One of the functional characteristics of life is responsiveness. This refers to .1) indigestible food residues stimulating the excretory system 2) sensing changes in the environment and then reacting or responding to them 3) the nervous system causing all living things to sometimes experience anger 4) the necessity for all organisms to reproduce

2) sensing changes in the environment and then reacting or responding to them

Explanation:

Living things are said to possess the quality of life. There are several functional characteristics of life that make use classify something as a living thing. One of the functional characteristics of life that all living organisms possess is RESPONSIVENESS.

The ability of living organisms to respond to external stimuli or changes in the environment is what is referred to as RESPONSIVENESS. Living things respond to various external stimuli or changes in the environment such as sound, mechanical contact, light, heat etc.

For example, most plants respond to light. This can be seen when a plant is placed in a dark room that has a part that allows light to penetrate partially. The plant would respond to the light by growing towards the light.

Also, flowers of plants respond to light, as most petals of flowers begin to close as night falls, while they slowly open as the day breaks.