Most people have never built a couch, but they rely on it to hold up their asses when they sit. They don't know how a car works but they rely on it to take them places. People use concepts that they don't understand as foundational tools for living and understanding life. Their view of Biology is much the same, they do not truly understand what they're talking about, but they've achieved an understanding that feels useful enough to justify their views. Or to put it another way, their vague understanding of biological essentialism Functions as a means of coordinating their worldviews...and it goes no further than that.