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Flashcards in Evolutionary origin of flight Deck (12)
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1
Q

Benefits of flight

A
  • makes less vulnerable to predators
  • efficient foraging
  • cost efficient (j/km) - especially gliders
  • fast locomotion
  • colonise remote habitats and islands
  • migration across world
2
Q

Constraints on birds by flight

A
  • uniform morphology compared to other taxa
  • need to be light
  • need high metabolic rate and body temp
  • bill mush lighter, gizzard for crushing food (not jaws), streamlines, no teeth
  • cannot exceed 12kg for flight
3
Q

Origins of flight hypotheses

A

H1 = cursorial theory - birds started by running on ground, using wings to stabilise then to catch prey
H2 = arboreal theory - climbs trees and other objects, gliding from heights
H3 = WAIR - wing-assisted incline running - can use height to protect selves, to glide and fly actively
H4 = pouncing pro-avis H - use wings for extra acceleration when going after prey

4
Q

Cursorial…

A

•archaeopteryx feathers suggest could fly
-joints not considered sufficiently flexible to support active flight - Archaeopteryx could glide
•spread of feathered forelimbs (wings) originally stabilised for running
-lack of trees where A found

5
Q

Problems with cursorial theory

A

•max running speed 2m/s - estimated min needed 6m/s
-velocity gap
-experiments test it acc could though…
•high energy demands of evolving flight - fighting against gravity
•problems of explaining origin of flight stroke in earthbound organism

6
Q

Support for Arboreal

A

•supported by hoatzin spp - lives in trees, has claws on wings can use for climbing trees
-similar claws to archaeopteryx and showed could be used for this locomotion
•A’s forewing fell among climbers, and hind wings amongst perching - supporting it could climb trees

7
Q

Origins of feathers

A
  • first appeared in theropods
  • homologues with reptilian scales - but different to hair
  • flight not only function - display/colouration, thermoregulation and waterproofing
  • made of B-keratin >90%, 1% lipids, 8% water and pigments
  • barbs have tiny barbules with hooks, interlock between barbs = strong connections
8
Q

Different types of feathers

A
  • remiges-wing feathers
  • rectrices-tail feathers
  • down - trap air
  • contour feathers - typical body feathers
  • bristles - help for sensory, catch prey etc.
9
Q

Physical principles of flight

A

•wings have to be aerofoil - lifting surface and forward motion - propeller
•shape, area and position can be modified
•bottom surface concave and upper is convex
-bottom pushes air forward and down, creating area of high pressure below wing and low pressures above (creates lift)
•retain 1 digit that has an alula, group of feathers to create slot reducing turbulence

10
Q

Flapping flight

A
  • lift and drag together make flight a resultant force
  • primary feathers give thrust
  • secondary feathers closest to body create lift
  • in flight, primaries twist more than secondaries = thrust
11
Q

Ventilation in bris

A
  • unidirectional airflow
  • into air sacs, trachea, sucked into lungs, into different air sac and out
  • very efficient
12
Q

Colouration of feathers

A

•important in sexual selection and crypsis
•combination of pigmentation and structural characteristics - reflection of specific wavelengths depend on pigment particle size
-black = eumelanin
-red/brown = phaeomelanins
-red-yellow = carotenoids (from diet)
-UV sensitive = porphyrins
•layers in feathers and gaps between were precise wave-lengths of light are reflected = iridescence