Population Pulse Slides
Field Research Dossier
POPULATION PULSE
Analyzing Ecosystem Dynamics through Percent Change Calculations
The Hook: Rapid Growth
Imagine a population of invasive Lionfish in a new reef.
"Looking at this trend, how fast is this population actually growing?"
In science, we don't just say "fast" or "slow." We use Percent Change to get the pulse of the ecosystem.
50
200
800
3,200
Year 1 Year 2 Year 3 Year 4
The Growth Formula
Percent Change Formula
New Value − Original Value
Original Value
× 100%
1
Subtract the starting amount from the end amount.
2
Divide by the original amount.
3
Multiply by 100 to get your percentage.
Always divide by the starting value!
Case Study: Cat Population
Watch: 7:35 → 9:12
Embedded media
Research Question
The population of Island X was 1,500. It grew by 250.
Is 250 the "New Value"?
How do we find the "New Value" if it grew by a certain amount?
Ecosystem Analyst Mission
Your Role
Analyze raw field data from four distinct species across five years of monitoring.
Your Task
Calculate year-over-year percent change for each species to identify trends.
The Goal
Classify each population as Stable, Exploding, or Collapsing.
Pro-Tip: Round your answers to the nearest 1%!
Classifying the Pulse
STABLE
Change is between -5% and +5%
The population is maintaining its size. Resources and predators are in balance.
Exploding
Growth is consistently >10%
Often seen in invasive species or when a new food source is found.
Collapsing
Decline is consistently < -10%
Indicates loss of habitat, disease, or extreme over-predation.
Ecosystem Analyst Worksheet
Global Ecosystem Monitoring Unit
Ecosystem Analyst Report
Dossier # BIO-7-2026
Lead Analyst Name
Observation Date
Reference Formula
\( \text{Percent Change} = \frac{\text{New Value} - \text{Original Value}}{\text{Original Value}} \times 100\% \)
Positive (+) = Increase
Negative (-) = Decrease
Part 1: Population Data Tracking
Species A: Gray Wolves (Yellowstone Region)
Native Species
| Year 1 | Year 2 | Year 3 | Year 4 | Year 5 |
|---|
| 100 | 104 | 108 | 112 | 117 |
Y1 → Y2 Change
Y2 → Y3 Change
Y3 → Y4 Change
Y4 → Y5 Change
Species B: Lionfish (Atlantic Reef Site)
Invasive Species
| Year 1 | Year 2 | Year 3 | Year 4 | Year 5 |
|---|
| 50 | 150 | 450 | 1,350 | 4,050 |
Y1 → Y2 Change
Y2 → Y3 Change
Y3 → Y4 Change
Y4 → Y5 Change
Species C: Monarch Butterflies (Migration Count)
Endangered Status
| Year 1 | Year 2 | Year 3 | Year 4 | Year 5 |
|---|
| 5,000 | 3,000 | 1,800 | 1,080 | 648 |
Y1 → Y2 Change
Y2 → Y3 Change
Y3 → Y4 Change
Y4 → Y5 Change
Part 2: Ecosystem Diagnosis
1. Based on your calculations, classify each population as Stable, Exploding, or Collapsing. Justify your answer with the average percent change.
Gray Wolves
Lionfish
Monarchs
2. Extension: Predictive Modeling
Pick ONE species. Calculate its average percent change across all years. Use that average to predict the population for Year 6. Show your work.
Average % Change Calculation
Year 6 Population Prediction
Ecosystem Analyst Answer Key
Instructional Resource
Answer Key: Ecosystem Analyst
Grade Level 7th Science/Math
Part 1: Population Data Calculations
Species A: Gray Wolves (Stable Pattern)
Y1 → Y2
+4%
\( \frac{104-100}{100} \)
Y2 → Y3
+3.8%
\( \frac{108-104}{104} \)
Y3 → Y4
+3.7%
\( \frac{112-108}{108} \)
Y4 → Y5
+4.5%
\( \frac{117-112}{112} \)
Species B: Lionfish (Exploding Pattern)
Y1 → Y2
+200%
\( \frac{150-50}{50} \)
Y2 → Y3
+200%
\( \frac{450-150}{150} \)
Y3 → Y4
+200%
\( \frac{1350-450}{450} \)
Y4 → Y5
+200%
\( \frac{4050-1350}{1350} \)
Species C: Monarch Butterflies (Collapsing Pattern)
Y1 → Y2
-40%
\( \frac{3000-5000}{5000} \)
Y2 → Y3
-40%
\( \frac{1800-3000}{3000} \)
Y3 → Y4
-40%
\( \frac{1080-1800}{1800} \)
Y4 → Y5
-40%
\( \frac{648-1080}{1080} \)
Part 2: Ecosystem Diagnosis Answers
1. Classifications
- Gray Wolves: STABLE. The average change is approx. +4%, which falls within the +/- 5% "Stable" bracket.
- Lionfish: EXPLODING. The population is consistently growing by 200% each year, far exceeding the 10% threshold.
- Monarchs: COLLAPSING. The population is consistently declining by -40% each year, which is far below the -10% threshold.
2. Extension Sample (Monarchs)
Average % Change: -40% (or -0.40 as a decimal)
Year 6 Prediction Calculation:
Year 5 Population × (1 + Average % Change)
648 × (1 - 0.40) = 648 × 0.60 = 388.8 (approx. 389 butterflies)
