The
skeleton
, Supporting systems and movement in animals
Hydrostatic skeletons
Hydrostatic skeletons: Soft-bodied invertebrates (eg. jellyfish, slugs) supported by fluid inside bodies.
Fluid fills cells & cavities in body. muscles contract against fluid, setting up a pressure.
Fluid, not compressible, provides support, fluid has no shape. rely on surrounding muscles to determine shape.
Advantages Disadvantages
* does not require support structures/tissues * animal limited in size can reach & speed at which it move
* if bodies dry out, have no protective body covering.
Exoskeletons
Hard outside, or externally
Cover bodies of arthropods (Eg spiders, crabs) made up of chitin. chitin forms body plates w/ flexible joints.
Animals muscles attach to exoskeleton allow controlled movement.
Insects developed wings to fly.
Advantages Disadvantages
* good body support & attachment for muscles. Chitin cannot stretch animal moult to grow.
* reduces water loss
During moulting, body unprotected, easy prey
A protects animal from injury.
size of animal limited because exoskeleton must get
* thin & flexible at joints for quick movement.
bigger. exoskeleton heavy limit animal's movement,
Endoskeletons
Skeletons inside body. True endoskeletons found in vertebrates. belong to larger group called chordates.
All chordates have single supporting rod, lies below central nerve cord. In lower chordates, rod called notochord.
Notochord acts as internal skeleton that muscles act against to support animal & allow movement .
In vertebrates, notochord replaced by vertebral column, made of cartilage/bone. surrounds & protects central
nerve cord. notochord in embryos of chordates confirms group evolved from common ancestor.
Advantages Disadvantages
* development of joints at ends bones, body flexible. * takes long time to repair when damaged,
* grow larger size as tissues of skeleton grow. eg bones broken.
* protects internal organs. * provide structural support
* provide more positions for muscle attachment, improves
power of muscles.
skeleton
, Supporting systems and movement in animals
Hydrostatic skeletons
Hydrostatic skeletons: Soft-bodied invertebrates (eg. jellyfish, slugs) supported by fluid inside bodies.
Fluid fills cells & cavities in body. muscles contract against fluid, setting up a pressure.
Fluid, not compressible, provides support, fluid has no shape. rely on surrounding muscles to determine shape.
Advantages Disadvantages
* does not require support structures/tissues * animal limited in size can reach & speed at which it move
* if bodies dry out, have no protective body covering.
Exoskeletons
Hard outside, or externally
Cover bodies of arthropods (Eg spiders, crabs) made up of chitin. chitin forms body plates w/ flexible joints.
Animals muscles attach to exoskeleton allow controlled movement.
Insects developed wings to fly.
Advantages Disadvantages
* good body support & attachment for muscles. Chitin cannot stretch animal moult to grow.
* reduces water loss
During moulting, body unprotected, easy prey
A protects animal from injury.
size of animal limited because exoskeleton must get
* thin & flexible at joints for quick movement.
bigger. exoskeleton heavy limit animal's movement,
Endoskeletons
Skeletons inside body. True endoskeletons found in vertebrates. belong to larger group called chordates.
All chordates have single supporting rod, lies below central nerve cord. In lower chordates, rod called notochord.
Notochord acts as internal skeleton that muscles act against to support animal & allow movement .
In vertebrates, notochord replaced by vertebral column, made of cartilage/bone. surrounds & protects central
nerve cord. notochord in embryos of chordates confirms group evolved from common ancestor.
Advantages Disadvantages
* development of joints at ends bones, body flexible. * takes long time to repair when damaged,
* grow larger size as tissues of skeleton grow. eg bones broken.
* protects internal organs. * provide structural support
* provide more positions for muscle attachment, improves
power of muscles.
