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 European 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 passage and the lecture both discuss the causes for the extinction of a large sea mammal which lived close to Bering island off the coast of Siberia. The author of the article introduces three possible theories for the disappearance of the sea cow. However, the speaker in the lecture casts doubt on all the claims made in the reading. He indicates several problems with each proposed theory.
To begin with, the lecturer refutes the idea of overhunting by native Siberian villagers by pointing out the massive size of the sea cows. He further states that one sea cow was 9 meters long and weighed around 10 tons. As a result, a couple of sea cows could have fed a small Siberian village for months. Hence, even if the Siberians hunted this sea mammal, they would have hunted it in very small numbers, which was not enough to drive the entire species to total extinction.
Moreover, the lecturer opposes the idea that severe ecological changes have led to shortage in sea cow's main source of food. He holds that if that was the case, those changes should have affected other species in the area such as whales. Nevertheless, no fishing ships reported decline in the whale population during that time. Consequently, there must have been other cause for the sea cow extinction.
Finally, the author assumes that the arrival of European with weapons that were capable of killing large number of sea cows quickly for their fur was probably the main cause for the dying out of this animal. Nonetheless, this point is challenged by the lecturer. He explains that the sea cow population was very small when Europeans arrived and the population was already diminishing. According to the lecturer, evidence showed that sea cow population was at its largest hundreds of years before the 1700s. Thus, the number of sea cows was going under long before the europeans discovered that area.
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Grammar and spelling errors:
Line 13, column 601, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...ore the europeans discovered that area.
^^^^^^
Transition Words or Phrases used:
consequently, finally, hence, however, if, moreover, nevertheless, nonetheless, so, thus, such as, as a result, to begin with
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 11.0 10.4613686534 105% => OK
Auxiliary verbs: 4.0 5.04856512141 79% => OK
Conjunction : 3.0 7.30242825607 41% => More conjunction wanted.
Relative clauses : 13.0 12.0772626932 108% => OK
Pronoun: 22.0 22.412803532 98% => OK
Preposition: 41.0 30.3222958057 135% => OK
Nominalization: 9.0 5.01324503311 180% => OK
Performance on vocabulary words:
No of characters: 1584.0 1373.03311258 115% => OK
No of words: 323.0 270.72406181 119% => OK
Chars per words: 4.9040247678 5.08290768461 96% => OK
Fourth root words length: 4.23936324884 4.04702891845 105% => OK
Word Length SD: 2.45808735519 2.5805825403 95% => OK
Unique words: 183.0 145.348785872 126% => OK
Unique words percentage: 0.566563467492 0.540411800872 105% => OK
syllable_count: 484.2 419.366225166 115% => 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: 8.0 8.23620309051 97% => 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: 17.0 13.0662251656 130% => OK
Sentence length: 19.0 21.2450331126 89% => OK
Sentence length SD: 40.0844264731 49.2860985944 81% => OK
Chars per sentence: 93.1764705882 110.228320801 85% => OK
Words per sentence: 19.0 21.698381199 88% => OK
Discourse Markers: 7.35294117647 7.06452816374 104% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 1.0 4.33554083885 23% => More positive sentences wanted.
Sentences with negative sentiment : 7.0 4.45695364238 157% => OK
Sentences with neutral sentiment: 9.0 4.27373068433 211% => Less facts, knowledge or examples wanted.
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.205522693402 0.272083759551 76% => OK
Sentence topic coherence: 0.0676073632431 0.0996497079465 68% => OK
Sentence topic coherence SD: 0.0573207660231 0.0662205650399 87% => OK
Paragraph topic coherence: 0.124206090257 0.162205337803 77% => OK
Paragraph topic coherence SD: 0.0376668979147 0.0443174109184 85% => OK
Essay readability:
automated_readability_index: 11.1 13.3589403974 83% => 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: 11.14 12.2367328918 91% => OK
dale_chall_readability_score: 8.44 8.42419426049 100% => OK
difficult_words: 79.0 63.6247240618 124% => OK
linsear_write_formula: 8.0 10.7273730684 75% => OK
gunning_fog: 9.6 10.498013245 91% => OK
text_standard: 10.0 11.2008830022 89% => OK
What are above readability scores?
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Write the essay in 20 minutes.
Rates: 73.3333333333 out of 100
Scores by essay e-grader: 22.0 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.