Support, Movement and Growth in Animals

6.1

Support, Movement and Growth in Animals

Skeleton

Skeleton is the support system for all types of animals

There are 3 types of support:

Support

Type of support	Explanation and Example
Endoskeleton	Support all vertebrates Made up of internal bones and cartilage Example: Cat, frog, fish, crocodile
Exoskeleton	Support most invertebrate Consists of an outer layer of waxy chitin or shell Example: Spider, prawn, scorpion, crab
Hydrostatic skeleton	Support some vertebrate with soft bodies The pressure of the fluid in the coelem produces movement Example: Starfish, jelly fish, earthworm, leech

Importance of support system:

Exoskeleton size with growth

Chitin is hard and cannot be expanded
- Inhibit the growth of animals
Ways to overcome
- Ecdysis: moutling the exoskeleton repeatedly before reaching adulthood
Ecdysis process
- A new and soft exoskeleton is formed under the old skeleton
- The animals will suck in air to expand their bodies
- The action of sucking air will break the previous exoskeleton that is hard
- Rapid growth will occur to increase the size of the organism before the new exoskeleton hardens
- Hormone control every stage of the ecdysis
The diagram below shows the step-shaped growth curve graph of animals with exoskeleton

Relating the hydrostatic skeleton with movement

Earthworm has hydrostatic skeleton
It moves with the aid of chaetae
It has 2 types of muscle
- Circular muscles
- Longitudinal muscles
Muscles in earthworm act antagonistically and it exerts a hydrostatic pressure on the fluid in the earthworm body

The human skeletal system

Axial skeleton: skull, vertebral column, sternum and ribs
Appendicular skeleton: pectoral girdle, the upper limbs, pelvic girdle and lower limbs

Skull	Cranial bones - protect the brains Facial bones - provide the basic shape for the face and support the teeth
Vertebral column	Consists of 33 small bones of vertebrae Protect the spinal cord
Clavicle	Parts of pectoral girdles - connects the upper limbs to axial skeleton
Scapula	Parts of pectoral girdles - connects the upper limbs to axial skeleton
Ribs	Consists of 12 pairs of ribs that joined to the thoracic vertebra Seven pairs of ribs connect to sternum and three more connect to cartilage Protect main organs
Sternum	Connects 7 pairs of ribs
Humerus	The upper end of humerus connects to the pectoral girdle The lower end connects to ulna and radius
Pelvic girdle	Formed from a pair of hip bones Connect to the axial skeleton Supports weight, protects the bladder and the reproductive organs
Ulna	Attached to carpus bones to form the wrist
Radius	Attached to carpus bones to form the wrist
Metacarpus	Attached to carpus bones Form the palm
Phalanx	Attached to metacarpus bones Form the fingers
Femur	Upper end of the femur connects to pelvic girdle Lower end of the femur attached to tibia and fibula
Patella	Functions primarily as an anatomic pulley for the quadriceps muscle
Fibula	The bones of calf Attached to the tarsus, the ankle
Tibia	The bones of calf Attached to the tarsus, the ankle
Metatarsus	Attached to tarsus to form the foot
Phalanx	Attached to metatarsus to form the bone of toe

Factor of stability in animals

Centre of gravity	Base area
The lower the position of the center of gravity, the higher its stability	The larger the base area, the higher its stability
Tortoise, mice	Crocodiles, crabs
The giraffe lowers the center of gravity while drinking water so that it does not fall easily	Kangaroos use their tails as strut to increase base area when not moving