Ecosystems — BIOLOGY STD 12 Science — Question

1. Mention the exact location or the site in a flowering plant, where the following developments take place:

1. Deposition of sporopollenin.
2. Triple fusion.
3. Release of male gametes.
4. Megasporogenesis.

2. Draw a labelled diagram of a male gametophyte of an angiosperm.

Emigration, Immigration, More mortality, Unlimited resources, More natality, Continuous reproduction.

Column A	Column B
(1) Decrease in population density	————–
(2) Increase in population density	—————
(3) Exponential growth	————–

Given below are the sequences of nucleotides in a particular mRNA and amino acids coded by it.
UUU AUG UUC GAG UUA GUG UAA
Phe - Met - Phe - Glu - Leu – Val
Write the properties of genetic code that can be and that cannot be correlated from the above given data.

Give reasons : There is steady concentration of ozone in the stratosphere.

While holding a tea cup Mr. Kothari’s hands rattle. Which disorder he may be suffering from and what is the reason for this?

What is the difference between a primary oöcyte and a secondary oöcyte?

Sketch and label human male reproductive system'.

What is the effect of UV-B radiation on body?

Why did Hershey and Chase work with bacteriophages in their experiments to prove that DNA is the genetic material? Explain.

1. 'Organisms may be conformers or regulators'. Explain this statement and give one example of each.
2. Why are there more conformers than regulators in the animal world?