Name an environmental change that an animal must respond to in order to keep a stable internal environment. what might happen to an organism if it could not adapt to an external change?

Temperature is the most important environmental change that an animal must respond to in order to keep a stable internal environment. A right internal temperature of the body is crucial for working of enzymes present in the body and if these enzymes do not get the right temperature they will not work properly and the animal will dye.

There are two types of animals cold-blooded and warm-blooded. Cold-blooded animals require sun energy to raise their body temperature but warm-blooded animals like mammals auto regulate their body temperature which requires lots of energy.

If an organism could not adapt to an external environment like temperature then it will dye soon or later because natural selection eliminates those organisms which are unable to adapt the changing environment.

i think the answer is

mass

this is a good question! i'll do some research and come back when i have the answer!