Why are human bones not cartilage like sharks?

Why are human bones not cartilage like sharks? – Natalya N, Age 12, California, United States

First, let’s talk about the difference between bone and cartilage. Both were materials that could make a skeleton, but they were very different.

Ordinary bones cannot be bent and are very strong, but they can crack under a lot of pressure. While cartilage, although not as strong as ordinary bone, but can be bent and more flexible.

The human skeleton is made of bone, but we also have cartilage in our ears and nose and pads in our joints. In fact, most of our skeleton is cartilage when we are babiesbut as we grow they are replaced by bones.

Cartilage is too elastic to support a person’s weight. If our skeleton was made of cartilage, we would fall under the weight of gravity. Our bodies need strong bone strength to support our weight on land.

In the water, however, the shark’s cartilaginous skeleton has helped them survive and thrive. Because cartilage is lighter than bone, sharks don’t have to work as hard to swim. This is very important, because they drown if they stop swimming. If they had a heavier frame, they would have to work harder and expend more energy just to keep moving.

Cartilage is strong but flexible, which helps sharks become fast and maneuverable swimmers. It helps them catch prey and avoid predators. And sharks do have predators. Lots of big sharks, like big hammer, likes to eat small sharks. And orcas, or killer whales, will eat great white sharks. Some sharks, like lemon sharkwill even eat smaller members of its own species.

Bone benefits

Today there are about 1,000 species of fish with cartilage as their skeleton, and more than 28,000 species of fish with ordinary bones as their skeleton. The nature of bones that cannot bend and can become very strong can help muscles work better by providing strong support. So having bones allows the body to be able to move in the water.

For example, there are many forms of bony fish. Many of them use pectoral fins on their sides to move, instead move yourself with a tail like a shark . That allows them to move back and forth, which is especially useful for moving in and out of tight spaces, such as corners on coral reefs.

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More than 400 million years ago, an ancient group of fish called placodermi was the first fish to develop jaws. This is important because it helps them become impressive predators.

Placodermi have extraordinary plates of bone that can protect their heads and body parts, but the rest of their skeleton is made of cartilage. That’s one of the reasons we find fossils of their heads and jaws, but not their skeletal remains. Cartilage rarely fossilizes.

Suspicious family tree

Placodermi probably the ancestor of two major groups of fish – modern sharks and rays, with skeletons made of cartilage, and bony fish. Both groups have survived for hundreds of millions of years. But the bony fish are the ones creating amphibians – the first creatures to leave the sea and develop limbs and lungs that allowed them to live on land.

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That amphibian with a bony skeleton creating reptilesand from reptiles came birds and mammals and finally includes humans. That means we can trace our bones to ancient fish. There are currently about 60,000 species on Earth with skeletal bones that swim, live on land or fly in the air.

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Arina Apsarini Putri Asrofi translated this article from English

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