Account for the following briefly:
Twins may or may not be identical.
Sometimes, two eggs are released from the ovaries at a time and both may get fertilised by two different sperms. Such twins are dizygotic and are not identical.
While in other situations, a single fertilised egg may split during the early stages of cell division. Such twins are monozygotic and are identical. Therefore, twins may or may not be identical.
Account for the following briefly:
(iv) Herbaceous plants growing in well-watered soils are found to wilt on a hot day.
Draw a diagram of the nucleus of a cell, having chromosome number 6, as it would appear in the metaphase stage of mitosis and label the following parts in the diagram:
1. Aster
2. Achromatic spindle
3. Chromatid
4. Centromere
Mention the difference between mitosis and meiosis with reference to
1. Number of daughter cells formed at the end of the division.
2. The chromosome number of the daughter cells formed.