Question

Describe how both gametophytes and sporophytes have changed between the three main groups of plants?

Answer 1

Different plant groups complete their life cycle in different ways.

1.HAPLONTIC LIFE CYCLE: In this case the dominant photosynthetic phase is a gametophyte produced by haploid spores. The gametophyte produces gametes by mitosis. The gametes fuse to form a diploid zygote. It represents the sporophytic generation.

Zygote undergoes meiosis to form haploid spores. Algae like volvox,spirogyra represent this pattern of life cycle.

2. DIPLONTIC LIFE CYCLE: In this type of life cycle the diploid sporophyte is the dominant photosynthetic independent phase of the plant. Gametophtic phase of the plant is represented by a single to a few celled haplpid gametophyte. The kind of lifr cycle is termed as diplontic life cycle. All seed bearing plants like gymnosperms and angiosperms follow this pattern of life cycle.

3 HAPLO-DIPLONTIC LIFE CYCLE : Here both haploid and diploid phases are multicellular and often free living. Bryophytes and Pteridophytes exhibit this pattern of life cycle but they differ in the dominant phases.In bryophytes the dominant thalloid plant body represents the haploid gametophytic phase. It alternates with short lived multicellular sporophyte totally or partially dependent on the gametohyte for support of nutrition.

In pteridophytes the diploid sporophyte is the dominant independent photosynthetic vascular plant body. It alternates with independent short lived haploid gametophyte.

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