SSC Stenographer 2026 – 10 September 2026 Shift 1 · Evidences of evolution (homologous and analogous organs, fossils)
Q1. Which of the following is an example of an homologous organ?
- (a) Wings of a bird and wings of a butterfly
- (b) Flippers of a whale and forelimbs of a human
- (c) Eyes of an octopus and eyes of a human
- (d) Sweet potato and potato (as storage organs)
Answer & solution
Answer: (b) Flippers of a whale and forelimbs of a human
Answer: Option 2 — Flippers of a whale and forelimbs of a human
Homologous organs share the same basic structure and embryonic origin but do different jobs.
A whale's flipper and a human arm are both built on the same pentadactyl forelimb plan — humerus, radius, ulna, carpals, metacarpals and phalanges.
Revision note — Evidence of evolution
• Homologous organs — same structure and origin, different function: the forelimbs of a whale, bat, horse, cat and human.
• In plants, the thorn of Bougainvillea and the tendril of Cucurbita are homologous — both are modified stems.
• Homology points to a common ancestor and is the mark of divergent evolution.
• Analogous organs — different structure and origin, same function: the wings of a bird and of an insect, the eye of an octopus and of a human. These show convergent evolution.
• Vestigial organs are reduced, functionless remains: in humans the vermiform appendix, the nictitating membrane, wisdom teeth and the coccyx.
• Fossils give direct evidence — Archaeopteryx is the connecting link between reptiles and birds.
• Embryology (all vertebrate embryos show gill slits and a tail) and biochemistry (the shared DNA and protein code) are further lines of evidence.
Do not mix these up
• Homologous vs analogous — homologous means same structure, different function (divergent evolution); analogous means different structure, same function (convergent evolution).
• Sweet potato vs potato — the sweet potato is a modified root and the potato a modified stem, so although both store food they are analogous, not homologous.
Also asked from this topic: Darwin's “descent with modification” (populations change genetically through natural selection); what small variations over many generations produce (the evolution of biodiversity).
Homologous organs share the same basic structure and embryonic origin but do different jobs.
A whale's flipper and a human arm are both built on the same pentadactyl forelimb plan — humerus, radius, ulna, carpals, metacarpals and phalanges.
Revision note — Evidence of evolution
• Homologous organs — same structure and origin, different function: the forelimbs of a whale, bat, horse, cat and human.
• In plants, the thorn of Bougainvillea and the tendril of Cucurbita are homologous — both are modified stems.
• Homology points to a common ancestor and is the mark of divergent evolution.
• Analogous organs — different structure and origin, same function: the wings of a bird and of an insect, the eye of an octopus and of a human. These show convergent evolution.
• Vestigial organs are reduced, functionless remains: in humans the vermiform appendix, the nictitating membrane, wisdom teeth and the coccyx.
• Fossils give direct evidence — Archaeopteryx is the connecting link between reptiles and birds.
• Embryology (all vertebrate embryos show gill slits and a tail) and biochemistry (the shared DNA and protein code) are further lines of evidence.
Do not mix these up
• Homologous vs analogous — homologous means same structure, different function (divergent evolution); analogous means different structure, same function (convergent evolution).
• Sweet potato vs potato — the sweet potato is a modified root and the potato a modified stem, so although both store food they are analogous, not homologous.
Also asked from this topic: Darwin's “descent with modification” (populations change genetically through natural selection); what small variations over many generations produce (the evolution of biodiversity).