ממן 12 אנגלית למתקדמים ב למדעים קורס שמספרו 31001
Which Came First, The Feather Or The Bird?
Questions Pre-Reading – Based on the first two pages.
1.
Read the title, the sentence under the title, the caption of the picture on the first page and the box at the top of the second page.
1 a.
In your own words, what specific question is the article hoping to answer? איך ולמה הנוצות של הציפורים התפתחו Whether feathers first evolved with birds or with dinosaurs that preceded the …..
Evo-Devo Comes to the Feather 5.
Fill in the chart based on paragraphs 10 – 13 and the graphic on the sixth page of the article titled “EVO-DEVO AND THE FEATHER” Stage How we see the feather
1 (the tubular elongation of the placode from a feather germ and follicle. This yielded the first feather—)an unbranched, hollow cylinder.

2 the inner layer became the longitudinal barb ridges, and the outer layer became a protective sheath a tuft of barbs fused to the hollow cylinder
3 a + b -The first double-branched feathers, exhibiting a rachis, barbs and barbules.
4
the capacity to grow differentiated barbules evolved.
hooklets at the ends of barbules that are attached to the grooved barbules of the adjacent barbs creating a pennaceous feather with a closed vane 5
the asymmetrical vane of a flight feather.
(15
points) 9
The Supporting Cast
6 . The authors give two reasons to believe that their theory is correct. What are those two reasons?
1. The diversity of feathers among modern birds, which sport feathers representing every stage of the model
2 . Exciting molecular findings that have confirmed the first three stages of the evo-devo model (9 points) 9
The Stars of the Drama 7. How do the dinosaur fossils prove the developmental theory of feather evolution?
Give 3 specific examples.
1. A chicken-size coelurosaur (Sinosauropteryx), that was found in 1997, had small tubular and perhaps branched structures emerging from its skin ____ The most primitive feathers known—those of Sinosauropteryx—are the simplest tubular structures and are remarkably like the predicted stage 1 of the developmental model._
2 . A turkey-size oviraptoran dinosaur (Caudipteryx) that had beautifully preserved, modern-looking pennaceous feathers on the tip of its tail and forelimbs. These feathers obviously had differentiated barbules and coherent planar vanes, as in stage 4
of the model._ (Some skeptics have claimed that Caudipteryx was merely an early flightless bird, but many phylogenetic analyses place it among the oviraptoran theropod dinosaurs
3 . Subsequent discoveries at Liaoning have revealed pennaceous feathers on specimens of dromaeosaurs, the theropods that are hypothesized to be most closely related to birds but that clearly are not birds Sinosauropteryx, Sinornithosaurus and some other nonavian theropod specimens show open tufted structures that lack a rachis and are strikingly congruent with stage 2 of the model.                                                                                                                     (9
points)
3
8 .
Paragraph 23 states that what it means to be a bird had been redefined. How has “bird” been redefined? birds are a group of the feathered theropod dinosaurs that evolved the capacity of powered flight                                                                                                                                           (6
points)
6 Dinosaur or Bird? The Gap Narrows 9. How was Microraptor different from modern birds?
Modern birds hava two winged, and Microreptor has four wings                                                                                                                                           (5
points) 5
1 0a.
What are the two competing hypotheses on how flight evolved?
1 .  flight evolved from the trees through a gliding stage
2 . flight evolved from the ground through a powered running stage
1 0b.
Which hypothesis is stronger?
The trees-down theory, because it gets some additional new support with the discovery of a functional glider in the theropod dinosaurs most closely related to birds.                                                (6+4     10 points) 10 A Fresh Look
1 1.
How do feathers grow differently than scales?
Feathers are tubes; the two planar sides of the vane—the front and the back—are created by the inside and outside of the tube only after the feather unfolds from its cylindrical sheath. In contrast, the two planar sides of a scale develop from the top and bottom of the initial epidermal outgrowth that forms the scale.
(6
points)
6
1 2.
What has been the change in the theory of why feathers evolved?
בעבר חשבו שנוצות התפתחו כדי לשרת את הצורך בתעופה, דבר שהתברר כלא נכון Now we believe they evolved for some other purpose that provided some kind of survival advantage                                                                                                                      (6
points)
3
1 3.
What is the authors’ point in the last paragraph?
a. New theories of feather evolution help to prove that evolution skeptics are correct.
b. New theories of how scales evolved into feathers show the beauty of evolution.
c. New theories of feather evolution help to prove that evolution skeptics are wrong.
d. New theories of feather evolution show the insufficiency of evolutionary theory.
(6
points)
6