Human Reproduction — BIOLOGY STD 12 Science — Question

Mention any two autosomal genetic disorders with their symptoms.

What is a biogeochemical cycle. What is the role of the reservoir in a biogeochemical cycle. Give an example of a sedimentary cycle with reservoir located in earth’s crust.

Illustration below is a DNA segment, which constitutes a gene:

1. Name the shaded and unshaded regions of gene.
2. Explain how these genes are expressed.
3. How is this gene different from prokaryotic gene in its expression?

Answer the following questions:
Explain the role of any two accessory glands in human male reproductive system.

Describe the human male reproductive system.

1. Draw a diagram of a mature embryo sac of an angiosperm and label the following parts in it:

1. Filiform apparatus.
2. Synergids.
3. Central cell.
4. Egg cell.
5. Polar nuclei.
6. Antipodals.

2. Write the fate of egg cell and polar nuclei after fertilisation.

One chromosome contains one molecule of DNA. In eukaryotes the length of the DNA molecule is enormously large. Explain how such a long molecule fits into the tiny chromosomes seen at metaphase.

Ramesh is a small scale farmer and holds 2.5 acres of land. He would like to increase the yield in his farm. Rahul, a student of MSc. (Agriculture) advised him to go to the agricultural department centre of his locality to get biofertilisers according to the variety of the crop. He also suggested Ramesh to stop the use of chemical fertilisers.

1. Explain the term biofertilisers.
2. Name the biofertiliser that is used mostly in paddy fields.
3. What are the values shown by Rahul?