Well, neither, really. Sperm are not autonomous beings like tadpoles or bacteria; for one thing, they have only a half-set of genes (the egg contributes the other half to create a human embryo). Sperm are simply cells produced by a man's body. They're almost like blood cells, except that as you noted, they are mobile thanks to their tadpole-like tail. But they can't really "choose" to go anywhere, since being single-celled they obviously lack any kind of nervous system or brain, although they do respond to certain stimuli and move in particular directions to maximize their chances of finding an egg to fertilize. And unlike truly living beings, egg fertilization is their one and only function; they don't eat anything and cannot reproduce themselves, two things that all true living things do. So all in all sperm are pretty stupid, even by bacteria standards! But they sure do get the job done.
Do you find yourself masturbating more often during some seasons than others? Why?
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