Birds can see colours, just as people do. Birds need to see colours when they fly because they need to find places to land (着陆). Colours help them know 1 the place is and what it is like so that they can catch flying things in the air or land on something they think safe.
Birds can "tell" the differences between colours. But for some 2 animals, such as wolves, the world looks like a black and white photo. Wolves look for food mainly by 3 .
They can hear 4 when the animals they hunt move. But other animals seem to know this. For example, a rabbit will stop moving when it finds there is something 5 . Then the wolves 6 not find it at all. However, birds are better than wolves in these ways. They can see dead insects from far away.
Some birds' eyesight is 7 than people's. They can see small insects 8 they fly in the sky. Because they are able to 9 colours, they can find food easily and 10 if (是否) there are other animals that are dangerous to them.
The koala
Appearance: The koala with thick hair looks cute but it has very sharp teeth and claws (爪子). The male koala is larger than the female one.
Size: 70-90cm Weight: 5-14kg
Food: The koala eats eucalyptus leaves (桉树叶). Each koala eats about 500 grams of leaves per day.
Habit: The koala sleeps for up to 16-18 hours. It prefers to move around in the evening.
Baby fact: A healthy female koala can have one child each year. A baby koala is very small when it is born—only a quarter of an inch. It has no hair and it can't see either. It lives in its mother's pouch (育儿袋) for half a year. During this time, it only drinks its mother's milk.
Danger: The number of koalas in Australia is getting smaller every year, mainly because of people. People cut down a lot of trees, so many koalas have no places to live in and they don't have enough leaves to eat. There are fewer than 100,000 koalas in the world. Some scientists say if people don't protect them, we won't have any koalas within 30 years.
The elephant is the largest of all animals that live on land. An elephant's trunk(象鼻)is rather like an arm and a hand. It is used to pick up and pull things in its mouth. It is also used to pull up trees when the elephant wants to make path (道路)through the forests.
The African elephant is usually larger than the Indian elephant. It often stands 10 or 11 feet high, and weighs over 6 tons(吨). Both males and females grow trunks. But only male Indian elephants have tusks.
The elephant lives mostly on grass, leaves and fruits. It has been easy for men to train elephants. They are used to carry heavy things. Elephants can live for about fifty years or more.
Death Valley, an area in Nevada and California, is one of the most famous deserts in the United States. Almost 20 percent of this area is below sea level. Badwater, a salt water pool, is about 280 feet below sea level and it is the lowest point in the United States.
Long ago, the Panamint Indians called this place "Tomesha"—the land of fire. The present name, Death Valley,can date back to 1849, when a group of miners became lost in it and their adventure turned out to be a sad story. Today Death Valley has become a National Monument (遗址) and is crossed by several roads where good services can be found easily. Luckily the change created by human has hardly destroyed the special beauty of this place.
Here there are a lot of surprising natural scenes. One of the most surprising and variable (多变的) parts of Death Valley is Devil's Golf Course, where it seems hard for people to tell reality from terrible dreams. Sand sculptures (沙雕) stand on the frightening ground, as evening shadows (暮色) move and lengthen.
In the past 300 years, more than 130 kinds of animals have become extinct. One of these extinct kinds is the passenger pigeon (旅鸽). At one time there were millions of these birds in North America, but now there are none. The last one died in the Cincinnati Zoo in 1914. Another extinct animal is the cape lion (西非狮). The animal has been extinct since 1860. What causes animals to become extinct? Too much hunting is one cause; pollution is another. Governments around the world have begun to protect wild animals in danger. In the United States, the US Fish and Wildlife Service is responsible for (承担义务) endangered animals. It has listed nearly 200 kinds of endangered animals in North America.
