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.
Both the reading passage and the lecture discuss whether Steller's sea cows have been become extinct. The former presents three theories about the causes of extinction, but the latter challenges each of these reasoning.
First of all, the author of the article claims that the sea cows have been extinct because of overhunting by native people, since the sea cows were a good source of food. However, the lecturer contends that there was no need of overhunting as the number of people in those village of Siberia was small. In addition, the sea cows were massive in size (9m) and weight (10 ton). So, a few of them was enough for the entire village to eat several months.
Secondly, the text mentions that the population of kelp declined because of ecosystem disturbance. Hence, the sea cow became extinct as kelp was the main source of food. In contrast, the speaker argues that the ecosystem imbalance didn't take place. If the disturbance had happened, other marine animals such as whales would have also become extinct. But the population of whale never declined. Therefore, the number of kelp was enough to feed the sea cow.
Finally, the last theory in the text suggest that the population of sea cows diminished because of European fur traders who had killed a lot of sea cows. Conversely, the lecture asserts that the number of sea cow declined long before the European fur traders have arrived. The population of sea cow was largest hundreds of years before 1700. But the fur traders arrived after 1700, and hence they were unlikely the reason of extinction of sea cows.
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Comments
Essay evaluations by e-grader
Grammar and spelling errors:
Line 3, column 335, Rule ID: ADJECTIVE_IN_ATTRIBUTE[1]
Message: A more concise phrase may lose no meaning and sound more powerful.
Suggestion: massive
...s small. In addition, the sea cows were massive in size 9m and weight 10 ton. So, a few of them...
^^^^^^^^^^^^^^^
Line 5, column 232, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: didn't
...ker argues that the ecosystem imbalance didnt take place. If the disturbance had happ...
^^^^^
Line 7, column 300, Rule ID: THE_SUPERLATIVE[2]
Message: A determiner is probably missing here: 'was the largest'.
Suggestion: was the largest
...have arrived. The population of sea cow was largest hundreds of years before 1700. But the ...
^^^^^^^^^^^
Transition Words or Phrases used:
also, but, conversely, finally, first, hence, however, if, second, secondly, so, therefore, in addition, in contrast, such as, first of all
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 11.0 10.4613686534 105% => OK
Auxiliary verbs: 2.0 5.04856512141 40% => OK
Conjunction : 6.0 7.30242825607 82% => OK
Relative clauses : 7.0 12.0772626932 58% => More relative clauses wanted.
Pronoun: 10.0 22.412803532 45% => OK
Preposition: 36.0 30.3222958057 119% => OK
Nominalization: 10.0 5.01324503311 199% => OK
Performance on vocabulary words:
No of characters: 1312.0 1373.03311258 96% => OK
No of words: 271.0 270.72406181 100% => OK
Chars per words: 4.84132841328 5.08290768461 95% => OK
Fourth root words length: 4.05734859645 4.04702891845 100% => OK
Word Length SD: 2.40987944943 2.5805825403 93% => OK
Unique words: 144.0 145.348785872 99% => OK
Unique words percentage: 0.531365313653 0.540411800872 98% => OK
syllable_count: 404.1 419.366225166 96% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 0.0 3.25607064018 0% => OK
Article: 12.0 8.23620309051 146% => OK
Subordination: 2.0 1.25165562914 160% => 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: 16.0 13.0662251656 122% => OK
Sentence length: 16.0 21.2450331126 75% => The Avg. Sentence Length is relatively short.
Sentence length SD: 33.6103011553 49.2860985944 68% => OK
Chars per sentence: 82.0 110.228320801 74% => OK
Words per sentence: 16.9375 21.698381199 78% => OK
Discourse Markers: 8.6875 7.06452816374 123% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 4.0 4.33554083885 92% => OK
Sentences with negative sentiment : 5.0 4.45695364238 112% => OK
Sentences with neutral sentiment: 7.0 4.27373068433 164% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.228792408006 0.272083759551 84% => OK
Sentence topic coherence: 0.0765777258946 0.0996497079465 77% => OK
Sentence topic coherence SD: 0.0567214795412 0.0662205650399 86% => OK
Paragraph topic coherence: 0.134834245711 0.162205337803 83% => OK
Paragraph topic coherence SD: 0.0272142764104 0.0443174109184 61% => OK
Essay readability:
automated_readability_index: 9.8 13.3589403974 73% => Automated_readability_index is low.
flesch_reading_ease: 63.7 53.8541721854 118% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 8.4 11.0289183223 76% => OK
coleman_liau_index: 10.5 12.2367328918 86% => OK
dale_chall_readability_score: 7.63 8.42419426049 91% => OK
difficult_words: 55.0 63.6247240618 86% => OK
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 8.4 10.498013245 80% => OK
text_standard: 8.0 11.2008830022 71% => 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.
