Endotherms are animals such as modern birds and mammals that keep their body temperatures constant. For instance, humans are endotherms and maintain an internal temperature of 37°C, no matter whether the environment is warm or cold. Because dinosaurs were reptiles, and modern reptiles are not endotherms, it was long assumed that dinosaurs were not endotherms. However, dinosaurs differ in many ways from modern reptiles, and there is now considerable evidence that dinosaurs were, in fact, endotherms.
Polar dinosaurs One reason for believing that dinosaurs were endotherms is that dinosaur fossils have been discovered in polar regions. Only animals that can maintain a temperature well above that of the surrounding environment could be active in such cold climates.
Leg position and movement There is a connection between endothermy and the position and movement of the legs. The physiology of endothermy allows sustained physical activity, such as running. But running is efficient only if an animal’s legs are positioned underneath its body, not at the body’s side, as they are for crocodiles and many lizards. The legs of all modern endotherms are underneath the body, and so were the legs of dinosaurs. This strongly suggests that dinosaurs were endotherms.
Haversian canals There is also a connection between endothermy and bone structure. The bones of endotherms usually include structures called Haversian canals. These canals house nerves and blood vessels that allow the living animal to grow quickly, and rapid body growth is in fact a characteristic of endothermy. The presence of Haversian canals in bone is a strong indicator that the animal is an endotherm, and fossilized bones of dinosaurs are usually dense with Haversian canals.
Many scientists have problems with the arguments you read in the passage. They don’t think those arguments prove that dinosaurs were endotherms
Take the polar dinosaur argument. When dinosaurs lived, even the polar regions where dinosaur fossils have been found were much warmer than today—warm enough during part of the year for animals that were not endotherms to live. And during the months when the polar regions were cold, the so-called polar dinosaurs could have migrated to warmer areas or hibernated like many modern reptiles do. So the presence of dinosaur fossils in polar regions doesn’t prove the dinosaurs were endotherms.
Well, what about the fact that dinosaurs had their legs placed under their bodies, not out to the side, like a crocodile’s? That doesn’t necessarily mean dinosaurs were highenergy endotherms built for running. There’s another explanation for having legs under the body: this body structure supports more weight. So with the legs under their bodies, dinosaurs could grow to a very large size. Being large had advantages for dinosaurs, so we don’t need the idea of endothermy and running to explain why dinosaurs evolved to have their legs under their bodies.
OK, so how about bone structure? Many dinosaur bones do have Haversian canals, that’s true, but dinosaur bones also have growth rings. Growth rings are a thickening of the bone that indicates periods of time when the dinosaurs weren’t rapidly growing. These growth rings are evidence that dinosaurs stopped growing or grew more slowly during cooler periods. This pattern of periodic growth—ya know, rapid growth followed by no growth or slow growth and then rapid growth again—is characteristic of animals that are not endotherms. Animals that maintain a constant body temperature year round, as true endotherms do, grow rapidly even when the environment becomes cool.
In lecture teacher beleives that argument in the reading passage are not strong enough to conclude that dinosaurs were endotherms.
First, polar regions in past were much warmer than polar region today. There is climate cylcle in polar region, warm season and cold season. Polar dinosaurs might have lived in polar regions in hot season and migrated to different place in coldern season. Or polar dinosaurs might have hibrenated during colder season as most of modern reptiles do. So, there might be no need to maintain body temperature.
Furtherore, positioning of legs under body is not an indication of that dinosaurs were endotherms. It does not dinosaurs were high energy endotherms. Legs might be underneath body to support more weight that dinosaurs possess. More weight and large size have many other advantages and benefits.
Moreover, while dinosaurs possess haversian canals like endotherms they also possess growth rings. Growth rings are thickening of bones when muscles are not growing rapidly. This is indication that dinosaurs muscles might not have grown rapidly in colder season which is not a charecteristic of endotherms. Endotherms maintain a constant body temperature even in colder season and their muscles grow rapidly despite of seasons. Growth rings are not found on the body of endotherms.
