How did dinosaurs evolve?

Scientists believe that dinosaurs came into being about 180,000,000 years ago and died out about 60,000,000 years ago. Since dinosaurs were reptiles, they must have developed from reptiles that lived before them. Reptiles, by the way, are a separate class of animals with these characteristics: They are cold-blooded; they can live on land; they have a distinctive type of heart; and most of them have scales.

The first reptiles appeared long before the dinosaurs. They looked like Amphibian (able to live in water and on land), but their eggs could be hatched on land. The young ones had legs and lungs, could breathe air, and probably ate insects.

Then the reptiles became larger and stronger. Some looked like big lizards and others like turtles. They had short tails, thick legs, and big heads. They ate plants.

The first dinosaurs to develop resembled their rep­tile ancestors, who were like lizards, and who could walk on their hindlegs. The first dinosaurs were slen­der, about as large as a turkey, and could also walk on their hindlegs. Some kinds remained small, but others grew heavier and longer. In time, many of them were six to eight feet long. There were even a few 20 feet long and weighing as much as an elephant. They had small heads, short, blunt teeth, which were only good for eating plants. They lived in low, swampy places.

Then came the next period in the Age of Reptiles. Some of the plant-eating dinosaurs became so large that even four legs couldn't support them on land. They had to spend most of their lives in rivers and swamps. One of these giants was Brontosaurus, 70 to 80 feet long and weighing about 38 tons!

At the same time, other dinosaurs were able to walk about on land. One of these, Allosaurus, was 34 feet long, had sharp teeth and claws, and fed on Brontosaurus and other plant-eaters! So dinosaurs were a stage in the development of the reptiles. They may have disappeared because of changes in the climate of the Earth, which robbed them of places to wade and feed.

Tornadoes

Tornadoes are the most violent of all storms. They are so powerful that no one can predict what they may do. Tornadoes uproot large trees, overturn houses, and carry away telephone booths and cars.

One tornado picked up a schoolhouse, turned it around, and then set it down backwards.

Another one carried off a horse, then dropped it on the ground. Luckily, the animal remained alive.

In Russia, during one tornado, people were amazed to see money falling out of the sky. At least a thousand coins dropped from the clouds. The winds had removed the earth from a buried treasure and picked up the coins.

A typical tornado is usually shaped like a funnel — wide at the top and narrow at the bottom. When it has picked up enough material (leaves, dirt, pieces of wood, etc.), it some­times looks like a giant elephant. But tornadoes can come in other shapes, too.

Tornadoes consist of twisting winds that are probably the strongest on earth. Scientists say that they can reach speeds of up to 320 kilometres an hour. That is why they are so danger­ous.

Most tornadoes last less than an hour, but some can last several hours. Such tornadoes are especially destructive.

A tornado's path is narrow, but within this narrow path a tornado can destroy everything. It can even kill people.

The greatest killer tornado in history roared through Missouri, Illinois, and Indiana on March 18, 1925. It killed 689 people. This tornado was one of the largest and fastest tornadoes ever recorded. Its path was about 354 kilometres long and up to 1.6 kilometres wide. The storm travelled at a speed of about 97 kilometres an hour.

Tornadoes occur throughout the world, but mostly in the United States. The central states, from Texas to Michigan, have probably more tornadoes than any other place on earth.

Most tornadoes occur in spring. A hot, humid day in the afternoon or in the early evening is the most likely time for this dangerous storm. Large clouds appear in the sky- They become darker and darker. There are sounds of thunder in the distance. Bright flashes of lightning are seen. A cloud then forms a funnel and begins to twist. A hissing sound begins the funnel cloud moves towards the earth. It moves faster and faster. The faster the winds, the louder the noise. If the funnel touches the ground, it picks up everything it can. The hissing becomes a loud roar. The violent winds of a tornado blow down almost everything in its path.

Scientists have often wondered what the inside of a- torna­do is really like. Only a few people who saw the heart of a tor­nado have lived to describe it later. One of these people was Will Keller whose farm was in Kansas where tornadoes are com­mon. He described what he saw when a tornado swept over him.

"At first everything was as still as death. There was a strong gassy smell, and it seemed as though I could not breathe. There was a screaming, hissing sound coming directly from the end of the funnel. I looked up. To my astonishment, I saw right into the heart of the torna­do. In the centre of the column there was a circular opening about a hundred feet wide. It extended straight upward for about half a mile."

While inside the walls of the circular funnel Will Keller saw bolts of lightning everywhere. Flashes shot from side to side of the funnel.

Keller always remembered those few seconds when he looked up into

the heart of a mighty tornado. When it finally moved away, he saw it pass over a neighbour's house and barn and tear the buildings apart.

Fortunately. meteorologists can predict tornadoes, and today, people have a much better chance of pro­tecting themselves.