The Evolution Of Sleep

I have a marine aquarium and I have noticed that when I wake in the morning and turn on they're light some of them are huddled along the rock snoozing away. One of my fishes pigments is even a paler color when he first wakes up.My birds sleep balanced on one leg. I wonder why not on two??Dogs dream of chasing rabbits and such, but do they dream in color if they see in shades of gray?One last question, how is it our memory of dreams fade so quickly? I could have the most lucid fantastic dream with every intention of remembering it. And in the space of taking a shower completely fail to recall most details.

I saw a tv program about sleep and dreaming last month and some of the researchers suggested that dreams are a way for our brain to run simulations. So that if and when confronted with some horrifc or stressful event whilst awake there is a mechanism in place to deal with it. Its a untested hypothesis/ speculation.