My Science School

          Dog has been a faithful friend of man for thousands of years. Most dogs are kept as pets to do useful work like herding sheep or guarding buildings. Today, there are more than 100 breeds of dog of many colours, shapes and sizes.

          Dogs see a world that is blurred and has no colour. They are short sighted and see only shades of grey. But a dog’s sense of smell is thousand times better than that of ours. If it passes through one place, it can identify the same place again due to its acute smelling power. Therefore trained dogs are used in the modern security system. They can sniff illegal drugs and culprits. Customs officers use specially trained dogs for sniffing out illegal drugs. It is not necessary to open cases or crates – one sniff is enough for a dog, even if the drugs are packed in tins. 

          In our nasal cavity there is a yellowish area of about 250 sq. mm. This contains millions of hair-like cells which are sensitive to smell. These are called chemoreceptors. They are always wet because of the mucus present there. Chemoreceptors are connected to the olfactory bulb in the brain. When we smell something its particles along with the air reach the chemoreceptors. There they produce electrical impulses in the nerves. These electrical impulses reach the olfactory bulb and we identify the smell.

          The smelling power, in fact, mainly depends upon the size of the olfactory bulb. Bigger the olfactory bulb better is the smelling power. Studies have revealed that a dog’s olfactory bulb is bigger than that of a man that is why the dogs have a greater power of smell. Another reason for this characteristic is that the dog’s nasal cavity is wetter as compared to that of human beings. This wetness further helps in identifying the smells.

          Dogs make use of the strong sense of smell in feeding, hunting and identifying enemies. 

          Rabbit is a small furry mammal with a short tail and large pointed ears. Rabbits live in burrows in the ground. Each burrow is the home of a single family. The first fossils which can be attributed to this family came from North America. But now they are found in most parts of the world. As compared to the rest of its body the rabbit has large-sized ears.

          Rabbit is a weak and timid animal and is usually surrounded by many enemies. Therefore nature has provided it with large ears to enable it to hear even the faintest of sounds. The large area of the ear catches most of the sound waves produced in the air and passes them into the inner ear. This enables the rabbit to detect its enemies in time and to run to safety areas.

         You must have noticed that a rabbit washes its ears by repeatedly licking its forepaws and rubbing them over the surface of its ears. It does this just not to keep its ears clean, but also to take into its mouth the natural oil which covers the ear surface. This oil is important in forming Vitamin D which in turn is necessary for the growth of the healthy bones. If the rabbit is prevented from doing this, it will develop rickets.

          Wild rabbits spend most of the day underground and usually come out for food only between dusk and dawn. They also have a keen sense of smell. They have long, hind legs which give them a good speed. A rabbit can run at a speed of 65 km per hour. Rabbits feed mainly on grass but eat other vegetation also. Their fertility rate is very high. Only their extraordinary fertility has enabled them to survive inspite of their many enemies. On an average a doe (female rabbit) produces 10 to 12 young ones every year. The natural enemies of rabbits are cats, dogs, foxes, minks, weasels and wolves. Man is the biggest enemy of rabbits because he hunts them for their skin, fur and meat.