However, that range varies enormously from species to species and from individual to individual within a species. On the broadest scale, this is obvious. Few would keep a bearded lizard, a desert species, in the same terrarium designed to house a pond turtle.
But, sadly for the animals, consideration of individual needs does not go much, if any, further than that. Virtually all sellers and dealers of "pet" reptiles try to minimize the amount of information and effort required to care for species and individual animals.
And, they get away with it because, for most people, disease, illness, stress, or suffering in reptiles is difficult (if not impossible) to determine. I've seen reptiles on the verge of starvation offered for sale to an unsuspecting public. The death rates of captive reptiles (and amphibians, collectively known as "herptiles" or "herps") are far greater than those of any other commonly-kept "pet" species.
Reptiles seek to keep a specific body temperature for any given period of the day, or a specific activity, which varies according to the individual's specific needs and activity. There are times when they need to be one temperature and times when they need to be another. Thus, they must seek, within a variable environment, to adjust postures and to move from one location to another that provides "microclimate" variations too subtle for us to easily detect. That they can do this owes everything to their having evolved within the ecological conditions where they naturally occur.