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 reading and listening both dicuss the extinction of Steller's sea cow living in the Bering Isaland. While the reading indicates some of the theories that may cause the disappearance of these species, the lecture casts doubt those ideas by giving the reasonable explanation.
To begin with, the passage mentions that overhunting from native Siberian people is considered one theory since hundred years of hunting led to the decrease in huge population of sea cow. The professor, by contrast, points out that the sea cow size was quite massive which means that they could supply for human nutrition for a month. Therefore, there was no reason for the native Siberian to hunt a large amount of them resulting in the extinction.
Secondly, ecosystems disturbance which was a feature in destroying sea cow's main food source becomes a potential reason for the sea cow deduction in number as the reading points out. The professor is at a loggerhead. If one food source breaks down, the other animal in the whole systems will be highly affected such as whale or marine species. However, no research included this information. As a result, ecosystems disturbance was not a factor.
Finally, the reading signifies that the presence of European fur traders who came to the island for commercial. They caught sea cows to extract their fur by using a tool which killed large figure of animals immediately. Hence, the plunge in population of these species might come from the arrival of the Euroupean. On the other hand, the lecture explains that the little number of sea cows remained when the European set their foot on. Thus, sea cows number decreased by other factors which already occurred for a long period before the fur traders came.
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Grammar and spelling errors:
Line 1, column 132, Rule ID: SOME_OF_THE
Message: Simply use 'some'.
...ng Isaland. While the reading indicates some of the theories that may cause the disappearan...
Line 3, column 113, Rule ID: NODT_DOZEN
Message: Use simply: 'a hundred'.
Suggestion: a hundred
...n people is considered one theory since hundred years of hunting led to the decrease in...
Transition Words or Phrases used:
finally, hence, however, if, may, second, secondly, so, therefore, thus, while, such as, as a result, to begin with, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 7.0 10.4613686534 67% => OK
Auxiliary verbs: 4.0 5.04856512141 79% => OK
Conjunction : 2.0 7.30242825607 27% => More conjunction wanted.
Relative clauses : 12.0 12.0772626932 99% => OK
Pronoun: 15.0 22.412803532 67% => OK
Preposition: 38.0 30.3222958057 125% => OK
Nominalization: 12.0 5.01324503311 239% => Less nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1450.0 1373.03311258 106% => OK
No of words: 290.0 270.72406181 107% => OK
Chars per words: 5.0 5.08290768461 98% => OK
Fourth root words length: 4.12666770723 4.04702891845 102% => OK
Word Length SD: 2.60470625008 2.5805825403 101% => OK
Unique words: 171.0 145.348785872 118% => OK
Unique words percentage: 0.589655172414 0.540411800872 109% => OK
syllable_count: 445.5 419.366225166 106% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 1.0 3.25607064018 31% => OK
Article: 9.0 8.23620309051 109% => 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: 15.0 13.0662251656 115% => OK
Sentence length: 19.0 21.2450331126 89% => OK
Sentence length SD: 44.7410326211 49.2860985944 91% => OK
Chars per sentence: 96.6666666667 110.228320801 88% => OK
Words per sentence: 19.3333333333 21.698381199 89% => OK
Discourse Markers: 8.93333333333 7.06452816374 126% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 2.0 4.19205298013 48% => OK
Sentences with positive sentiment : 3.0 4.33554083885 69% => OK
Sentences with negative sentiment : 7.0 4.45695364238 157% => 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: 0.19344672099 0.272083759551 71% => OK
Sentence topic coherence: 0.0623191460432 0.0996497079465 63% => OK
Sentence topic coherence SD: 0.0541907812308 0.0662205650399 82% => OK
Paragraph topic coherence: 0.11281016544 0.162205337803 70% => OK
Paragraph topic coherence SD: 0.00943408656874 0.0443174109184 21% => Paragraphs are similar to each other. Some content may get duplicated or it is not exactly right on the topic.
automated_readability_index: 11.8 13.3589403974 88% => Automated_readability_index is low.
flesch_reading_ease: 60.65 53.8541721854 113% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 9.5 11.0289183223 86% => OK
coleman_liau_index: 11.72 12.2367328918 96% => OK
dale_chall_readability_score: 8.61 8.42419426049 102% => OK
difficult_words: 74.0 63.6247240618 116% => OK
linsear_write_formula: 14.5 10.7273730684 135% => OK
gunning_fog: 9.6 10.498013245 91% => OK
text_standard: 12.0 11.2008830022 107% => OK
What are above readability scores?
Rates: 75.0 out of 100
Scores by essay e-grader: 22.5 Out of 30
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.