Is a measure of the average kinetic energy of a substance

Temperature is the measure of the average kinetic energy of a substance.

Explanation:

First of all, it is important to understand what energy is. It is the capacity that a system has to do work. In that sense, there are many types of energy such as Mechanical Energy, Nuclear Energy, Chemical Energy or Kinetic Energy just to mention a few of them.  The observable movement or change of an object is called kinetic energy. The walking of a person, a basketball being shoot, an ant carrying a piece of a leaf are examples of this type of energy. As well, even if in those actions there may be some other types of energy involved, the temperature is related to the kinetic energy of the molecules.  

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;