The answer is dusk and dawn.
Crepuscular animals are active during twilight (latin crepusculum). Twilight is a period after dawn and before dusk, so crepuscular animals want to avoid dusk and dawn. Animals' activity in different periods during the day depends on temperature or other biotic factors. It also depends on predators' activities or local competition.
Its stabilising. Since the selection pressure is against the extremes which are the normal blood and the sickle cell anaemia.
Answer:
Explanation:
(in an echinoderm) each of a large number of small flexible hollow appendages protruding through the ambulacra, used either for locomotion or for collecting food and operated by hydraulic pressure within the water-vascular system.
