SUPPORT AND MOVEMENT IN ANIMALS

Necessity for support and movement in animals.

Animals move from place to place:

1. In search of food.
2. To escape from predators.
3. To escape from hostile environment.
4. To look for mates and breeding grounds.
5. The skeleton, which is a support structure, helps to maintain the shape of the body.
6. Movement is effected by action of muscles that are attached to the skeleton.

Types and Functions of Skeletons

1. Two main types will be considered.
2. These are exoskeleton and endoskeleton.

Exoskeleton

1. Exoskeleton is hard outer covering of arthropods made up of mainly chitin.
2. Which is secreted by epidermal cells and hardens on secretion?
3. It is strengthened by addition of other substances e.g. tannins and proteins to become hard and rigid.
4. On the joints such as those in the legs the exoskeleton is thin and flexible to allow for movement.

Functions of Exoskeleton

1. Provide support.
2. Attachment of muscles for movement.
3. Protection of delicate organs and tissues.
4. Prevention of water loss.

Endoskeleton:

1. It forms an internal body framework.
2. This is a type of skeleton characteristic of all vertebrates.
3. The endoskeleton is made of cartilage, bone or both.
4. It is made up of living tissues and grows steadily as animal grows.
5. Muscles are attached on the skeleton.
6. The muscles are connected to bones by ligaments.

Functions

1. The functions of endoskeleton include support, protection and movement.
2. Locomotion in a finned fish e.g. tilapia.
3. Most of the fishes are streamlined and have backward directed fins to reduce resistance due to water.

External features of Tilapia

1. Scales tapers towards the back and overlap forwards to provide a smooth surface for a streamlined body.
2. The head is not flexible.
3. This helps the fish to maintain forward thrust.
4. Slimy mucous enables the fish to escape predators and protects the scales from getting wet.
5. The pectoral and pelvic fins are used mainly for steering, ensuring that the fish is balanced.
6. They assist the fish to change direction.
7. The dorsal and anal fins keep the fish upright preventing it from rolling sideways.
8. 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.
9. In order to change position in water, the fish uses the swim bladder.
10. When filled with air the relative density of the body is lowered and the fish moves up in the water.
11. When air is expelled, the relative density rises and the fish sinks to a lower level.
12. Swimming action in fish is brought about by contraction of muscle blocks (myotomes).
13. These muscles are antagonistic when those on the left contract, those on the right relax.
14. The muscles are attached to the transverse processes on the vertebra.
15. The vertebra is flexible to allow sideways movement.