EasyBiologyHigh School (11–12)Diversity of Living Organisms › Gymnosperms and AngiospermsNumericalBoard Exam
Draw an embryo sac from memory and label its parts…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Draw an embryo sac from memory and label its parts. How many cells and how many nuclei does it have? How many of its nuclei take part in fertilisation?
Need a reminder? The key ideaShow
In angiosperms, ovules lie inside an ovary. The embryo sac has 7 cells and 8 nuclei: the egg, 2 synergids, 3 antipodals and the central cell with 2 polar nuclei. One pollen tube brings two male gametes. Syngamy (gamete and egg) gives the zygote, . Triple fusion (gamete and two polar nuclei) gives the primary endosperm nucleus, .
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. The cells. The egg, synergids, antipodals and central cell: cells.
Step 2. The nuclei. Every cell has one nucleus, except the central cell, which has two: nuclei.
Step 3. Fertilisation. The egg nucleus fuses with one male gamete, and the two polar nuclei fuse with the other: nuclei of the embryo sac take part.
Answer: cells and nuclei; of the nuclei take part in fertilisation.
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