Man: a Most Adaptable Animal
There are many areas in this world where not every kind of organism can live. For example, there are no trees in the Arctic regions, the land of the polar bear. Of course, there are no polar bears in the lush vegetation of the tropics. Man, on the other hand, lives successfully in both of these environments. In fact, he has found ways to survive anywhere on Earth. He has learned to alter this environment to suit him. If he needs large amounts of water for big cities, he builds dams. If he needs water for farming the desert, he builds irrigation canals. Neither the highest mountain nor the deepest rivers stop the movement of man. How does he overcome such obstacles?
Medicines and insecticides help man destroy organisms that he considers a threat of his food supply. He has learned to survive in unfavourable or hostile environment. For example, he tunnels underground, works in the frigid Polar Regions, and explores at various depths in the oceans. Also he can live at high altitudes where no other organism can exist. If a man moves from sea level to 5,000 feet above sea level, where the air has less oxygen, certain functional adaptations will enable him to survive in the "thin" air. His breathing will increase. The number of his red blood cells will increase, and his heart will beat faster, causing the red blood cells to circulate more quickly. Most other animals can adjust to this slight change in environment. Suppose, however, that an animal is carried to a height of 25,000 feet. Will it survive? It probably would not be able to adjust to the reduced air pressure and to the lack of oxygen at this altitude. Man is exception, however, because he has survived at this altitude for extended periods of time. In fact, you may have done so yourself. Have you ever flown in an airplane? Jet airplanes fly above 25,000 feet. How do passengers survive? Do they adapt to this almost-oxygen-free environment? Of course not. The plane cabins are pressurized so that the environment resembles that at a lower altitude.
Man has this selective advantage over the plants and other animals: if he cannot adapt to a changing environment, he adapts the environment. "A question of survival", Life.
From "English for Second Cycle"