Reproductive Health — BIOLOGY STD 12 Science — Question

Draw a longitudinal section of a post-pollinated pistil showing entry of pollen tube into a mature embryo sac. Label filiform apparatus, chalazal end, hilum, antipodals, male gametes and secondary nucleus.

In the metropolitan cities of India, many children are suffering from allergy/ asthma. What are the main causes of this problem. Give some symptoms of allergic reactions.

Explain the mechanism of DNA replication with the help of a replication fork. What role does the enzyme DNA-ligase play in a DNA replication fork?

Name the type of interaction seen in each of the following examples:

1. Ascaris worms living in the intestine of human.
2. Wasp pollinating fig inflorescence.
3. Clown fish living among the tentacles of sea-anemone.
4. Mycorrhizae living on the roots of higher plants.
5. Orchid growing on a branch of a mango tree.
6. Disappearance of smaller barnacles when Balanus dominated in the Coast of Scotland.

An organic farmer relies on natural predation for controlling plant pests and diseases. Justify giving reasons why this is considered to be a holistic approach.

How has RNAi technique helped to prevent the infestation of roots in tobacco plants by a nematode Meloidogyne incognita?

Name the stages when oogenesis and spermatogenesis initiate in human female and male, respectively.

Name the important mammary gland secretions that help in resistance of the new born baby.

During an excavation assignment, scientists collected pollen grains of a plant preserved in deeper layers of soil. Analyse the properties of pollen grains which help in the fossilization.

People are quite apprehensive to use GM crops. Give three arguments in support of GM crops so as to convince the people in favour of such crops.