So, it is diffucult to reach a conclusion from these argument more information is needed to qualify that dinosaurs were endotherms.
| Post date | Users | Rates | Link to Content |
|---|---|---|---|
| 2020-01-21 | liboooyang | 81 | view |
| 2020-01-04 | Tharwat | 83 | view |
| 2019-12-19 | savikx | 66 | view |
| 2019-12-18 | TEJAS PATIL | 80 | view |
| 2019-12-14 | fafar | 80 | view |
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Grammar and spelling errors:
Line 9, column 48, Rule ID: THIS_NNS[2]
Message: Did you mean 'this argument' or 'these arguments'?
Suggestion: this argument; these arguments
...is diffucult to reach a conclusion from these argument more information is needed to qualify t...
^^^^^^^^^^^^^^
Transition Words or Phrases used:
also, first, if, moreover, so, while
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 17.0 10.4613686534 163% => OK
Auxiliary verbs: 6.0 5.04856512141 119% => OK
Conjunction : 6.0 7.30242825607 82% => OK
Relative clauses : 8.0 12.0772626932 66% => More relative clauses wanted.
Pronoun: 12.0 22.412803532 54% => OK
Preposition: 30.0 30.3222958057 99% => OK
Nominalization: 5.0 5.01324503311 100% => OK
Performance on vocabulary words:
No of characters: 1229.0 1373.03311258 90% => OK
No of words: 229.0 270.72406181 85% => More content wanted.
Chars per words: 5.36681222707 5.08290768461 106% => OK
Fourth root words length: 3.89008302616 4.04702891845 96% => OK
Word Length SD: 2.68536584434 2.5805825403 104% => OK
Unique words: 124.0 145.348785872 85% => More unique words wanted.
Unique words percentage: 0.541484716157 0.540411800872 100% => OK
syllable_count: 378.9 419.366225166 90% => OK
avg_syllables_per_word: 1.7 1.55342163355 109% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 3.0 3.25607064018 92% => OK
Article: 0.0 8.23620309051 0% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 1.0 2.5761589404 39% => More preposition wanted as sentence beginning.
Performance on sentences:
How many sentences: 16.0 13.0662251656 122% => OK
Sentence length: 14.0 21.2450331126 66% => The Avg. Sentence Length is relatively short.
Sentence length SD: 28.0554696093 49.2860985944 57% => The essay contains lots of sentences with the similar length. More sentence varieties wanted.
Chars per sentence: 76.8125 110.228320801 70% => OK
Words per sentence: 14.3125 21.698381199 66% => OK
Discourse Markers: 2.25 7.06452816374 32% => More transition words/phrases wanted.
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 8.0 4.33554083885 185% => OK
Sentences with negative sentiment : 3.0 4.45695364238 67% => 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: 0.14610134293 0.272083759551 54% => OK
Sentence topic coherence: 0.0534886915833 0.0996497079465 54% => OK
Sentence topic coherence SD: 0.0558250462939 0.0662205650399 84% => OK
Paragraph topic coherence: 0.0686816975555 0.162205337803 42% => OK
Paragraph topic coherence SD: 0.0442547955643 0.0443174109184 100% => OK
Essay readability:
automated_readability_index: 11.0 13.3589403974 82% => Automated_readability_index is low.
flesch_reading_ease: 48.81 53.8541721854 91% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 9.9 11.0289183223 90% => OK
coleman_liau_index: 13.27 12.2367328918 108% => OK
dale_chall_readability_score: 8.19 8.42419426049 97% => OK
difficult_words: 56.0 63.6247240618 88% => OK
linsear_write_formula: 6.5 10.7273730684 61% => OK
gunning_fog: 7.6 10.498013245 72% => OK
text_standard: 11.0 11.2008830022 98% => OK
What are above readability scores?
---------------------
Rates: 83.3333333333 out of 100
Scores by essay e-grader: 25.0 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.