【明報專訊】Like land animals, sea animals have their own classes. A class of animals means a group of animals that have similar characteristics. There are many classes of animals, like mammals, birds, fish and reptiles. For example, whales and sharks may look similar, but they belong to different classes. The Smarties are going scuba diving and are trying to distinguish between various classes of sea animals.

˙Whale

Although whales swim in the sea, they are not fish! Whales are mammals because they give birth to baby whales instead of laying eggs. Since they are not fish, they have to rise to the water surface regularly to breathe.

Depending on its species, a whale weighs from approximately 135 kilograms to 180 tonnes. The blue whale (藍鯨) is the largest animal in the world!

˙Shark

Sharks are fish. They have no bones. They only have cartilage. They began to live on earth around 450 million years ago. Do you know why sharks can't get cavities? The reason is that the exterior of the shark tooth is made of fluoride (氟化物), which is used in toothpaste!

Sharks replace their teeth throughout their lives and are dangerous to humans. We often hear tragic news of shark attacks, but the fact is that humans kill over 73 million sharks a year for their fins alone.

˙Seahorse

Scientists classify seahorses as fish. Different from most other aquatic life, seahorses swim upright. They have no teeth. They use their tube-shaped noses to suck small fish and shrimps. As they have no stomachs, food passes through their digestive systems very quickly. Therefore, they must eat constantly to stay alive. Moreover, the seahorse is the only animal of which the male gets pregnant and gives birth!

■Mission 1

Ocean Park Hong Kong is an amusement park with an ocean theme. In it there are attractions and shows about different kinds of animals living in the ocean, the rainforest, the mountain and the poles. Do you know what the animal is in its logo?

■Mission 2

Seahorses usually live in pairs. Can you find which one of the nine seahorses does not form a pair with another?

(see the picture)

■Mission 3

The coral (珊瑚) is a very special kind of animal. Let's learn more about it by filling in the blanks with correct prepositions.

Some people think corals are plants but they are in fact animals. Corals are formed 1. _____ an accumulation of polyps (珊瑚蟲). They are originally colourless, but gain colours 2. _____ the algae that lives 3. _____ their surfaces. Corals are therefore colourful.

Corals belong to a group of animals called invertebrates (無脊椎動物) because they have no backbones. A relative of theirs, which is also an invertebrate, is the jellyfish (水母). Jellyfish look like umbrellas and they are often nearly transparent. However, we should be aware 4. _____ them, as they can be deadly when they sting.

(answers on next text)

■English highway﹕-words and collocations

belong to

If a person belongs to a group, he or she is a member of it. If a thing belongs to you, you own it.

e.g. The boys belong to the basketball club.

e.g. This bicycle belongs to me.

■Key words

mammals 哺乳類動物

cartilage 軟骨

aquatic life 水生生物

backbone 脊骨

■Glossary

scuba diving (n phr) 水肺潛水

distinguish (v) 區分

approximately (adv) 大約

exterior (n) 外部

tragic (adj) 令人悲痛的

digestive (adj) 消化的

pregnant (adj) 懷孕

transparent (adj) 透明的