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 and the lecture are both about the causes of the sea cow extinction in Siberia. The author of the reading argues that there are three possible theories of this extinction. The lecturer casts doubt on the claims made in the article. He believes that there are different main reasons that contribute to this.
First of all, the author claims that the native people may overhunted the sea cows, because they are a good source of food in a harsh environment. However, this point is challenged by the lecturer. He says that the sea cows are a massive creature, they could grow over ten tons of weight. As the food source for the local people, a sea cow can feed them for months. In this case, native people won't overhunt sea cows.
Secondly, the author states that the ecosystem disturbance may have the impact on the kelp populations, the main source of food for sea cows. The sea cows could undergo the food shortage. The lecturer rebuts this argument. He suggests that if there was a severe ecosystem disturbance at that time, the other marine species should also decline. Nonetheless, the fishing ship didn't report the decrease of the marine species and kelp populations were growing fine. So the sea cows should have enough food sources to survive.
Finally, the author mentions that the European fur traders who had been recorded that caught the last sea cow in 1768. Having the weapons with them, they were able to kill enormous sea cows. The lecturer, on the other hand, feels that before European came, the sea cows population had already declined significantly. They were only accidentally participate in this extinction.
| Post date | Users | Rates | Link to Content |
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| 2022-10-26 | _sta | 80 | view |
| 2022-10-25 | rassata | 85 | view |
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| 2022-09-17 | Ibne Arabi | 75 | view |
| 2022-06-29 | ellen87713 | 86 | view |
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Grammar and spelling errors:
Line 1, column 185, Rule ID: ENGLISH_WORD_REPEAT_BEGINNING_RULE
Message: Three successive sentences begin with the same word. Reword the sentence or use a thesaurus to find a synonym.
...e possible theories of this extinction. The lecturer casts doubt on the claims made...
^^^
Line 5, column 375, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: didn't
... decline. Nonetheless, the fishing ship didnt report the decrease of the marine speci...
^^^^^
Line 7, column 266, Rule ID: POSSESIVE_APOSTROPHE[1]
Message: Possible typo: apostrophe is missing. Did you mean 'cows'' or 'cow's'?
Suggestion: cows'; cow's
...eels that before European came, the sea cows population had already declined signifi...
^^^^
Transition Words or Phrases used:
also, but, finally, first, however, if, may, nonetheless, second, secondly, so, first of all, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 11.0 10.4613686534 105% => OK
Auxiliary verbs: 7.0 5.04856512141 139% => OK
Conjunction : 2.0 7.30242825607 27% => More conjunction wanted.
Relative clauses : 12.0 12.0772626932 99% => OK
Pronoun: 26.0 22.412803532 116% => OK
Preposition: 26.0 30.3222958057 86% => OK
Nominalization: 8.0 5.01324503311 160% => OK
Performance on vocabulary words:
No of characters: 1370.0 1373.03311258 100% => OK
No of words: 280.0 270.72406181 103% => OK
Chars per words: 4.89285714286 5.08290768461 96% => OK
Fourth root words length: 4.09062348924 4.04702891845 101% => OK
Word Length SD: 2.4706026696 2.5805825403 96% => OK
Unique words: 150.0 145.348785872 103% => OK
Unique words percentage: 0.535714285714 0.540411800872 99% => OK
syllable_count: 413.1 419.366225166 99% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 7.0 3.25607064018 215% => Less pronouns wanted as sentence beginning.
Article: 14.0 8.23620309051 170% => OK
Subordination: 2.0 1.25165562914 160% => OK
Conjunction: 0.0 1.51434878587 0% => OK
Preposition: 2.0 2.5761589404 78% => OK
Performance on sentences:
How many sentences: 19.0 13.0662251656 145% => OK
Sentence length: 14.0 21.2450331126 66% => The Avg. Sentence Length is relatively short.
Sentence length SD: 33.1660808608 49.2860985944 67% => OK
Chars per sentence: 72.1052631579 110.228320801 65% => OK
Words per sentence: 14.7368421053 21.698381199 68% => OK
Discourse Markers: 5.84210526316 7.06452816374 83% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 2.0 4.33554083885 46% => More positive sentences wanted.
Sentences with negative sentiment : 9.0 4.45695364238 202% => Less negative sentences wanted.
Sentences with neutral sentiment: 8.0 4.27373068433 187% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.126402045248 0.272083759551 46% => OK
Sentence topic coherence: 0.0398853164396 0.0996497079465 40% => OK
Sentence topic coherence SD: 0.0384534681628 0.0662205650399 58% => OK
Paragraph topic coherence: 0.0785611697934 0.162205337803 48% => OK
Paragraph topic coherence SD: 0.0178333911802 0.0443174109184 40% => Paragraphs are similar to each other. Some content may get duplicated or it is not exactly right on the topic.
Essay readability:
automated_readability_index: 9.0 13.3589403974 67% => Automated_readability_index is low.
flesch_reading_ease: 65.73 53.8541721854 122% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 7.6 11.0289183223 69% => OK
coleman_liau_index: 10.49 12.2367328918 86% => OK
dale_chall_readability_score: 7.66 8.42419426049 91% => OK
difficult_words: 59.0 63.6247240618 93% => OK
linsear_write_formula: 6.5 10.7273730684 61% => OK
gunning_fog: 7.6 10.498013245 72% => OK
text_standard: 8.0 11.2008830022 71% => OK
What are above readability scores?
---------------------
Rates: 70.0 out of 100
Scores by essay e-grader: 21.0 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.