MediumBiologyHigh School (11–12)Diversity of Living Organisms › Bryophytes and PteridophytesNumerical
A cone of Selaginella has 20 microsporangia, each with 30 microspore mother cells, and 6…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cone of Selaginella has microsporangia, each with microspore mother cells, and megasporangia, each with one megaspore mother cell. Each mother cell divides by meiosis into spores. (a) How many microspores does the cone make? (b) How many megaspores? (c) How many microspores are there for each megaspore?
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
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. Microspores. microspores.
Step 2. Megaspores. megaspores.
Step 3. The ratio. microspores for each megaspore.
Answer: (a) ; (b) ; (c) .
Discussion (0)
Log in to join the discussion.
Loading…