Choose a vertebrate animal from this list: bat, whale, horse, cat, or bird. Find a picture that shows the bones inside one of its limbs. Find a picture of a human arm.

Question

Sketch a picture of the bones in the human arm and a picture of the bones inside the animal’s limb. Use labels or colors to show which bones are similar. Write a claim about how the bones in the human limb and the bones in the animal limb are evidence that vertebrates share a common ancestor. Write an argument based on evidence in the picture and from what you have learned to support your claim.

Answer 1

Claim:

The bones in the human arm and the bones in the bat’s wing (for example) provide evidence that vertebrates share a common ancestor due to the presence of homologous structures, which exhibit similar body plans despite their different functions.

Argument:

In examining the skeletal structures of a human arm and a bat's wing, we can observe notable similarities despite their different appearances and functions.

1. Homologous Structures: Both the human arm and the bat's wing contain similar bone structures. For example, the humerus, radius, and ulna in the human arm have corresponding bones in the bat's wing—albeit adapted for flight. This similarity in bone arrangement indicates that these species diverged from a common ancestor that possessed a similar skeletal framework.

2. Adaptation for Different Functions: While the human arm is adapted for manipulation and grasping, the bat's wing is adapted for flying. This divergence demonstrates how similar anatomical structures can evolve into different forms to fulfill various ecological roles, supporting the concept of evolutionary change from a common ancestor.

3. Color-Coded Labels: On a sketch comparing the two structures, we might color-code the bones (e.g., blue for the humerus, green for the radius, and red for the ulna) to highlight the similar positioning and structure. Identifying these homologous bones visually reinforces the idea that the basic blueprint of vertebrate limb structure has remained consistent through evolutionary history, despite functional adaptations.

4. Genetic Evidence: Modern genetic studies further strengthen this argument, as the genetic similarities between vertebrates indicate a shared lineage. The commonality in bone structure is reflected in the underlying genetic makeup, tying back to the concept of descent with modification and evolutionary biology.

Through examining the skeletal structures of different vertebrates, we can conclude that the similarities in bone arrangements and functions demonstrate the profound connection shared among all vertebrates through common ancestry. This underscores the importance of evolutionary biology in understanding the history of life on Earth.