A huge marine mammal known as Steller's sea cow once lived in the waters around Bering lsland off the coast of Siberia. lt was described in 1741 by Georg W. Steller, a naturalist who was among the first Europeans to see one. ln 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. lf 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. lt is possible that ecological changes near Beringlsland some time before1768 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. lt is recorded that the fur traders caught the last sea cow in 1768.lt 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.
In the reading passage, the author concentrates on several theories about the main cause of the extinction of sea cows near Bering Island waters. However, the lecturer casts doubt on these theories and respectively points out problems with all the author's assertions.
Firstly, the author argues that native Siberian people might be responsible for the significant decline in the number of sea cows by overhunting them. By contrast, the lecturer challenges this idea and states that sea cows were quite massive creatures, and a couple of them were enough to feed a small village for months. Since there were not many native people there at that time, they don't actually need to hunt a lot of these enormous animals.
Secondly, the author suggests that ecological changes near Bering Island might have negative impacts on the sea cows' main source of food, Kelp, and then sea cows became extinct due to lack of food. Nevertheless, the lecturer brings up the fact that if the severe ecosystem disturbances were the main cause of the extinction, it would have also affected other parts of the ecosystem, and caused the fall in the population of other marine species like whales. However, fishing records don't demonstrate any remarkable change in their population.
Lastly, the author asserts that European fur traders were the main cause of the sea cows' extinction. Conversely, the lecturer refutes this claim too and clarifies that sea cows were starting to become extinct before Europeans arrived in Bering Island, and when they arrived, the number of sea cows was quite small, showing that there should be another thing responsible for their extinction.
Grammar and spelling errors:
Line 2, column 387, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: don't
... native people there at that time, they dont actually need to hunt a lot of these en...
^^^^
Line 3, column 483, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: don't
...s like whales. However, fishing records dont demonstrate any remarkable change in th...
^^^^
Transition Words or Phrases used:
actually, also, conversely, first, firstly, however, if, lastly, nevertheless, second, secondly, so, then, another thing
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 9.0 10.4613686534 86% => OK
Auxiliary verbs: 5.0 5.04856512141 99% => OK
Conjunction : 7.0 7.30242825607 96% => OK
Relative clauses : 9.0 12.0772626932 75% => More relative clauses wanted.
Pronoun: 19.0 22.412803532 85% => OK
Preposition: 36.0 30.3222958057 119% => OK
Nominalization: 6.0 5.01324503311 120% => OK
Performance on vocabulary words:
No of characters: 1388.0 1373.03311258 101% => OK
No of words: 270.0 270.72406181 100% => OK
Chars per words: 5.14074074074 5.08290768461 101% => OK
Fourth root words length: 4.05360046442 4.04702891845 100% => OK
Word Length SD: 2.55941737197 2.5805825403 99% => OK
Unique words: 154.0 145.348785872 106% => OK
Unique words percentage: 0.57037037037 0.540411800872 106% => OK
syllable_count: 423.0 419.366225166 101% => OK
avg_syllables_per_word: 1.6 1.55342163355 103% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 2.0 3.25607064018 61% => OK
Article: 9.0 8.23620309051 109% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 4.0 1.51434878587 264% => Less conjunction wanted as sentence beginning.
Preposition: 3.0 2.5761589404 116% => OK
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: 27.0 21.2450331126 127% => The Avg. Sentence Length is relatively long.
Sentence length SD: 63.6616053835 49.2860985944 129% => OK
Chars per sentence: 138.8 110.228320801 126% => OK
Words per sentence: 27.0 21.698381199 124% => OK
Discourse Markers: 12.0 7.06452816374 170% => 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 : 4.0 4.45695364238 90% => OK
Sentences with neutral sentiment: 3.0 4.27373068433 70% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.123027450324 0.272083759551 45% => OK
Sentence topic coherence: 0.0502186699373 0.0996497079465 50% => OK
Sentence topic coherence SD: 0.0471213559273 0.0662205650399 71% => OK
Paragraph topic coherence: 0.079391120561 0.162205337803 49% => OK
Paragraph topic coherence SD: 0.0380722719362 0.0443174109184 86% => OK
Essay readability:
automated_readability_index: 16.3 13.3589403974 122% => OK
flesch_reading_ease: 44.07 53.8541721854 82% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 13.8 11.0289183223 125% => OK
coleman_liau_index: 12.83 12.2367328918 105% => OK
dale_chall_readability_score: 8.89 8.42419426049 106% => OK
difficult_words: 67.0 63.6247240618 105% => OK
linsear_write_formula: 11.0 10.7273730684 103% => OK
gunning_fog: 12.8 10.498013245 122% => OK
text_standard: 13.0 11.2008830022 116% => 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.