BIOLOGY FORM 5 NOTES CHAPTER 2 : LOCOMOTION AND SUPPORT

2.1 SUPPORT AND LOCOMOTION IN HUMANS AND ANIMALS

2.1.1 Introduction

1. Locomotion = The ability of an organism to move in a particular direction in its environment.

2. Support and humans and animals is provided by a framework called a skeleton.

3. There are 3 types of skeleton:

(a)  Hydrostatic skeleton

-       The support is derived from the body fluid contained within the body cavity

-       The fluid maintains the body shape and provide support for internal organs

-       Examples: earthworms, leeches and caterpillars

(b)  Exoskeleton

-       Found in the bodies of arthropods, the shell of molluscs and the bony plates of tortoise.

-       The exoskeleton supports important body organs, protects the internal structure from damage and allows the animals to move from place to place.

-       Examples: insects, crabs, snails

(c)  Endoskeleton

-       Found in the bodies of all vertebrates

-       The endoskeleton consists of hard skeleton of bones found inside the body.

-       The endoskeleton supports the body and also protects the organs

-       Examples: human, fish, amphibians and birds

4. The functions of skeleton:

(a)  Protection

-       The skeleton protects the organs

-       Example: The skull protects the brain, the vertebral column protects the spinal cord and the rib cage protects the heart and lungs

(b)  Support

-       The skeleton acts as a framework to support soft body parts, to maintain the upright position and to keep the body stable.

(c)  Movement

-       Bones interact with the skeletal muscle to enable the movement of the body.

(d)  Blood cell formation

-       Most of the blood cells are formed in the bone marrow of the long bones

(e)  Mineral storage

-       Bones act as a reservoir for calcium and phosphorus.

2.1.2 The human skeletal system

1. The skeletal system can be divided into the axial skeleton and the appendicular skeleton.

2. The axial skeleton:

-       Made up of the bones that form the vertical axis of the body.

-       It supports and protects the organs of head, neck and trunk.

-       Includes: the skull, vertebral column and rib cage

3. The appendicular skeleton:

-       Made up of the bones that are attached to the axial skeleton

-       Includes: bones of the limbs (forelimb and hindlimb), the pectoral girdle and the pelvic girdl

      4.  Axial skeleton

Type of skeleton	Characteristics & explanation

5.  Structure of a typical vertebra

Structure	Function
Transverse foramen
Vertebral foramen
Spinous processes, Transverse processes
Centrum

6.  Type of vertebral

Type of vertebral	Characteristics & explanation
	Atlas
	Axis
	3rd-7th cervical vertebrae
	Thoracic vertebrae Lumbar vertebrae  Sacrum and Coccyx

7. Appendicular skeleton

Type of skeleton	Characteristics & explanation
	Pectoral girdle
	Pelvic girdle
	Upper limb Lower limb

8. Structure of a joint

·         A joint is a place where 2 or more bones meet.

·         Structures of a joint:

a)  bones

b)  muscles

c)  ligaments (elastic fibres, prevent dislocation of the joints during movement.)

d)  cartilage ( absorb shock, reduce friction)

e)  synovial membrane ( reduce friction, protect the bones from wearing away.)

·         Two types of joint:

(a)  Hinge joint:

-              Allow movement of bones in one plane only (door hinge)

-              Examples: elbow joint, knee joint and some of the joints between the finger or toe bones

(b)  Ball-and-socket joint

-              Allow rotational movement of bones in 3 planes ( all directions)

-              Examples: shoulder joint and hip joint.

9. Ligaments, Tendons and Muscles

     

(a)  Ligaments

·         Joints two or more bones together at a joint.

·         Ligaments are tough and strong connective tissues.

·         They are elastic and allow the movement of bones at a joint

(b)  Tendons

·         Joints muscles to the bones

·         Ligaments are tough and strong an d inelastic strands of dense connective tissues.

(c)  Muscles

                      i.        Skeletal muscles

-  can only contract when there are impulses. If the nerve to the skeletal muscle is damaged or blocked, the muscle will completely paralysed.

-  Produce movement by exerting the force to pull on the tendons which are attached to bones. As muscle contracts, it becomes shorter as it pulls on the attached bone.

-  Produce movement by exerting the force to pull on the tendons which are attached to bones. As muscle contracts, it becomes shorter as it pulls on the attached bone.

                    ii.        Smooth muscles

-  can contract spontaneously even in the absence of nervous stimulation.

iii.       Cardiac muscles

-  can contract spontaneously even in the absence of nervous stimulation.

10.                                                         The structure of skeletal muscles

·         Consists of bundles of muscle fibres, nerves and blood vessels.

·         Muscle fibres is a long cylindrical cell that contain numerous nuclei.

·         Each muscle fibre is made up of many myofibrils

·         Each myofibril has section of sacromere.

·         A sacromere consists of myosin and actin which interact to bring about muscle contraction.

