My Science School

 

                     Turtles, crocodiles and snakes are all found in the sea. Turtles and sea crocodiles lay their eggs on land, but most sea snakes give birth to live young at sea. Many types of sea snake have extremely powerful venom.

                     Turtles are found in most warm seas, coming ashore to bury their eggs in warm sand. They feed on animals and plants, and some can grow very large. The leatherback turtle is the largest turtle of all. It can reach a length of 2.1 m and a weight of 540 kg, and there have been reported sightings of far bigger specimens.

 

                 The largest surviving land-dwelling reptile is the Komodo dragon, a gigantic monitor lizard living on the small island of Komodo, in Indonesia. This aggressive lizard grows to a length of 3 m and can weigh up to 135 kg. It is a carrion eater with a keen sense of smell but it can also hunt and kill larger animals, including humans. This fearsome lizard is known to live for about 100 years. The giant tortoise of the Galapagos Islands is just as heavy as the Komodo dragon, reaching a length of 1.3 m.

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                 Giant tortoises are known to have lived for 177 years. Reptiles usually only die because of an accident, disease or a predator. The chemical reactions powering reptiles’ bodies take place very slowly, and this is thought to extend their lives.

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                   The sea, or estuarine, crocodile can reach a length of 9 m, although it is usually much smaller. It is one of the most dangerous types of crocodile. Because sea crocodiles frequently enter the sea and travel for long distances, they are sometimes found in areas that were thought to be free of these dangerous animals. Some prehistoric crocodiles reached a length of 15 m. Surviving relatives include the alligator of North America, the caiman of South America and the gavial of India. True crocodiles live in Asia, Africa and Australia.

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               Every year about one million people are bitten by poisonous snakes, mostly in tropical regions of the world. Between 30,000 and 40,000 of these people die.

               There are several groups of poisonous snakes, and their venom can attack the body in many different ways. Venom can attack the blood, the nervous system or, in the case of the rattlesnake, most of the body organs. The danger depends on how much venom is injected into the body through the snake’s hollow fangs when it bites.

                Rattlesnakes and copperheads are common hazards in North America, while vipers and their relatives, together with cobras and mambas, are common dangers in Africa and Asia. The spitting cobra is most unusual because it sprays venom into the eyes of its victim to blind it, rather than biting. Snake bites on humans are nearly always acts of defence. This is because the snake thinks that it is being attacked.

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The tuatara is a lizard-like animal, 70 cm long that lives only on small islands off New Zealand. Its most interesting feature is a very primitive third eye, which is thought to be sensitive to light.

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                  Some types of small lizard often deliberately lose their tail when attacked by a predator. This is a defence mechanism, because the predator usually seizes the lizard by the tail as it tries to escape. The lizard’s tail may continue to wriggle for a while after coming free, distracting the predator while the lizard escapes. The stump of the tail is quickly sealed over by special muscles that stop the bleeding. A new tail is gradually grown to replace the one that was lost.

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                 Most reptiles lay eggs or give birth to live young, which can then immediately live an independent existence.

                 Crocodiles, on the other hand, care for their young. They bury their eggs in warm sand and guard the nest until the young are ready to hatch. The mother will often carry the baby crocodiles in her mouth to the water, where they will be guarded for several weeks until they are old enough to live independently. However, an adult is quite happy to eat the babies of other crocodiles.

                      Snakes have several ways of moving about. The most common way is to throw their body into loops and move forward by pressing against anything solid in their environment.

                      Another way in which snakes move is by waves of muscular contraction, which push the body along rather like a concertina being squeezed open and shut. The desert-living sidewinder moves by throwing a loop out to one side, then sliding its body towards the loop while throwing another loop sideways at the same time. The sidewinder looks like a spring rolling along the sand, but this is an effective way of moving on this soft surface. Most snakes are able to swim effectively by using a wriggling motion.

 

                   A reptile is an air-breathing animal with a body structure between that of the amphibians and the birds and mammals. Reptiles are generally scaly and their eggs are fertilized internally.

                   Living reptiles include crocodiles, tortoises and turtles, snakes and lizards. There are about 6,000 surviving species. Long ago there were many more kinds of reptile, such as the dinosaurs and the flying pterosaurs.

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                      Most birds fly at speeds of 32-48 km/h. In general, the heavier the bird the faster it needs to fly in order to stay in the air.

                     However, a racing pigeon has been timed at more than 150 km/h, and it is claimed that the Indian spine-tailed swift can fly at more than 320 km/h. The peregrine falcon is a very fast flyer, and is said to travel at more than 320 km/h when diving on its prey. Strictly speaking this is not flight, because the falcon closes its wings and drops like a stone to pick up speed. The prey is usually killed outright by the strength and speed of the falcon’s strike. Powerful muscles in the bird’s legs help to cushion the enormous impact of the strike. Afterwards, the falcon follows the dead or stunned prey to the ground and often feeds there, as the prey may be too large for the bird to carry it away.

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                     Some birds live only in certain areas of the world, but the most successful birds are found almost everywhere.

                     Settlers introduced the starling and the sparrow into most countries. Like rats, these birds are so adaptable that they have increased in enormous numbers. The most common bird of all was the passenger pigeon, which lived in North America in such huge flocks that they darkened the skies for days during their migrations. These birds were hunted nearly to extinction during the 1800s, and the last one died in a zoo in 1914.

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                     Swifts and frigate birds spend almost all their life in the air. They never walk on the ground, because the length of their wings would stop them from taking off again. Swifts rest by clinging to a vertical surface and they then launch themselves into the air. Frigate birds are large seabirds that sleep on the wing, using only a section of their brain to keep flying.

 

 

 

                        The longest distance regularly travelled by birds is the annual migration of Arctic terns from the Arctic to the Antarctic. They travel 30,000 km each year. Even the tiny hummingbird is able to travel enormous distances and they have been known to cross the Gulf of Mexico, which is a vast distance of 800 km.

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Most plants and animals have popular names that vary from place to place. Scientific names are given so that the same name is recognized everywhere.

Latin is used for scientific names. Centuries ago, it was the language of learned people. Scientific names are in two parts. The first is the generic name, which describes a group of related living things, and the second name is the specific name, which applies only to that living thing.

The specific name may describe the living thing, or it could include the name of the person who discovered it. For example, a human being is called Homo sapiens (thinking man). A fossil form of Homo, or man, is Homo habilis (tool-using man).

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