Sexual Reproduction in Flowering Plants — BIOLOGY STD 12 Science — Question

Ankit attended a blood donation camp to donate blood and came to know that he was HIV positive. He lost interest in studies knowing that. He remained absent from school for a long time. The biology teacher visited his house and talked to him. Ankit started coming to school again and showed interest in studies.

1. A person detected to be HIV positive should be isolated by the society. Do you agree? Why/ why not?
2. Write the processes through which, AIDS does not spread.
3. Who are at higher risk of encountering AIDS?
4. What sense of responsibility did the biology teacher exhibit?

Rearrange the following in the correct sequence to accomplish an important biotechnological reaction:

1. In vitro synthesis of copies of DNA of interest,
2. Chemically synthesised oligonucleotides,
3. Enzyme DNA-polymerase,
4. Complementry region of DNA,
5. Genomic DNA template,
6. Nucleotides provided,
7. Primers,
8. Thermostable DNA-polymers (From Thermus aquaticus),
9. Denaturation of dsDNA.

Why are biogas plants more suitable and advantageous in rural area?

Draw the diagram of a mature embryo sac and show its 8-nucleate, 7-celled nature. Show the following parts: antipodals, synergids, egg, central cell, polar nuclei.

Write a note on barrier method: (i) Condoms (ii) Diaphragm, cervical caps, vaults

1. Draw a labelled schematic diagram of a replication fork showing continuous and discontinuous replication of DNA strands.
2. State a reason why is the replication continuous and discontinuous in the diagram drawn.

Community service department of your school plans a visit to a slum area near the school with an objective to educate the slum dwellers with respect to health and hygiene.

1. Why is there a need to organise such visits?
2. Write the steps you will highlight as a member of this department, in your interactions with them to enable them to lead a healthy life.

How does a transgenic organism differ from the rest of its population? Give any two examples of such organism for human advantage.

Write the modes of asexual reproduction in the following organisms.
Sycon, Penicillium, Spongilla, Paramecium, Yeast, Marchantia, Amoeba and Chlamydomonas.

Bio-diversification of life started to occur almost 3 billion years ago. Since then new species have been evolving and then disappearing en masse from earth.
a. How many episodes of mass extinctions of species have already taken place and which one is in progress in the current era?
b. How is current episode in progress different from the previous episodes and why? Explain.