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Origin of Feathers: Their Initial Purpose

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.

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Origin of Feathers: Their Initial Purpose

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  1. Origin of Feathers:Their Initial Purpose Ethan Weitz Matt Kennedy Jennifer Greenwood

  2. 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.

  3. 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

  4. For what purpose did feathers evolve first?

  5. 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

  6. 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.

  7. 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.

  8. Hypothesis 4: Communication and Crypsis • Sexual selection through plumage displays • Sexual dimorphism • Camouflage

  9. Hypothesis 5: Defense • Modern feathers-not so much. • Early in feather development the pointed, keratinous structures were similar to the modern porcupine.

  10. Which hypothesis do you support? • Flight • Thermoregulation and heat shielding • Water repellency • Communication and Crypsis • Defense

  11. Works Cited • Aparicio, J. M., Bonal, R., & Cordero, P. J. (2003). Evolution of the Structure of Tail Feathers: 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 Zoology, 285(4), 291-306. • Prum, R. O., & Brush, A. H. (2002). The Evolutionary Origin and Diversification of Feathers. The Quarterly Review of Biology, 77(3), 261-295. • Regal, P. J. (1975). The Evolutionary Origin of Feathers. The Quarterly Review of Biology, 50(1), 35-66. • 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.

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