4 facts
A newborn baby has around 300 bones, while an adult has 206. Many of a baby's bones are made of cartilage and eventually fuse together as they grow, like those in the skull and spine, forming stronger, larger structures.
The hydrochloric acid in the human stomach has a pH between 1.0 and 2.0, which is incredibly acidic. While it won't instantly vaporize a razor blade, it can indeed corrode it over time, breaking down the metal.
Instead of bones, sharks have skeletons made entirely of cartilage, a flexible and durable connective tissue. This makes them lighter and more agile in the water, contributing to their impressive predatory abilities.
Two hearts pump blood through the gills, while a third circulates it to the rest of the body. Their copper-based hemocyanin gives their blood a distinctive blue hue, unlike the iron-based hemoglobin in human blood.