Locomotion and skeleton in vertebrates.

Locomotion and skeleton in vertebrates.

Invertebrates, skeletal muscles, and skeleton help in locomotion.

Swimming in Fishes

Swimming in water has different problems than walking on land like a man or flying in the air like a bird. There is the following adaptation in fishes for swimming:

1. The body of most of the fishes is streamlined. In this case, the body is tapering at both ends. Thus water flows readily over the body surface and water show minimum resistance.

2. No other structures project from the body of fish except fins. Thus the body becomes more perfectly streamlined.

3. The mucus or oil glands produce a slimy secretion. These secretions keep the dermal denticles of cartilaginous fish and the scales of bony fish moist. It also considerably reduces friction between fish and water.

4. Fish move efficiently through the water with the help of its fins. Fins perform the following functions:

➤ The dorsal and ventral, unpaired fins help to stabilize the fish.

➤ The paired pectoral and pelvic fins are used for steering and balancing the animals.

➤ The caudal or tail fin coordinate with paired fins provides forward movement of fish through water.

5. Buoyancy in the water is maintained by a specialized structure in bony fish called swim bladder.

Locomotion In Amphibian

The amphibians have a fish-like body plan. They have following adaptations for locomotion:

➤ They wriggle along their belly on the ground with the help of segmentally arranged muscles. It looks as it "swims on land". Their legs hardly touch the ground when they move deliberately.

➤ A few amphibians raise up their body on the legs. They then propel themselves as movable levers.

➤ The anurans (frog) show peculiar swimming and jumping methods of locomotion. The entire skeleton and muscular system have become specialized for this mode of locomotion. Both kinds of limbe, act together and produce extensor thrusts.

➤ Frogs and toads, also walk and hop (move by jumping) on land due to its strong hind limbs.

Locomotion In Reptiles:

The reptiles show striking adaptations for locomotion. They move better than amphibians due to the evolution of a skeleton. The reptiles use the method of walking and running. The general form of the reptilian skeleton is based on one inherited from ancient amphibians. There are following adaptations for locomotion in reptiles:

➤ The skeleton is highly ossified to provide greater support.

➤ Reptiles have cervical vertebrae. The first two cervical vertebrae (atlas and axis) provide greater freedom of movement for the head. The axis is modified for rotational movement.

➤ The ribs of reptiles are highly modified. The ribs of snakes have muscular connections with the large belly scales. They help in locomotion.

➤ Many prehistoric reptiles were bipedal. Bipedal means that they walked on hind limbs. They had a narrow pelvis and heavy outstretched tail for balance. Bipedal locomotion frees the front appendages. So front appendages became adapted for capturing of prey or flight in some animals.

Locomotion in Air:

The skeleton of a bird is modified for flight. There are following flight adaptations in bird:

1. They have developed bones with large air space. It has made the bone lighter.

2. The forelimbs have changed into wings. These wings have very strong pectoral muscles. These muscles pull the wings up and down.

3. The sternum is modified to form the keel. The keel is needed for the attachment of muscles.

4. The body is covered with feathers. The feathers give the wing a large surface area for the flight. They also keep their bodies warm. Thus they can produce enough energy for flight.

5. Their body is streamlined to cut through the air. The feathers lie smoothly against its body. So that the air can easily flow over them.

A bird can fly either passively by gliding or actively by flapping its wings.

Passive flight:

The birds fly passively by gliding. The wings act as aerofoils during gliding. An aerofoil is any smooth surface that moves through the air at an angle to the airstream. The air flows over the wing in such a way that the bird is given lift. The amount of lift depends on the angle at which the wing is

held relative to the air-stream:

Active flight:

The birds fly actively be flapping their wings. The upward air currents give little or no support. Thus the same effect can be achieved by flapping the wings. As the birds move through the air, the air flows more quickly over the curved upper surface than over the lower surface. This reduces the air pressure on the top of the wing as compared to air pressure below the wing. Therefore there is, a net upward pressure on the wing. This gives a lift to the bird.

Mammals.

The most efficient way of supporting the body is seen in mammals. The limbs of the mammals have undergone further modifications to produce the following modes of locomotion.

1. Plantigrade:

In this mode of locomotion, the mammals walk on their soles. So their palm, wrist, and digits all rest more or less on the ground. Example: monkeys, apes, man, and bear, etc.

2. Digitigrades:

Some mammals tend to walk on their digits only. They run faster than plantigrade animals. In these mammals, the first digit usually reduces or completely st as in rabbit, rodents, etc.

3. Unguligrade:

These mama's nails walk on the tips of toes. These toes are modified into hoof as deer, goat. It'is the swiftest type of locomotion.