Category Biology

    Normally when images of an object are formed on the retina of the two eyes, the two fields of vision overlap to some extent at the centre and provide a perception of depth. But for aiming at a distant object, depth perception is not as important as the proper line of alignment. For arches and shooters, the main objective is to find the line of alignment of the target and not its depth because the distance of the target is usually known. Since our two eyes are separated by a distance, they give two separate lines of alignment which can never allow the archer to aim exactly at the target. But on closing one eye, the archer can aim at the                                                                                    target more precisely by aligning his eye with the tip of                                                                               the arrow or gun sight and the target and shoot accurately.

            Our mouth starts watering on seeing or smelling a spicy food because of the reflex action. The salivary glands in our mouth become active when we eat. The enzymes present in the saliva help in the digestion of food. But, sometimes, the glands start secreting large amounts of saliva even when there is no food in the mouth. This happens in anticipation of eating a tasty or spicy food when we see or smell it.

            On seeing or smelling a spicy food, nerve cells are stimulated and signals are sent to the brain which activate the salivary glands. The latter start secreting and our mouth start watering.

 The hair growing on our bodies have different characteristics. Those on our head grow long, whereas the hair on our skin and eyelids (eyelashes) are short. Our eyelashes keep falling out at regular intervals and are replaced by newer ones. This is an evolved trait and has become a part of the genetic make-up of any organism.

  Wounds on the tongue heal fast because the tongue has a rich supply of blood vessels. This helps the which blood cells to easily reach the site of wound to fight any infection by bacteria and other microorganisms which can delay healing. The saliva too helps in healing as it bathes the tongue in a chemical Iysozyme that kills bacteria. Besides, the cells of upper layer of the tongue divide very rapidly and so the wound in the tongue heals fast.

            Usually a person’s fingerprints do not change during the lifetime. Minor and superficial cuts that he’ll do not affect the pattern formed by the ridges that cover the skin of the fingertips. Ridges are the impressions which make fingerprints. However, extensive or deep wounds, severe burns, surgery or disease may destroy these ridges and lead to a change in fingerprint patterns. Deep wounds damage the underlying dermis of the skin and healing often leads to scar formation. Since scar tissue does not                                                                                 show secondary modifications such as hair, it does                                                                                  not show the ridge pattern either. However, these are                                                                             extremely unlikely events and usually fingerprints                                                                                  are for life.