Human Health and Disease — BIOLOGY STD 12 Science — Question

Describe briefly about embryonic stages in human being.

Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.

1. Salvinia.
2. Opuntia.
3. Rhizophora.
4. Mangifera.

Describe the process of decomposition of detritus under the following heads: Fragmentation; leaching; catabolism; humification andmineralisation.

With the help of a diagram explain the structure of DNA.

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.

Write an article on vaccination and immunization.

Show that Darwin's natural selection is based on theoretical factual observations, with an example for each.

More than 25% of human population is suffering from hunger and malnutrition. Scientists have developed techniques where microbes are grown on industrial scale as a source of good protein which can be grown from waste water, animal manure and even sewage.
Based on the above information answer the following questions.

1. In what ways would it be helpful to humans?
2. What can be the response to such new ventures?
3. What values have been manifested in the above case?

Explain the Law of Dominance using a monohybrid cross.

A flower of tomato plant following the process of sexual reproduction produce 240 viable seeds.
Answer the following questions giving reasons:
What would have been the minimum number of ovules present in the ovary?