Question

The chromosome number in the foot of fern embryo is 20 the number in its spore is
A. 40
B. 20
C. 10
D. 05

Answer 1

Hint: The genetic cells undergo meiotic division of the cells to form the germinative part spore. The embryo is formed after the fusion of male and female gametes after the process of fertilization.

Complete answer: 1. Spore is the germinative part of the fern. It is obtained by the meiotic division or the reduction division in which the number of chromosomes gets reduced to half of its number in the somatic cell.
2. The spores in the fern are stored in the sporangium, a bag like structure which protects the spore from the adverse environmental conditions. Also, spores have a very thick outer layer on it which helps it survive in adverse environmental situations like high temperature, low pH, very low temperature.
3. Spores are produced by the spore mother cells.
These spore mother cells undergo meiosis for the production of spores, so in meiosis, the number of chromosomes will become half of the mother cell hence spore are haploid cells.
4 . Embryo is developed from the zygote which is obtained after the fusion of male and female gametes known as the process of fertilization.
Here two haploid cells come and fuse with each other two forms a new embryo.
5 . When two haploid cells fuse with each other and form a new cell then the ploidy of the organism will be diploid so the embryo is in diploid conditions.

So if the embryo has 20 chromosomes then the spore has only 10 chromosomes.

So the option C is correct

Note: After fertilization zygote is formed and the zygote undergoes mitotic division for the development of an embryo from the zygote.