Short Answer Type(a) How do organic farmers control pests ? Give two examples.
(b) State the difference in their approach from that of conventional pest control methods.
(a) Name the selectable markers in the cloning vector pBR322 ? Mention the role they play.
(b) Why is the coding sequence of an enzyme 
-galactosidase a preferred selectable marker in comparison to the ones named above ?
(a) Why must a cell be made 'competent' in biotechnology experiments ? How does
calcium ion help in doing so ?
(b) State the role of 'biolistic gun' in biotechnology experiments.
Explain Parasitism and co. evolution with the help of one example of each.
Parasitism - is a non-mutual symbiotic relationship between species, where one species, the parasite, benefits at the expense of the other, the host. For example the relationship between the human liver fluke and its hosts that is the snail and a fish.
In the case of co-evolutiion, the species interact so intimately that they can cause evolutionary changes in each other over time.The term coevolution is used to describe cases where two (or more) species reciprocally affect each other's evolution. So for example, an evolutionary change in the morphology of a plant, might affect the morphology of a herbivore that eats the plant, which in turn might affect the evolution of the plant, which might affect the evolution of the herbivore. For example, the Mediterranean orchid Ophrys bears flowers, the petals of which bear uncanny resemblance with the female bee. If there are any changes in the female bee's colour or pattern, the plant will also co-evolve to maintain the resemblance.
Long Answer TypeA large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being childless.
(a) Why in your opinion the female partner is often blamed for such situations in India ? Mention any two values that you as a biology student can promote to check this social evil.
(b) State any two reasons responsible for the cause of infertility.
(c) Suggest a technique that can help the couple to have a child where the problem is with the male partner.
(a) What is polygenic inheritance ? Explain with the help of a suitable example.
(b) How are pleiotropy and Mendelian pattern of inheritance different from polygenic pattern of inheritance ?
(a) Name the stage in the cell cycle where DNA replication occurs.
(b) Explain the mechanism of DNA replication. Highlight the role of enzymes in the process.
(c) Why is DNA replication said to be semiconservative ?
(a) Name the two growth models that represent populations growth and draw the respective growth curves they represent.
(b) State the basis for the difference in the shape of these curves.
(c) Which one of the curves represent the human population growth at present ? Do you think such a curve is sustainable ? Give reason in support of your answer.
(a) Taking an example of a small pond explain how the four components of an ecosystem function as a unit.
(b) Name the type of food chain that exists in a pond.
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