Pterosaurs were an ancient group of winged reptiles that lived alongside the dinosaurs. Many pterosaurs were very large, some as large as a giraffe and with a wingspan of over 12 meters. Paleontologists have long wondered whether large pterosaurs were capable of powered flight (flying by flapping their wings) or whether they were able only to glide. Several arguments have been made against powered flight.
Doubters point out that since modern reptiles are cold-blooded, ancient reptiles such as pterosaurs were probably cold-blooded as well. Cold-blooded animals typically have a slow metabolism and are unable to produce a lot of energy. Powered flight is an activity requiring a lot of energy, which is why all modern vertebrates that fly are warm-blooded, not cold-blooded. It seemed unlikely that pterosaurs would have been able to generate the energy needed to fly.
Second, there is a limit to the weight of animals that can be kept airborne by powered flight. Pterosaurs that were as large as a giraffe were probably so heavy that they would not have been able to flap their wings fast enough to stay aloft for any length of time.
Third, all animals with powered flight are able to take off from the ground. For example, birds take off by jumping from their legs or running to gain speed and then jumping. But these methods would not have worked for large pterosaurs. Large pterosaurs would have needed big, powerful muscles in their back legs to launch themselves into the air, and we know from fossilized bones that their back leg muscles were too small and weak to allow the pterosaurs to run fast enough or jump high enough to launch themselves into the air.
Now listen to part of a lecture on the topic you just read about.
Recent research has revealed that pterosaurs may, in fact, have been capable of powered flight.
First, the issue of pterosaur metabolism. Some recently discovered pterosaur fossils indicate that pterosaurs had a dense, hairlike covering, somewhat similar to fur. Hair or fur covering is typical of warm-blooded animals because those animals need to maintain a high body temperature when external conditions are cold. So, if the metabolism of pterosaurs was more like that of warm-blooded animals, and so faster than the reading suggests, then it would have supplied them with the energy needed for powered flight.
Second, the idea that large pterosaurs couldn’t use powered flight because they were too heavy. We now know that pterosaurs had anatomical features that made them unusually light for their size. For example, the bones of pterosaurs were hollow instead of solid. Hollow, lightweight bones would have kept the pterosaurs’ weight low despite their large body frames. The pterosaurs’ weight was probably low enough to allow them to keep themselves airborne by flapping their wings. Third, takeoff would indeed be a problem for pterosaurs—if they took off the way birds do. But there are important differences between birds and pterosaurs. Birds only use their hind limbs—their legs—for walking on the ground, so they only have two limbs to push off from when they launch. But pterosaurs walked on all four limbs while on the ground.
There are modern flying animals that walk on all four limbs—bats, for example—and they use all four limbs to push off the ground, not just the back ones. Studies indicate that even the largest pterosaurs would’ve had no trouble using all four limbs to run fast enough or jump high enough to launch themselves into the air.
The article mentioned three reasons to support the argument that the Pterosaurs were not capable of powered flight. The professor countered three reasons given in the articles and argued that the Pterosaurs were probably capable of powered flight.
The first reason against the ability to powered flight, given by the doubter, was that Pterosaurs were cold-blooded, similar to reptiles now, and therefore could not generate enough energy needed to fly. The professor objected to the doubter's idea by citing that there were new evidence demonstrating that Pterosaurs may have hair-like covering, such as furs. Given that hair-like covering were a feature solely for warm-blooded animals, this evidence suggested that the Pterosaurs were warm-blooded.
Then, the doubter argued that the animals capable of powered flight were usually light so that they could keep themselves airborne by powered flight. The professor challenged this idea by claiming that Pterosaurs were not as heavy as expected. She pointed out that there were some features of Pterosaurs' bodies, such as hallow bones, making them actually lighter than the sizes of their body frames suggested. Hence, Pterosuars might be light enough for powered flight.
Finally, the doubter claimed that the Pterosuars were too large and too heavy to jump and take off only by their legs. The professor disagreed with this judgment. She first mentioned that the birds only use their two hind limbs, i.e., legs, to run and jump in order to take off. In contrast, she then pointed out, the Pterosuars had all four limbs on the ground, and therefore could use four limbs to run fast enough and jump high enough to take off from the ground.
