Q17 of 30 Page 1

The gradual and predictable change in the species composition of a given area is called ecological succession. What do you understand with the pioneer and climax community in this context?

The gradual and predictable change in the species composition of a given area is called ecological succession.


The species which invade the bare area are called pioneer species.


The changes lead finally to a community which is in near equilibrium with the environment and that is called the climax community.


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DDT content in the water of a lake that supplies drinking water to the nearby villages is found to be 0.004 ppm. The pelicans of that area are reported to have 2.6 ppm of DDT. Why has the concentration increased in these birds? What possible harm will this cause to the bird population? Name the phenomenon.

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Write the names of causal organisms of the following:

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d) Amoebiasis


OR


Expand the following:


a) AIDS


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(i) 6-15 days


(ii) 16 - 25 days


(iii) 26 - 28 days (if the ovum is not fertilized)