Sexual Differences

Most animals develop into two sexes, determined by genes or the environment. The differences in sexually mature individuals advertise that they are ready to produce offspring of their own. In some animals this sexual dimorphism is reflected in body size. In many mammals the males are bigger than females. In addition, the larger the male, the more likely he is to succeed with choosy females. In other species, such as some fish, a larger female may produce more eggs or bigger offspring, increasing their chances of survival.