• (A) D, E, C, A, B
• (B) E, D, C, B, A
• (C) B, A, D, E, C
• (D) B, A, E, C, D

Detailed Explanation

The life cycle of a pteridophyte follows a specific alternation of generations. Let's trace the sequence starting from the diploid sporophyte:

• Stage B: In the sporophyte, specialized cells called spore mother cells undergo meiosis to produce haploid spores. This is the starting point of the haploid generation.
• Stage A: Spores germinate to give rise to a multicelluar, free-living, mostly photosynthetic thalloid gametophyte called the prothallus.
• Stage D: The gametophyte (prothallus) develops multi-cellular sex organs: antheridia (male) and archegonia (female).
• Stage E: Male gametes called antherozoids are released from the antheridia. Water is essential for the transfer of these antherozoids to the mouth of the archegonium.
• Stage C: Fusion of the male gamete with the egg present in the archegonium results in fertilisation, forming a diploid zygote that eventually grows into a new sporophyte.

Thus, the correct sequence is B → A → D → E → C.

Related Theory

Pteridophytes, which include horsetails and ferns, are the first terrestrial plants to possess vascular tissues—xylem and phloem. Their life cycle is uniquely characterized by an independent sporophyte and an independent gametophyte.

1. The Independent Generations

The main plant body is a sporophyte (2n), which is differentiated into true root, stem, and leaves. However, they also produce a small but independent gametophyte (n). Because the gametophyte requires cool, damp, and shady places to grow, and water is mandatory for fertilisation, the spread of living pteridophytes is limited and restricted to narrow geographical regions.

2. Sporophylls and Spores

Sporophytes bear sporangia that are subtended by leaf-like appendages called sporophylls. In some cases, sporophylls may form distinct compact structures called strobili or cones (e.g., Selaginella, Equisetum). The sporangia produce spores by meiosis in spore mother cells.

3. The Prothallus

The spores germinate to produce a prothallus. Key characteristics include:

• Inconspicuous, small, but multicellular.
• Free-living and mostly photosynthetic.
• Requires water for the movement of male gametes.

4. Homosporous vs. Heterosporous

Most pteridophytes produce similar kinds of spores (homosporous). However, genera like Selaginella and Salvinia produce two kinds of spores: macro (large) and micro (small) spores, and are known as heterosporous. This heterospory is considered an important precursor to the seed habit.

5. Common Mistakes to Avoid

• Sequence Error: Forgetting that meiosis happens *before* the prothallus is formed.
• Water Requirement: Thinking only bryophytes need water; pteridophytes strictly require water for the transfer of antherozoids.
• Dominance: Confusing the dominant phase; in pteridophytes, the sporophyte is the dominant phase, unlike bryophytes where the gametophyte is dominant.

Frequently Asked Questions (FAQs)