The flea lives on the body of its host and feeds on its blood. why is it in the best interest of the flea not to kill its host?

If the flea were to kill the host, it wouls have to do extra work to find another food source because it just eliminated the food source or host it had previously found. To clarify, it is not in its best interest to kill the host because it wants/needs to continue to use it as a food source instesd of having to find another one.

What is an organ-systemOrgan System

An organ system is a group of organs that work together as a biological system to perform one or more functions. Each organ does a particular job in the body, and is made up of distinct tissues.

Explanation:Why is it important

The most complex organisms have organ systems. ... One of the most important functions of organ systems is to provide cells with oxygen and nutrients and to remove toxic waste products such as carbon dioxide. A number of organ systems, including the cardiovascular and respiratory systems, work together to do this.