Detection of Bile Salt in Urine :-
Bile is a yellow-green fluid that contains water and organic molecules such as cholesterol, bile acids, and bilirubin. In humans, the two main function of bile are digestion and absorption of fats and eliminating bile salts from the body by secretion into bile. In humans and most vertebrates, bile is produced by the liver.

We can test for the presence of bile salt in urine using Smith’s reagent and Pattern Raffo’s test. On adding urine to the Smith’s reagent, a green ring is formed in the presence of bile salt in urine. Pattern Raffo’s test gives a red colour in the presence of bile salt.

This video explains how to detect the presence of bile salt in urine.
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To Study Plant Population Density by Quadrat Method :-
Density represents the numerical strength of a certain plant species in the community per unit area. The number of individuals of the species in any unit area is its density. The unit area may be as small as 5 square cm to as large as 10 square metre depending on the size and nature of the plant community under study. For herbaceous vegetation a metre square quadrat is normally used. Density which gives an idea of degree of competition is calculated as follows.

Density= Total number of individual(s) of the species in all the sampling unit (S) / Total number of sampling units studied (Q)

The value thus obtained is then expressed as number of individuals per unit area. When the measured unit area is divided by the number of individuals the average area occupied by each individual is obtained.

This video explains how to study plant population density by the quadrat method.

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