2.4 Comprehension

English home language

Grade 6

Module 8

Comprehension

COMPREHENSION

Read the following passage carefully and answer the questions orally:

DEADLY DENTURES

It's the height of the summer season. You are splashing about in the waves, without a care in the world. You dive under a breaker, and suddenly you see it. A monster shark, 20 ... no, 30 metres long! It approaches you with gaping jaws, revealing razor-sharp teeth the length of your hand. Aaarghhh!

The bad news is that this massive shark isn't a product of the human imagination, it's real. The good news is that it lived long long ago - even before Tyrannosaurus rex stamped across the land. So the only place you might encounter even a model of it is in a museum.

Fossils of enormous shark teeth, some of them exceeding 15 cm in length, have been dredged up from ocean floors. Some experts believe the owners may have been between 15m to 20m long; others put them at an awesome 30m.

Either way this ancient giant makes the infamous great white shark that prowls our modern oceans seem like child's play. The great white is a diminutive descendent of this prehistoric monster.

Teeth are the hallmark of sharks - as victims of shark bites demonstrate very clearly. In most sharks the mouth is on the underside of the head, although in a few species it is at the front. The powerful jaws, which are made of cartilage, are lined with several rows of teeth - in one species as many as 14.

However, only the front row is used at any one time to snatch a mouthful of flesh. The rows behind it are replacement teeth. Every week or so a new set of teeth moves forward to replace the front ones as they wear off or are lost by accident.

Shark teeth come in a variety of shapes, depending on the kind of food eaten. Most sharks, especially large hunters such as great white and tiger sharks, have roughly triangular teeth with pointed tips. In many, the teeth have serrated edges. They are used to cut through the skin, flesh and bones of victims and rip off large chunks of food. The tiger shark can even bite through turtle shells and crocodile skins.

Some sharks, on the other hand, have flat, molar like teeth used to crush and grind the hard shells of molluscs and crustaceans.

A few species such as whale and basking sharks are harmless plankton-eaters, which feed by straining food off the water through gill clefts. Their minute teeth, set in several rows, are used as a rough sort of file.

As though the teeth in their jaws are not enough, a shark’s skin is studded with thousands of sharp tiny teeth called "denticles".

Brush a shark's skin from head to tail, and it feels smooth. Brush it the other way, and it feels like sandpaper. Dried shark's skin, called shagreen, was once sold as sandpaper for polishing wooden furniture.

The bad reputation sharks have, though, is largely undeserved. For one thing, most are harmless to people. For another, attacks on humans by large predatory sharks are comparatively rare - many more people die from drowning every year than from shark wounds.