11. Antagonistic muscles

·         A pair of muscles work together to allow coordinated movement of the skeletal joints.

·         When one muscle contracts, the other muscle relaxes.

·         One muscle pulls the bones in one direction and the other pulls it in the opposite direction.

12. Action of ligaments, tendons and muscles in the moving of a limb.

     (c)  Walking

§  The calf muscle of right leg contracts to raises the heel.

§  The flexor muscle at the thigh (biceps femoris / hamstring muscle) contracts while the extensor muscle (quadriceps femoris) relaxes to pull the tibia and fibula backwards and bend the leg at knee.

§  The leg is raised. The weight of the body is now supported by the left leg which is still in contact with the ground.

§  Then, the quadriceps femoris contracts while the biceps femoris relaxes to pull tibia and fibula the forward and extends the leg.

§  The tibialis contracts to lower the heel onto the ground.

§  The right leg regains contact with the ground. The weight of the body is now supported by the right leg.

§  The whole process is repeated with the left leg.

2.1.3     Consequences of impaired musculoskeletal system

           

Impaired musculoskeletal system	Causes	Signs and syndromes	Prevention and treatment
Muscle cramp
Impaired musculoskeletal system	Causes	Signs and syndromes	Prevention and treatment
Osteoporosis
Muscular dystrophy
Impaired musculoskeletal system	Causes	Signs and syndromes	Prevention and treatment
Arthritis (a) Osteoarthritis (b)   Rheumatoid  arthritis

2.1.4     The mechanism of locomotion in animals

1.    The locomotion of earthworm

·         Earthworms have two antagonistic muscles: circular muscles and longitudinal muscles.

·         When circular muscles contract, the longitudinal muscles relax, the earthworm becomes thinner and longer.

·         When longitudinal muscles contract, the circular muscles relax, the earthworm becomes shorter and thicker.

·         During locomotion, the circular and longitudinal muscles contract rhythmically to produce peristaltic waves along the body.

·         The waves begin at the front and move towards the end of the body.

·         The earthworms have bristles called chaetae which anchor parts of the body to the ground so that other parts can be pulled towards.

2.    Locomotion in an animal with an exoskeleton

·         A grasshopper has antagonistic muscles: flexor muscle and extensor muscle.

·         When flexor muscle contracts and the extensor muscle relaxes, the leg is bent at joint.

·         When extensor muscle contracts and the flexor muscle relaxes, the leg is straightened.

(a)  Walking

·         A grasshopper uses three legs to support the body off the ground, while the other three legs move together to make successive steps while walking.

(b)  Jumping / Hopping

·         The rear legs (hind legs) of a grasshopper are adapted for hopping. The legs are long and muscular.

·         When the flexor muscle contract, the lower leg is pulled towards the body. The long hind legs are folded in shape of Z. The grasshopper is ready for a jump.

·         When the extensor muscle contracts, the leg jerks backwards.

·         The grasshopper is propelled forward and upwards to the air.

      3.   Locomotion in an animal with an endoskeleton

(A) Locomotion in fish

·         Problems faced by fish in locomotion:

(a)  water is viscous and dense

(b)  gravity

·         The adaptations of fish in locomotion:

(a)  Fish have streamlined body shapes to overcome water resistance.

(b)  The overlapping scales on the body of a fish facing backwards to reduce resistance when swimming.

(c)  The body of fish is covered by a slimy coating to minimize frictional drag and maintains a smooth flow of water over the body.

(d)  The vertebral column of the fish is flexible to allow the movement of the body.

(e)  The movement of the fish is controlled by the contraction and relaxation of myotomes (W-shaped muscle) which causes different parts of the body to be swept from side to side pushing the water backwards and sideways and the body forwards.

·         Forward movement

(a)  During swimming, the tail is swept from side to side to bend the body on either side alternately and produce a thrust that propels the fish forward.

(b)  The contraction of the myotome on the right side of the body will bend the tail to the right; the contraction of the myotome on the left side of the body will bend the tail to the left.

(c)  The continuous sweeping movement of the tail from side to side produces a thrust that propels the fish forward on a straight path.

·         Balancing the body

(a)  The function of fins of fish is to maintain the balance of the body during swimming.

(b)  The paired fins consist of Pectoral fins and Pelvic fins:

i)        Pectoral fins: used for steering, to change the direction and as a brake to slow down or stop the movement.

ii)      Pelvic fins: used for balance and to keep the fish steady by preventing diving and rolling.

(c)  The unpaired fins consist of one dorsal fin, one ventral fin and one caudal fin or tail.

i)        Tail: propulsion organ

ii)      Dorsal fin and ventral fin: prevent yawing and rolling

(a)  Many bony fish have swim bladders to help them maintain buoyancy in the water. The swim bladder is a sac inside the abdomen that contains gas. By controlling the amount of gas in the swim bladder, a fish can change its buoyancy.

