MediumBiologyHigh School (11–12)Diversity of Living Organisms › Plant Life Cycles and Alternation of GenerationsDiversity of Living Organisms › Gymnosperms and AngiospermsConceptualBoard Exam
Read the four descriptions and name the pattern of each life cycle…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Read the four descriptions and name the pattern of each life cycle. (a) A green pond alga whose only diploid cell is a thick-walled zygote. (b) A seaweed whose large body is diploid, and whose only haploid cells are its gametes. (c) A leafy green plant on a wet wall; a stalked capsule grows out of it and makes spores. (d) A plant with fronds and vascular tissue, whose spores grow into small, heart-shaped prothalli.
Need a reminder? The key ideaShow
The gametophyte () makes gametes; the sporophyte () makes spores by meiosis. Haplontic: the gametophyte is the main plant and the zygote is the only diploid cell (Spirogyra, Volvox). Diplontic: the sporophyte is the main plant (seed plants, Fucus). Haplo-diplontic: both are many-celled (bryophytes with the gametophyte main, pteridophytes with the sporophyte main).
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Only the zygote is diploid: haplontic, like Spirogyra.
Step 2. (b) The body is diploid, and only the gametes are haploid: diplontic, like Fucus.
Step 3. (c) The leafy plant is a moss gametophyte, and the capsule is its sporophyte. Both are many-celled: haplo-diplontic, with the gametophyte as the main plant.
Step 4. (d) A fern sporophyte and its prothallus are both many-celled: haplo-diplontic, with the sporophyte as the main plant.
Answer: (a) haplontic, (b) diplontic, (c) and (d) haplo-diplontic.
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