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
TOEFL iBT Writing Work Sample/p. 4
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.
The lecture aims to discredit the postulation that dinosaurs are endotherms. The examples of presence of dinosaur fossils in the polar region, the presence of Haversian canals in their fossils and the width of their legs have been reasoned to give more emphasis to the fact that they are only reptiles and not capable of regulating their own body temperature.
Taking the case of polar dinosaurs. Many scientists believe that the presence of dinosaur fossils in the polar region does not indicate that they were able to regulate their temperature in that region. During the time the dinosaurs lived, they argue that the polar temperature was warm enough for animals to live without the need to regulate their body temperature. Even when it was cold enough to press for the need to regulate the body temperature, the dinosaurs could simply have migrated to warmer climates or even hibernated which is what most modern reptiles do. This provides an alternative explanation to the presence of dinosaur fossils in the polar region, also being more plausible given its relevance with modern day reptiles.
The next evidence the passage gives is the position of the dinosaur’s legs and its movement. The passage reasons that, the legs are positioned to facilitate fast movement like running which is a physiology of endothermy. The passage also mentions that the reptiles which do not have endothermy have their legs either side of their body. But the scientists also challenge this theory. They, believe that the presence of the dinosaur’s legs under their body had a different purpose – To support their weight. This positioning of the legs enabled them to grow bigger which had other benefits for the dinosaurs other than just running, which then again discredits the theory that the running movement facilitated by legs present underneath is proof enough to ascertain them as “Endothermic”.
Finally, to utterly discredit the theory, the scientists also mention that the presence of growth rings in the bones of the dinosaur. Growth rings are thickening of the bone which indicates a period of slow growth in a dinosaur’s life. The rings appear in animals who have had a period of rapid growth, then slowed growth or no growth followed by a period of rapid growth and the cycle continues. Each period with slow/ no growth would develop growth rings in the bones of the animal. The presence of the Haversian canals in the fossils of the dinosaur can be attributed to the period of rapid growth. So, even though the animal houses Haversian canals in its bone structure, it does not necessitate that the dinosaur was an endotherm.
To sum up, while the passage offers certain reasons to postulate that dinosaurs could have been endotherms and different from the modern-day reptiles, the scientists in the lecture have provided alternate theories for all the reasons which in fact seem more plausible. Hence, based on the current context we cannot ascertain that dinosaurs were endotherms, on the contrary we are leaning towards them not being endotherms.
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| 2019-10-30 | rohanrajeev07 | 73 | view |
| 2019-04-25 | Dharapatel23 | 70 | view |
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Grammar and spelling errors:
Line 7, column 227, 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.
...ng which is a physiology of endothermy. The passage also mentions that the reptiles...
^^^
Transition Words or Phrases used:
also, but, finally, hence, if, so, then, while, in fact, on the contrary, to sum up
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 19.0 10.4613686534 182% => OK
Auxiliary verbs: 7.0 5.04856512141 139% => OK
Conjunction : 8.0 7.30242825607 110% => OK
Relative clauses : 23.0 12.0772626932 190% => OK
Pronoun: 39.0 22.412803532 174% => Less pronouns wanted
Preposition: 67.0 30.3222958057 221% => Less preposition wanted.
Nominalization: 16.0 5.01324503311 319% => Less nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 2596.0 1373.03311258 189% => OK
No of words: 504.0 270.72406181 186% => Less content wanted.
Chars per words: 5.15079365079 5.08290768461 101% => OK
Fourth root words length: 4.73813722054 4.04702891845 117% => OK
Word Length SD: 2.80031039631 2.5805825403 109% => OK
Unique words: 222.0 145.348785872 153% => OK
Unique words percentage: 0.440476190476 0.540411800872 82% => More unique words wanted or less content wanted.
syllable_count: 805.5 419.366225166 192% => OK
avg_syllables_per_word: 1.6 1.55342163355 103% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Article: 12.0 8.23620309051 146% => OK
Subordination: 2.0 1.25165562914 160% => OK
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 4.0 2.5761589404 155% => OK
Performance on sentences:
How many sentences: 21.0 13.0662251656 161% => OK
Sentence length: 24.0 21.2450331126 113% => OK
Sentence length SD: 67.6892995225 49.2860985944 137% => OK
Chars per sentence: 123.619047619 110.228320801 112% => OK
Words per sentence: 24.0 21.698381199 111% => OK
Discourse Markers: 3.95238095238 7.06452816374 56% => More transition words/phrases wanted.
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 11.0 4.33554083885 254% => Less positive sentences wanted.
Sentences with negative sentiment : 2.0 4.45695364238 45% => More negative sentences wanted.
Sentences with neutral sentiment: 8.0 4.27373068433 187% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.170352588812 0.272083759551 63% => OK
Sentence topic coherence: 0.0549153494707 0.0996497079465 55% => OK
Sentence topic coherence SD: 0.0459569010997 0.0662205650399 69% => OK
Paragraph topic coherence: 0.0999261420555 0.162205337803 62% => OK
Paragraph topic coherence SD: 0.0391469315797 0.0443174109184 88% => OK
Essay readability:
automated_readability_index: 14.8 13.3589403974 111% => OK
flesch_reading_ease: 47.12 53.8541721854 87% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 12.7 11.0289183223 115% => OK
coleman_liau_index: 12.89 12.2367328918 105% => OK
dale_chall_readability_score: 8.27 8.42419426049 98% => OK
difficult_words: 110.0 63.6247240618 173% => OK
linsear_write_formula: 11.0 10.7273730684 103% => OK
gunning_fog: 11.6 10.498013245 110% => OK
text_standard: 13.0 11.2008830022 116% => OK
What are above readability scores?
---------------------
Write the essay in 20 minutes.
Rates: 73.3333333333 out of 100
Scores by essay e-grader: 22.0 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.