When a given species of animal is bred in isolation from its wild habitat and at the same time protected against unfavorable conditions, specific traits start to appear that disadvantage the animal in a natural environment and would keep it out of the reproductive process in the wild—either because markedly different individuals are easier victims for predators or because no partner will accept them. These different traits are not kept in the wild populations or are very rare. Conversely, these individuals were of interest to humans because of their different appearance or their submissive nature. After some time, the changes in the nature, behavior, and in the reproduction cycle become distinctive in domestic animals. They also become stratified in their genetic make-up.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.