flight Flashcards

1
Q

hypotheses for why flight evloved?

A
• Textbook lists several hypotheses: 
		○ Escape from terrestrial predator 
		○ A leaping insectivore 
		○ A pouncing proavis 
		○ A balancing raptor 
	• More traditional hypotheses: 
		○ Arboreal ("tree down")
		○ Cursorial ("ground up")
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2
Q

describe arboreal theory

A
• Arboreal (tree down) 
	• Flight evolved in an arboreal climber 
	• Evidence from Archaeopteryx 
		○ Upright body posture 
		○ Grasping claws on forewings 
		○ Claw curvature like living climbers/perchers 
		○ Long tail for balance on trees 
	• Critique 
		○ Was it coordinated enough for land?
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3
Q

describe cursoiral theory

A

• Cursorial (ground up)
• Forearms used as planning surfaces
○ Origin of flight in bipedal runners
• Flapping provided propulsion
○ Critique- flapping would reduce traction
• John Ostrum (1986)
○ Proposed running forms used wings to capture prey
• Archeopteryx not well designed for strong flight
○ Heavy skeleton (solid bones)
○ Small sternum lacking keel
○ Unfused carpometacarpus

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4
Q

flight diagram

A
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5
Q

origin of flight late triassic? (proto)

A

• Origin of flight- late triassic birds?
Protoavis- although it
predates Archaeopteryx by 75 million years, it is considerably more advanced than Archaeopteryx…Protoavis is more closely related to
modern birds than is Archaeopteryx.
— Sankar Chatterjee

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6
Q

describe birds. derived from?

A

• “birds are glorified reptiles” - huxley
• Derived from theropod dinosaurs
○ Dromeosaurian theropods

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7
Q

bird synapomorphies with theropods

A

• Synapomorphies: birds and generalized theropods

	1. Hollow, pneumatic bones 
	2. Elongate, mobile S-shaped neck 
	3. Foot with three toes pointed forward and one extending backward 
	4. Digitigrade posture 
	5. Ankle joint forms between tarsal bones, not between tarsals and tibia + fibula 
	6. Feather precursors or true feathers
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8
Q

cladogram for bird origin

A
  • Cladistically, birds are part of coelursaurian monophyletic clade
    • Transition from nonavian dinosaurs to birds happened in a stepwise fashion
    • Hence, transitional forms present mosaic of plesio and apomorphic states
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9
Q

describe Sinosaurpteryx

A

filamentous protofeather in basal theropod

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10
Q

describe Sinornithosaurus. feathers?

A

• Early cretaceous dromosaur
• Liaoning fossil beds, china
• Body covered with a layer of integumentary filaments
○ Hollow; 1-5 cm long
○ Very little resemblance to avian feathers
Probably not for insulation, but for camouflage, display, and species recognition

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11
Q

describe the other two feathered dinos

A
• Protarchaeopteryx & Caudipteryx
	• Late jurassic to early cretaceous 
	• Liaoning, china 
	• Vaned feathers 
		○ Flat surfaces on both sides of a central shaft
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12
Q

feather phylogeny

A
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13
Q

describe feather structure - functions of calamus and rachis? tracts? areas without feathers?

A

• Develop from follicles (pits)
• Form tracts called pterylae
• Body regions without feathers called apteria
• Calamus
○ Base of the feather (“quill”)
○ Hollow to provide blood supply
• Rachis
○ Hollow section - blood vessels and nerves can run through
○ supports the barbs (side branches)
○ Barbs are collectively called vane - more SA, serves as a blanket, windbreaker, display color, etc - resist mechanical pressure by interlocking barbs = serves as a sheath

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14
Q

feather structure: barbules?

A

• Barbules
○ Finer filaments branching perpendicularly from the barbs:
○ Proximal barbules:
§Extend from lower (proximal) surface of barbs
○ Distal barbules:
Extend from upper (distal) surface of the barbs
○ Have hooklets that wrap around proximal barbules of preceding barb = maintains the structure of the vane

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15
Q

pic of feather structure

A
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16
Q

types of feathers?

A
1. Contour 
	• Body feathers 
	• Flight feathers 
	2. Semiplume 
	3. Down 
	• Various types 
	4. Bristles 
	5. Filoplumes
17
Q

selective pressures imposed by flight?

A
  1. Uniform body shape
    • Flight requires aerodynamic shape to reduce resistance (narrow front tip to reduce friction)
    1. Limited body size
      • Power output (two times body mass need 2.25 times the power for take-off)
18
Q

what is power a function of? what is wingloading?

A

• Power is a function of:
○ Muscular force per beat
○ Wingbeat frequency
§ Wingbeat frequency is indirectly related to body size
• Therefore, to fly, larger birds must increase muscle mass as they get larger (must reduce weight elsewhere)
• Wingloading: mass of bird divided by the wing area - indication of the power
• The lighter the wing loading, the less power needed to sustain flight

19
Q

when did feathers appear? why?

A

• Appeared long before true flight
• Perhaps arose multiple times; some not true feathers (protofeathers)
• Thermoregulation?
Possibly used for social display, camouflage, species recognition, covering nests (heat)

20
Q

non avian feathered?

A

microraptor gui - feathers lack barbules

anchiornis huxleyi has feathers that lack barbules and preserve pigments

21
Q

Archaeopteryx reptilian traits

A
  • Thecodont teeth
    • Long bony tail (no pygostyle)
    • Claws on forelimbs
    • Abdominal ribs
    • Sternum poorly developed
    • Bone not hollow - lack pneumatic ducts
    • Amphicoelous vertebrae
    • Small synsacrum
22
Q

Archaeopteryx derived avian traits?

