Monday, December 14, 2009


TORTOISES AND TURTLES are unique among animals, having their whole bodies enclosed in a bony box. This is built from the rib cage which grows and joins up outside the limbs. The earliest tortoise show separate ribs but even these are already flattened as if about to join together. This peculiarity goes back even before the dinosaurs, so that chelonians (the name of the order to which tortoises and turtles belong are the oldest group of reptiles. They even have the oldest individuals on earth today- the giant tortoises which can live to a hundred and fifty years or more.

Chelonians are of three kinds-tortoises, turtles and terrapins. Tortoises are land reptiles with domed shells and stumpy legs. They move about clumsily and feed mostly on plants and fruit. The largest are the giant tortoises of the Galapagos Islands in the Pacific, and the Aldabra Islands in the Indian Ocean. They can weigh up to 550 kilograms and measure almost two meters in length. Tortoises sold in shops as pets come from the Mediterranean countries, and have been known to live up to a hundred years. Eggs are laid in the ground and left to hatch in the sun.
Turtles are sea-going chelonians, with flatter shells than tortoises and more paddle – like feet for swimming. At night the females come ashore on some lonely tropical beach where there is sand. They dig pits in which up to 150 eggs may be laid. These are covered up and the mother then returns to the sea. Later the babies hatch out, struggle to the surface, then make as fast as they can for the water. On the way many are caught by the waiting sea-birds. Because turtles are also caught for food and their eggs dug up, some are now becoming rare.

One or two countries do protect turtles by fencing off some of the beaches where they lay their eggs, later collecting the young and taking them out to sea where they will be safe to grow up. The largest turtles, up to 400 kilograms and one and a half meters long, is the Leathery Turtle. The Green Turtle is the species usually caught for making turtle soup, and the Hawksbill Turtle for its shell, called tortoiseshell. Terrapin is an American Indian name for freshwater tortoises which swim in rivers and marshes, catching fish and water animals. They spend hours basking in the sun at the waterside, but dive in at any sign of danger.


Reptiles are air-breathing vertebrates which have limbs (except snakes and some lizards), are cold-blooded and have horny covering of scales or horny plates. There are about 3,000 species. The four orders of modern reptiles are the crocodiles and alligators, tortoises and turtles, snakes and lizards and the Tuatara.

The last-named order means break headed, and the Tuatara, which is a Maori name, is the only survivor of it. Looking rather like a lizard with a beaked face it lives on some of the lonely islands off the coast of New Zealand. It is truly a precious living fossil, since this reptile order goes back to the time of the dinosaurs. The Tuatara seems to be slow in everything it does, even to its movements. It lives in underground burrows, often in company with a sea-bird, a species of petrel. The reptile sleeps there by night and the bird by day. The eggs have a long incubation period and it is sometimes as much as eighteen months before the young hatch out.


These are plants which grow in or near water and are adapted according to whether they live on the surface, or are submerged, or grow in the mud at the edge of the water.Some are a combination of all these and have several different types of leaves. Some hydrophytes (for example water lily) are anchored to the bottom by roots, and send up leaves on long stems until they reach the surface, when they unfold and spread out. The giant water lily (Victoria regia) is an extreme example of this. The flowers too come up on a long stem and open out above the water.

Some water plants are not rooted to the bottom and merely float on the surface (for example duckweed) or under the surface (for example bladderwort). Such water plants can only live in still waters but some submerged plants are anchored to the bottom by roots and produce long growth with small leaves and these are better adapted to life in running water. The leaves of most water plants have large air cavities in them to act as ‘water wings’, and some produce large bladder-like swellings for the same purpose(for example water hyacinth).

The water crowfoot is amphibious, that is it can live both in water and at the edge in the damp mud. It has surface leaves which are flat and large compared to the submerged leaves which, when living in water, are finely divided with narrow lobes. These smaller leaves disappear if the water level drops and the plants are left at the edge.


Some tiny plant organisms produce substances which are capable of killing bacteria, and penicillin and streptomycin are two examples of these. The organisms producing these useful antibiotics are in fact fungi, and are cultivated by man in order to obtain large quantities for treating diseases. Viruses are organisms which are very much smaller even than bacteria and very little is known about them. They seem to be on the borderline between the living and non-living although they do have the ability to increase and spread. They cause many diseases to plants and animals and in man are thought to be responsible for such things as colds, influenza and measles. In plants they produce disorders such as wrinkling and yellowing of leaves. They seldom kill plants, but completely upset their normal way of life, and because they can ruin crops are a problem to man. Unlike a lot of bacterial and fungal diseases in plants, they cannot be killed by chemical sprays.

Wednesday, May 20, 2009


Tornado is a rotating column of air which is in contact with both the surface of the earth and a cloud.  'Tornada'  in spanish means thunderstrom.  Tornados occur in many sizes and are encompassed by a cloud of dust.  They look like a thin tube between the earth and the cloud.  They are sometimes too violent and are capable of tremendous distruction.


They basically form from thunderstroms majorly.  when two air masses of warm, moist air and cold dry air come into contact they cause instability in the atmosphere and gives raise to Tornado.  Tornado have varying wind speeds ranging between 40 mph to 100 mph.  They stretch more than a mile on the ground.  Tornado have occured in all continents except for Antartica.  They commonly occur in south -central America, South Canada, new zealand.


Funnel clouds are the initial stages of the tornado.  The rotating column of air before it touches the ground is called the Funnel cloud.  Weaker tornado that occurs over water are called water spouts.

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