Moving through fluids: water and air
Term Test some feedback
Lift and drag: hydrofoils and aerofoils
Flight muscles of birds
Air sac functions
‘effectiveness of a force’ where
forces tend to make things rotate
effectiveness depends on the
distance between its line of action
and the axis of rotation
Moment: product of magnitude of
force and perpendicular distance to
axis
Some questions that were on the term test
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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
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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?
RECALL
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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.
redtailed
hawk
Locomotion in fluids
involves hydrofoils and
aerofoils
creole
wrasse
heterocercal shape to shark tail fin
Blair Wainman
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
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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.
• 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.
Conservation of mass
Structures generating lift, thrust (and drag): hydrofoils aerofoils
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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 ?
The flight of birds is made possible by close integration of the muscle system with their
respiratory system: the two systems are closely coordinated. Flight and ventilation are linked
Costal suction pump
Intercostal muscles run between
ribs and contract to move
ribs forward and down during
inspiration: sternum moves
forward and down.
Forward and down the volume
of thoracic cavity greatly
increased with accompanying
reduced internal pressure
causing air inrush.
Sternum moved down (and up) by supracoracoideus and pectoralis major operating
during flight: flight directly linked to ventilation
Bird lung below with air sacs
shown to the right
Syrinx located at junction
of trachea and bronchi is
an organ for sound
generation
Tiny air capillaries within the lung proper
are 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.
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 airsacs 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: