Human Reproduction — BIOLOGY STD 12 Science — Question

State and explain with the help of a cross, the law of segregation as proposed by Mendel.

Explain with the help of one example how genetically modified plants can:

1. Reduce usage of chemical pesticides.
2. Enhance nutritional value of food crops.

In a field of sugarcane, all the plants have been damaged during an epidemic of a fungal disease, whereas, in another field in the same area, there were many plants that were not affected by the disease.

1. Explain the reason for this observation.
2. An expert explains to the farmer, how the unaffected plants can be used to increase their number. Can you enumerate them?
3. Is there any method to recover disease-free plant from diseased ones.
4. What values are shown by the expert?

(i) Explain the significance of each of the following features present in plants given below:, (a) In rose-bay plant the stamens ripen before the stigma., (b) In certain species of primrose, the flowers have short stamen and long style., (c) The bisexual flower of mustard exhibits rejection of self-pollen grain., (ii) Explain how autogamy is prevented in castor and papaya plant respectively.

State and explain the “law of independent assortment” in a typical Mendelian dihybrid cross.

Enumerate the differences between asexual and sexual reproduction. Describe the types of asexual reproduction exhibited by unicellular organisms.

1. Distinguish between parasitism and predation, with an example of each.
2. Name two groups of animals, that are regulaters.
3. When does the growth curve assume of J shape?

Justify the following statement in terms of ecosystem dynamics. “Nature tends to increase the gross primary productivity, while man tends to increase the net primary productivity”.

What is organic farming? Discuss the benefits of organic farming as a viable practise in the context of developing nations like India.

Differentiate between: Ovipary and Vivipary. Cite an example for each type.