Artificial heart valve and boyle’s air pump: what they have in common

1. Step 1. Artificial heart valve — has part — Check valve. It works as a check valve.
2. Step 2. Check valve — is part of — Vacuum pump. Valves stop air from flowing back.
3. Step 3. Vacuum pump — evolved into — Boyle’s air pump. An improved version of Guericke’s pump.

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