March 14

Estimating Population Size: Capture & Recapture Method 🐟📊

📅 Lesson Overview:
In this activity, students used the "capture-recapture" method in a Gizmo simulation to estimate the population size of fish in a pond. This method is widely used by ecologists to study wildlife populations, especially when direct counting is not possible.

📝 What We Covered:

1️⃣ Why Estimate Population Size?

• Scientists often cannot count every individual in a population, so they use mathematical models to estimate population sizes.

• Methods include direct observation, sampling, mark and recapture, and mathematical estimation.

2️⃣ Capture-Recapture Method

• Scientists capture, tag, and release a group of organisms.

• After some time, they capture another sample and count how many are previously tagged.

• Using proportions, they estimate the total population size.

3️⃣ Using the Gizmo Simulation

• Step 1: Set the number of tagged fish and release them into the pond.

• Step 2: Catch a new sample and count how many are previously tagged.

• Step 3: Use a mathematical proportion to estimate the total population:

• Step 4: Compare the estimate to the actual population size and calculate percent error.

• Step 5: Repeat the process with different sample sizes to see how accuracy improves with larger data sets.

4️⃣ Key Factors Affecting Population Estimates

• Sample Size: Larger samples give more accurate estimates.

• Animal Movement: Immigration, emigration, or random movement can affect estimates.

• Predation & Death Rates: If individuals are lost before recapture, it may skew results.

📌 Activity Details:

✅ Gizmo Simulation – Practiced tagging, recapturing, and estimating population size.
✅ Proportion Calculations – Used math skills to estimate total fish populations.
✅ Percent Error Analysis – Compared estimated vs. actual population size.
✅ Discussion Questions – Examined why larger sample sizes produce better estimates and how scientists apply these techniques in real-world conservation efforts.

🌍 Why This Matters:

Understanding how scientists estimate population size helps us monitor endangered species, manage wildlife populations, and study ecosystems. This technique is essential for conservation biology and environmental science!

✅ Great job today! Keep thinking about how population estimates influence conservation efforts. 🌱🐾✨