By countering all three reasons given by the doubter, the professor disagreed with the idea of the doubter, and maintained that Pterosuars were actually capable of powered flight.
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Comments
Essay evaluations by e-grader
Grammar and spelling errors:
Line 2, column 1, Rule ID: ENGLISH_WORD_REPEAT_BEGINNING_RULE
Message: Three successive sentences begin with the same word. Reword the sentence or use a thesaurus to find a synonym.
...re probably capable of powered flight. The first reason against the ability to pow...
^^^
Line 2, column 204, Rule ID: ENGLISH_WORD_REPEAT_BEGINNING_RULE
Message: Three successive sentences begin with the same word. Reword the sentence or use a thesaurus to find a synonym.
...t generate enough energy needed to fly. The professor objected to the doubters idea...
^^^
Line 2, column 234, Rule ID: POSSESIVE_APOSTROPHE[1]
Message: Possible typo: apostrophe is missing. Did you mean 'doubters'' or 'doubter's'?
Suggestion: doubters'; doubter's
...d to fly. The professor objected to the doubters idea by citing that there were new evid...
^^^^^^^^
Transition Words or Phrases used:
actually, finally, first, hence, may, so, then, therefore, in contrast, such as
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 13.0 10.4613686534 124% => OK
Auxiliary verbs: 5.0 5.04856512141 99% => OK
Conjunction : 8.0 7.30242825607 110% => OK
Relative clauses : 14.0 12.0772626932 116% => OK
Pronoun: 26.0 22.412803532 116% => OK
Preposition: 39.0 30.3222958057 129% => OK
Nominalization: 4.0 5.01324503311 80% => OK
Performance on vocabulary words:
No of characters: 1572.0 1373.03311258 114% => OK
No of words: 302.0 270.72406181 112% => OK
Chars per words: 5.20529801325 5.08290768461 102% => OK
Fourth root words length: 4.1687104957 4.04702891845 103% => OK
Word Length SD: 2.50849178379 2.5805825403 97% => OK
Unique words: 142.0 145.348785872 98% => OK
Unique words percentage: 0.470198675497 0.540411800872 87% => More unique words wanted or less content wanted.
syllable_count: 467.1 419.366225166 111% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Article: 10.0 8.23620309051 121% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 3.0 1.51434878587 198% => OK
Preposition: 3.0 2.5761589404 116% => OK
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 21.0 21.2450331126 99% => OK
Sentence length SD: 44.5540259066 49.2860985944 90% => OK
Chars per sentence: 112.285714286 110.228320801 102% => OK
Words per sentence: 21.5714285714 21.698381199 99% => OK
Discourse Markers: 5.64285714286 7.06452816374 80% => OK
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 1.0 4.33554083885 23% => More positive sentences wanted.
Sentences with negative sentiment : 8.0 4.45695364238 179% => OK
Sentences with neutral sentiment: 5.0 4.27373068433 117% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.235773373574 0.272083759551 87% => OK
Sentence topic coherence: 0.0975178810701 0.0996497079465 98% => OK
Sentence topic coherence SD: 0.0640479095601 0.0662205650399 97% => OK
Paragraph topic coherence: 0.140805328723 0.162205337803 87% => OK
Paragraph topic coherence SD: 0.0596540872497 0.0443174109184 135% => OK
Essay readability:
automated_readability_index: 13.9 13.3589403974 104% => OK
flesch_reading_ease: 58.62 53.8541721854 109% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 10.3 11.0289183223 93% => OK
coleman_liau_index: 12.94 12.2367328918 106% => OK
dale_chall_readability_score: 7.97 8.42419426049 95% => OK
difficult_words: 63.0 63.6247240618 99% => OK
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 10.4 10.498013245 99% => OK
text_standard: 11.0 11.2008830022 98% => OK
What are above readability scores?