A
• Feathers (??) (contour flight)
	• Furcula (wishbone) (17 on diagram) 
	• Tibiotarsus (3)
		○ Some ankle bones (tarsals) fused to tibia 
	• Tarsometatarus (2)
Other tarsals fuse with the metatarsals
23
Q

Archaeopteryx feathers

A
• Well developed 
	• Asymmetrical vanes 
	• Arrangement of flight feathers 
		○ Like modern birds 
		○ Primaries on phalanges and seconderies on radius/ulna 
	• Arrangement of tail feathers 
		○ Different than modern birds 
	• Body covering of feathers 
		○ Similar to modern birds 
	• Feathers on legs
23
Q

Archaeopteryx feathers

A
• Well developed 
	• Asymmetrical vanes 
	• Arrangement of flight feathers 
		○ Like modern birds 
		○ Primaries on phalanges and seconderies on radius/ulna 
	• Arrangement of tail feathers 
		○ Different than modern birds 
	• Body covering of feathers 
		○ Similar to modern birds 
	• Feathers on legs
24
Q

origin of feathers and initial role?

A

• Ancestrally from epidermal scales
○ Embryonically a mix of dermis and epidermis
○ Like reptile scales also contain beta-keratin
• Ectotermic thermoregulation
○ Initial role of feathers probably in temperature regulation
○ Social?
• Aerodynamic design
○ Well developed in archaepteryx

25
Q

weight reducing adaptations - pneumonic bones? body size?

A
  1. Pneumatic bones
    ○ Spaces with cross struts - strong even though its hollow
    ○ Varies with body size and lifestyle
    • Skeleton vs body mass (how much of the mass the skeleton is):
    • Rat: 5.6% body mass
    • Pigeon: 4.4% body mass
    • Frigate bird: wing span of 2.3 m; skeleton 4 ounces (115 gms), less than its feather weight
26
Q

weight reducing - fusion of skeletal elements !!!!

A

• Synsacrum
○ Fused:
§ Last thoracic; all lumber; 2 sacral; anterior few caudal
§ Also fusion with pelvic girdle to some extent
• Tail
○ Short; approx. 5 caudal vertebrae; forms pygostyle - much more reduced than ancestors who needed more balancing
• Ribs
○ Long, thin, jointed - allow for movement for breathing
§ Uncinate process
• Skull
○ Extensive fusion; teeth lost (use gizzard)

27
Q

weight reducing - strength !!!!

A

• Increased strength and skeletal rigidity
• Synsacrum
○ Broad, flat - support in the pelvic region
• Ribs
○ Thin, flat
○ Uncinate process - gives strength
• Thoracic vertebrate
○ Joined via strong ligaments
• Tail
○ Short; approx. 5 caudal vertebrae; pygostyle
• Strong pectoral girdle
○ Scapula, coracoid, sternum
○ Clavicles fused to form furcula (wishbone) - increased strength

28
Q

which flight muscles are enlarged? ratio?

A
• Large flight muscles 
	• Pectoralis 
		○ Pulls wing downward
		○ Sternum to humerus 
	• Supracoracoideus 
		○ Pulls wings upward 
		○ Sternum to coracoid 
	• Ratio of pectoralis to supracoracoideus 
		○ Smaller species: 20:1 
		○ Larger species: 3:1
29
Q

muscle in species with short and rapid flight?

A

• Species with short, rapid flights (grouse, ptarmigans)
○ Use twitch fibres (anaerobic)
○ Have few mitochondria and little myoglobin (“white meat”)
Fatigue easily - rapid glycogen depletion; rapid lactic acid buildup

30
Q

muscle n species with long sustained flights

A

• Species with long sustained flights (ducks, songbirds)
○ Lots of oxidative fibres (aerobic)
○ Abundant mitochondria and myoglobin (“red meat”)
○ Very resistant to fatigue

31
Q

describe blood flow and respiration for flight. go back and look at diagram !!!

A

• Circulation and gas exchange
• Large heat; high blood flow - 4 chambers (2 for inspiration 2 for expiration)
• Respiration unique with air sacs and 2 cycle air flow (2 inspirations and 2 expirations that does away with residual air)
• Parabronchial lung (modified faveolar lung)
• 9-12 air sacs depending on species
○ Air in parabronchi and blood capillaries flow at right angles to each other
○ More efficient than concurrent flow
Oxygen and glycogen = fuel , oxygen combusts it
use The secondary bronchi and parabronchi
most

32
Q

aves taxonomy

A
33
Q

describe palaeognathe aves - dont fly

A

• Ratites - flightless
○ Rheas, ostriches, Emus, Kiwis (4 orders)
• Share a palaeognathus palate
○ Long prevomers - extended to articulate with palatines ans pterygoids
○ Large basipterygoid process

34
Q

palaeognthae phylogeny controversy

A

• Controversy on phylogeny
○ Evolved from a single ancestor
§ Southern hemisphere distribution resulted from breakdown of Gondwanaland
§ DNA analysis supported this view
○ Evolved convergently from a number of different groups
§ Similar selective pressure from a common life-style (all 4 orders have a strong tie to the ancestor)
§ Palate - primitive - not indicate relationship: might also be via neoteny from neognathus form

35
Q

bird synapomorphies with coelursaurs

A

Additional synapomorphies with coelurosaurs (a more derived theropod)
7. Furcula (wishbone) by fusion of clavicles
8. Fused bony sternum
9. Birdlike sleeping posture with head tucked under forearm (wing)
• Recent studies: collagen from a 68 my old T.rex similar to peptides from a bird
• Dromeosaurs and bird like features
○ Flexing of wrists sideways
○ Shoulder joint allowing more range of movement of arms