Evolution — BIOLOGY STD 12 Science — Question

What are the different ways in which organisms adapt to the changes in the environment?

1. In humans, males are heterogametic and females are homogametic. Explain. Are there any examples where males are homogametic and females heterogametic?
2. Also describe as to, who determines the sex of an unborn child? Mention whether temperature has a role in sex determination.

1. Draw a schematic labelled diagram of a fertilised embryo sac of an angiosperm.
2. Describe the stages in embryo development in a dicot plant.

Discuss about physiological effects and applications of ethylene.

In case of polyembryony, If one embryo develops from the synergid and another from the nucellus, which one is haploid and which is diploid? Describe polyembryony and also mention how can it be commercially exploited.

Write an account of auxins as growth regulators.

Explain with suitable diagram how test cross is used to find out genotype of dominant plant.

What are the different components of ecosystem?

Any recombinant DNA with desired gene is required in billion copies for commercial use. How is this amplification done? Explain.