【雅思聽力】海洋生物(3/4)

It is called the laternal line and is used to detect sound vibrations and changes in water pressure. All living things, whether they live on land or in the sea, must fight to stay alive, that is to survive. Each plant and each animal has to feed on something and at the same time avoid being eaten. Therefore every plant and animal has to solve this big problems of staying alive in it's own way. The danger of being eaten in the sea is great. Those plants and animals that do survive usually reproduce very fast and in great numbers. The single-cell plant, the diatom, can multiply itself into a billion new distoms in one month. Certain sea animals have defensive devices that help them to survive. Sea urchins, for example, grow spines to protect themselves. The sea awesome and jellyfish have poisonous tentacles, which are used for attack and defense. Another method of survival which sea plants and animals use is disguise or camouflage. They usually have the same colour as their surroundings. The sargassum fish looks very much like the sargassum seaweed among which it lives.