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Why are so many deep-sea animals red?

Algebra 1Exponential decayabout 3 minCCSS HSF.LE.A.1.aCCSS HSF.LE.A.1.c

Take a red fish down into the sea, then light up the deep.

Lesson Plan

Explore exponential decay, where a quantity falls by the same percent over each equal step, and compare it with linear change.

  1. Question: Ask what students spot and what they are curious about. Read “Two layers: how much red gets through?” aloud. Have each student guess and say why.

  2. Question: Read “At 20 m: what color does it look?” aloud. Have partners explain their guesses to each other.

  3. Big idea: Pause. Ask a student to say the idea in their own words.

  4. Your turn: Have students try their own. Ask them to predict before they test.

How to run it

  1. Whole classPut the lesson on the board. At each choice the class votes, then you select the winner.
  2. SoloShare the link, QR code, or post to Google Classroom. Each student gets to take their own path.