Have you ever wondered what your dog dreams about? What about that snoozing lion cub at the zoo? As it turns out, many of our favorite animals aren't so different from us when it comes to sleep.

Scientists are still on the fence about how certain animals catch their z's. Sleep in human beings still isn't completely understood, which is pretty wild considering we spend a full third of our lives sleeping or trying to do so. The human race's need for sleep isn't up for debate--it's universally accepted that we need sleep to survive--but our biological purpose for doing so has remained somewhat of a mystery. The act of sleep affects almost every part of the human body, from the brain, heart, and lungs to the metabolism, immune system, and mood. Even more importantly, a lack of sleep or poor sleep quality can increase the risk of cardiovascular disease, diabetes, obesity, and even depression.

A common question regarding non-human animals and sleep is the presence of dreams. Humans spend about two hours a night dreaming even if we can't remember most, or anything, about those dreams. Many researchers believe dreams exist to help us process our emotions; however, the purpose of dreaming remains a mystery.

LOOK: 30 fascinating facts about sleep in the animal kingdom

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