Authentic Lessons for 21st Century Learning

Parrots, Penguins, and Parts

Homologous Structures 

Teresa Randall | Published: November 4th, 2022 by K20 Center

  • Grade Level Grade Level 6th, 7th, 8th
  • Subject Subject Science
  • Course Course
  • Time Frame Time Frame 3-4 class period(s)
  • Duration More 180 minutes


In this lesson, students will learn to compare anatomical similarities and differences between organisms and explain the relationship between organisms based on homologous structures. They begin by reading a recent research article on either parrots or penguins. Then, students learn about the ancient roots of modern-day birds by playing a game about evolutionary traits, created by The Cornell Lab. The class explores homologous structures as a source of evidence for evolution; then, in groups, students examine the bone structures of several mammals and develop a claim, reasoning, and evidence about evolutionary relationships.

Essential Question(s)

How do scientists determine relationships between today’s organisms and their ancestors using their physical appearance and characteristics?



Students use the How I Know It strategy to evaluate what they know about parrots or penguins. Then, they read articles containing recent research on parrots or penguins.


Students watch or play the science game "Flap to the Future," drawing on what they see to create a Cognitive Comic depicting an organism's evolutionary change.


Students view a diagram and discuss their observations on similar mammalian bone structures, then watch a clip to develop an understanding of homologous structures.


Students view x-rays of animal hands and match them to various animals. Then, students develop a Claim, Evidence, Reasoning (CER) statement about the relationship between those animals based on their bone structures.


Students share what they used to think about homologous structures versus what they now know, post-lesson.


  • CER handout (attached; one per group of 3 students)

  • Cognitive Comics handout (attached; one per student)

  • Hand It to the Animals handout (attached; one per student)

  • Hand It to the Animals digital handout (linked)

  • How I Know It handout (attached; one per student)

  • I Used to Think... But Now I Know handout (attached; one per student)

  • Lesson Slides (attached)

  • Markers (at least one per student)

  • "Flap to the Future" online game (linked below; optional)

  • Internet-enabled devices for students (Chromebooks, etc.) (optional)


Begin on slide 4 of the attached Lesson Slides. Hand each student a copy of the attached I Used to Think... But Now I Know handout. Invite students to follow the I Used to Think… But Now I Know strategy to answer the Essential Question on the slide: “How do scientists determine relationships between today’s organisms and their ancestors using their physical appearance and characteristics?” Ask students to write down their answers to this question in the "I Used to Think..." column of the handout. Then, ask students to put this aside for now; they will continue using it later in the lesson.

Go to slide 5. Hand each student a copy of the attached How I Know It handout. Tell students they have a choice to complete the handout for either penguins or parrots. Invite students to follow the How I Know It strategy as follows: in the inside of the circle, ask them to write down everything they already know about the animal. On the outside of the circle, ask them to write down how they came to know each piece of information they’ve written down. They will draw a line between what they know (inside) and how they know it (outside).

Go to slide 6. After students have completed the How I Know It handouts, have them group up with two other students who selected the same animal they did. Print and hand out one copy of the article per student or instruct each student to access the research article online. Ask each group to read the research articles using the Jigsaw reading strategy. This involves each student reading a portion of the article, and when the whole group is finished reading their section, they should share with the group the content of their part of the reading. Tell the students they may want to take a few notes on their section before sharing. They can add anything they learn to their How I Know It handouts, but should do so in a different color was used previously.


After having students read the article about their chosen bird, invite them to learn more by watching gameplay videos of Flap to the Future, a browser-based web game created by The Cornell Lab. To begin this activity, hand out a copy of the attached Cognitive Comics handout to each student. Move to slide 7. Ask students to follow along with the videos in the lesson slides as they work on their handouts, completing the handouts via the Cognitive Comics strategy. Ask students to use this strategy to show how the organisms they play change throughout the game. Beginning with level 1, students should watch the level 1 gameplay video on the slide, drawing the organism they see and making notes in the appropriate panel. Then, move to slide 8 and repeat with the level 2 gameplay video. Repeat again with slide 9 and the level 3 gameplay video, and again with slide 10 and the level 4 gameplay video.

When students are finished drawing, move to slide 11 and pose the guiding questions on the slide (also listed below) to students using the Think-Pair-Share strategy. Have students consider the first two questions on their own, then discuss their answers with an Elbow Partner.

  1. Were there any differences between the organisms? What were they?

  2. Were there any similarities between the organisms? What were they?

  3. What did the game say about the relationship between the organisms?

Solicit a few answers from volunteer pairs in a brief class discussion.


Move to slide 12. Use the Picture Deconstruction strategy to discuss with students the picture on this slide (there is no need to divide this picture into quadrants as the strategy suggests, however). Be sure to not define or mention homologous structures or homology and do not describe the picture. Instead, ask students to describe what they see without interpreting it. After students have had time to describe what they see, ask them to interpret the image by posing the question, "What do you think this represents?"

Move to slide 13. Show students this Bozeman Science video clip (also linked on slide 13) about homologous structures. The video should automatically start at the appropriate point (1:35); be sure to pause at 2:08.

Ask students to identify evidence in the picture on slide 13 that suggests that these organisms are related. Solicit a few answers from the class.


Move to slide 14. Show students this slide to illustrate that some animals share similar body structures. Images of a human nose, a pig’s snout, and an elephant’s trunk are all “noses.” Point out that they have different functions and appearances, but they all have similar structures and locations. Tell students that these are called homologous structures.

Move to slide 15. Invite students to look at x-rays of 10 different zoo animals with the Hand It to the Animals handout.

Invite students to note on their printed handouts, describing for each linked x-ray what they see, stating the function of the limb, and guessing which animal it is from the list of possible answers provided on the handout.

Move to slide 16. Place students into groups of three or fewer. Give each group a copy of the attached CER Handout. Invite each group to complete the handout with the Claim. Evidence, Reasoning (CER) strategy using the following prompt: “What is the relationship between the animals? Base your claim on what you see in the x-rays.” Allow students time to answer this prompt with their groups. Then, ask for volunteers to share their CER with the class for discussion.


Move to slide 17. Have students get out the I Used to Think... But Now I Know handouts they started at the beginning of the lesson. Invite students to utilize the I Used to Think… But Now I Know strategy again, comparing their thoughts before and after the lesson about the similarities, differences, and relationships between organisms. They should add new notes to the "But Now I Know" column now that they've completed the lesson. Students can refer to their How I Know It handout from the beginning of the lesson if they need help getting started.