Flight adaptation and flight mechanism in birdsPresented by:- Manish Kumar

Dash

+3 2nd yr. Sc. (Zoology)Roll:- BS12-004

Key Points Adaptation Flight Adaptations in birdsI. Morphological adaptationsII. Anatomical adaptation Some terminology related to flight Mechanism of flight

Adaptation Any alteration in the structure or function

of an organism or any of its parts that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment.

Greater the degree of adaptation- more is the deviation from the normal morphology.

Flight adaptation in birds Morphological adaptations Anatomical adaptations

Morphological adaptations

Body contourI. Spindle shaped body to ensure least wind resistance.II. High position of light organs (lungs and air sacs) and low

position of heavy muscles, sternum, digestive system.III. Low Centre of gravity (average location of weight of an

object.)

Presence of feathersI. Makes the body stream-lined and reduces the friction to

the minimum.II. Very light, hardly adds weight to the bird.III. Serves as a blanket enveloping air around the body and

adds buoyancy.IV. Feathers of wings increases the surface area for striking

the air.

Morphological adaptations (cont.)

Forelimbs modified into wings: forelimbs becomes modified into unique and powerful propelling organs, which propel the body high up in the air. mobile neck and beak: modification of forelimbs is compensated by mobile neck and beak. enables the bird for feeding, nest-building, offence and defense, preening, etc. Bipedal locomotion: hind limbs supports the body weight and acts

as locomotory organs in the ground.

Morphological adaptations (cont.)

Perching strongly developed muscles so modified that when a bird sits in a perch, the toes automatically grips the perch. Short tail and tail feathers serves as a rudder during flight and assist in steering, lifting and counterbalancing.

Morphological adaptations (cont.)

Anatomical modifications Endoskeleton:I. light and provides

large surface for attachment of muscles.

II. Bones are pneumatic filled with airspaces, the extension of air sacs.

III. Skeletal framework is compact, centralized and relatively rigid due to fusion of bones.

Anatomical modification (Cont.)

Muscles of flight muscles on the back are much reduced and flight muscles on the breast are strongly developed. Digestive organs digestive system is efficient, rectum reduced and never stores the undigested food because they cannot afford extra burden of faeces, hence is immediately got rid.

Respiratory System

Air in the bird respiratory system passes through in two breath cycles. • On the initial inhalation air is passed through straight ducts, the

bronchi and mesobronchi, to posterior air sacs. • The following exhalation moves this air into the parabronchi of the

lungs. • The second inhalation moves this air on into the anterior air sacs. The

second exhalation then passes the air through the bronchi and out of the system.

Anatomical modification (Cont.)

Circulatory system heart is large and efficient complete separation of pure and impure blood Reproductive system single ovary and an oviduct in female is a weight-reducing device.

AirfoilLiftGlidingDragFlapping

Terminology

The wings provide lift by creating a situation where the pressure above the wing is lower than the pressure below the wing. Since the pressure below the wing is higher than the pressure above the wing, there is a net force upwards. To create this pressure difference, the surface of the wing must satisfy one or both of the following conditions. The wing surface must be: • Cambered (curved); and/or • Inclined relative to the airflow direction.

EXPLANATION OF HOW IT WORKS

Airfoil

Lift Lift force is produced by the action of air

flow on the wing, which is an airfoil. The lift force occurs because the air has a lower pressure just above the wing and higher pressure below.

Gliding When gliding, birds obtain both, a

vertical and a forward force from their wings. This is possible because the lift force is generated at right angles to the air flow. The lift force, therefore, has a forward component that counteracts drag.

Drag Apart from its weight, there are three

major drag forces that impede a bird’s aerial flight: frictional drag (caused by the friction of air and body surfaces), form drag (due to frontal area of the bird, also known as pressure drag), and lift-induced drag (caused by the wingtip vortices). These forces are reduced by streamlining the bird’s body and wings.

Flapping When a bird flaps, its wings continue to

develop lift, but the lift is rotated forward so providing thrust, which counteracts drag and increases its speed.

Mechanism of flight During flight the wings become unfolded, stretched

and raised vertically upwards.

These then move downward and forward (down stroke) and finally upward and backward (up stroke).

Downstroke is achieved by the action of pectoralis minor,so that the wing is lowered down. The wing is raised by the contraction of pectoralis minor, and other muscles.

During downstroke, the wing is thrust downwards like an oar impermeable to air. It moves forward and vertically upwards with little air resistance for the next powerful downstroke.

The body moves forward in upstroke.

Flight mechanism

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