One advantage of sexual reproduction over asexual reproduction is that it helps species to survive over long evolutionary time. This is because sexual reproduction produces :
- (a)more offspring in each reproductive cycle.
- (b)robust and healthy offspring.
- (c)genetically similar offspring.
- (d)more variation in offspring.
Correct — D, more variation in offspring. Sexual reproduction shuffles genes — through meiosis (crossing over and independent assortment) and the random fusion of two gametes — so offspring differ genetically from their parents and from each other. This variation is the raw material for natural selection, letting a species adapt and survive over long evolutionary time.
- (a)more offspring in each reproductive cycle. — Asexual reproduction usually produces more offspring faster; sexual reproduction's evolutionary edge is variety, not sheer numbers.
- (b)robust and healthy offspring. — Sexual reproduction does not guarantee individually healthier offspring; its advantage is genetic diversity across the population, not robustness of each individual.
- (c)genetically similar offspring. — This describes asexual reproduction, which yields near-identical clones. Sexual reproduction does the opposite — it increases genetic difference.
In sexual reproduction, meiosis and fertilisation recombine genes from two parents, generating offspring with new gene combinations. This continual genetic variation gives populations the flexibility to adapt to changing environments — the long-term survival advantage over cloning.
Distinguish 'good for the individual' from 'good for the species over evolutionary time.' Speed and numbers favour asexual reproduction, but variation — the correct answer — is what helps a species endure environmental change and disease.
- Meiosis introduces variation via crossing over and independent assortment.
- Random fusion of gametes at fertilisation adds further variation.
- Variation is the raw material on which natural selection acts.
- Asexual reproduction produces genetically identical clones.
Sexual reproduction's edge is genetic variation — option (d).
- Confusing 'more offspring' (asexual) with the true advantage of variation.
- Thinking sexual reproduction makes each individual healthier.
Asked as a 'why is sexual reproduction advantageous over evolutionary time' reasoning item.
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
Same theme — modes of reproduction. That item tests asexual reproduction (fission) and the false claim that all unicellular organisms are asexual; this one contrasts sexual reproduction's advantage of variation.
- practice — not a real PYQ
The main source of genetic variation in sexually reproducing organisms is
- (a)mitosis
- (b)meiosis and fertilisation
- (c)binary fission
- (d)budding
Answer(b) meiosis and fertilisation — together they recombine parental genes.
- practice — not a real PYQ
Offspring produced by asexual reproduction are best described as
- (a)genetically identical clones
- (b)highly variable
- (c)always healthier
- (d)always fewer in number
Answer(a) genetically identical clones — asexual reproduction copies one parent's genes.