Organisms and Populations — BIOLOGY STD 12 Science — Question

How do homogametes differ from heterogametes? Give an example of an organism for each of the two kinds.

A patient complains of suffering from constipation, stomach ache, stool with blood clots and excess mucous.
The physician diagnosed it as amoebiasis, after stool test.
a. Write the scientific name of the microbe identified in the stool sample.
b. How do you think, the patient must have contracted it?
c. Write your suggestions to the patient to avoid infection in future.

Discuss briefly the following:

1. Radioactive wastes.
2. Defunct ships and e-wastes.
3. Municipal solid wastes.

Baculoviruses are good examples of biocontrol agents. Justify giving three reasons.

List all the wastes that you generate, at home, school or during your trips to other places, could you very easily reduce? Which would be difficult or rather impossible to reduce?

Define external fertilisation. Mention its disadvantages.

(i) Write the name of the agent that causes typhoid (intermittent fever) in humans.
(ii) Write the name of the test that confirms this disease.
(iii) How does its pathogen enter the human body? Write its clinical symptoms and in severe cases, name the body part that is affected by it.

1. Expand BOD.
2. At a particular segment of a river near a sugar factory, the BOD is much higher than the normal level. What is it indicative of? What will happen to the living organisms in this part of the river?
3. Under what conditions will the BOD be lowered in the river? How will it affect the aquatic life?

A person has to perform crosses for the purpose of studying inheritance of a few traits/ characters. What should be the criteria for selecting the organisms?