Best Answer: The pupil size limits the the amount of light that enters the eye. There are also day-time photoreceptors, the cones, which occur with three kinds of photo-sensitive pigments, for red, yellow-green, and blue.
Those âdevotedâ dogs lying on their mastersâ graves? Theyâre depressed. âMany dogs are simply depressed for their whole lives because theyâre deprived of the normal amount of attention, exercise, and stimulation they need from day one. These humans wonât know they have a problem and wonât want the dog any livelier as that wouldnât fit in with their lifestyle,â says Tamara.
Metabolic depression can occur as a very rapid response to decreased levels of energy intake, and is most clearly demonstrated by animals that undergo periods of torpor (Hudson, 1973, Mrosovsky and Sherry, 1980 and Merkt and Taylor, 1994).