Polluted water bodies have usually very high abundance of plants like Nostoc and Oscillitoria. Give reasons.

During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reasons.

Excessive nutrients in a fresh-water body cause fish mortality. Give two reasons.

Figure shows a potentiometer with a cell of 2.0 V and internal resistance 0.40 Omega maintaining a potential drop across the resistor wire AB. A standard cell which maintains a constant emf of 1.02 V (for very moderate currents upto a few mA) gives a balance point at 67.3 cm length of the wire. To ensure very low currents drawn from the standard cell, a very high resistance of 600 k Omega is put in series with it, which is shorted close to the balance point. The standard cell is then replaced by a cell of unknown emf epsilon and the balance point found similarly, turns out to be at 82.3 cm length of the wire. What purpose does the high resistance of 600 kOmega have? :

Veracular names given to the organisms in a particular language and region of the world. There are several types of names like English, Hindi, Gujrati, Marathi, Bengali, Tamil, etc. The names have been in use since times immemorial. New names are added whenever outside organisms are introduced into the area. Why veracular names can not be used by biologists? Give two reasons.

Trophical regions are likely to have more biological diversity than temperate ones. Give two reasons to justify the statement.