UPSC Prelims 2005 Q86: Science & Technology – Biology
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
Answer: (c) A is true but R is false
Explanation
Reproduction in amoeba and unicellular organisms
| Part | Verdict |
|---|---|
| A. Amoeba reproduces by fission | True — binary fission |
| R. All unicellular organisms reproduce asexually | False: some, like Paramecium, also reproduce sexually by conjugation |
A is true; R is too general, since several unicellular organisms use conjugation, a sexual process.
Answer: (c) A is true but R is false.
Why each option is right or wrong
- (a) Incorrect. R is false, so it cannot explain A.
- (b) Incorrect. R is not true, because some unicellular organisms conjugate.
- (c) CORRECT. A is true as amoeba divides by binary fission, but R is false because of conjugation.
- (d) Incorrect. A is true, since amoeba does divide by fission.
Key point
Amoeba: binary fission. Yeast: budding. Plasmodium: multiple fission. Paramecium: fission and conjugation.
Remember
Not all unicellular organisms reproduce only asexually.
Common mistakes
- Taking the sweeping word all as true.
- Forgetting conjugation in Paramecium.
- Confusing binary fission with budding in yeast.
Exam tip
Watch for absolute words like all and only in R statements.
Sources
- NCERT Class X Science — How do Organisms Reproduce?
- NCERT Class XII Biology — Reproduction in Organisms