🦈🔬 If you were asked to describe a #shark, you’d probably mention a dorsal fin, gills, and a #skeleton made of cartilage. But as this deep dive explains, defining exactly what makes a shark a shark is one of #biology's trickiest challenges.

👉 https://www.popularmechanics.com/science/animals/a70747636/what-is-a-shark/

#sharks #marinebiology #science #evolution #taxonomy #oceanlife #biology #education #nature #paleontology