help with number 5!!!! ck dv Thl Fig. 1. Leg feathers in the basal avialan Sapeo
ID: 66954 • Letter: H
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help with number 5!!!!
ck dv Thl Fig. 1. Leg feathers in the basal avialan Sapeorvis. Photograph (A) and drawing (B). Abbreviations:cv cervical vertebrae; dv, dorsal vertebrae; If, leg feathers hl, left hindlimb; lil, left ilium; lis, left ischium; rhl, right hindlimb; sk, skllt tail feather Fig. 4. Evolution of leg feathers in cochurosaurian dinosaurs. Four major stages in the evolution of integumentary structures on the hindlimb are represented by the compsognathid Sinocalliopteryx (short filamentous feathers covering legs, including fect); the basal deinonychosaurian Anchiorvis and the basal avialan Sapeornis (large pennaccous feathers on legs, including feet, forming a winglike structure); the enantiornithine Cathayornis (large femoral and crural feathers forming a reduced winglike structure); and ornithuromorphs (small femoral and crural feathers and featherless feet).Explanation / Answer
The arboreal glider hypothesis states that the ancestor of birds started their flight by climbing trees and gliding down by making use of their incipient feathers.Gradually with time they developed larger feathers and the birds evolved as completely air-borne with the evolution of flapping flight.But there are certain doubts.Archaeopteryx and its maniraptoran dinosaur cousins did not showed any adaptions which are arboreal in nature for example feet adaption for perching and also did not have any adaptations like broad membrane connecting forelimbs and hind limbs as seen in gliders.There were lack of evidences and convincing explanations as to how they used to climb trees only with forelimbs.
WAIR hypothesis states that the development of aerodynamic function in wings is actually the outcome of the need to run quickly up very steep slopes for example tree trunks and to escape from predators.This wing assisted inclined running(WAIR) adaptation in birds helps in their locomotion and flight.WAIR have also been found useful in producing a lift in babies which is very useful and is even responsible for accelaration in the body and very much helpful in flight.
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