Organisms and Populations — BIOLOGY STD 12 Science — Question

Define the terms and give one example for each: Parasitism

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 visualize DNA bands.

State the views of Oparin and Haldane on evolution. How does S.L. Miller's experiment support their views?

OR

1. Explain the theory of abiogenesis.
2. How did Miller demonstrate experimentally the chemical evolution that happened three billion years ago?

What are chasmogamous flowers? Can cross-pollination occur in cleistogamous flowers? Give reasons for your answer.

Co-evolution is a spectacular example of mutualism between an animal and a plant. Describe co-evolution with the help of an example.

How have human activities caused desertification? Explain.

Name the regions marked A, B and C.

Discuss the mode of action and advantages/ disadvantages of hormonal contraceptives.

Name the tissue which lines the inner surfaces of fallopian tube.

With the help of a schematic diagram, explain the location and role of the following in a transcription unit.
Promoter, structural gene, terminator.