Flight in Birds: Evolution, Morphology, Muscular System with MCQs

Evolution of Flight

The flight would evolve millions of years ago in all groups that can fly today. We cannot observe habits and morphology that evolution of flight involved. But we have fossil records which are products for three primary groups (Pterosaurs, birds, and bats) that progress real flight. Evolution does not ask “why”.

It has no sense of future. The here and now is the only place where evolution takes place. If an adaptation is useful the possibilities are more that it will preserve. If adaptation is coopted from previous to new use then it is called exaptation.

How and why did wings evolve

A comparative research study of the functional morphology of wings of the earliest known flying member of linage with pre wing structure of ancestor offers evidence for how wings evolved. Why wings evolve is a matter of contention. The different hypothesis was offered as:

• 1) Wings evolve from arms used to catch little prey.
• 2) Wings evolve since bipedal animals were leaping in the air. Large wings assisted leaping.
• 3) They were used as sexual display structure. Larger wings were preferred by males.
• 4) Developed from Moving forefathers, who began to flap their gliding structure in order to produce thrust.

Morphology of Structures that involve in Flight

• 1) Ribs of birds are ossified. Thoracic ribs have flat uncinated procedures each of which overlaps the next rest posterior rib and added support to the chest and attachment site for muscles. The ossified sternum articulates with the pectoral girdle and ribs.
• In carinate, (flying) birds and penguins which are powerful swimmers, the chest bone has a midventral keel or carina for the attachment of large flight muscles. In general ratites (flightless birds) such as ostrich and emus did not have the keeled chest bone.
• 2) In the pectoral muscles insert primarily or the humerus (bone of anterior appendage) and supply the power for flight. While the air moving over the convex surface of the wings provides the essential lift.
• 3) Ilium (bone of pelvic girdle) is broad and used up for the attachment of appendicular muscles which are extremely developed for bipedal locomotion.

Muscular System Involved in External Adaptation for Flight:

Although numerous birds have actually lost their muscular metamerism and developed muscle bundles. Due to the fact that the vertebral column in the trunk region is more or less rigid. Epaxial muscles in the trunk area are less or improperly established. Differentiation of the abdominal wall muscles is significantly lowered and metamerism is no longer apparent. External and internal muscles are present to assist in breathing.

Two kinds of Skeletal Muscle Tissue

Two-color types of skeletal tissue exist in birds.

• 1) Red muscle fiber
• 2) White muscle fiber

✓ Red Muscle Fiber:

These are smaller sized in diameter have a richer blood supply and include more mitochondria and nuclei than white muscle fiber. In addition to hemoglobin red muscle fibers likewise, consist of myoglobin. Myoglobin found in the flight muscles of numerous birds which accounts for the selection of white meat and dark meat. Red muscles are created for continual activity.

✓ White Muscle Fiber:

1. White muscle is developed for brief bursts of extreme activity. Such as turkey passerines and aquatic species developed for the diverse use of their legs. Amongst the most crucial feature of the thermal physiology of flight is considerably increased heat production produced by the flight muscles and the increased oxygen uptake. For example, the metabolic rate of costa’s hummingbird throughout hovering flight was 7 times the standard rate. The metabolic rate varies with the flight speed. A few of the heat produced during flight is stored in the bird most of the heat produced is lost by evaporative cooling.
2. For extremely short periods of flight oxygen uptake of the night grosbeak, ring-billed gull and black duck were 12-13 times the resting value.
3. iii. Branchiomeric muscles serve the exact same functions as they carry out in reptiles. They operate jaws the hyoid skeleton and its derivatives as well as vocal cords and larynx.
4. Both extrinsic and intrinsic muscles exist in birds. Extrinsic muscles allow independent movement of the skin. Intrinsic muscles are primarily smooth muscles that attach to the feather hair follicles.
5. These muscles are used to ruffle the plumes for the insulation, for display and emotional response to danger, taking off, and flying a brief range. Some muscles might be composed of red fibers in one species and white fibers in another species depending upon their function. Even in the same species, the kind of muscle fiber in a given muscle might differ, (e.g., breast muscle in a wild turkey is red and in domestic turkey is white.).

✓ Appendicular muscles in Birds:

1) These muscles are highly modified for flight as well as for perching, grasping, strolling, happing, and swimming.

2) The biggest and most powerful muscles in carinate birds are the extrinsic muscles of the wings. These pectoral or breast muscles are attached mostly to the keeled breast bone in addition to the coracoids and furcula. Contraction of pectoralis muscles pulls the wings downward and forward to offer a lift. Elevation of the wings is brought about mostly by the contraction of the supracoracoideus, which also stems on the forward side of the breast bone. The intrinsic musculature of the wings is reduced. On the other hand, the musculature of the hind limbs is well established. Specialized muscles are essential in the legs and feet of raptors.

Types of Flight

Gliding

When a bird is gliding, it doesn’t have to do any work. The wings are held out to the side of the body and do not flap. As the wings move through the air, they are held at a small angle, which deflects the air downwards and triggers a reaction in the opposite direction, which is lifted. However, there is likewise drag (air resistance) on the bird’s body, so every so often, the bird has to tilt forward and enter into a slight dive so that it can keep forward speed.

Soaring

Soaring flight is a unique type of slide in which the bird flies in an increasing air current (called a thermal). Because the air is increasing, the bird can keep its height relative to the ground. The albatross uses this type of soaring to support its multi-year trips at sea.

Flapping

Birds’ wings flap with an up-and-down motion. This moves them forward. The whole wingspan needs to be at the best angle of attack, which means the wings need to twist (and do so automatically) with each downstroke to keep aligned with the direction of travel.

MCQs

 

FAQs (Frequently Asked Questions)