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6.1 |
Support, Movement and Growth in Animals |
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1. Skeleton is the support system for all types of animals
2. There are 3 types of support:
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Type of support |
Explanation and Example |
Endoskeleton |
- Support all vertebrates
- Made up of internal bones and cartilage
Example: Cat, frog, fish, crocordile
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Exoskeleton |
- Support most invertebrate
- Consists of an outer layer of waxy chitin or shell
Example: Spider, prawn, scorpion, crab
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Hydrostatic skeleton |
- Support some vertebrate with soft bodies
- The pressure of the fluid in the coelem produces movement
Example: Starfish, jelly fish, earthworm, leech
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3. Importance of support system:
- Support body weight
- Maintain body shape
- Protect internal organs
- Movement
4. 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
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5. 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
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6. The human skeletal system
- Axial skeleton: skull, vertebral column, sternum and ribs
- Appendicular skeleton: pectoral girdle, the upper limbs, pelvic girdle and lower limbs
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Skull
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- Cranial bones - protect the brains
- Facial bones - provide the basic shape for the face and support the teeth
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Vertebral column
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- Consists of 33 small bones of vertebrae
- Protect the spinal cord
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Clavicle
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- Parts of pectoral girdles - connects the upper limbs to axial skeleton
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Scapula
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- Parts of pectoral girdles - connects the upper limbs to axial skeleton
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Ribs
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- 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
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Sternum
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Humerus
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- The upper end of humerus connects to the pectoral girdle
- The lower end connects to ulna and radius
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Pelvic girdle
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- Formed from a pair of hip bones
- Connect to the axial skeleton
- Supports weight, protects the bladder and the reproductive organs
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Ulna
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- Attached to carpus bones to form the wrist
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Radius
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- Attached to carpus bones to form the wrist
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K
Metacarpus
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- Attached to carpus bones
- Form the palm
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Phalanx
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- Attached to metacarpus bones
- Form the fingers
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Femur
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- Upper end of the femur connects to pelvic girdle
- Lower end of the femur attached to tibia and fibula
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Patella
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- Functions primarily as an anatomic pulley for the quadriceps muscle
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Fibula
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- The bones of calf
- Attached to the tarsus, the ankle
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Tibia
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- The bones of calf
- Attached to the tarsus, the ankle
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Metatarsus
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- Attached to tarsus to form the foot
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Phalanx
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- Attached to metatarsus to form the bone of toe
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7. Factor of stability in animals |
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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 |
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