Hi, I have a question regarding the life cycles of these plants. PLEASE be very

Question

Hi,

I have a question regarding the life cycles of these plants. PLEASE be very thorough and detailed with your responses

1. Compare the life cycle of the bryophytes with a pteridophyte. In what ways are the pteridophytes better adapted to the land environment? If the Earth were to return to a warmer, wetter climate, would the fern still be better adapted than the bryophyte? Why?

2. Compare the life cycle of a green alga with a bryophyte. In what ways are the bryophytes better adapted to the land environment?

Explanation / Answer

1. Bryophytes: They include plants called mosses, hornworts and liverworts that live in amphibious environments. The plant body is leafy or thalloid. The cells of the plant body are haploid. Vascular tissues like xylem and phloem are absent. In the lifecycle gametophytic phase is dominant (haploid). The sporophytic phase (diploid) is completely depends on gametophytic phase. The life cycle is haplodiplontic. Exaples, Marchantia, Funaria, Anthoceros etc.

Pteridophytes: They are the first vascular cryptogams. The life cycle contains 2 stages. First diploid and vegetative sporophytic stage and second sexual haploid gametophytic stage. The pteridophytes include Lycopsida - Lycopodium, Selaginella; Sphenopsida - Equisetum; Psilopsida - Psilotum and Filicopsida - ferns. The plant body in pteridophytes is differentiated into roots, stem and leaves. The cells in the plant body are diploid. primitive type of vascular tissue consisting of xyem and phloem is present. Sporophytic generation is dominant. The sporophytic phase is independent from gametophyte and autotrophic. The life cycle is diplohaplontic.

The bryophytes are amphibious plants and need both soil and water to lead their lifecycle. The pteridophytes are completely land plants. Moreover the prteidophytes have vascular tissues that able to absorb nutrients and water from soil. Hence, in warmer and wet conditions the vascular cryptogams or pteridophytes like ferns are to survive better than bryophytes.

2. The plant body is thallus in both green algae and bryophytes. In green algae single cell to multicellular and plant like organization is observed. Both are nonvascular and autotrophic. The gametophytic plant body is green thalloid in bryophytes resembles the plant body of green algae. The cells of vegetative phase are haploid. The life cycle is haplodiplontic in both green algae and bryophytes. The green algae are mostly aquatic and bryophytes are amphibious. The sperms swim in water to reach egg is observed in both and reminds the ancestory of green algae to bryophytes.

In green algae the sexual reproduction is isogamous, anisogamous and oogamous types. In bryophytes only oogamous type of sexual reproduction is observed. The female sex organ is oogonium in algae and archegonium in bryophytes. The sporophyte is independent in algae and sporophyte depends on gametophyte in bryophytes. The sporophyte is devided into foot, seta and capsule in bryophytes and no such differentiation is observed in green algae. The lifecycle is homologous in algae and is heteromorphic in bryophytes.

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