Algal Reproduction: Vegetative to Sexual — NEET Biology
📚 Practice ConceptThe algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction is by fragmentation. Each fragment develops into a thallus. Asexual reproduction is by the production of different types of spores, the most common being the zoospores. They are flagellated (motile) and on germination gives rise to new plants. Sexual reproduction takes place through fusion of two gametes. These gametes can be flagellated and similar in size (as in Ulothrix) or non-flagellated (non-motile) but similar in size (as in Spirogyra). Such reproduction is called isogamous. Fusion of two gametes dissimilar in size, as in species of Eudorina is termed as anisogamous. Fusion between one large, non-motile (static) female gamete and a smaller, motile male gamete is termed oogamous, e.g., Volvox, Fucus.
Which of the above statements are correct? S1: Fragmentation is a vegetative reproductive method in algae, where each fragment can develop into a new thallus. S2: Asexual reproduction in algae commonly involves the production of flagellated zoospores. S3: Isogamous sexual reproduction in algae is characterized by the fusion of gametes that are dissimilar in size, as seen in Volvox. S4: Oogamous reproduction typically involves the fusion of a large, non-motile female gamete and a smaller, motile male gamete. S5: All forms of sexual reproduction in algae require flagellated gametes for fusion.
View solution & NCERT explanation
Correct answer: B — S1, S2 and S4 are correct
The core concept tested here is the different methods of reproduction in algae. Vegetative reproduction occurs by fragmentation, where each fragment grows into a new thallus, making S1 correct. Asexual reproduction is primarily by motile, flagellated zoospores, thus S2 is correct. Isogamous reproduction involves the fusion of gametes that are similar in size (e.g., Ulothrix or Spirogyra), while gametes dissimilar in size (anisogamous, e.g., Eudorina) or a large non-motile female and smaller motile male gamete (oogamous, e.g., Volvox, Fucus) are distinct forms. Therefore, S3 is incorrect as Volvox exhibits oogamy, not isogamy, and isogamous gametes are similar in size. S4 accurately describes oogamous reproduction, making it correct. S5 is incorrect because some forms of isogamy, such as in Spirogyra, involve non-flagellated (non-motile) gametes. Based on the analysis, S1, S2, and S4 are correct. Final Answer: The correct option is B because statements S1, S2, and S4 accurately describe the reproductive methods in algae according to NCERT.
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