Transcript Origin of Feathers: Flight or Thermoregulation?

Origin of Feathers:
Their Initial Purpose
Ethan Weitz
Matt Kennedy
Jennifer Greenwood
Development of Feathers
 Stage 1: The follicle originated with a
cylindrical epidermal invagination around
the base of the feather papilla.
 Stage 2: The inner layer of the collar
differentiated into horizontal barbs which
grew unbranching keratin filaments.
 Stage 3: The rachis is formed by the fusion
of barb ridges on the midline of the follicle.
 Stage 4: Proximal and distal barbules
created the first closed, pennaceous vane.
 Stage 5: Additional structural diversity
allowed for asymmetrical flight feathers with
vanes of different widths.
Hypotheses of Feather Evolution
 Flight
 After stage I, feathers become flat allowing for
flight
 Interlocking barbules
 Stages II & IV
 Thermoregulation
 Stage I feathers are thin, numerous, and
pliable
 Stage II feathers are heavier and filamentous
 Heat Shielding
 Protection from solar radiation
 Water Repellency
 Possible by Stage II
 Communication and Crypsis
 Sexual selection
 Camouflage
 Defense
 Pointed keratinaceous structures
 Stage I
For what purpose did
feathers evolve first?
Hypothesis 1: Flight
 Escape predators
 Migration
 Leaping, jumping and other
fighting behaviors
associated with sexual
selection could have been
pre-adaptive to flight.
 Jumping to avoid predation
may have lead to leaping
between trees, then
parachuting, gliding, and
eventually active flight.
 Video
Hypothesis 2: Thermoregulation & Heat Shielding
 Using reptiles as a
conceptual model it is
suggested feathers
arose as adaptations to
intense solar radiation.
 Lizards in hot climates
have elongated scales.
 Having broad, insulating
structures allowed the
animal to control the gain
and loss of heat.
Hypothesis 3: Water Repellency
 Pennaceous structure
and the keratinous
material of feathers
allows water to roll off the
surface.
 Some birds posses an oil
producing gland which
they spread over their
feathers to increase
water repellency.
Hypothesis 4: Communication and Crypsis
 Sexual selection through
plumage displays
 Sexual dimorphism
 Camouflage
Hypothesis 5: Defense
 Modern feathers-not so
much.
 Early in feather
development the pointed,
keratinous structures
were similar to the
modern porcupine.
Which hypothesis do you support?
Flight
Thermoregulation and heat shielding
Water repellency
Communication and Crypsis
Defense
Works Cited
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Implications for the Theory of Sexual Selection. Evolution, 57(2), 397-405.
 Badyaev, A. V., & Landeen, E. A. (2007). Developmental Evolution of Sexual Ornamentation: Model
and a Test. Integrative and Comparative Biology, 47(2), 221-233.
 Bennett, P. M., & Owens, I. P. (2001). Evolutionary Ecology of Birds. New York: Oxford University
Press.
 Cowen, R., & Lipps, J. H. (1982). An Adaptive Scenario for the Origin of Birds and Flight in Birds.
Proceedings of the Third North American Paleontological Convention, 1, 109-112.
 Gill, F. B. (2007). Ornithology. New York: W. H. Freeman and Company.
 http://65.111.167.185/S/e/x/Sexual_dimorphism.png
 http://farm5.static.flickr.com/4039/4682629858_b4ded90106.jpg
 http://wiseacre-gardens.com/wildlife/porcupine-dead.jpg
 Perrins, C. (2009). The Princeton Encyclopedia of Birds. Princeton: Princeton University Press.
 Podulka, S., Rohrbaugh Jr., R. W., & Bonney, R. (2004). Handbook of Bird Biology. Princeton: Cornell
Lab of Ornithology in association with Princeton University Press.
 Prum, R. O. (1999). Development and Evolutionary Origin of Feathers. Journal of Experimental
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Quarterly Review of Biology, 77(3), 261-295.
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 Ruben, J. A., & Jones, T. D. (2000). Selective Factors Associated with the Origin of Fur and Feathers.
American Zoologist, 40(4), 585-596.
 Tarsitano, S. F., Russell, A. P., Horne, F., Plummer, C., & Millerchip, K. (2000). On the Evolution of
Feathers from an Aerodynamic and Constructional View Point. American Zoologist, 40(4), 676-686.