data (Use for Calculations)
| Cheetah mass: | 50 kg |
| Gazelle mass: | 25 kg |
| Gazelle acceleration during collision: | 20 m/s² |
You will need a calculator!
The Key Physics Insight
| Step | Calculation | Result |
|---|---|---|
| 1. Force on gazelle | F = m × a = 25 kg × 20 m/s² | 500 N |
| 2. Force on cheetah | Newton's 3rd Law: Equal! | 500 N |
| 3. Cheetah acceleration | a = F/m = 500 N / 50 kg | 10 m/s² |
| 4. Gazelle acceleration | a = F/m = 500 N / 25 kg | 20 m/s² |
Conclusion: Same force, but the gazelle accelerates TWICE as fast! This is the physics of escape.
CRITICAL CONCEPT - Newton's Third Law in Action
|
WRONG Thinking: "The cheetah exerts more force because it's bigger" |
CORRECT Thinking: "Forces are ALWAYS equal. Mass determines acceleration." |
How You'll Be Scored (20 points total):
| Criteria | Points |
|---|---|
| Identify action-reaction force pairs correctly | 4 |
| Apply N3L to collision (forces are equal) | 4 |
| Calculate force using F=ma with work shown | 6 |
| Compare accelerations and connect to survival | 6 |
Complete the Form Below:
Show your work on all calculations! Include units.
Before Moving to Station 2, Check:
- ☐ I can identify action-reaction force pairs
- ☐ I calculated F = 500 N using F = ma
- ☐ I understand forces are equal but accelerations differ
- ☐ I can explain why smaller mass = survival advantage
- ☐ I clicked "Submit" on the form
🧬 Station 2 – Trait Variation Simulation
21 Points | ~15 Minutes | INTERLEAVED RETRIEVAL
🧬 Your Mission: Model Natural Selection in Action
Use a bean simulation to see how trait variation leads to different survival rates. Watch natural selection happen before your eyes!
Simulation Rules
- Scatter beans (different colors) on a background
- Hunt (grab beans) for 10 seconds – you're the predator!
- Count survivors by color
- Survivors "reproduce" – add more of that color
- Repeat for 3+ generations
🏠 COMPLETING THIS AT HOME? (No beans needed)
Use the PhET Natural Selection simulation instead:
🖥️ Click to Load PhET: Natural Selection Simulation (saves memory until opened)
How to use: Add mutations (fur color, teeth, ears), add selection pressures (wolves, food shortage), and watch the bunny population evolve over generations. Track trait frequencies!
Record your data: Run 3 generations and note which traits became more/less common.
🧬 Interactive: Population Genetics Simulator (Click to expand - saves memory until opened)
How to use: Create organisms with trait variation, set an environment (grass, sand, snow, or dark), then run generations to see how selection pressure changes trait frequencies. Watch evolution happen!
The Key Biology Insight
| Concept | What Happens |
|---|---|
| Variation | Different colored beans = different traits in population |
| Selection Pressure | You (predator) catching beans based on visibility |
| Differential Survival | Camouflaged beans survive more often |
| Population Change | Trait frequency shifts over generations |
Key Point: The POPULATION changes over time. Individual beans don't change color!
Connect to Physics: Selection Pressure is Like Force!
| Physics | Biology |
|---|---|
| Force changes motion | Selection pressure changes trait frequency |
| No force = no acceleration | No selection = no population change |
| Stronger force = faster change | Stronger selection = faster evolution |
Complete the Form Below:
Record your data from the simulation and analyze the patterns.
Before Moving to Station 3, Check:
- ☐ I recorded data for 3+ generations
- ☐ I identified which trait became more/less common
- ☐ I can explain what the selection pressure was
- ☐ I connected selection pressure to force (both cause change)
- ☐ I clicked "Submit" on the form
🔧 Station 3 – Design a Survivor
25 Points | ~20 Minutes | ENGINEERING DESIGN
🛠️ Your Challenge: Design an Organism Optimized for Survival
Design an organism that can survive predation pressure. You MUST use physics principles (F=ma, Newton's Laws) to justify every design choice!
Design Constraints:
- Habitat: Open grassland
- Main predator: Wolves (can run 35 mph, hunt in packs)
- You must choose: A specific mass for your organism (in kg)
- You must calculate: The force needed to escape (F = ma)
- Required: Physics justification for EVERY choice!
