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 of 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 ecosystem 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 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.
The reading passage and the lecture both mainly discuss the reasons for the extinction of a huge marine mammal under the name, Steller's sea cow, which had been living around Bering Island of Siberia. While the writer provides three different reasons explaining the main causes of extinction, the lecturer disputes these explanations, he adds that we do not know what happened exactly, and each reason given by reading has a problem.
Firstly, according to the author, sea cows might have been extinct due to the overhunting by native people. However, the lecturer opposes this idea saying that, since sea cows are enormous animals and Siberian people have consisted of small villages, they would not have needed to hunt a lot of them.
Secondly, the reading suggests a possibility that drastic ecological changes near Bering Island could have caused a decrease in the kelp which was their main source of food. On the other hand, the man on the audio argues that, if severe changes affected the ecosystem, it might have affected other marine animals, like whales. In light of the fact that no evidence of a decline in other creatures had been recorded, therefore, sea cows had been growing just fine without feeling any shortage in their food.
Lastly, the author posits that the main cause of the extinction of sea cows could have been European fur traders, who possessed weapons that would enable them to hunt a large number of the animals. In contrast, the lecturer asserts that the extinction of the sea cows just happened right after the arrival of European fur traders, and the population of sea cows had already been declined hundred years before their arrival. Consequently, whatever the cause of their extinction is, it might have occurred long before the European traders which only captured the last sea cow.
Grammar and spelling errors:
Line 7, column 168, Rule ID: LARGE_NUMBER_OF[1]
Message: Specify a number, remove phrase, or simply use 'many' or 'numerous'
Suggestion: many; numerous
... weapons that would enable them to hunt a large number of the animals. In contrast, the lecturer ...
^^^^^^^^^^^^^^^^^
Line 7, column 389, Rule ID: NODT_DOZEN[1]
Message: Use simply: 'a hundred'.
Suggestion: a hundred
...n of sea cows had already been declined hundred years before their arrival. Consequentl...
^^^^^^^
Transition Words or Phrases used:
consequently, first, firstly, however, if, lastly, second, secondly, so, therefore, while, in contrast, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 9.0 10.4613686534 86% => 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: 21.0 22.412803532 94% => OK
Preposition: 37.0 30.3222958057 122% => OK
Nominalization: 7.0 5.01324503311 140% => OK
Performance on vocabulary words:
No of characters: 1530.0 1373.03311258 111% => OK
No of words: 304.0 270.72406181 112% => OK
Chars per words: 5.03289473684 5.08290768461 99% => OK
Fourth root words length: 4.17559525986 4.04702891845 103% => OK
Word Length SD: 2.40598860418 2.5805825403 93% => OK
Unique words: 173.0 145.348785872 119% => OK
Unique words percentage: 0.569078947368 0.540411800872 105% => OK
syllable_count: 464.4 419.366225166 111% => 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: 7.0 8.23620309051 85% => OK
Subordination: 3.0 1.25165562914 240% => Less adverbial clause wanted.
Conjunction: 2.0 1.51434878587 132% => OK
Preposition: 6.0 2.5761589404 233% => Less preposition wanted as sentence beginnings.
Performance on sentences:
How many sentences: 10.0 13.0662251656 77% => Need more sentences. Double check the format of sentences, make sure there is a space between two sentences, or have enough periods. And also check the lengths of sentences, maybe they are too long.
Sentence length: 30.0 21.2450331126 141% => The Avg. Sentence Length is relatively long.
Sentence length SD: 35.4716788438 49.2860985944 72% => OK
Chars per sentence: 153.0 110.228320801 139% => OK
Words per sentence: 30.4 21.698381199 140% => OK
Discourse Markers: 12.1 7.06452816374 171% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 2.0 4.19205298013 48% => OK
Sentences with positive sentiment : 2.0 4.33554083885 46% => More positive sentences wanted.
Sentences with negative sentiment : 3.0 4.45695364238 67% => 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: 0.187339361574 0.272083759551 69% => OK
Sentence topic coherence: 0.0809893753494 0.0996497079465 81% => OK
Sentence topic coherence SD: 0.0727137416363 0.0662205650399 110% => OK
Paragraph topic coherence: 0.109948958462 0.162205337803 68% => OK
Paragraph topic coherence SD: 0.0373554043604 0.0443174109184 84% => OK
Essay readability:
automated_readability_index: 17.5 13.3589403974 131% => OK
flesch_reading_ease: 49.49 53.8541721854 92% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 13.8 11.0289183223 125% => OK
coleman_liau_index: 12.49 12.2367328918 102% => OK
dale_chall_readability_score: 9.33 8.42419426049 111% => OK
difficult_words: 81.0 63.6247240618 127% => OK
linsear_write_formula: 13.0 10.7273730684 121% => OK
gunning_fog: 14.0 10.498013245 133% => OK
text_standard: 14.0 11.2008830022 125% => OK
What are above readability scores?
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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.