MediumBiologyHigh School (11–12)Diversity of Living Organisms › Bryophytes and PteridophytesNumericalBoard Exam
A thallus of Marchantia growing on a flowerpot has 9 gemma cups, and each cup holds 14 gemmae…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A thallus of Marchantia growing on a flowerpot has gemma cups, and each cup holds gemmae. Rain splashes them out. (a) How many gemmae are there in all? (b) If only two in every three gemmae land on damp soil and grow, how many new thalli form? (c) Will the new thalli be like the parent, or different? Why?
Need a reminder? The key ideaShow
Bryophytes (liverworts and mosses) live in damp places and need water for fertilisation. The main plant body is the haploid gametophyte, held by rhizoids, with no vascular tissue. Antheridia make biflagellate antherozoids; archegonia make one egg. The zygote grows into a sporophyte (foot, seta, capsule) that depends on the gametophyte and makes spores by meiosis. Liverworts make gemmae in gemma cups; mosses grow from a protonema. Sphagnum holds much water and forms peat.
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. All the gemmae. gemmae.
Step 2. The ones that grow. new thalli.
Step 3. Like the parent. Gemmae are multicellular buds made without meiosis or fertilisation. This is asexual reproduction, so each new thallus is like the parent.
Answer: (a) gemmae; (b) new thalli; (c) like the parent, because gemmae are made asexually.
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