Principles of Inheritance and Variation — BIOLOGY STD 12 Science — Question

Explain convergent and divergent evolution with the help of one example of each.

Draw a schematic transverse section of a mature anther of an angiosperm. Label its epidermis, middle layers, tapetum, endothecium, sporogenous tissue and the connective.

What is vegetative propagation? Give two suitable examples.

A student on a school trip started sneezing and wheezing soon after reaching the hill station for no explained reasons. But, on return to the plains the symptoms disappeared. What is such a response called? How does the body produce it?

Although Mendel published his work on inheritance of characters in 1865, for several reasons, it remained unrecognised till 1900. Explain giving three reasons, why it did take so long.

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.

hCG [human chorionic gonadotropin].

Differentiate between zona pellucida and corona radiata.

Rajesh was doing gel electrophoresis to purify DNA fragments. Given below is the sketch of the observations of the experiment performed by him.

1. At which end he would have loaded the samples and where?
2. Analyse the reason for different positions taken up by the DNA bands.
3. Elaborate the step he would have followed to visualise DNA bands.

Two types of aquatic organisms in a lake show specific growth patterns as shown below, in brief period of time. The lake is adjacent to an agricultural land extensively supplied with fertilisers.

Answer the questions based on the facts given above:

1. Name the organisms depicting the patterns A and B.
2. State the reason for the growth pattern seen in
3. Write the effects of the growth patterns seen above.