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.
There is a heated debate on the reasons of Steller's sea cow extinction. The author in the reading passage explores three possibilities, while the professor, in the lecture, contradicts all these assumptions by using three specific points as supports.
First, the author asserts it was the overhunting by native Siberian people that caused the extinction, the professor opposes this view by pointing out that Steller's sea cow is quite massive, with 9 meters long and 10 tons weight. One sea cow is enough for native Siberian people to eat for months, as their population is not very large. Thus, they do not need to hunt the sea cow a lot and such hunt would not cause sea cow extinction.
Second, the reading passage suggests the decline in their main source of food due to ecosystem disturbances would be responsible, the professor stresses that if there is a severe decline in sea cow's food source, it would affect not only just the sea cow itself but also other marine animals, like whales, as well. The fact is that there is no relevant evidence recorded. Thus, the professor concludes that Steller's sea cow has not experienced a food shortage.
Third, despite the claim from the reading part that European fur traders might be the main cause of the extinction, the professor emphasizes that it is true that the sea cow extincted when the European fur trader arrived. However, at that time the number of sea cow has already been quite small. The sea cows have met their peak number hundred of years before. The professor stresses that main reasons should be explored rather than the traders who last arrived.
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Grammar and spelling errors:
Line 13, column 337, Rule ID: NODT_DOZEN[1]
Message: Use simply: 'a hundred'.
Suggestion: a hundred
...The sea cows have met their peak number hundred years before. The professor stresses th...
^^^^^^^
Transition Words or Phrases used:
also, but, first, however, if, second, so, third, thus, well, while, it is true
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 : 3.0 7.30242825607 41% => More conjunction wanted.
Relative clauses : 12.0 12.0772626932 99% => OK
Pronoun: 20.0 22.412803532 89% => OK
Preposition: 22.0 30.3222958057 73% => OK
Nominalization: 6.0 5.01324503311 120% => OK
Performance on vocabulary words:
No of characters: 1333.0 1373.03311258 97% => OK
No of words: 274.0 270.72406181 101% => OK
Chars per words: 4.86496350365 5.08290768461 96% => OK
Fourth root words length: 4.0685311056 4.04702891845 101% => OK
Word Length SD: 2.4937585256 2.5805825403 97% => OK
Unique words: 150.0 145.348785872 103% => OK
Unique words percentage: 0.547445255474 0.540411800872 101% => OK
syllable_count: 393.3 419.366225166 94% => OK
avg_syllables_per_word: 1.4 1.55342163355 90% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 2.0 3.25607064018 61% => OK
Article: 10.0 8.23620309051 121% => OK
Subordination: 3.0 1.25165562914 240% => Less adverbial clause wanted.
Conjunction: 0.0 1.51434878587 0% => OK
Preposition: 5.0 2.5761589404 194% => OK
Performance on sentences:
How many sentences: 12.0 13.0662251656 92% => OK
Sentence length: 22.0 21.2450331126 104% => OK
Sentence length SD: 79.9817253433 49.2860985944 162% => OK
Chars per sentence: 111.083333333 110.228320801 101% => OK
Words per sentence: 22.8333333333 21.698381199 105% => OK
Discourse Markers: 6.58333333333 7.06452816374 93% => OK
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 : 3.0 4.45695364238 67% => OK
Sentences with neutral sentiment: 4.0 4.27373068433 94% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.163543452449 0.272083759551 60% => OK
Sentence topic coherence: 0.0674941564836 0.0996497079465 68% => OK
Sentence topic coherence SD: 0.0456932275731 0.0662205650399 69% => OK
Paragraph topic coherence: 0.0992509522515 0.162205337803 61% => OK
Paragraph topic coherence SD: 0.0274444099005 0.0443174109184 62% => OK
Essay readability:
automated_readability_index: 12.9 13.3589403974 97% => OK
flesch_reading_ease: 66.07 53.8541721854 123% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 9.5 11.0289183223 86% => OK
coleman_liau_index: 11.2 12.2367328918 92% => OK
dale_chall_readability_score: 7.84 8.42419426049 93% => OK
difficult_words: 54.0 63.6247240618 85% => More difficult words wanted.
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 10.8 10.498013245 103% => OK
text_standard: 11.0 11.2008830022 98% => OK
What are above readability scores?
---------------------
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.