A huge marine mammal known as Steller's sea cow once lived in the waters around Bering Island off the coast of Siberia. It was described in 1741 by Georg W. Steller, a naturalist who was among the first Europeans to see one. In 1768 the animal became extinct. The reasons for the extinction are not clear. Here are three theories about the main cause of the extinction.
First, the sea cows may have been overhunted by groups of native Siberian people. If this theory is correct, then the sea cow population would have originally been quite large, but hundreds of years off too much hunting by the native people diminished the number of sea cows. Sea cows were a good source of food in a harsh environment, so overhunting by native people could have been the main cause of extinction.
Second, the sea cow population may have become extinct because of ecosystems disturbances that caused a decline in their main source of food, kelp (a type of sea plant). Kelp populations respond negatively to a number of ecological changes. It is possible that ecological changes near Bering Island some time before 1768 caused a decrease of the kelp that the sea cows depend on.
Third, the main cause of extinction of the sea cows could have been European fur traders who came to the island after 1741. It is recorded that the fur traders caught the last sea cow in 1768. It thus seems reasonable to believe that hunting by European fur traders, who possessed weapons that allowed them to quickly kill a large number of the animals, was the main cause of the sea cow's extinction.
Recently, there has been a ton of debates about the real causes of the steller's sea extinction on the coast of Siberia. More specifically, regarding the passage, the writer puts forth the idea that there are three ideas about the main causes of extinction. In the listening passage, the lecturer is quick to point out there are some serious flaws in the writer's claims. The professor believes that there are problems with the theories in the passage, and addresses in detail the trouble with each point made in the reading text.
First and foremost, the author of the reading states that the native Siberian people have hunted all Steller's sea cows. Some professionals in the same field, however, stand infirm opposition to this claim. In the listening, such as the professor states that Steller's sea cow was a massive creäture and a little number of them are enough to feed the native people. He goes on to say that native Siberian people do not need to hunt many of sea cows.
One group of scholars, represented by the writer, think that the decrease of food source in the ecosystem is the second possible reason for the extinction. Of course, though, not all experts in this field believe this is correct. Again, the speaker specifically addresses this point when he states that is the ecosystem had witnessed disturbances, it would affect other parts of the ecosystem like whales. On the contrary, some ships do not detect any decline in the number of whales on the coast of Siberia.
Finally, the author wraps his argument by positing that a European fur trader who killed many of Steller's sea cows is the third possible reason for the extinction of this creäture. Not surprisingly, the lecturer takes this issue with his claim by contending that there is evidence shows that Steller's sea cow started to decline hundred of years before European traders arrived on the coast.
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Grammar and spelling errors:
Line 13, column 329, Rule ID: NODT_DOZEN[1]
Message: Use simply: 'a hundred'.
Suggestion: a hundred
...hat Stellers sea cow started to decline hundred of years before European traders arriv...
^^^^^^^
Line 13, column 352, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...arted to decline hundred of years before European traders arrived on the coast. ...
^^
Line 13, column 393, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
... European traders arrived on the coast.
^^
Transition Words or Phrases used:
finally, first, however, if, regarding, second, so, third, of course, such as, on the contrary
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 12.0 10.4613686534 115% => OK
Auxiliary verbs: 2.0 5.04856512141 40% => OK
Conjunction : 3.0 7.30242825607 41% => More conjunction wanted.
Relative clauses : 12.0 12.0772626932 99% => OK
Pronoun: 22.0 22.412803532 98% => OK
Preposition: 49.0 30.3222958057 162% => OK
Nominalization: 7.0 5.01324503311 140% => OK
Performance on vocabulary words:
No of characters: 1575.0 1373.03311258 115% => OK
No of words: 322.0 270.72406181 119% => OK
Chars per words: 4.89130434783 5.08290768461 96% => OK
Fourth root words length: 4.23607819155 4.04702891845 105% => OK
Word Length SD: 2.51472458608 2.5805825403 97% => OK
Unique words: 167.0 145.348785872 115% => OK
Unique words percentage: 0.518633540373 0.540411800872 96% => OK
syllable_count: 476.1 419.366225166 114% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 2.0 3.25607064018 61% => OK
Article: 7.0 8.23620309051 85% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 5.0 2.5761589404 194% => OK
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 23.0 21.2450331126 108% => OK
Sentence length SD: 39.5843197156 49.2860985944 80% => OK
Chars per sentence: 112.5 110.228320801 102% => OK
Words per sentence: 23.0 21.698381199 106% => OK
Discourse Markers: 6.71428571429 7.06452816374 95% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 4.0 4.33554083885 92% => OK
Sentences with negative sentiment : 3.0 4.45695364238 67% => OK
Sentences with neutral sentiment: 7.0 4.27373068433 164% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.152052925348 0.272083759551 56% => OK
Sentence topic coherence: 0.0502403139462 0.0996497079465 50% => OK
Sentence topic coherence SD: 0.0550497100799 0.0662205650399 83% => OK
Paragraph topic coherence: 0.0879428489607 0.162205337803 54% => OK
Paragraph topic coherence SD: 0.0475769488228 0.0443174109184 107% => OK
Essay readability:
automated_readability_index: 13.1 13.3589403974 98% => OK
flesch_reading_ease: 56.59 53.8541721854 105% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 11.1 11.0289183223 101% => OK
coleman_liau_index: 11.38 12.2367328918 93% => OK
dale_chall_readability_score: 7.96 8.42419426049 94% => OK
difficult_words: 65.0 63.6247240618 102% => OK
linsear_write_formula: 9.0 10.7273730684 84% => OK
gunning_fog: 11.2 10.498013245 107% => OK
text_standard: 12.0 11.2008830022 107% => OK
What are above readability scores?
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Write the essay in 20 minutes.
Rates: 80.0 out of 100
Scores by essay e-grader: 24.0 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.