Question

Example of homologous organs is :

• A. Fore arm of human and wings of bird
• B. Wings of insect and bird
• C. Vermi form appendix and nictilating membrane
• D. Muscles of pinna and tail vertebrae

Hint:

{Homo}logous = {Same} basic structure from a common ancestor, but possibly {different functions}. (e.g., Human arm, bird wing, whale flipper, bat wing - all have similar bone patterns). {Ana}logous = {Different} structure and origin, but {similar functions}. (e.g., Wings of a bird and wings of an insect - both for flight, but very different structures). Option (1) is the classic example of homology.

Answer 1

The Correct Option is A

Concept: Homologous organs are organs in different species that have a similar basic anatomical structure and embryonic origin, inherited from a common ancestor, but may have evolved to perform different functions. This is evidence of divergent evolution. Step 1: Defining Homologous and Analogous Organs
Homologous Organs: Similar underlying structure, common evolutionary origin, can have different functions. (Think: Same ancestor, different job).
Analogous Organs: Different underlying structure, different evolutionary origin, but perform similar functions. This is evidence of convergent evolution. (Think: Different ancestor, same job). Step 2: Analyzing the options
(1) Forearm of human and wings of bird:
Structure: Both the human forearm and the bird wing have a similar skeletal structure: humerus, radius, ulna, carpals, metacarpals, and phalanges.
Origin: They share a common ancestral origin from the forelimbs of early vertebrates.
Function: The human forearm is used for grasping, manipulation, etc. The bird wing is adapted for flight. These fit the definition of homologous organs (similar structure, common origin, different functions).
(2) Wings of insect and bird:
Structure: Insect wings are typically made of chitinous cuticle with veins, lacking bones. Bird wings have an internal skeleton of bones. The underlying structures are very different.
Origin: They have different evolutionary origins.
Function: Both are used for flight. These are analogous organs (different structure, different origin, similar function).
(3) Vermiform appendix and nictitating membrane: These are generally considered vestigial organs in humans. The vermiform appendix is a remnant of a larger cecum used for digesting cellulose in ancestral herbivores. The nictitating membrane (third eyelid) is functional in many animals (birds, reptiles) but is reduced to a small fold (plica semilunaris) in humans. While both are vestigial, comparing them as homologous requires looking at their counterparts in other species. This option is more about vestigial structures than a direct comparison of homologous active organs between two species.
(4) Muscles of pinna and tail vertebrae (in humans): These are also examples of vestigial structures in humans. The muscles of the pinna (external ear) are poorly developed in humans but functional in many animals for ear movement. Tail vertebrae (coccyx) are remnants of a tail. Similar to option (3), this points to vestigial organs. Step 3: Identifying the best example of homologous organs The forearm of a human and the wing of a bird is a classic example of homologous organs, demonstrating how a common ancestral limb structure has been modified for different functions.