The brain keeps you balance and it keeps the heart beating in you don't even think about it because The brand is smart and it could work your body without even thinking about it
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Survival of the fittest is talking about when you have traits that will help you, you are more likely to live rather than not having those traits. For example, a bird that swims a lot has webbed feet so it has a better chance of surviving then a bird who does not have webbed feet
