Tibetans and the the Tibetan Mastiff are known to have a special mutant DNA called the EPAS1 which allows them to process oxygen at a high altitude. Most people have the common EPAS1 DNA. So when they travel to high altitude the hemoglobin level rises. Because there is less oxygen, the body naturally creates more blood to transport the same amount of oxygen. The danger is that this results in the thickening of the blood leading to high blood pressure and possible heart attacks. The Tibetans and the Sherpas have the mutant DNA which prevents this.
Yak is another animal that can go up to 20,000 feet easily. They have enlarged hearts and lungs so they can intake more oxygen. They also have two layered fur coat which protects them from the cold.
In 2008 a bee colony was discovered at the height of 18,000 feet in Mt. Everest. This holds the record for insects found found in the highest altitude.
Himalayan jumping spider lives at the height of 22,000 feet
Some strange animals called tardigrades are found up to 18,000 feet in the Himalayas
Lichens and Mosses are known to be found 21,000 feet. These are the highest growing plants.