Design Decisions to Make
| Decision | Physics Trade-off |
|---|---|
| Mass | Smaller = faster acceleration, but less momentum |
| Leg strength | More force = more acceleration, but costs energy |
| Body shape | Streamlined = less air resistance, but less surface for muscles |
| Speed vs. Endurance | Sprint muscles vs. stamina muscles = different survival strategies |
Example of a GOOD Justification:
"My organism has a mass of 20 kg because smaller mass means higher acceleration when the same force is applied (a = F/m). If a wolf applies 400 N of force during contact, my organism would accelerate at 20 m/s² (400/20), while a heavier 40 kg animal would only accelerate at 10 m/s². This higher acceleration helps escape after initial contact. The trade-off is less momentum, so my organism relies on agility rather than pushing through."
Notice: Specific numbers, F=ma calculation, and explains the trade-off!
How You'll Be Scored (25 points total):
| Criteria | Points |
|---|---|
| Identify survival challenges in the environment | 5 |
| Choose and justify mass using F=ma reasoning | 5 |
| Calculate escape force correctly with work shown | 5 |
| Analyze design trade-offs using physics | 5 |
| Connect physics to biology in final paragraph | 5 |
Complete the Form Below:
Describe your design and justify every choice with physics!
Before Moving to Exit Ticket, Check:
- ☐ I chose a specific mass and explained why using F=ma
- ☐ I calculated the escape force needed (F = m × 15 m/s²)
- ☐ I explained what trade-offs I made
- ☐ I connected physics principles to biological survival
- ☐ I clicked "Submit" on the form
🎓 Exit Ticket – Forces & Evolution
22 Points | ~15 Minutes
🎯 Final Check: Can You Connect Physics to Evolution?
This exit ticket tests whether you can apply Cycle 2 physics to understand natural selection. There are 6 questions: 2 NEW (natural selection), 2 SPIRAL (Cycle 2 forces), 1 INTEGRATION (connects both), and 1 SEP-1 (asking scientific questions).
What You'll Be Asked:
| # | Topic | Type |
|---|---|---|
| 1 | Explain how variation leads to natural selection | NEW |
| 2 | Compare forces when predator tackles prey (N3L) | SPIRAL |
| 3 | Calculate population change after selection (% survivors) | NEW |
| 4 | Calculate acceleration given force and mass (a = F/m) | SPIRAL |
| 5 | Predict population change using selection + physics concepts | INTEGRATION |
| 6 | Write 2 scientific questions about natural selection or forces | SEP-1 |
Tips for Strong Answers:
- Use vocabulary: natural selection, variation, trait frequency, force, acceleration, mass
- Show your math work with units on calculations
- Connect physics to biology: "Because of F=ma, smaller animals accelerate faster, which..."
- For population change: Populations change, individuals don't!
STOP! Self-Check Before You Begin:
- ☐ I can state Newton's Third Law [Review Hook]
- ☐ I can calculate F=ma and a=F/m [Review Station 1]
- ☐ I can explain how selection pressure changes populations [Review Station 2]
- ☐ I can connect physics to survival advantages [Review Station 3]
Complete the Exit Ticket Below:
Take your time. Show what you've learned today!
You're Done When:
- ☐ I answered all 6 questions thoughtfully
- ☐ I showed my work on calculations
- ☐ I connected physics concepts to natural selection
- ☐ I wrote 2 testable scientific questions (SEP-1)
- ☐ I clicked "Submit" on the form
Congratulations! You Connected Physics to Evolution!
Today you discovered something powerful: the physics you learned in Cycle 2 explains how natural selection works! Forces, mass, and acceleration determine who survives—and that drives evolution over millions of years.
🏆 What You Learned Today
1. Newton's Third Law in Predator-Prey Interactions
- Forces between predator and prey are ALWAYS equal and opposite
- Size and strength don't change this—physics is physics!
- What differs is acceleration (because of different masses)
2. F=ma Explains Survival Advantages
- Same force on smaller mass = greater acceleration
- This is why smaller prey can escape larger predators after contact
- Gazelles accelerate faster than cheetahs even though forces are equal!
3. Natural Selection Changes Populations
- Variation exists in every population
- Selection pressure determines who survives
- Trait frequency changes over generations (NOT individuals changing)
Need Help or Want to Learn More?
| Contact Rosche | Extra Practice |
|---|---|
|
Coming Up: Week 2
Next week: Why do whales have finger bones? You'll investigate evidence for evolution—fossils, homologous structures, and DNA evidence. How do we know evolution happened?
Grade 8 Science | Cycle 3, Week 1
The Cheetah-Gazelle Arms Race
Louis Rosche | Kairos Academies | 2024-2025
Questions? louis.rosche@kairosacademies.org