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 excerpt states that there three theories about the main cause of the extinction of a huge marine mammal known as Steller's sea cow, the author provide three reasons for support. However, the lecture's audio explains that there a lot of problems with the author theories and he refutes each of them by stating the cause of these ideas is not obvious.
To begin with, the article claims that the sea cows may have been overhunted by groups of native Siberian people. In contrast, the professor opposes this point of view by saying that these animals were huge about ten tones weight, in the same hand, the population of people was not large. Thus, only two of these sea cows were enough to provide them with food for about one month. So, there was no need to hunt a lot. Hence, this theory contradicts what the professor explained.
Second, the passage posits that the sea cow population may have become extinct because of ecosystems disturbances that caused a decline in their main source of food, kelp which is a type of sea plant.
On the other hand, the speaker asserts this outlook and explains that if there was a sever ecosystem disturbance by 1768. So, that effect should be not only on the Kelp but other marine animals also such as whales. However, there was not any decline of whales at that time. Thus, there was not any food shortage.
Third, the excerpt mentions that the main cause of extinction of the sea cows could have been European fur traders who came to the island after 1741. This cast doubt on what the lecturer avers which says that after the European arrival the number of these animals was quite small. Moreover, that disappearance began 100 years before their arrival. Thus, they are not the main cause since they were the last to arrive.
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Grammar and spelling errors:
Line 1, column 203, Rule ID: POSSESIVE_APOSTROPHE[1]
Message: Possible typo: apostrophe is missing. Did you mean 'lectures'' or 'lecture's'?
Suggestion: lectures'; lecture's
...three reasons for support. However, the lectures audio explains that there a lot of prob...
^^^^^^^^
Transition Words or Phrases used:
also, but, hence, however, if, look, may, moreover, second, so, third, thus, in contrast, such as, to begin with, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 15.0 10.4613686534 143% => OK
Auxiliary verbs: 5.0 5.04856512141 99% => OK
Conjunction : 3.0 7.30242825607 41% => More conjunction wanted.
Relative clauses : 15.0 12.0772626932 124% => OK
Pronoun: 27.0 22.412803532 120% => Less pronouns wanted
Preposition: 42.0 30.3222958057 139% => OK
Nominalization: 6.0 5.01324503311 120% => OK
Performance on vocabulary words:
No of characters: 1471.0 1373.03311258 107% => OK
No of words: 314.0 270.72406181 116% => OK
Chars per words: 4.6847133758 5.08290768461 92% => OK
Fourth root words length: 4.20951839842 4.04702891845 104% => OK
Word Length SD: 2.17567208659 2.5805825403 84% => OK
Unique words: 168.0 145.348785872 116% => OK
Unique words percentage: 0.535031847134 0.540411800872 99% => OK
syllable_count: 443.7 419.366225166 106% => OK
avg_syllables_per_word: 1.4 1.55342163355 90% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 5.0 3.25607064018 154% => OK
Article: 9.0 8.23620309051 109% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 0.0 1.51434878587 0% => OK
Preposition: 4.0 2.5761589404 155% => OK
Performance on sentences:
How many sentences: 16.0 13.0662251656 122% => OK
Sentence length: 19.0 21.2450331126 89% => OK
Sentence length SD: 52.4972841559 49.2860985944 107% => OK
Chars per sentence: 91.9375 110.228320801 83% => OK
Words per sentence: 19.625 21.698381199 90% => OK
Discourse Markers: 8.1875 7.06452816374 116% => OK
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 1.0 4.19205298013 24% => 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: 0.194821211987 0.272083759551 72% => OK
Sentence topic coherence: 0.0597361935647 0.0996497079465 60% => OK
Sentence topic coherence SD: 0.0435915691535 0.0662205650399 66% => OK
Paragraph topic coherence: 0.101075656688 0.162205337803 62% => OK
Paragraph topic coherence SD: 0.0256080402195 0.0443174109184 58% => OK
Essay readability:
automated_readability_index: 10.4 13.3589403974 78% => Automated_readability_index is low.
flesch_reading_ease: 69.11 53.8541721854 128% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 8.3 11.0289183223 75% => OK
coleman_liau_index: 9.86 12.2367328918 81% => OK
dale_chall_readability_score: 7.6 8.42419426049 90% => OK
difficult_words: 60.0 63.6247240618 94% => OK
linsear_write_formula: 13.0 10.7273730684 121% => OK
gunning_fog: 9.6 10.498013245 91% => OK
text_standard: 10.0 11.2008830022 89% => OK
What are above readability scores?
---------------------
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.