Home › PYQs › Environment › All questions › 2005 · Reproduction
UPSC Prelims 2005 · Environment · Species Watch
Assertion (A): Amoeba reproduces by fission. Reason (R): All unicellular organisms reproduce by asexual methods.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is not the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Show the answer and explanation
Answer: (c) A is true but R is false
Amoeba does reproduce by binary fission, but not all unicellular organisms are asexual — Paramecium conjugates, Chlamydomonas forms gametes.
The idea
Amoeba simply divides into two: this is binary fission, a form of asexual reproduction. But many single-celled organisms can also reproduce sexually, by joining and exchanging genetic material. So the reason, which says “all”, is false.
Fission: amoeba, bacteria → Budding: yeast → Spores: many fungi and algae → Sexual union of two cells: Paramecium, Chlamydomonas
The trap
“All” in R — one exception (Paramecium) breaks it.
Elimination technique
The reason says “All unicellular organisms…”. Absolute words usually mark the false statement in Environment PYQs. With R false, only option (c) fits.
Also know
Asexual reproduction is fast but makes exact copies. Sexual reproduction mixes genes, which gives variety and a better chance of surviving change.
🔒 Amoeba: binary fission. Paramecium: fission + conjugation. Yeast: budding + spores.