âº a gradual process of change and development. âº biology Evolution is the process by which the physical characteristics of types of creatures change over time, new types of creatures develop, and others disappear. (Definition of âevolutionâ from the Cambridge Academic Content Dictionary Â© Cambridge University Press)
You can remember the difference between endotherms and ectotherms if you remember that endo- means inside endo- = inside and ecto- means outside ecto- = outside, so endotherms generate their own heat from within, and ectotherms get their heat from the outside.
Testicles might be outside the body because temperature influences the sex of human children. A temperature-sensitive gender switch that makes hot sperm male could be a relic from our evolutionary past, argue John McLachlan and Helen Storey, citing evidence that more males are born in hot climates.Temperature determines sex in many reptiles.For example, alligators that develop at or below 30 ÂºC turn out to be female, whereas hotter eggs yield males. Such a system wouldn't work in mammals: they maintain a constant body temperature and carry their young within.or example, it might be just as easy to move the temperature switch to a hotter point as to avoid it by moving testicles outside the body. But the idea that the sex switch is still there is testable, argues McLachlan.