MediumBiologyHigh School (11–12)Diversity of Living Organisms › Bryophytes and PteridophytesNumerical
A cell of the thallus of a liverwort has 9 chromosomes.
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cell of the thallus of a liverwort has chromosomes. How many chromosomes are in (a) one of its spores, (b) an antherozoid, (c) the zygote, and (d) a cell of the seta?
Need a reminder? The key ideaShow
Most pteridophytes are homosporous. Selaginella and Salvinia are heterosporous: microspores grow into male gametophytes, megaspores into female gametophytes. A megasporangium has one megaspore mother cell and makes 4 megaspores. The female gametophyte stays on the parent, and the embryo starts to grow inside it: a forerunner of the seed habit. Gametophytes are haploid, sporophytes diploid.
The worked solution
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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. Haploid parts. The thallus, its gametes and the spores are haploid: the spore has and the antherozoid has chromosomes.
Step 2. Diploid parts. Fertilisation joins two haploid gametes: the zygote has . The seta grows from the zygote, so its cells have .
Answer: (a) ; (b) ; (c) ; (d) .
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