• Question: Why some animals have bones and some have none?

    Asked by George to Carrie, Cedric, Ellen, Ines, Rupert on 10 Mar 2017.
    • Photo: Carrie Ijichi

      Carrie Ijichi answered on 10 Mar 2017:

      lots of invertebrates have an exoskeleton which protects them even better than our skeleton does. Think about a tiny insect falling from a great height – they just get up and walk off! Skeletons help give you structure and protect organs but they also limit your movement (try licking your elbow to find out!) so some animals benefit by not having one. Everything is about balancing pros and cons and each animals has developed to be well suited to the world they live in.

    • Photo: Ellen Williams

      Ellen Williams answered on 10 Mar 2017:

      This is a good question – I guess just all animals are different and they all have different needs in their lives and so therefore different bodily structures. But as Carrie says many invertebrates have different ways of protecting themselves. Every animal is unique and every animal is perfectly designed for what it needs to do in life 🙂

    • Photo: Rupert Marshall

      Rupert Marshall answered on 11 Mar 2017:

      Muscles pull things together. So for birds to fly something needs to hold the wings straight AND they need a hinge so they can flap. A bit like your elbow arm bones and your elbow. If you didn’t have arm bones your arm would just hang down. if you didn’t have an elbow the two bits of the arm would be very difficult to control. If there were no bones at all the muscles would pull the body into a wobbly ball of flesh.

      There are three main types of skeleton. Some animals have skeletons on the inside, like us. We call these animals vertebrates as they have a backbone made from lots of vertebrae joined together. Some animals have a different sort of skeleton on the outside, like insects. We call this an ex0-skeleton and the animals are invertebrates because they don’t have a backbone made from vertebrae. Some animals like worms and jellyfish have a hydrostatic skeleton: instead of bones there are lots of water-filled tubes, like a bicycle tyre’s inner tube. The muscles can pull against these. There’s a fun video explaining what would happen if humans didn’t have a skeleton here:

    • Photo: Ines Goncalves

      Ines Goncalves answered on 11 Mar 2017:

      Bones are just hard structures that help keep everything else in its place, and are particularly important for large terrestrial animals because otherwise, we’d be a bit of a lumpy mess and not very mobile. Another way to keep internal organs in place and protected is by having an exoskeleton, that is, an external skeleton, like crabs or insects. These are just different ways of achieving similar results and a god example of how creative nature can be.

    • Photo: Cedric Tan

      Cedric Tan answered on 12 Mar 2017:

      Good question! Most of the animals on land have bones to support their bodies in light of the gravitational pull. In water, the bouyancy counteracts gravity explaining why we float. Therefore many of the marine animals do not have bones.

      In fact astronauts that go to the moon for some time often come back with lighter bones because of the weaker gravity faced in space and on the moon.!

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