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.
Recent research has revealed the 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, hair-like 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, light-weight 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 have had no trouble using all four limbs to run fast enough or jump high enough to launch themselves into the air.
In the reading passage, three reasons are mentioned to prove pterosaurs were not able to fly. However, the lecturer objects them.
The first point is about energy. Powerful flights require much energy. But it is impossible for cold-blooded animals to produce so much energy due to their slow metabolism. And scientists believed the pterosaurs were cold-blooded just as many other ancient reptiles. But from the fossils researchers found hair-like layers, like furs on bird to keep body's temperature, which indicates the pterosaurs were probably warm-blooded animals with high enough metabolism.
Secondly, the pterosaurs should not be so heavy or they can not flap theirs wings so fast to stay aloft in the air. However, the pterosaurs could have ways to reduce their weight. Their bones were probably hallow, which could lower their weight sharply.
The third concern is about the way of taking off from the ground. If the pterosaurs took off just like the modern birds, the muscles on their back legs should be big and powerful enough. But the fact is the muscles were too small and weak to support their jumping and running to launch themselves. However, the pterosaurs could have another way to take off. They used all their four legs to push them off the ground. This way has been proved available to launch the pterosaurs.
| Post date | Users | Rates | Link to Content |
|---|---|---|---|
| 2019-12-06 | marii.r67 | 80 | view |
| 2019-11-13 | shirley5001 | 80 | view |
| 2019-11-13 | shirley5001 | 80 | view |
| 2019-11-03 | Seema Modak | 78 | view |
| 2019-11-03 | Seema Modak | 78 | view |
Grammar and spelling errors:
Line 5, column 207, Rule ID: BEEN_PART_AGREEMENT[2]
Message: Consider using a past participle here: 'hallowed'.
Suggestion: hallowed
...their weight. Their bones were probably hallow, which could lower their weight sharply...
^^^^^^
Transition Words or Phrases used:
but, first, however, if, second, secondly, so, third
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 13.0 10.4613686534 124% => OK
Auxiliary verbs: 6.0 5.04856512141 119% => OK
Conjunction : 8.0 7.30242825607 110% => OK
Relative clauses : 2.0 12.0772626932 17% => More relative clauses wanted.
Pronoun: 15.0 22.412803532 67% => OK
Preposition: 29.0 30.3222958057 96% => OK
Nominalization: 0.0 5.01324503311 0% => More nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1117.0 1373.03311258 81% => OK
No of words: 221.0 270.72406181 82% => More content wanted.
Chars per words: 5.05429864253 5.08290768461 99% => OK
Fourth root words length: 3.85565412703 4.04702891845 95% => OK
Word Length SD: 2.51691112854 2.5805825403 98% => OK
Unique words: 133.0 145.348785872 92% => More unique words wanted.
Unique words percentage: 0.601809954751 0.540411800872 111% => OK
syllable_count: 318.6 419.366225166 76% => OK
avg_syllables_per_word: 1.4 1.55342163355 90% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 3.0 3.25607064018 92% => OK
Article: 7.0 8.23620309051 85% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 4.0 1.51434878587 264% => Less conjunction wanted as sentence beginning.
Preposition: 2.0 2.5761589404 78% => OK
Performance on sentences:
How many sentences: 16.0 13.0662251656 122% => OK
Sentence length: 13.0 21.2450331126 61% => The Avg. Sentence Length is relatively short.
Sentence length SD: 40.2878315996 49.2860985944 82% => OK
Chars per sentence: 69.8125 110.228320801 63% => OK
Words per sentence: 13.8125 21.698381199 64% => OK
Discourse Markers: 3.25 7.06452816374 46% => More transition words/phrases wanted.
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 5.0 4.33554083885 115% => OK
Sentences with negative sentiment : 2.0 4.45695364238 45% => More negative sentences wanted.
Sentences with neutral sentiment: 9.0 4.27373068433 211% => Less facts, knowledge or examples wanted.
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.193781658546 0.272083759551 71% => OK
Sentence topic coherence: 0.0635931251951 0.0996497079465 64% => OK
Sentence topic coherence SD: 0.0679239702487 0.0662205650399 103% => OK
Paragraph topic coherence: 0.125214930417 0.162205337803 77% => OK
Paragraph topic coherence SD: 0.0233942465868 0.0443174109184 53% => OK
Essay readability:
automated_readability_index: 9.3 13.3589403974 70% => Automated_readability_index is low.
flesch_reading_ease: 75.2 53.8541721854 140% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 6.0 11.0289183223 54% => Flesch kincaid grade is low.
coleman_liau_index: 11.42 12.2367328918 93% => OK
dale_chall_readability_score: 7.43 8.42419426049 88% => OK
difficult_words: 44.0 63.6247240618 69% => More difficult words wanted.
linsear_write_formula: 6.0 10.7273730684 56% => Linsear_write_formula is low.
gunning_fog: 7.2 10.498013245 69% => OK
text_standard: 6.0 11.2008830022 54% => The average readability is low. Need to imporve the language.
What are above readability scores?
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Rates: 71.6666666667 out of 100
Scores by essay e-grader: 21.5 Out of 30
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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.