content: Types of skeletons, Tissues that make up the skeleton, Bone injuries, Human skeleton, Axial skeleton, Appendicular skeleton, Diseases of the skeletal system.
source of information from the Mind Action Series Life Sciences grade 11 textbook
Population and Community Ecology Summary - Gr 11 & Gr12 IEB Mind Action Series
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THE SKELETON
- Supports
- Protects
- Enables movement
Types of skeletons:
HYDROSTATIC:
- Fluid-filled, closed chambers within an organism.
- Made of water.
Advantages:
- Changes shape – this allows movement.
o Muscles contract & push against water
▪ Creates pressure
Disadvantages:
- No protection (skeletal defence mechanism)
- Restricted movement.
- Confined to water.
- Remain small.
Examples:
- Soft-bodied invertebrates.
- Coelenterates
o Jellyfish
o Anemones
- Annelids
o Earthworms
- Nematodes
o Roundworms
How they move:
- Contracting muscles surrounding fluid-filled cavity creates pressure
causing change in shape
- Causes movement
o Jellyfish
▪ Contract bell-shaped form, forcing water out
▪ This propels them forward
o Earthworm
▪ Change shape to move forward by peristalsis
▪ Circular + longitudinal muscles produce waves of contraction +
relaxation.
, EXOSKELETONS:
- Surround the body of an organism
- Made of chitin outside of the body
o Chitin – substance found in cell walls of plants – it is light and strong
Advantages:
- Support + protection.
- Muscle attachment – allows movement.
- Joints – move easily.
- Waxy cuticle – reduces loss of water loss.
Disadvantages:
- Rigid – limits movement.
- Heavy – limits growth so remains small.
- Vulnerable while moulting.
How disadvantages are overcome:
- Moult / ecdysis (shed skeleton) – grow bigger.
- Jointed limbs – range of movements.
Examples:
- Arthropods
o Insects
o Crustaceans
ENDOSKELETON:
- Made of bone within the body.
Advantages:
- Support.
- Shape.
- Can grow – in living tissue.
- Protects internal organs.
- Muscle attachment allows movement.
Disadvantages:
- Not all soft tissues protected.
Examples:
- Mammals
o Humans.
Tissues that make up the skeleton:
- CARTILAGE
- BONE
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