Grammar and spelling errors:
Line 3, column 335, Rule ID: ADJECTIVE_IN_ATTRIBUTE[1]
Message: A more concise phrase may lose no meaning and sound more powerful.
Suggestion: massive
...s small. In addition, the sea cows were massive in size 9m and weight 10 ton. So, a few of them...
^^^^^^^^^^^^^^^
Line 5, column 232, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: didn't
...ker argues that the ecosystem imbalance didnt take place. If the disturbance had happ...
^^^^^
Line 7, column 300, Rule ID: THE_SUPERLATIVE[2]
Message: A determiner is probably missing here: 'was the largest'.
Suggestion: was the largest
...have arrived. The population of sea cow was largest hundreds of years before 1700. But the ...
^^^^^^^^^^^
Transition Words or Phrases used:
also, but, conversely, finally, first, hence, however, if, second, secondly, so, therefore, in addition, in contrast, such as, first of all
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 11.0 10.4613686534 105% => OK
Auxiliary verbs: 2.0 5.04856512141 40% => OK
Conjunction : 6.0 7.30242825607 82% => OK
Relative clauses : 7.0 12.0772626932 58% => More relative clauses wanted.
Pronoun: 10.0 22.412803532 45% => OK
Preposition: 36.0 30.3222958057 119% => OK
Nominalization: 10.0 5.01324503311 199% => OK
Performance on vocabulary words:
No of characters: 1312.0 1373.03311258 96% => OK
No of words: 271.0 270.72406181 100% => OK
Chars per words: 4.84132841328 5.08290768461 95% => OK
Fourth root words length: 4.05734859645 4.04702891845 100% => OK
Word Length SD: 2.40987944943 2.5805825403 93% => OK
Unique words: 144.0 145.348785872 99% => OK
Unique words percentage: 0.531365313653 0.540411800872 98% => OK
syllable_count: 404.1 419.366225166 96% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 0.0 3.25607064018 0% => OK
Article: 12.0 8.23620309051 146% => OK
Subordination: 2.0 1.25165562914 160% => 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: 16.0 13.0662251656 122% => OK
Sentence length: 16.0 21.2450331126 75% => The Avg. Sentence Length is relatively short.
Sentence length SD: 33.6103011553 49.2860985944 68% => OK
Chars per sentence: 82.0 110.228320801 74% => OK
Words per sentence: 16.9375 21.698381199 78% => OK
Discourse Markers: 8.6875 7.06452816374 123% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 4.0 4.33554083885 92% => OK
Sentences with negative sentiment : 5.0 4.45695364238 112% => OK
Sentences with neutral sentiment: 7.0 4.27373068433 164% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.228792408006 0.272083759551 84% => OK
Sentence topic coherence: 0.0765777258946 0.0996497079465 77% => OK
Sentence topic coherence SD: 0.0567214795412 0.0662205650399 86% => OK
Paragraph topic coherence: 0.134834245711 0.162205337803 83% => OK
Paragraph topic coherence SD: 0.0272142764104 0.0443174109184 61% => OK
Essay readability:
automated_readability_index: 9.8 13.3589403974 73% => Automated_readability_index is low.
flesch_reading_ease: 63.7 53.8541721854 118% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 8.4 11.0289183223 76% => OK
coleman_liau_index: 10.5 12.2367328918 86% => OK
dale_chall_readability_score: 7.63 8.42419426049 91% => OK
difficult_words: 55.0 63.6247240618 86% => OK
linsear_write_formula: 10.5 10.7273730684 98% => OK
gunning_fog: 8.4 10.498013245 80% => OK
text_standard: 8.0 11.2008830022 71% => 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.