In Bryophytes & Pteridophytes the number of male gametes produced is several thousand times the numbe of female gametes produced. Reason : Large number of male gametes fail to reach the female gametes during transport.
The assertion states: "In Bryophytes & Pteridophytes the number of male gametes produced is several thousand times the number of female gametes produced."
In both Bryophytes (like mosses, liverworts) and Pteridophytes (like ferns), reproduction involves distinct male and female reproductive structures.
The male reproductive structure, the antheridium, produces numerous motile male gametes called antherozoids (or spermatozoids).
The female reproductive structure, the archegonium, typically produces a single, non-motile female gamete called the egg (or oosphere).
Since each antheridium releases many antherozoids, and each archegonium contains only one egg, the total number of male gametes produced by a plant or population of plants is vastly greater than the number of female gametes.
Therefore, the assertion is correct.
Analysis of the Reason:
The reason states: "Large number of male gametes fail to reach the female gametes during transport."
Fertilization in both Bryophytes and Pteridophytes requires water.
The motile antherozoids are released into the external environment (usually a film of water) and must swim towards the archegonium to reach the egg.
This transport process is subject to environmental factors and chance. Many antherozoids may get washed away, dry out, be consumed, or simply fail to locate the chemical signals guiding them to the archegonium.
Consequently, a significant proportion of the male gametes produced do not succeed in reaching a female gamete.
Therefore, the reason is correct.
Relationship between Assertion and Reason:
The production of a vastly larger number of male gametes (Assertion) is an evolutionary strategy to compensate for the high probability of loss during transport (Reason).
By producing thousands of male gametes for every female gamete, the chances of at least one male gamete successfully reaching and fertilizing the egg are significantly increased, despite the inefficiency of the water-dependent transport mechanism.
Thus, the reason provides a valid explanation for the assertion.
Conclusion:
Both the Assertion and the Reason are correct statements, and the Reason correctly explains the Assertion.
Therefore, the correct option is: Both Assertion and reason are correct.
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Bryophytes and Pteridophytes rely on water for the movement of their male gametes (antherozoids), which are motile. These gametes must swim through a thin film of water to reach the egg cell present inside the archegonium. Since many of these gametes do not successfully reach the female gametes due to environmental barriers and the randomness of movement in water, the plant compensates by producing male gametes in huge numbers. The assertion that the number of male gametes produced is several thousand times the number of female gametes is correct. The reason that large number of male gametes fail to reach the female gametes during transport is also correct.
