5 Apex Predators-Mid

Apex Predators FOCUS Question How do top predators shape ecosystems?

顶级掠食者焦点问题顶级掠食者如何塑造生态系统?

Life at the Top A polar bear silently slips into the Arctic Sea. On a nearby iceberg, a seal snoozes in the sun. It has no idea that a massive hunter is sneaking up behind it... Half a world away, a herd of wildebeest approach a river cautiously, sniffing the air. They know that crocodiles lurk in these waters, but the river looks clear. The first wildebeest bends down to drink. As it drinks, a crocodile breaks the surface and moves forward, barely making a ripple...

一头北极熊悄悄地溜进了北冰洋。 在附近的冰山上，一只海豹在阳光下打盹。 它完全不知道一个巨大的猎人正偷偷地从它身后靠近…… 在地球的另一端，一群角马小心翼翼地靠近一条河，嗅着空气。 他们知道鳄鱼潜伏在这片水域，但河水看起来很清澈。 第一只角马弯下腰喝水。 当它喝水时，一只鳄鱼冲出水面向前移动，几乎没有激起涟漪……

All animals must eat other living things, whether they eat plants or other animals. They need matter to build their bodies and energy to stay alive. Plants produce energy and matter by making food from sunlight, water, and air. Herbivores eat those plants, and predators eat other animals. This movement of energy and matter from one living thing to another is called a food chain. Small predators are often a food source for larger predators. But some predators are so big and powerful that no other animals prey on them. They are called apex predators. They sit at the top of a food web. Apex predators play a powerful role in every ecosystem on Earth. Word Wise Apex means "top" or "highest point."

所有的动物都必须吃其他生物，无论是植物还是其他动物。 它们需要物质来构建身体，需要能量来维持生命。 植物利用阳光、水和空气制造食物，从而产生能量和物质。 食草动物吃这些植物，食肉动物吃其他动物。 这种能量和物质从一种生物到另一种生物的运动被称为食物链。 小型掠食者通常是大型掠食者的食物来源。 但有些食肉动物体型庞大，力量强大，没有其他动物会捕食它们。 它们被称为顶级掠食者。 它们位于食物链的顶端。 顶级掠食者在地球上的每一个生态系统中都扮演着强大的角色。 Word Wise Apex的意思是“顶部”或“最高点”。

The Great Hunters Apex predators can be found everywhere on Earth, from the tops of mountains to the bottom of the sea. They range from tigers to eagles, pythons to sharks, but they all have a couple of things in common. Most are carnivores— animals that eat only meat. Also, most apex predators are not picky eaters. They often eat dozens of different types of animals that are lower on the food chain. Most apex predators fall into one of the following groups: Big Cats All cats are excellent hunters— even your cute house cat. Big cats hunt everything from mice to hippopotamuses. Crocodilians, Crocodilians including crocodiles and alligators, are such effective hunters that their bodies and behavior have not changed in millions of years. Bears Not all bears are apex predators, or even carnivores. But the two largest—grizzly bears and polar bears—can strike bison, elk, seals, and even small whales that get too close to shore.

伟大的猎人顶级掠食者在地球上随处可见，从山顶到海底。 它们从老虎到老鹰，从蟒蛇到鲨鱼，但它们都有一些共同点。 大多数是食肉动物——只吃肉的动物。 而且，大多数顶级掠食者都不挑食。 他们经常吃几十种不同类型的动物，这些动物处于食物链的较低位置。 所有的猫都是优秀的猎手——即使是你可爱的家猫。 大型猫科动物捕食从老鼠到河马的一切动物。 鳄鱼目动物，包括鳄鱼和短吻鳄在内的鳄鱼目动物是非常有效的猎手，它们的身体和行为在数百万年里都没有改变。 并非所有的熊都是顶级掠食者，甚至是食肉动物。 但是两种最大的熊——灰熊和北极熊——可以攻击野牛、麋鹿、海豹，甚至是离海岸太近的小鲸鱼。

Dogs Many large dog species, such as wolves and wild dogs, are pack hunters. Working together, they can run down animals far larger than themselves. Birds of Prey Birds of prey hunt both fish and land animals. They eat live animals as well as carrion, or dead animals. Sharks Most sharks are small. But the largest sharks are unstoppable apex predators. They eat both fish and aquatic mammals such as seals. Toothed Whales Some whales have teeth and are apex predators. Orcas are efficient seal hunters. Sperm whales dive to the black depths to hunt giant squid. Squid and Octopuses Squid, along with their clever cousin the giant octopus are fierce deep-ocean hunters. Billfish Swordfish and their relatives are the fastest swimmers on Earth, making them expert predators.

许多大型犬类，如狼和野狗，都是群体猎手。 齐心协力，它们可以撞倒比自己大得多的动物。 猛禽猛禽既捕食鱼类也捕食陆生动物。 他们吃活的动物，也吃腐肉或死的动物。 大多数鲨鱼都很小。 但最大的鲨鱼是不可阻挡的顶级掠食者。 它们既吃鱼，也吃水生哺乳动物，如海豹。 有些鲸有牙齿，是顶级掠食者。 虎鲸是高效的海豹猎手。 抹香鲸潜入深海捕食巨型乌贼。 乌贼和章鱼乌贼和它们聪明的表亲巨型章鱼是凶猛的深海猎手。 旗鱼和它们的亲戚是地球上游泳最快的，使它们成为专业的掠食者。

Keystone Species All the organisms within a food web are dependent upon each other. As plant populations increase or decrease, herbivores have more or less food to eat. When herbivores are plentiful, predators have more animals to hunt. Apex predators have an especially powerful effect on food webs. One reason is that apex predators are often rare within an ecosystem. A mountain lion might be the only apex predator in its 250-square-kilometer (100 sq. mi.) territory. If anything happens to that mountain lion, no other species can replace it. The prey population will rise. Second, apex predators hunt many different kinds of prey. A mountain lion eats mice, birds, deer, elk, and more. These animals, in turn, affect all the grasses, insects, and trees that they eat.

食物网中的所有生物都相互依赖。 随着植物数量的增加或减少，食草动物有更多或更少的食物可吃。 当食草动物数量充足时，掠食者就有更多的动物可以猎杀。 顶端捕食者对食物网的影响尤其大。 原因之一是，在生态系统中，顶端捕食者通常很少。 美洲狮可能是其250平方公里(100平方公里)范围内唯一的顶级掠食者。 mi)的领土。如果美洲狮发生了什么事，没有其他物种可以取代它。 猎物的数量会增加。 其次，顶端掠食者捕食许多不同种类的猎物。 美洲狮吃老鼠、鸟、鹿、麋鹿等等。 这些动物反过来又会影响它们所吃的草、昆虫和树木。