SUPPORT AND MOVEMENT IN ANIMALS
Necessity for support and movement in animals.
Animals move from place to place:
- In search of food.
- To escape from predators.
- To escape from hostile environment.
- To look for mates and breeding grounds.
- The skeleton, which is a support structure, helps to maintain the shape of the body.
- Movement is effected by action of muscles that are attached to the skeleton.
Types and Functions of Skeletons
- Two main types will be considered.
- These are exoskeleton and endoskeleton.
- Exoskeleton is hard outer covering of arthropods made up of mainly chitin.
- Which is secreted by epidermal cells and hardens on secretion?
- It is strengthened by addition of other substances e.g. tannins and proteins to become hard and rigid.
- On the joints such as those in the legs the exoskeleton is thin and flexible to allow for movement.
Functions of Exoskeleton
- Provide support.
- Attachment of muscles for movement.
- Protection of delicate organs and tissues.
- Prevention of water loss.
- It forms an internal body framework.
- This is a type of skeleton characteristic of all vertebrates.
- The endoskeleton is made of cartilage, bone or both.
- It is made up of living tissues and grows steadily as animal grows.
- Muscles are attached on the skeleton.
- The muscles are connected to bones by ligaments.
- The functions of endoskeleton include support, protection and movement.
- Locomotion in a finned fish e.g. tilapia.
- Most of the fishes are streamlined and have backward directed fins to reduce resistance due to water.
External features of Tilapia
- Scales tapers towards the back and overlap forwards to provide a smooth surface for a streamlined body.
- The head is not flexible.
- This helps the fish to maintain forward thrust.
- Slimy mucous enables the fish to escape predators and protects the scales from getting wet.
- The pectoral and pelvic fins are used mainly for steering, ensuring that the fish is balanced.
- They assist the fish to change direction.
- The dorsal and anal fins keep the fish upright preventing it from rolling sideways.
- The caudal or tail fin has a large surface area, and displaces a lot of water when moved sideways creating forward movement of the fish.
- In order to change position in water the fish uses the swim bladder.
- When filled with air the relative density of the body is lowered and the fish moves up in the water.
- When air is expelled, the relative density rises and the fish sinks to a lower level.
- Swimming action in fish is brought about by contraction of muscle blocks (myotomes).
- These muscles are antagonistic when those on the left contract, those on the right relax.
- The muscles are attached to the transverse processes on the vertebra.
- The vertebra is flexible to allow sideways movement.
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