Category Zoology

               Penguins are a peculiar category of sea birds which can stand up straight and flat-footed like us. Do you know where these birds are found?

               Penguins are found in Southern hemisphere. They live along the Antarctic continent and islands as well as on the cool Southern hemisphere coast of Africa, Australia, New Zealand and South America.

              The wings of penguins have evolved into flippers. As a result, they can not fly but they are excellent swimmers. They walk in a strange manner. In the earlier phases of evolution they could fly like other birds. But over a period of time, their wings became very short. The reason is that penguins lived in the remote areas of Antarctica, where they had practically no enemies to attack them. So they lived safely in land and water without ever using their wings and in course of time their wings became very small. 

               Penguins live in flocks. A single rookery may contain more than a million penguins. They feed on fish, squids and crustaceans.

               Penguins withstand extremely cold conditions on account of a very dense plumage all over their bodies. These feathers are waterproof and have tiny air spaces that help them keep warm. Underneath this thick coat of feathers, there is an insulating layer of blubber. This helps to keep the body warm and store food and water. They also have a thick coat of fat to protect them from the cold.

               Female penguins lay one or two eggs, which are brooded by both parents. They do not take food during incubation. Young penguins are fed by regurgitation. There are 17 species of penguins. The species differ mainly in head pattern and in size. Their sizes vary from 40 cm (fairy penguin) to almost 120 cm (Emperor penguin). Both sexes are alike in size. Only two, the Emperor and Adelie penguins breed on the Antarctic coast. King, Macaroni, Chinstrap and Gentoo penguins breed on Sub-Antarctic islands. The remaining 11 species breed farther North.

          It has often been said that a dog is a man’s best friend. In fact, the dog was the first animal to be domesticated by man. But dogs can also be a source of danger under certain conditions.

         A dog can harm people by biting or transmitting several bacterial, viral, parasitic, fungal and rickettsial diseases.

          Bacterial diseases transmitted by dogs are mainly tuberculosis brucellosis, splenic fever, scarlet fever, diphtheria etc. Dogs carry Salmonella enteriditis and S. typhinurium pathogens which cause gastroenteritis and typhoid in man.

Dogs along with other animals can transmit fungal diseases such as ringworm.

          Rabies is the most dangerous viral disease caused by a dog-bite. Rabies virus is found in the saliva of rabid dogs. Sometimes even pet dogs can be the cause of this disease. Therefore it is essential that they should be vaccinated against rabies every three years.

          Dogs occasionally get measles and mumps and can cause this infection to spread to human beings.

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               The largest of all living birds is the African Ostrich which cannot fly at all. It measures upto 2.4 m in height and may weigh more than 133 kg. On account of its weight, it finds it impossible to lift its body in the air.

               The two groups of flying birds that have the largest wingspread are the albatross and the condors. Both of them weigh about 13.5 kg. 

          The wandering albatross leads among the largest flying birds with a wing-spread of 3.3 to 3.6 m. The albatross has a long, heavy beak and long, narrow wings. It is mainly found in places south of the equator. It is a sea bird. It needs some wind and a run before taking off. So it either runs along the ground or paddles with its webbed feet across the water for a long time before being able to fly.

               Next comes the condor which has a wingspread of 3 to 3.3 m. It is a carnivorous bird. There are two species of condors in the world. The Andean condor lives in the Andes Mountains in South America. The other one is the Californian condor which is found in the mountains of Southern California. They feed on carcasses of animals. While searching for food, the condor uses its broad wings to glide high in the air.

              The third bird in this line is the king vulture which is found in South America, Mexico and Central America. It has a wingspread of 2.7 to 3 m. The white pelican comes after the king vulture. It has a wingspread of 2.4 to 2.7 m. It is found in Canada. One of its distinguishing features is a bag-like pouch under its bill. Functioning like the radiator in a car, it helps the pelican to keep cool.

   The great bustard, a large goose-like bird related to the cranes comes next. It is found in parts of Europe, Asia and Africa and has a wingspread of 2.4 to 3.7 m. The American bald eagle is the next largest flying bird having a wingspread of 2.1 to 2.4 m. Then comes the sandhill crane, with a wingspread of 1.8 to 2.1 m.

