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Darwinian Fitness

K20 Center, Alexandra Parsons, Tiamber Derrick | Published: June 8th, 2022 by K20 Center

  • Grade Level Grade Level 6th, 7th, 8th, 9th, 10th, 11th, 12th
  • Subject Subject Science
  • Course Course Biology I
  • Time Frame Time Frame 1-2 class period(s)
  • Duration More 90 minutes


This lesson is intended to be either an introduction or a refresher of Darwinian fitness. Students think about what it means to be 'fit' and the impact humans have had on this natural mechanism.

Essential Question(s)

Why is biological fitness such a difficult concept to describe?



Students examine and discuss their prior knowledge about fitness.


Students complete the Mice Living in a Desert activity to gain a more in-depth working definition of fitness.


After a class discussion about Darwin's five factors that influence survival, students identify evidence of the factors from the Mice Living in a Desert activity.


Students read a story about coral reefs and discuss how the story shows evidence of each factor that influences survival.


Students create a cartoon to illustrate their understanding of the coral reef story or another example in nature that shows how the five factors influence survival in an organism. Students provide a final definition of fitness based on evidence from the reading or research from the real-world example and share out with the class.


  • Prompt Slide - "Is It Fitter?"

  • Activity Handout - Mice Living in a Desert

  • Activity Handout - The Peppered-Moth Story

  • Colored Pencils, pencils, markers, and highlighters

  • Activity Handout - Blank Cartoon Template

  • Chromebooks

  • Evolution and Fitness Teacher Slides


Post four signs around the room for the Four Corners strategy.

  1. Dora- "I think ‘fit' means being bigger and stronger."

  2. Lance- "I think 'fit' means being more likely to reproduce."

  3. Felix- "I think ‘fit' means being able to run faster."

  4. Keisha- "I think ‘fit' means being more intelligent."

Open the Evolution and Fitness Teacher Slides and display slide 2, which contains different student statements about fitness. Tell students to read the statements, and then move around the room to the "corner" with the name of the student whose definition of 'survival of the fittest' they agree with the most.

Once the students have chosen a corner, have them talk with others at that corner to build an 'argument' of why the statement they chose is the best. Have each group share its argument.


Show slide 3, which includes pictures of a variety of animals. Have the students answer the questions on the slide. What makes the animals special? What is 'useful' about what makes them special?

  • Wolf Spider- camouflage to hide in leaf litter, venom to paralyze prey, keen sense of sight and vibrations.

  • Owl- camouflage to hide in tree, fringed feathers for silent flight, large eyes to hunt at night, turn head all the way around to track prey, talons to grab prey while flying.

  • Moth- Camouflage to hide on trees, thin body and wings allow them to fly quickly or hover over flowers.

  • Pufferfish- Artificial bigness to scare off predators, sharp spines that can excrete poison for protection.

  • Crocodile- Camouflage in the water, high acidic stomach contents to allow wide range of foods, cold blooded so they can regulate their own metabolic rate.

  • Flounder- Camouflage to the ocean floor, eyes on the same side to see as they travel along the ocean floor.

Once they're done thinking of answers, move to slide 4. Have students create an Example Non-Example chart in their notes. Have them think back on how they defined the term "survival of the fittest" in the Engage section. Have them list each animal that supports that definition as an example and each animal that doesn't support that definition as a non-example.

Pass out the Mice Living in a Desert activity to each student. Allow them to work in groups of two or three, and allow them about 20 minutes to answer the questions.


Start with talking about the last question of the handout (which references the four definitions of fitness again). Have students share out their answers in a way that is comfortable to you and your class.


Pass out the article titled 'Coral Reef and Fitness' to students.

Have students read the article and use the Why-Lighting strategy as they read. Directions for students are on slide 5.

  • Prompting question: "What is the human influence on Darwinian fitness?"

  • Highlight phrases within the article that contribute to answer the question.

  • Write in the margins why you highlighted that phrase.

After students are done, have them jot all of their margin justifications on a sheet of paper.

From their margin writings, ask students to put together a PSA (Public Service Announcement) Cognitive Comic about how animals or organisms are influenced by humans, for good and for bad.

Tell students:

  • There needs to be a message, but this is also a comic so see if you can add in some laughs

  • This is a great time to reflect on how good your margin notes were. What was helpful and what was hurtful toward making your comic?

  • How will your illustrations help with the message? They need to be more than just a person standing there talking.

When students have completed their comics, post their work around the room (or in the hall) for everyone to see.


Post slide 6, which asks students to reflect on their learning using a modified Metacognitive Cards strategy. Stress to the students that they are reflecting on how they learned, not what they learned. Have them put this reflection in their notebook so that they can revisit it the next time you do a similar activity or the next time you ask them to reflect on their metacognition.