(B) Locomotion in birds

·         The adaptations of birds in flying:

(a)  Birds have streamlined body shapes to reduce resistance in the air when flying.

(b)  The body is light as the bone is hollow, the head is small and the body is free of fats. Some of the internal organs such as kidney and testis are reduced to one to reduce weight.

(c)  The feathers on the tail and wings provide a large surface area for flight.

(d)  The body is covered by waterproof feathers to prevent it to become wet.

(e)  The feathers are arranged to overlap one another and pointed backwards to keep the body its streamlined shape and to prevent it from being ruffled by the wind.

The wings are aerofoiled in shape to provide an upward thrust that carries the bird forward and upward

5 Whole

·         Flight

(a)  When the wings move down:

i)        The major pectoralis muscle on both wings contract.

ii)      The wings are pulled down during downstroke.

iii)    The air resistance produced as a result of lowering the wings provides an upward thrust on the wings.

iv)    The thrust is transmitted from the wings to the coracoid.

v)      The whole body is lifted up.

(b)   When the wings move up:

i)        The minor pectoralis muscle on both wings contract.

ii)      The wings are pulled up during upstroke.

iii)    The air resistance is very low.

iv)    This returns the wings to the starting position for the next downstroke.

(c)  The wings which move up and down rhythmically generate the forward thrust as well as provide the lift for the flying bird.

2.1  APPRECIATING A HEALTHY MUSCULOSKELETAL SYSTEM

1.    The various ways to care for the musculoskeletal system:

(a)  Having a well-balanced diet

(b)  Having a good posture

(c)  Using proper attire for daily activities

(d)  Taking appropriate precautions during vigorous activities

(e)  Practicing correct and safe exercise technique

2.1       SUPPORT IN PLANTS

1.    Support in plants is necessary to:

(a)  enable the plants to stay upright

(b)  enable the plants to obtain sufficient sunlight

(c)  bear weight of the plant

(d)  provide strength to withstand wind resistance

2.    The support in plants is provided by:

(a)  the turgidity of cell

(b)  vascular tissue

(c)  buoyancy of water (aquatic plants)

3.    Support in aquatic plants

(a)  Two types of aquatic plants:

(i)    Submerged plants

(ii)  Floating plants

(b)  Aquatic plants obtain support from buoyancy of water. The buoyancy of water is greater than the pull of gravity enables the aquatic plants to float or stay upright in the water.

(c)  Adaptation of Submerged plants:

(i)    Thin, narrow and flexible leaves to reduce water resistance so that the plant can be pulled by water current without being damage.

(ii)  Fine stems and leaves with a lot of airspaces to keep them float close to the surface to obtain maximum sunlight.

(iii) Do not have woody tissue in stem and the cuticle of plant is thin and easily permeable to water. These plants can absorb water, mineral, carbon dioxide and oxygen over its whole surface.

(d)  Adaptation of floating plants:

(i)    Have broad leaves that are firm but flexible enough to resist tearing by wave action.

(ii) Have aerenchyma tissues (spongy tissues with large air spaces between the cells) in the stems and eaves to provide buoyancy for the plants to float on the surface of water.

(iii) The surface of the floating leaf is covered with a waxy cuticle to prevent stomata being blocked by the water.

4.    Support in terrestrial  plants

                                                               

(a)  Herbaceous plants

(i)    Support in herbaceous plants is provided by the turgidity of parenchyma and collenchyma cells.

(ii) The turgor pressure of the fluid content in the central vacuole pushes the cell membrane and the cell content against cell wall, creating support for the stem root and leaves.

(iii) The thickening of the cell walls with cellulose and pectin the collenchyme cells provide additional mechanical support for herbaceous plants.

(a)  Woody plants

(i)    Support in woody plants is provided by sclerenchyma and xylem tissue.

(ii)  Sclerenchyma tissue composed of cells with secondary cell wall with is lignified to support the non-growing parts of plants because the cells have thick, rigid and non-stretchable cell walls.

(iii) Xylem tissues consist of xylem vessel and tracheids which are strengthened with lignin. As the plant grows, it undergoes secondary growth which results in the formation of secondary xylem called wood. The wood makes the plant stronger and provides support to it.

(iv) Each year, a new layer of xylem tissues is added and this forms an annular ring in the stem called growth ring.

(v)  This way, the stem increases its diameter and strength to support the plants.

(a)  Tropical trees

(i)    Tropical trees have buttress roots.

(ii) These are roots that come out from the lower part of the trunk and grow into the ground, providing support for the tree.

(a)  Creepers, vines and lianas

(i)          Cucumber

-      Tendrils are found on the stems which twine themselves around a support to help the plant to support its weight and climb easily.

(ii)          Gloriasa sp.

-      Tendrils are found at the end of the leaves enable the plants to obtain support.

(iii)         Pepper plant

-      Pepper plant has modified roots to twine around an object for support.

(iv)         Morning Glory

-      Morning glory has shoots which are able to twine around an object.