Internal And External Environment

Step outside on a harmattan morning in Jos and then again at midday in Lagos in the rains, and the air around you could not be more different: cold and dry, then hot and humid. Yet a healthy goat standing in either place keeps almost exactly the same body temperature, the same blood chemistry, the same steady internal state. That contrast, a constantly shifting outside against a remarkably steady inside, is the starting idea of environmental physiology and the foundation for everything this section of the syllabus will teach.

In this lesson you will learn what farm animal scientists mean by the internal environment and the external environment, the specific factors that make up each one, and how the two relate: the animal's body works continuously to hold its internal environment steady despite an external environment that never stops changing. Grasp this one relationship and the next three lessons, homeostasis, the effects of climate, and how farmers modify the environment, will all make immediate sense.