Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings?
In birds, sex determination is of ZW – ZZ type.
In this type, the males are homogametic and have ZZ sex chromosomes, and females are heterogametic with ZW pair of sex chromosomes.
| Parents: | Male | X | Female |
| ZZ | ZW | ||
| Gametes: | (Z)(Z) | (Z)(W) | |
| F1: | ZW | ZZ | |
| Female | Male |
whereas, in human beings, the chromosomal mechanism of sex determination is of XX – XY type. The human male is heterogametic and has XY sex chromosomes and the human female is homogametic with XX sex chromosomes.
“India has greater ecosystem diversity than Norway.” Do you agree with the statement? Give reasons in support of your answer.
With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations?
Organic farmers prefer the biological control of diseases and pests of the use of chemicals for the same purpose. Justify.
How has the use of Agrobacterium as vectors helped in controlling Meloidogyne incognita infestation in tobacco plants? Explain in the correct sequence.
Select and write analogous structures from the list given below:
(i) Wings of butterfly and birds
(ii) Vertebrate hearts
(ii) Tendrils of bougainvillaea and Cucurbita
(iv) Tubers of sweet potato and potato
Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organisation.
Although a prokaryotic cell has no defined nucleus, yet DNA is not scattered throughout the cell. Explain.
