Movement
Movement
It's a simple fact, most animals move.
Humans (like you) can move because your body is supported by an internal skeleton - that's right, you are just a bag of bones!
All vertebrate animals (fish, amphibians, reptiles, birds and mammals) have internal skeletons. Although they look quite different at first glance, they share some basic characteristics.
What does your skeleton do?
The bones in your skeleton act as anchors for all your muscles. Muscles work to pull your bones in different directions.
Take the muscles in your arm. Like most muscles they work in pairs - as one expands (gets bigger) the other contracts (gets smaller) allowing you to move your arm around the elbow joint.
Muscle movement: biceps relaxed, triceps contracted
Muscle movement: biceps contracted, triceps relaxed
Your skeleton also provides you with support and protection. Imagine the damage you could do to your brain if you didn't have a skull to protect it.
What about other animals?
Not all animals walk and run around as humans do - their skeletons have adapted to different forms of movement.
Fish swim, their long flexible backs and strong fins allow them to glide through water easily. Frogs hop, their strong back legs and large feet help them jump. Birds fly, their 'arms' have turned into wings and they have evolved extremely light, hollow bones to enable them to fly.
Barn Owl skeleton
Some animals, like insects and crabs, have a completely different type of skeleton from ours - their skeletons are external (on the outside of their bodies). This is called an exoskeleton. Some exoskeletons are hard, such as those found on crabs or insects. Others are soft, such as the hydrostatic skeleton found in jellyfish. These animals are called invertebrates because they do not have a backbone made up of vertebrae.
Horseshoe Crab
Have a look at the skeletons on the right and compare them to the human skeleton on the left.
Can you recognise the skull, the leg bones and the spine in the pelican, frog and tiger?
Click on the images to find out more.
Do you know how the animals in the images below move?
How do you think their skeletons have changed to allow this movement?
Fact File
Need to know: All insects have six legs
Name: Moth
Group: Insects
Type of skeleton: Exoskeleton - it is an invertebrate
Movement: Moths and butterflies move in different ways at different times of their lifecycle.
When they are caterpillars they crawl along on small stumpy legs.
As adults they fly - they need to find a mate quickly and reproduce in the short summer months.
Fact File
Name: European pond tortoise
Group: Reptiles
Country of origin: Spain and France
Type of skeleton: Internal skeleton - a vertebrate
Movement: Tortoises hold their legs out to the sides of their bodies (this is true of all reptiles with legs). This makes them waddle from side to side as they walk. Generally tortoises are quite slow walkers.
Did you know? Tortoise shells are actually modified rib-cages. The ribs have become fused and surround the animal.
Fact File
Name: Eastern coral snake
Group: Reptiles
Country of origin: southeastern United States
Type of skeleton: Internal skeleton - a vertebrate
Movement: Snakes have very different skeletons to other vertebrates - they have no legs! This means they cannot walk like we do - they slide their bodies in an 'S' shape from side to side, using muscles in their long bodies to creep along the ground.
Did you know? Snakes can have up to 500 vertebrae in their back bones - humans have 32 to 34!
