All dogs have keenly developed senses of smell and hearing. Dogs naturally depend on their sense of smell to identify friends and foes. They also mark off their territory with their own urine which is individually recognizable to themselves and other dogs. Human beings also have individual ‘smells’ although they are usually unable to identify it. Each individual has a unique odour -the product of diet and subtle differences in metabolism.
Dogs can ‘read’ these individual odour signatures and distinguish between different individuals and follow the scent-trail for long distances even in the absence of other clues.
Breeds such as the Blood hound, German shepherd and Beagle are famous for their tracking skills.
Artificial insemination is a method used in animal husbandry to genetically upgrade stock by producing good quality off springs. In humans, the process is used to induce pregnancy in case of reproductive blocks.
Vitamin D is a group of about 10 fat soluble compounds. The form of vitamin D produced in humans is called vitamin and that in plants is called vitamin . Both vitamin and can be formed from their respective precursors in the presence of sunlight. In humans, exposure to sunlight leads to secretion of a compound called 7-dehydrocholesterol at the surface of the skin. The ultraviolet rays in sunlight convert 7-dehydrocholesterol into vitamin D by means of a series of chemical reactions. The vitamin D formed at the surface of the skin is reabsorbed into the blood stream.
Water supplied to cities and towns is usually taken from rivers or lakes and contain various kinds of pollutants, and so has to be purified. First, the raw water is passed through screens to separate coarse solids and it is then fed into settling tanks where the suspended solids settle out. Some times, substances such as alum are added to aid the settling process.
