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.
The article state that the steller's sea cow became extinct and provides three theories to explain the cause of the extinction. However, the professor holds this idea that the main cause of this extinction is still unknown and there are problems associated with the theories discussed in the article.
First, the article establishes that, the sea cow may have been hunted by native Siberian people. However, the professor believes that these creatures were incredibly large and massive. Each of them was about nine meters long and its weight was more than 10 tons. Consequently, a few number of them could feed those tribes for monthes. Considering the fact that the population of those people wasn't that much large, they could not have been able to hunt lots of those creatures.
Second, the article claims that, the shortage of food resources like the decline in klept was the cause of the extinction. The lecturer thinks this claim is problematic. The professor mentions that if a severe ecosystem disterbance was happened, it would have been affected not only klep but also other mairne species like whales. The population of whales should have been decreased as a result of these diterbances as well. Since the population of whales has not been decrease, it's unlikely that the sea cow became extinct because of food shortage.
Finally, the author points out that, the cause of extinction of the sea cows could have been the European fur traders. However, the professor explains that the sea cows became extinct soon after the Europeans arrived to the area. In fact, when the Europeans reached the region, the number of remaining sea cows was ralatively small. The population of the sea cows was at it's peak, hundereds of years before Europeans reach the Island. As a result, something else was the cause of the extinction, not Europeans that arrived last.
Grammar and spelling errors:
Line 2, column 1, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
The article state that the stellers sea ...
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Line 4, column 1, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...e theories discussed in the article. First, the article establishes that, the...
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Line 4, column 285, Rule ID: MANY_NN[1]
Message: Possible agreement error. The noun number seems to be countable; consider using: 'few numbers'.
Suggestion: few numbers
... was more than 10 tons. Consequently, a few number of them could feed those tribes for mon...
^^^^^^^^^^
Line 4, column 398, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: wasn't
...act that the population of those people wasnt that much large, they could not have be...
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Line 6, column 1, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...ble to hunt lots of those creatures. Second, the article claims that, the sho...
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Line 6, column 337, 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.
... also other mairne species like whales. The population of whales should have been d...
^^^
Line 8, column 1, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...me extinct because of food shortage. Finally, the author points out that, the...
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Transition Words or Phrases used:
also, but, consequently, finally, first, however, if, may, second, so, still, well, in fact, as a result
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 : 5.0 7.30242825607 68% => OK
Relative clauses : 13.0 12.0772626932 108% => OK
Pronoun: 27.0 22.412803532 120% => Less pronouns wanted
Preposition: 35.0 30.3222958057 115% => OK
Nominalization: 10.0 5.01324503311 199% => OK
Performance on vocabulary words:
No of characters: 1562.0 1373.03311258 114% => OK
No of words: 311.0 270.72406181 115% => OK
Chars per words: 5.02250803859 5.08290768461 99% => OK
Fourth root words length: 4.19942759058 4.04702891845 104% => OK
Word Length SD: 2.50192180143 2.5805825403 97% => OK
Unique words: 165.0 145.348785872 114% => OK
Unique words percentage: 0.530546623794 0.540411800872 98% => OK
syllable_count: 470.7 419.366225166 112% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 3.0 3.25607064018 92% => OK
Article: 16.0 8.23620309051 194% => OK
Subordination: 3.0 1.25165562914 240% => Less adverbial clause wanted.
Conjunction: 0.0 1.51434878587 0% => OK
Preposition: 3.0 2.5761589404 116% => OK
Performance on sentences:
How many sentences: 17.0 13.0662251656 130% => OK
Sentence length: 18.0 21.2450331126 85% => The Avg. Sentence Length is relatively short.
Sentence length SD: 30.8020805481 49.2860985944 62% => OK
Chars per sentence: 91.8823529412 110.228320801 83% => OK
Words per sentence: 18.2941176471 21.698381199 84% => OK
Discourse Markers: 6.11764705882 7.06452816374 87% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 7.0 4.19205298013 167% => OK
Sentences with positive sentiment : 6.0 4.33554083885 138% => OK
Sentences with negative sentiment : 3.0 4.45695364238 67% => OK
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: 0.168215192822 0.272083759551 62% => OK
Sentence topic coherence: 0.05959578245 0.0996497079465 60% => OK
Sentence topic coherence SD: 0.0527265159824 0.0662205650399 80% => OK
Paragraph topic coherence: 0.101814474723 0.162205337803 63% => OK
Paragraph topic coherence SD: 0.0558746676916 0.0443174109184 126% => OK
Essay readability:
automated_readability_index: 11.4 13.3589403974 85% => Automated_readability_index is low.
flesch_reading_ease: 61.67 53.8541721854 115% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 9.1 11.0289183223 83% => OK
coleman_liau_index: 11.84 12.2367328918 97% => OK
dale_chall_readability_score: 7.78 8.42419426049 92% => OK
difficult_words: 64.0 63.6247240618 101% => OK
linsear_write_formula: 8.0 10.7273730684 75% => OK
gunning_fog: 9.2 10.498013245 88% => OK
text_standard: 8.0 11.2008830022 71% => OK
What are above readability scores?
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Rates: 85.0 out of 100
Scores by essay e-grader: 25.5 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.