 Dear students, in this module we shall discuss the spectrum of study of physiology. We define physiology as the study of functions of cells, tissues, organs and organ systems of organisms. Our ultimate goal of the study of animal physiology is to understand the mechanisms that operate in animals at all levels in physical and chemical terms. Dear students, the laws of physics and chemistry, which you have studied in the last classes of physics and chemistry studies, have been applied to a lot of the laws on physiological mechanisms and processes. We will take a few examples from which we will look at the applications on physiological processes. First of all, you are familiar with Ohan's law. In physiology, this law is applicable to blood flow and pressure. It is also applicable to ionic currents and capacitance of the membrane. Then the Boy's law and very familiar ideal gas law, these two laws are applicable to gas exchange mechanisms in animals, that is, respiration. Then law of gravity is applicable to blood flow. They are applicable to muscle contraction in animals. They are also applicable to chest movements that occur during inhalation and exhalation. Similarly, the concepts of drag, inertia, momentum and velocity are applicable to locomotion in animals. Dear students, physiology is an interesting field and curiosity underlies the studies of physiology. The desire to know, that is, the justice or juxtaposition, is created because of interest. There are many things in physiology that bring our interest to our side. We will take a few classical curious questions from the example of physiology. There is a classical example, that a hummingbird, when hovering flies, its heart beats 20 times per second. How is it possible? Then insects can see in the ultraviolet spectrum, while we cannot. How? One more question, kangaroo rats are a small mammal like rats. How? So, these are some questions that provoke curiosity. Dear students, animal physiology is the basis of human physiology also. Because human species has a linked evolutionary history with all animals. That is why when we study comparative animal physiology, we come to understand many mechanisms that are operating in our own bodies. That is why the physiology, animal physiology lays the foundation of human physiology. That the human physiology lays the foundation of medical science. Actually, there is a lot of knowledge that we know about human physiology, about human tissues, about human organs, and that is based on those experiments that were carried on animals. Dear students, the human physiology has laid the foundation of human physiology. Modern medical science. That is the basis of scientific medical practice. Understanding the physiological basis of disease helps in developing the effective and sound treatments for human diseases. In the modern times, physiology has contributed through the development of special model organisms for specific human diseases. In the modern times, physiology has contributed through the development of special models organisms for specific human diseases. For example, diabetic mice, such as those who suffer from diabetes, congenitally fat rats, these models allow wide range of experimentation that provide insight into the physiological basis of disease.