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The fossil remains of the first flying vertebrates, the [#permalink]
01 Feb 2006, 05:19
The fossil remains of the first flying vertebrates, the pterosaurs, have intrigued paleontologists for more than two centuries. How such large creatures, which weighed in some cases as much as a piloted hang-glider and had wingspans from 8 to 12 meters, solved the problems of powered flight, and exactly what these creatures wereâ€”reptiles or birdsâ€”are among the questions scientists have puzzled over.
Perhaps the least controversial assertion about the pterosaurs is that they were reptiles. Their skulls, pelvises, and hind feet are reptilian. The anatomy of their wings suggests that they did not evolve into the class of birds. In pterosaurs a greatly elongated fourth finger of each forelimb supported a wing-like membrane. The other fingers were short and reptilian, with sharp claws. In birds the second finger is the principal strut of the wing, which consists primarily of feathers. If the pterosaurs walked on all fours, the three short fingers may have been employed for grasping. When a pterosaur walked or remained stationary, the fourth finger, and with it the wing, could only turn upward in an extended inverted V-shape along each side of the animalâ€™s body.
The pterosaurs resembled both birds and bats in their overall structure and proportions. This is not surprising because the design of any flying vertebrate is subject to aerodynamic constraints. Both the pterosaurs and the birds have hollow bones, a feature that represents a savings in weight. In the birds, however, these bones are reinforced more massively by internal struts.
Although scales typically cover reptiles, the pterosaurs probably had hairy coats. T. H. Huxley reasoned that flying vertebrates must have been warm-blooded because flying implies a high rate of metabolism, which in turn implies a high internal temperature. Huxley speculated that a coat of hair would insulate against loss of body heat and might streamline the body to reduce drag in flight. The recent discovery of a pterosaur specimen covered in long, dense, and relatively thick hairlike fossil material was the first clear evidence that his reasoning was correct.
Efforts to explain how the pterosaurs became airborne have led to suggestions that they launched themselves by jumping from cliffs, by dropping from trees, or even by rising into light winds from the crests of waves. Each hypothesis has its difficulties. The first wrongly assumes that the pterosaursâ€™ hind feet resembled a batâ€™s and could serve as hooks by which the animal could hang in preparation for flight. The second hypothesis seems unlikely because large pterosaurs could not have landed in trees without damaging their wings. The third calls for high waves to channel updrafts. The wind that made such waves however, might have been too strong for the pterosaurs to control their flight once airborne.
7. It can be inferred from the passage that some scientists believe that pterosaurs (A) lived near large bodies of water (B) had sharp teeth for tearing food (C) were attacked and eaten by larger reptiles (D) had longer tails than many birds (E) consumed twice their weight daily to maintain their body temperature _________________
It can be inferred from the passage that some scientists believe that pterosaurs (A) lived near large bodies of water (B) had sharp teeth for tearing food (C) were attacked and eaten by larger reptiles (D) had longer tails than many birds (E) consumed twice their weight daily to maintain their body temperature
my pick is D on this one..went by a process of elimination
1. is not mentioned anywhere in the passage
2. nothing related to teeth
3. we dont know if they were being preyed upon
4. YES (assumed ths right because others are wrong)
5. no support for this in the passage
Heh, I just did this one a couple days back and answered this question wrong also. I wont give away the answer but I am interested to know what other people are picking as the answer. _________________
"To hell with circumstances; I create opportunities." - Bruce Lee
My take is on A..
D is not mentioned..It just says that they had big wings, but nowhere it mentions that its wings were bigger than most birds...
A is mentioned in the passage in section where in the author is talking about how they learnt to fly..by riding on waves
I went through this passage a few weeks back. The Answer I came up was A.
"The third calls for high waves to channel updrafts. The wind that made such waves however, might have been too strong for the pterosaurs to control their flight once airborne"...
High waves can only happen in large bodies of water. _________________
reloading NEURON JELLY to reach another galaxy.