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 the lecture are both about the main cause of the extinction of the sea cows. While the passage declares three possible reasons for this extinction, the lecture contradicts these claims and provide evidence to the contrary.
To begin with, the author argues that the sea cows may have been overhunted by natives. Conversely, the lecturer brings up the idea that sea cows were enormous creatures which were up to 9 meters long and 10 tons. He mentions that the Siberian Native population was small and a couple of these massive sea cows were enough for a month.
Secondly, the reading passage states that a possible reason for sea cows extinction is ecosystems disturbances which declined their main food, Kelp. The lecture counters that argument by asserting that if a severe happening occurred, it should cause other marines like the Whales. And no report from fishing ships indicate a problem. Thus a food shortage couldn't be the main cause of sea cows extinction.
Finally, the reading asserts that European fur traders could have been the main cause of extinction. In contrast, the speaker believes that when traders arrived there, the population of sea cows was quite small and the main cause started at least hundreds of years before their arrival. He notes that whatever the main reason would be, the European Traders wouldn't be the reason.
Grammar and spelling errors:
Line 5, column 335, Rule ID: SENT_START_CONJUNCTIVE_LINKING_ADVERB_COMMA[1]
Message: Did you forget a comma after a conjunctive/linking adverb?
Suggestion: Thus,
... from fishing ships indicate a problem. Thus a food shortage couldnt be the main cau...
^^^^
Line 5, column 356, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: couldn't
...ndicate a problem. Thus a food shortage couldnt be the main cause of sea cows extinctio...
^^^^^^^
Line 7, column 358, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: wouldn't
...n reason would be, the European Traders wouldnt be the reason.
^^^^^^^
Transition Words or Phrases used:
conversely, finally, if, may, second, secondly, so, thus, while, at least, in contrast, 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: 4.0 5.04856512141 79% => OK
Conjunction : 6.0 7.30242825607 82% => OK
Relative clauses : 12.0 12.0772626932 99% => OK
Pronoun: 17.0 22.412803532 76% => OK
Preposition: 21.0 30.3222958057 69% => OK
Nominalization: 9.0 5.01324503311 180% => OK
Performance on vocabulary words:
No of characters: 1146.0 1373.03311258 83% => OK
No of words: 228.0 270.72406181 84% => More content wanted.
Chars per words: 5.02631578947 5.08290768461 99% => OK
Fourth root words length: 3.88582923847 4.04702891845 96% => OK
Word Length SD: 2.4456543076 2.5805825403 95% => OK
Unique words: 130.0 145.348785872 89% => More unique words wanted.
Unique words percentage: 0.570175438596 0.540411800872 106% => OK
syllable_count: 341.1 419.366225166 81% => 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: 10.0 8.23620309051 121% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 2.0 2.5761589404 78% => OK
Performance on sentences:
How many sentences: 12.0 13.0662251656 92% => OK
Sentence length: 19.0 21.2450331126 89% => OK
Sentence length SD: 35.6565406186 49.2860985944 72% => OK
Chars per sentence: 95.5 110.228320801 87% => OK
Words per sentence: 19.0 21.698381199 88% => OK
Discourse Markers: 8.41666666667 7.06452816374 119% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 0.0 4.33554083885 0% => More positive sentences wanted.
Sentences with negative sentiment : 6.0 4.45695364238 135% => OK
Sentences with neutral sentiment: 6.0 4.27373068433 140% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.0967176509609 0.272083759551 36% => The similarity between the topic and the content is low.
Sentence topic coherence: 0.0377045015851 0.0996497079465 38% => Sentence topic similarity is low.
Sentence topic coherence SD: 0.0264310684705 0.0662205650399 40% => Sentences are similar to each other.
Paragraph topic coherence: 0.0585077019591 0.162205337803 36% => Maybe some paragraphs are off the topic.
Paragraph topic coherence SD: 0.0278011764277 0.0443174109184 63% => OK
Essay readability:
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: 11.89 12.2367328918 97% => OK
dale_chall_readability_score: 8.46 8.42419426049 100% => OK
difficult_words: 56.0 63.6247240618 88% => OK
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 9.6 10.498013245 91% => OK
text_standard: 12.0 11.2008830022 107% => OK
What are above readability scores?
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It is not exactly right on the topic in the view of e-grader. Maybe there is a wrong essay topic.
Rates: 3.33333333333 out of 100
Scores by essay e-grader: 1.0 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.