The Extinction of the Steller’s Sea Cow
A huge marine mammal known as the Steller’s sea cow once lived in the waters around Bering Island off the coast of Siberia. It was described in 1741 by George W. Steller, a naturalist who was among the first Europeans to see one. In 1768, the animal became extinct. Although the reasons for the extinction are not clear, there are three theories about the main cause of their disappearance.
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 of too much hunting by the native people diminished the number of sea cows. In fact, they 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 ecosystem disturbances that caused a decline in their main source of food, kelp (a type of sea plant, like seaweed). Kelp populations respond negatively to a number of ecological changes. It is possible that ecological shifts near Bering island some time before 1768 caused a decrease in the kelp that the sea cows depended 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.
Summarize the points made in the lecture, being sure to explain how they cast doubt on the specific hypotheses proposed in the reading passage.
In the lecture, the professor discusses how the main cause of Steller’s sea cow’s extinction is unclear and how each of the stated theories has limitations. This casts doubt on the reading asserts that one of the three theories are the main cause of sea cow’s disappearance.
To begin with, the professor states that sea cows were massive about nine-meter-long and weigh ten ton; thus, a couple of sea cow would have fed the whole village. Moreover, the population of Siberian were small. Therefore, The Steller sew cow would not have been overhunted by Siberian people. This contradicts the text which claims that overfishing by native people could have been the main cause.
In addition, the lecturer argues that if a sever ecosystem disturbance really occurred then that would have affected the other marine animals such as wheels. In fact, fishing ships didn’t report any decline in wheels number. Furthermore, kelp plants were growing just fine and sea cows didn’t experience food shortage. This opposes the article which asserts that kelp population responded negatively to a number of ecological changes that could have led to the disappearance of sea cows.
Finally, the speaker explains why European fur traders could not have been the main cause. In fact, hundred of years ago the sea cows’ number were already less than it was in the 17th century. Moreover, the European fur traders came to the island after 1741. Hence, there was already ongoing reason that is responsible for sea cow’s extinction. This refutes the text which states that European would have killed sea cows to use their fur.
In conclusion, the speaker disagrees with the reading on all three points, and believes the text lacks credibility.
Grammar and spelling errors:
Line 3, column 401, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
... people could have been the main cause. In addition, the lecturer argues that if...
^^^^^^^
Line 6, column 499, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...e led to the disappearance of sea cows. Finally, the speaker explains why Europe...
^^^^^^^
Line 9, column 101, Rule ID: NODT_DOZEN[1]
Message: Use simply: 'a hundred'.
Suggestion: a hundred
... not have been the main cause. In fact, hundred of years ago the sea cows' number ...
^^^^^^^
Line 11, column 1, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...e killed sea cows to use their fur. In conclusion, the speaker disagrees wit...
^^
Transition Words or Phrases used:
finally, furthermore, hence, if, moreover, really, so, then, therefore, thus, in addition, in conclusion, in fact, such as, to begin with
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 12.0 10.4613686534 115% => OK
Auxiliary verbs: 7.0 5.04856512141 139% => OK
Conjunction : 4.0 7.30242825607 55% => More conjunction wanted.
Relative clauses : 12.0 12.0772626932 99% => OK
Pronoun: 15.0 22.412803532 67% => OK
Preposition: 29.0 30.3222958057 96% => OK
Nominalization: 9.0 5.01324503311 180% => OK
Performance on vocabulary words:
No of characters: 1491.0 1373.03311258 109% => OK
No of words: 284.0 270.72406181 105% => OK
Chars per words: 5.25 5.08290768461 103% => OK
Fourth root words length: 4.10515524023 4.04702891845 101% => OK
Word Length SD: 2.72478567102 2.5805825403 106% => OK
Unique words: 161.0 145.348785872 111% => OK
Unique words percentage: 0.566901408451 0.540411800872 105% => OK
syllable_count: 440.1 419.366225166 105% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Article: 9.0 8.23620309051 109% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 6.0 2.5761589404 233% => Less preposition wanted as sentence beginnings.
Performance on sentences:
How many sentences: 16.0 13.0662251656 122% => OK
Sentence length: 17.0 21.2450331126 80% => The Avg. Sentence Length is relatively short.
Sentence length SD: 36.3747315282 49.2860985944 74% => OK
Chars per sentence: 93.1875 110.228320801 85% => OK
Words per sentence: 17.75 21.698381199 82% => OK
Discourse Markers: 8.5625 7.06452816374 121% => OK
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 4.0 4.19205298013 95% => OK
Sentences with positive sentiment : 5.0 4.33554083885 115% => OK
Sentences with negative sentiment : 6.0 4.45695364238 135% => 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: 0.226731631162 0.272083759551 83% => OK
Sentence topic coherence: 0.0763532308252 0.0996497079465 77% => OK
Sentence topic coherence SD: 0.0677003832338 0.0662205650399 102% => OK
Paragraph topic coherence: 0.11734107367 0.162205337803 72% => OK
Paragraph topic coherence SD: 0.0733648834335 0.0443174109184 166% => OK
Essay readability:
automated_readability_index: 12.2 13.3589403974 91% => Automated_readability_index is low.
flesch_reading_ease: 62.68 53.8541721854 116% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 8.7 11.0289183223 79% => OK
coleman_liau_index: 12.87 12.2367328918 105% => OK
dale_chall_readability_score: 8.15 8.42419426049 97% => OK
difficult_words: 66.0 63.6247240618 104% => OK
linsear_write_formula: 8.5 10.7273730684 79% => OK
gunning_fog: 8.8 10.498013245 84% => OK
text_standard: 9.0 11.2008830022 80% => 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.