Moving through fluids: water and air

Term Test some feedbackLift and drag: hydrofoils and aerofoils

Flight muscles of birdsAir sac functions

‘effectiveness of a force’ where forces tend to make things rotateeffectiveness depends on the distance between its line of action and the axis of rotationMoment: product of magnitude of force and perpendicular distance to axis

Some questions that were on the term test

• 2. The statement is made (lab handout) that ‘Bees have evolved an important relationship to plants as pollinators”. Describe (with labelled diagrams) structural adaptations of bees that support this statement.

• 3. Justify, with specific labelled diagram examples, the claim that arthropod cuticle is multifunctional.

• 4. A grasshopper has a genetic disorder that gives it a rubber tentorium. What changes will this produce in the grasshopper’s feeding behaviour?

• 5. Use the opisthosoma of a spider to explain the term tagma, making clear the functionality of having this separate body region.

• 6. What is stridulation and why do crickets need to have a plectrum morphology that phase shifts the scraper wing relative to the file wing?

• 7. Explain what D’Arcy Thompson meant by ‘diagram of forces’ with reference to a specific animal structure.

• 8. Justify the claim that ‘helical crossed-fibre arrays of inextensible collagen’ are important in animal locomotion.

• 9. What functionality does a coelenteron have in common with a coelom; why does one name not do for both cavities?

Some additional questions that didn’t make the term test

• 2. Explain why possession of branched hairs is a useful structural adaptation for a bee.

• 3. Why do moths have wing scales?• 4. State functions of a tentorium and diagram (and label) a tentorium as it appears

in a prognathous insect.• 5. Explain how the thorax of a grasshopper can be termed a tagma, making clear

the functions of this body region.• 6. What forces of -- shear, compression, tension -- can you locate in the wings of a

cricket or katydid during stridulation?• 7. What is the role of the coelom in earthworm locomotion?• 8. What is a stabilimentum and what are its possible functions?

• Axial muscles left of the vertebral column are antagonized by those on the right and vice versa. ‘Chains’' of fibres (continuing across a series of 'zig-zag' myotomes) will all contract and shorten in phase with each other, reaching the same % shortening all at the same time and relaxing maximally at the same time. As they go through their cycle of contracting and relaxing, they are located at different distances between the skin and the backbone as they follow their helical pattern. So at the time these 'functional myotome series' contract simultaneously, they are at different phases of the retrograde body wave; if they were not at different phases they could not shorten by a uniform per cent.

RECALL

Locomotion in fluids involves hydrofoils and

aerofoils

Blair Wainman

redtailedhawk

creolewrasse

heterocercal shape to shark tail fin

The paper lifts because of Bernoulli

Hydrofoils and aerofoils: fluid that flows faster has lower pressure; fluid flows faster on the upper surface of an aerofoil or hydrofoil

explaining its relation to principle of

• Bernoulli's principle: within an airflow of constant energy, when the air flows through a region of lower pressure it speeds up {an area of higher pressure it slows down}. There is a direct mathematical relationship between pressure and speed.

• For any appendage generating lift, there must be a pressure imbalance: lower average pressure above than below.

• Bernoulli's principle states that this pressure difference must be accompanied by a speed difference.

Aerofoil/hydrofoil

• One large difference in the context of an aerofoil and a hydrofoil is the density of the medium in which its used.

• Hydrofoils will be heavier and stiffer than aerofoils: heaviness enabled by water buoyancy, stiffness needed to deal with greater magnitude of forces in water.

The aerofoils of birds -- the wing is an aerofoil by its transverse section shape --flat below, arched above, thick in front then tapering rearward.

It generates lift on both power and recovery stroke: improved efficiency.

Conservation of mass

• The picture shows that the upper stream tubes constrict as they flow up and around the airfoil. Conservation of mass says that the flow speed must increase as the stream tube area decreases.[12] Similarly, the lower stream tubes expand and the flow slows down.

Structures generating lift, thrust (and drag): hydrofoils aerofoils

• fish fins• bird and bat wings• flippers & flukes

Levator of the bird wing lies under its antagonist

Why is it the muscles that power flight are located below the wing? Flight muscles are 1/5 of the body mass: what effect would placing

them high have on stability ?

Costal suction pumpIntercostal muscles run between

ribs and contract to moveribs forward and down during inspiration: sternum moves

forward and down.Forward and down the volume

of thoracic cavity greatly increased with accompanying

reduced internal pressurecausing air inrush.

Sternum moved down (and up) by supracoracoideus and pectoralis major operatingduring flight: flight directly linked to ventilation

The flight of birds is made possible by close integration of the muscle system with theirrespiratory system: the two systems are closely coordinated. Flight and ventilation are linked

Bird lung below with air sacs shown to the right

Tiny air capillaries within the lung properare site of gas exchange.

There are 9 air sacs: an anterior group: interclavicular (1), cervical (2), anterior thoracic (2); posterior group: abdominal (2), posterior thoracic (2). Unpaired interclavicular air sac in anterior midline sends diverticulae into some of larger bones (sternum, pectoral girdle): called pneumatic bones: this serves to lighten the bird for flight.

Syrinx located at junction of trachea and bronchi is an organ for sound generation

Diagram to right is simplified bird lung, ‘it ‘groups’ anterior and posterior air sacs in order to more easily visualize the air circulation. The lungs cannot change their volume, but the air-sacs do. Two cycles of inspiration and expiration (powered by the muscles of flight , including the intercostal muscles between the ribs of the thorax) are required for one breath to make its way through the system, in and out again; it is a true circulation and not a tidal system such as in mammals. Follow one ‘breath’ through this system: