The first person to document hat internal environemts were very constant, even when conditions of the outside environment were different. He associated this with health and the ability to do things. Water, ions, glucose, ph, temperature, gases, wastes (co2) You want to control these variables and keep them in bound. You eat it goes up, then comes back down. Even though you have this variation, its held within a fairly narrow change and if it leaves this range you have a lot of problems (ex. diabetes). Whe(cid:374) so(cid:373)eo(cid:374)e"s ph goes out of (cid:449)ha(cid:272)k, it has se(cid:448)ere ph(cid:455)siologi(cid:272)al effe(cid:272)ts. Regulating temperature in a cold environment is costly in energy. Being a conformer saves more energy, but you must be able to handle the changes. It can regulate on either end, but it starts to conform. Those are the ranges that it will begin to struggle. The limits can set circumstances of where the organism can live.