Some living creatures may (36) the effects of cold by moving elsewhere (e. g. birds, fish) or by (37) movement (e.g. bees). Others may die when the cold weather (38) (e. g. land insects). Many mammals (39) the winter through the process of hibernation (from the Latin word meaning winter). One type of hibernation is known as (40) hibernation. This is brought about by the activation of a (41) called H. I.T. in the animal’ s blood. The temperature of the animal falls and metabolism is (42) The respiratory and heart (beat) rates (43) dramatically and the temperature falls (44) . However, the animal will be awakened by a special control system if it is danger of freezing and may also wake for a short to excrete waste substances or to eat. (45) . Energy is provided at the end of hibernation by the animal’ s store of brown fat. Some creatures do not actually hibernate, but enter a state of torpor. They show similar metabolic changes, (46) .