Secondary metabolites such as nicotine, strychnine and caffeine are produced by plants for their:

1. Growth response

2. Defence action

3. Effect on reproduction

4. Nutritive value

Which of the following is not an attribute of a population?

1.  Natality

2.  Mortality

3.  Species interaction

4.  Sex ratio

The process of growth is maximum during:

1. Lag phase

2. Senescence

3. Dormancy

4. Log phase

Consider the following water conservation mechanisms

A. Nasal countercurrent mechanism

B. Dependence on metabolic water

C. Highly hypertonic urine

D. Living one more on protein rich diet

The kangaroo rat living in desert can survive without drinking water because of

1. A, B & C

2. A, B & D

3. B, C & D

4. A, C & D

Match the items in Column-I with those in Column-II:

Select the correct option from the following:

The impact of immigration on population density is:

Between which of the following, the relationship is not an example of commensalism?

Carnivorous animals - lions and leopards, occupy the same niche but lions predate mostly larger animals and leopards take smaller ones. This mechanism of competition is referred to as:

Which two of the following changes (a-d) usually tend to occur in the plain dwellers when they move to high altitudes? (3,500 m or more)
(a) Increase in red blood cell size
(b) Increase in red blood cell production
(c) Increased breathing rate
(d) Increase in thrombocyte count
Changes occurring are:
1. (a) and (d)
2. (a) and (b)
3. (b) and (c)
4. (c) and (d)

Inspite of interspecific competition in nature, which mechanism the competing species might have evolved for their survival?