---------------------
Rates: 73.3333333333 out of 100
Scores by essay e-grader: 22.0 Out of 30
---------------------
Note: the e-grader does NOT examine the meaning of words and ideas. VIP users will receive further evaluations by advanced module of e-grader and human graders.
Grammar and spelling errors:
Line 2, column 1, Rule ID: ENGLISH_WORD_REPEAT_BEGINNING_RULE
Message: Three successive sentences begin with the same word. Reword the sentence or use a thesaurus to find a synonym.
...re probably capable of powered flight. The first reason against the ability to pow...
^^^
Line 2, column 204, Rule ID: ENGLISH_WORD_REPEAT_BEGINNING_RULE
Message: Three successive sentences begin with the same word. Reword the sentence or use a thesaurus to find a synonym.
...t generate enough energy needed to fly. The professor objected to the doubters idea...
^^^
Line 2, column 234, Rule ID: POSSESIVE_APOSTROPHE[1]
Message: Possible typo: apostrophe is missing. Did you mean 'doubters'' or 'doubter's'?
Suggestion: doubters'; doubter's
...d to fly. The professor objected to the doubters idea by citing that there were new evid...
^^^^^^^^
Transition Words or Phrases used:
actually, finally, first, hence, may, so, then, therefore, in contrast, such as
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 13.0 10.4613686534 124% => OK
Auxiliary verbs: 5.0 5.04856512141 99% => OK
Conjunction : 8.0 7.30242825607 110% => OK
Relative clauses : 14.0 12.0772626932 116% => OK
Pronoun: 26.0 22.412803532 116% => OK
Preposition: 39.0 30.3222958057 129% => OK
Nominalization: 4.0 5.01324503311 80% => OK
Performance on vocabulary words:
No of characters: 1572.0 1373.03311258 114% => OK
No of words: 302.0 270.72406181 112% => OK
Chars per words: 5.20529801325 5.08290768461 102% => OK
Fourth root words length: 4.1687104957 4.04702891845 103% => OK
Word Length SD: 2.50849178379 2.5805825403 97% => OK
Unique words: 142.0 145.348785872 98% => OK
Unique words percentage: 0.470198675497 0.540411800872 87% => More unique words wanted or less content wanted.
syllable_count: 467.1 419.366225166 111% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Article: 10.0 8.23620309051 121% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 3.0 1.51434878587 198% => OK
Preposition: 3.0 2.5761589404 116% => OK
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 21.0 21.2450331126 99% => OK
Sentence length SD: 44.5540259066 49.2860985944 90% => OK
Chars per sentence: 112.285714286 110.228320801 102% => OK
Words per sentence: 21.5714285714 21.698381199 99% => OK
Discourse Markers: 5.64285714286 7.06452816374 80% => OK
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 1.0 4.33554083885 23% => More positive sentences wanted.
Sentences with negative sentiment : 8.0 4.45695364238 179% => OK
Sentences with neutral sentiment: 5.0 4.27373068433 117% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.235773373574 0.272083759551 87% => OK
Sentence topic coherence: 0.0975178810701 0.0996497079465 98% => OK
Sentence topic coherence SD: 0.0640479095601 0.0662205650399 97% => OK
Paragraph topic coherence: 0.140805328723 0.162205337803 87% => OK
Paragraph topic coherence SD: 0.0596540872497 0.0443174109184 135% => OK
Essay readability:
automated_readability_index: 13.9 13.3589403974 104% => OK
flesch_reading_ease: 58.62 53.8541721854 109% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 10.3 11.0289183223 93% => OK
coleman_liau_index: 12.94 12.2367328918 106% => OK
dale_chall_readability_score: 7.97 8.42419426049 95% => OK
difficult_words: 63.0 63.6247240618 99% => OK
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 10.4 10.498013245 99% => OK
text_standard: 11.0 11.2008830022 98% => OK
What are above readability scores?
---------------------
Rates: 73.3333333333 out of 100
Scores by essay e-grader: 22.0 Out of 30
---------------------
Note: the e-grader does NOT examine the meaning of words and ideas. VIP users will receive further evaluations by advanced module of e-grader and human graders.