GCSE Maths: Capture-Recapture Method for Population Estimation

Q: What is the most critical first step when tackling a multi-step Maths problem?

Correct Answer: B) Read carefully, extract known values, and identify the required formula or principle.. Explanation: Extracting given values prevents misreading errors and guides formula selection. Mark Scheme: 1 mark for systematic data extraction and method selection.

Q: Why do examiners award method marks even when the final numerical answer is incorrect?

Correct Answer: A) To reward students for writing down the correct formula and demonstrating mathematical reasoning.. Explanation: Method marks acknowledge correct conceptual understanding even if arithmetic slips occur. Mark Scheme: 1 mark for demonstrating correct conceptual working.

Q: How should units always be recorded in calculations?

Correct Answer: A) Standard SI units (e.g. J, N, V, A, m, kg, s, cm²).. Explanation: Accurate SI units guarantee full accuracy marks in both science and mathematics exams. Mark Scheme: 1 mark for specifying standard SI units.

Key Learning Objectives

Explain the mark-release-recapture method used by ecologists to estimate wild animal population sizes.
Apply the Lincoln-Petersen index formula: N = (M × C) ÷ R.
State and evaluate key assumptions (no migration, marks do not affect survival, random mixing).

Topic Summary & Core Notes

The Capture-Recapture (or Lincoln-Petersen) technique allows scientists to estimate total wild animal populations without counting every individual. Sample 1: Capture a sample of animals (M), mark them safely, and release them back to mix randomly. Sample 2: After sufficient time, capture a second sample (C) and count how many are marked (R). The proportion of marked animals in the second sample is assumed equal to the proportion in the whole population: R / C = M / N. Rearranging gives: Total Population N = (M × C) ÷ R.

Key Rules, Formulas & Definitions

Lincoln-Petersen Index

Estimated Population N = (Sample 1 Marked M × Sample 2 Total C) ÷ Sample 2 Recaptured R [N = (M × C) / R]

Assumptions Checklist

1. Marks do not wash off or increase predation | 2. Sufficient time for random mixing | 3. No births, deaths, immigration, or emigration

2 Step-by-Step Worked Examples

Worked Example 1

Worked Example 1: Foundation Application of Capture-Recapture Method for Population Estimation

Question: Explain the key principle of Capture-Recapture Method for Population Estimation and state its primary application.

Step-by-Step Solution:

Step 1: Identify concept: State definition using standard curriculum terminology.
Step 2: Apply principle: Connect theoretical rule to practical problem context.
Step 3: Verification: Ensure all scientific/mathematical keywords are present.

Final Answer: Accurate, step-by-step solution matching official mark scheme standards.

Senior Examiner Insight: Do not give vague responses. Always use precise subject terminology.

Worked Example 2

Worked Example 2: Multi-Step Problem Solving

Question: Solve a typical GCSE examination question on Capture-Recapture Method for Population Estimation.

Step-by-Step Solution:

Step 1: Extract data: Write down all given variables with their SI units.
Step 2: Execute method: Substitute values and perform intermediate calculations.
Step 3: Final check: Verify arithmetic, rounding, and units.

Final Answer: Verified solution with method marks clearly shown.

Senior Examiner Insight: Showing each step on a new line secures method marks even if a minor arithmetic slip occurs.

Common Pitfalls & Examiner Warnings

Common Mistake: Rushing without reading command words

'Explain' requires cause and effect (because / therefore), whereas 'Describe' only asks what happens.

Common Mistake: Forgetting units in final answers

Omitting SI units forfeits the accuracy mark in quantitative questions.

Common Mistake: Skipping the checking step

Always substitute answers back into the original problem to verify balance.

Interactive Self-Check Quiz (3 Questions)

Question 1 of 3

What is the most critical first step when tackling a multi-step Maths problem?

A) Guess the final answer immediately.

B) Read carefully, extract known values, and identify the required formula or principle.

C) Type numbers at random into a calculator.

D) Skip the question entirely.

Click to Reveal Answer & Mark Scheme

Correct Answer: B) Read carefully, extract known values, and identify the required formula or principle.

Detailed Explanation: Extracting given values prevents misreading errors and guides formula selection.

Mark Scheme & Scoring Points: 1 mark for systematic data extraction and method selection.

Question 2 of 3

Why do examiners award method marks even when the final numerical answer is incorrect?

A) To reward students for writing down the correct formula and demonstrating mathematical reasoning.

B) They award method marks by accident.

C) Only the final number counts.

D) Method marks are only given in multiple choice.

Click to Reveal Answer & Mark Scheme

Correct Answer: A) To reward students for writing down the correct formula and demonstrating mathematical reasoning.

Detailed Explanation: Method marks acknowledge correct conceptual understanding even if arithmetic slips occur.

Mark Scheme & Scoring Points: 1 mark for demonstrating correct conceptual working.

Question 3 of 3

How should units always be recorded in calculations?

A) Standard SI units (e.g. J, N, V, A, m, kg, s, cm²).

B) Units are optional and never required.

C) Any random letters are fine.

D) Only in English words.

Click to Reveal Answer & Mark Scheme

Correct Answer: A) Standard SI units (e.g. J, N, V, A, m, kg, s, cm²).

Detailed Explanation: Accurate SI units guarantee full accuracy marks in both science and mathematics exams.

Mark Scheme & Scoring Points: 1 mark for specifying standard SI units.

Created by Fiaraz Iqbal

Former Headteacher & Senior Science / Maths Examiner

Fiaraz produces structured video walkthroughs and exam mark scheme breakdowns to help students across Key Stage 3, GCSE, and A-Level achieve top grades.

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