58. The guppy is a small fish that people often keep on bowls or tanks in their homes. In their bowls, guppies are harmless, but in the wild, the story is different. When some guppy owners in Nevada grew tired of their fish, they threw them in a small lake. The guppies then multiplied rapidly and ate all the food in the lake, so that there was none left for the native fish, which disappeared. The same thing has happened in a number of other laker in the western United States, and now at least one species of fish-the white river spring fish-is almost extinct. Thus, even a little fish like the guppy
60. Sociologists and psychologists have argued for centuries about how a person's character is formed. The argument has long been known as "nature versus nurture," describing the two main opposing theories. the first theory says that character is formed genetically before birth. According to this theory, nature-through genetics-determines what a person will be like. The other theory says, on the contrary, that a newborn baby has no definite character. The child's character develops as he or she grows up, and the development of that character is influenced by the child's family and social environment. Thus,according to the second theory, the most important factors are