There are four seasons in a year in Canada. They are spring, summer, autumn and winter. In spring, the weather is warm and sunny. I like to fly kites. In summer, it's hot. I like to swim. I often wear a pair of glasses and a hat. In autumn, it's always cool. I like to go to the park and ride down the street with my friends. In winter, it's cold and snowy. I like to go outside to skate and ski with my friends. Sometimes we make a big snowman, and then we dance and sing around it.

从男女生共36人的班中选出2名代表，每人当选的机会均等．如果选得同性代表的概率是$\frac{1}{2}$，求该班中男女生相差几名？

人在寒冷环境中，身体不会发生的变化是