MnSTEP Teaching Activity Collection > MnSTEP Activities > Comparative anatomy of bird vs. human leg bones.

Comparative anatomy of bird vs. human leg bones.

Valerie Jeffery, STMA Middle School, Saint Michael, MN
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Many people think a bird's leg bends backward as it perches but what they are most often looking at is the ankle, not the knee. Students will compare the anatomy of the leg bones of a bird vs. a human. They will color diagrams of similar leg parts of each organism (for example the femur on each will be orange) to see that the structure is similar, even though they appear different upon first glance, especially the foot and ankle. Students will be asked to compare and contrast the bones also. Students will then circle and label each diagram's "common" parts such as "hip," "knee," "ankle," "foot," and "toes." Students should be guided to notice in particular that birds don't use their "foot" like we do. They instead perch on their "toes." Students will then be guided to "walk" like a bird.

Learning Goals

This activity is designed for students to compare and contrast the anatomy of bird vs. a human leg bones. Students will kinesthetically model "walking" like a bird to note the differences in the foot bones.

Context for Use

Teachers in any context could use this lesson. It is meant to be an investigation into homologous structures. The lesson is intended for middle school through high school but could easily be adapted for the younger age levels as well. This lesson would work for any class size. It is intended to be completed in one class (50 minutes) session. The only materials necessary would be colored pencils/markers/or crayons and copies of the bone structure of a bird and a human. This activity could be easily adapted into many different settings and difficulty levels.

Subject: Biology:Evolution
Resource Type: Activities:Classroom Activity, Lab Activity
Grade Level: Middle (6-8), High School (9-12)

Description and Teaching Materials

This lesson can be introduced before, during, or after lessons on evolution and/or adaptation. Materials are simple – copies of the labeled bone structure of a bird and a human, and coloring materials. Consult your school's anatomy teacher or the internet or even your own textbook for examples. Students will be given the copies of the labeled bone structures and asked to color each similar bone type the same color (femur of both organisms orange, for example). Color does not matter, as long as the structures on each organism are the same color. Any different structures can be left blank (talons, for example). This will assist them to note differences later. After coloring, students can them make a list of the similarities and differences in the bone structures of each organism. A Venn diagram would be a good guide for comparison. Guide them particularly to the foot and ankle region of the bird, which "stands up" vs. on a human which lays flat. Guide students to take off their shoes if necessary to feel their own foot bones and have them lift their ankles off the floor while they are seated in a chair to observe how this positioning is similar to how a bird "perches" or stands. After students note the similarities and differences, guide them to circle and label the "common" part on each such as the "hip," "knee," "ankle," "foot" and "toes" of each. They should note the differences in the length of each but the similarities of how they bend (birds "knees" do NOT bend backwards – it is most often their "ankle" people think is the knee). Have students feel their own patella and direct them to the bird's patella. For closure, students can be challenged to "walk" like a bird. To do this, they can lift their ankles off the floor and walk on the ball of their feet and their bent toes. The teacher can ask how a bird's toes differ from a humans (much longer) and ask why they think this might be (to grasp a tree branch or food for example). This activity can easily be extended into discussions about anatomy and physiology (form and function), evolutionary tracks of prehistoric animals like dinosaurs, and even just bird identification, for example. In the case of comparing and contrasting to dinosaurs, it would be necessary to have illustrations of the bone structures of these as well. It could also be extended to other animals as well.

Teaching Notes and Tips

Many people think a birds leg bends backwards, but what they are most likely seeing is the ankle of the bird bending "backwards" and not the knee. The femur is often shorter and sometimes difficult to see. By having students carefully examine the two different organisms, they can likely see that they are not so different! This lesson can be easily extended into adaptations and comparative anatomy of other organisms or stand alone by itself.


Assessment is optional and open for significant variation depending on the learning goals of the teacher. Possibilities include but are not limited to: a Venn diagram to compare and contrast the bone structures, a "race" of birds (your students walking/running like birds), a vocabulary test, having students compare structure and function of each organism, etc. The main goal of this lesson is to compare anatomy of highly different organisms to note that structures are quite similar!


(2009) 7th grade 3.2.2 Use internal and external anatomical structures to compare and infer relationships between living organisms as well as those in the fossil record.
(2009) 9-12th grade 3.3.2 Use scientific evidence, including the fossil record, homologous structures, and genetic and/or biochemical similarities to show evolutionary relationships among species.

References and Resources