Dogs are often called "man's best friend" because they fit in with human life. Man refers to humankind and not just guys (Old English). Dogs can serve people in many ways. For example, there are guard dogs, hunting dogs, herding dogs, guide dogs for blind people, and police dogs. There are also dogs that are trained to smell for diseases in the human body or to find bombs or illegal drugs. These dogs sometimes help police in airports or other areas. Sniffer dogs (usually beagles) are sometimes trained for this job. Dogs have even been sent by Russians into outer space, a few years before any human being. The first dog sent up was named Laika, but she died within a few hours.
There are at least 800 breeds (kinds) of dogs. Dogs whose parents were the same breed will also be that breed: these dogs are called purebred or pure pedigree dogs. Dogs with parents from different breeds no longer belong to one breed: they are called "mutts", "mixed-breed dogs", "hybrids", or "mongrels". Some of the most popular breeds are sheepdogs, collies, poodles and retrievers. It is becoming popular to breed together two different breeds of dogs and call the new dog's breed a name that is a mixture of the parents' breeds' two names. A puppy with a poodle and a pomeranian as parents might be called a Pomapoo. These kinds of dogs, instead of being called mutts, are known as designer dog breeds. These dogs are normally used for prize shows and designer shows.
They can be guide dogs.
Blindness
Blindness is to not see anything. Some people are called blind, even though they can see a little bit. This is because they cannot see clearly, but only see unfocused shapes or colors.
In modern countries, few young people are blind. In all the world, blindness is mostly caused by malnutrition and diseases of old people, like cataracts and trachoma. People can become blind because of diseases or accidents, but sometimes people are born blind.
Some people are "color blind", which means they can see, but cannot tell certain colors apart.
When people are blind they use such things as the alphabet in "braille" and "guide dogs" to do every day life things.
Famous blind people have included Louis Braille, the inventor of the braille alphabet, Stevie Wonder, Ray Charles and Helen Keller.
Arctic
The Arctic is the area around the Earth's North Pole. The Arctic includes parts of Russia, Alaska, Canada, Greenland, Lapland and Svalbard as well as the Arctic Ocean. It is an ocean, mostly covered with ice. Most scientists call the area north of the treeline Arctic. Trees will not grow when the temperatures get too cold. The forests of the continents stop when they get too far north or too high up a mountain. (Higher places are colder, too.) The place where in the trees stop is called the tree line.
The area north of the treeline is not an empty ice field. In fact, the only large ice-covered land is central Greenland, which is covered year-round by a continental glacier. The land of the Arctic is around the edges of the Arctic Circle and is usually covered with tundra. A tundra is a cold, almost treeless plain covered with moss and grasslike plants called "sedges".
Tundras do not get very much rain or snow. However, they are very wet in the summer time because, three feet (1m) or so below the surface, the ground is always frozen. This permafrost is a layer of ice with the hardness of stone that keeps water from soaking into the earth beneath it. Permafrost can be thousands of feet thick. In the summer the ground on top thaws out when the sun shines and the snow that did fall melts. But the melted snow cannot drain into the ground; it just soaks the topsoil. There is no place for the water to go, except to form lakes and puddles on top of the ground until it freezes again or dries up.
In the Arctic, during summer there are nights when the Sun never sets. This is because during summer there, the North Pole points toward the Sun. So, sometimes people call it the Land of the Midnight Sun.
The word comes from the Greek word "αρκτος", meaning "bear". The North Pole aims at the stars called the Great Bear and the Little Bear. This is why it is called the Arctic.
In some parts of the Arctic the ground is covered with bright-colored flowers during the short summer. These little plants have very short stems. They must stay close to the ground, because the earth is warmer than the biting winds that blow above it. Even some rocks have plants growing on them. These rock plants are called lichens. Lichens will grow on the bare rocks. Yellow reindeer moss is really a lichen. It grows slowly, but often grows over six inches (15 cm) tall. It is spongy and full of water. This plant is the summer food for reindeer.
Trees are rare on the tundra. Only in the protected valleys or along the riverbanks are small trees able to grow. Rivers come into the Arctic from the warmer south. The places along their banks are a little bit warmer than the rest of the tundra, and trees can grow there. Otherwise only a few clusters of bushes grow sparingly. Berries are the only fruit that grows in the Arctic.
Each summer the ice and snow melt, allowing the animals to find food and the plants to flower. The moisture from the snow stays toward the top of the ground's surface. Plant roots can use it for their growth. Even so, in many places the soil is too poor for plant's growth. Less than half of the tundra has plants growing on it.
The polar bear is the world's largest meat-eating land animal. Polar bears are well adapted to hunt seals out on the ice. They are excellent swimmers, and the coldest water does not bother them. They wait by breathing holes if they pick up the scent of a seal. They can also break through the ice at thin areas. Sometimes they can sneak up on a sleeping seal. They have a very strong sense of smell, which they use to find prey out on the ice. Polar bears get most of their food when there is pack ice. They must eat and store fat before the ice is gone: they cannot catch seals in open water. After mating, females dig themselves into a den of snow on land for the rest of the winter. There, they have their cubs, usually twins. Bears usually eat fish, birds' eggs, seaweed, and dead whales, but they would rather have a meal of seal or walrus.
The Arctic fox often trails the bears onto the ice to eat their leftover food. The fox also eats rabbits, lemmings, and voles.
The lemmings and voles are the rats and mice of the Arctic. The lemmings have very short tails. They live underground in summer. Because the top soil freezes in the winter, they cannot burrow underground then, so they live under the snow during the colder months. They eat plants and roots. In a year with plenty of food, millions of lemmings will be roaming the tundra. The owls and foxes have more food than they can eat. They will have more young in years when there are many lemmings. However, the tundra does not have enough food for millions of lemmings. They rush across the tundra looking for food, and are eaten by predators or starve to death. Some try to swim across lakes or rivers and drown. The few that remain continue to have families.