Evidence for Evolution Homologous Structures
Homologous Structures
1. What are homologous structures?
Structures shared by organisms because they descended from a common ancestor. The
structures are built from the same bones, but can be modified in form and function.
2. Place the same letter or number on the corresponding bones in each of the front limbs pictured
below.
3. Based on the limbs above, what can you conclude about the ancestor shared by the organisms
above?
The common ancestor to these organisms had the same bones
4. Compare and contrast two limbs from questions 2. Your answer should include an analysis of
size, shape, and function.
The human and whale front limbs have the same bones in the same positions. The human limb
is used for grasping and its bones are longer and thin. The whale limb is used for steering and its
bones are shorter and wider.
5. How are the pictured limb structures used to support the theory of evolution?
The ancestor to these organisms had the same bones, but the limbs have been modified in form
and function (descent with modification).
6. Find a definition for a vestigial structure. Identify 1 structure that scientists classify as vestigial
that wasn’t presented in the notes.
Structures without a clear or current use in an organisms, but had a use in the ancestor.
EX: Sexual organs of dandelions
Activity 2. Evidence of Evolution Homologous Structures – Use your notes, book
and the Internet to answer the following questions on homologous structures.