            Fly is a two-winged insect that has some 90,000 different species of it. The housefly (musca domestica) is one of tie most common of all flies. You must have seen flies rubbing their legs together. Do you know why they do so?

            The housefly has a dull gray, bristled body that is about 7 mm in length. It has large reddish compound eyes. Its mouth cannot bite but consists of a spongy pad. It has a peculiar system of feeding itself. At first it releases saliva and digestive juices over food and then sponges up the resulting solution. In this way, flies contaminate large amounts of food with germs, and cause millions of deaths every year. Hence it is widely considered as a major health hazard.

            The whole body of the housefly, including claws and padded feet, is covered with bristles. Even its tongue is coated with sticky glue. A fly rubs its legs together just to clean itself. In the process of rubbing the legs, it scraps some of the material that has gathered on the bristles and thus drops germs of dangerous diseases on the food. When we eat this food, we may get infected. Some of the most common diseases spread by the housefly are typhoid, tuberculosis and dysentery. Flies gather such germs from garbage and sewage.

            Houseflies usually live and breed in or near garbage or organic wastes. The female lays about 100 eggs at a time and as many as 1000 during her life. The eggs hatch into larvae in 12 to 30 hours. The larvae moult several times before becoming pupae. Within a few days, the pupae become adult and the cycle begins again. Most houseflies have a lifespan of about 30 days during summer and longer when the weather is cooler. Cold weather usually kills the adults; but larvae and pupae are able to survive the winter.

          The world’s deadliest animal is the sea wasp. It is a kind of jellyfish known as chironex fleckeri. Its tentacles are loaded with hundreds of thousands of microscopic stinging cells which inject cobra-like venom with poisonous barbed threads into any unfortunate creature that happens to brush against them closely. This venom is highly toxic and kills anybody in a few minutes. Pain and burning sensation caused by its venom are insufferable.

          The sea wasp is a colourless creature and has a bell-shaped body which consists of 95% water. It is so elusive that only careful eyes can spot it drifting in shallow tropical waters of seashores and beaches. 

          The size of a sea wasp varies from 4 cm to 20 cm across and 10 cm long. It has purple or blue tentacles which can be seen coming out of the bell. These may reach up to a length of 120 cm. One wasp may have upto 50 tentacles and one such tentacle may have 750,000 individual stinging cells, capable of injecting venom. They are mainly meant for securing food, and also to serve as a defence mechanism.

          Chironex fleckeri is found in great numbers in waters of Northern Australia. They are also found in the United States, waters off the Atlantic coast from North Carolina to the south of Florida Keys. They have also been discovered in West Africa and Indian Ocean.

          Scientists have not yet been able to devise any effective remedy for its venom. So one must be very careful while swimming in tropical waters!

          There are also some very poisonous sea-snakes that live permanently in the sea and are fully adapted to an aquatic existence. They swim with a sculling action of the paddle-shaped tail. They feed on fishes after immobilizing them with potent, fast-acting venom. 

         Scientists have studied more than 800,000 species of insects. Do you know how they reproduce and develop?

          Reproduction in insects is usually sexual, the male inserting sperm into the female’s body. The fertilized eggs are usually not tended by the insects, but they develop near or in a source of nourishment and protection. In some cases, fertilization is external. This means that the female lays the eggs and then the male fertilizes them. Some insects produce eggs which develop into adults without being fertilized. This is a type of asexual reproduction and is known as parthenogenesis.

          As an egg develops, it goes through several stages before becoming an adult. Some primitive insects develop directly from the eggs. Most of them, however, go through several stages of development called metamorphosis. In complete metamorphosis, there are four stages of development: egg, larva, pupa and adult. In incomplete metamorphosis there are three stages: egg, nymph, adult. The nymph is like a small adult. As the insect goes through its development, it moults several times. The entire process of metamorphosis may take a few days or several years depending on species and environmental conditions. Many insects lay eggs which can survive the winter or other unfavourable conditions.

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