Counting Change: The Math of Natural Selection
Aligned to MS-LS4-6 — Next Generation Science Standards.
What this lesson teaches
Natural selection can be tracked with numbers. By counting how common a trait is in each generation, we can show mathematically that helpful traits increase in frequency while harmful ones decrease over time.
Worked example
If a population starts with 20 dark and 80 light moths, and pollution darkens the trees so birds eat more light moths, counting each generation might show dark moths rising to 60 out of 100 — the numbers make the shift clear.
Practice questions
- Count how many of two colors appear in a handful of mixed candies or beads.
- Model three generations by removing a fraction of one color each round and record the counts.
- Use your numbers to explain how natural selection increased one trait and decreased another over time.
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Contar el cambio: la matemática de la selección natural
La selección natural se puede seguir con números. Al contar qué tan común es un rasgo en cada generación, podemos mostrar matemáticamente que los rasgos útiles aumentan en frecuencia mientras que los perjudiciales disminuyen con el tiempo.
Ejemplo: Si una población empieza con 20 polillas oscuras y 80 claras, y la contaminación oscurece los árboles de modo que las aves comen más polillas claras, contar cada generación podría mostrar que las polillas oscuras suben a 60 de 100 — los números dejan claro el cambio.
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