Homologous and Analogous Organs

Aim

To study homologous and analogous organs in organisms and understand evolutionary relationships.

Materials Required

• Charts or models of limbs of different organisms
• Reference diagrams
• Notebook and pen for observation

Key Concepts

Homologous Organs: Organs which have the same fundamental structure but different functions are called homologous organs. Example: Forelimbs of a human, a dog, a whale, and a bat. They show divergent evolution from a common ancestor.

Analogous Organs: Organs which have different fundamental structures but perform similar functions are called analogous organs. Example: Wings of a bird and wings of an insect. They show convergent evolution, where unrelated organisms evolve similar traits to adapt to similar environments.

Procedure

1. Observe the forelimbs of different vertebrates (e.g., human, dog, whale, bat) carefully.
2. Identify the common bone structure (Humerus, Radius, Ulna, Carpals, Metacarpals, Digits).
3. Note down the function of each forelimb in these animals.
4. Next, observe the wings of a bird and a butterfly (or an insect).
5. Compare their internal structures and their functions.
6. Record your observations in the table.

Precautions

• Observe the charts and models very carefully to trace the bone similarities.
• Do not confuse structure with function when identifying homology vs analogy.