let me rephrase:
the heart increases blood pressure, making it possible for blood to be circulated at a reasonable speed throough an organism that is larger than an amoeba, and also has a body which can rapidly change shape and contortion, like a snail, rather than a sea fan, or a tree.
rather than relying on passive osmosis and gravity to do the circulation, you spend some joules on a muscle to pump the shit around for you
