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 and lecture discuss the Stellar Sea-cow extinction from Bering Islands, Siberia. The article describes three plausible theories to explain the cause of Sea-cow extinction- The overhunting theory, The ecological disturbance theory, and the European trader's theory. However, the lecturer refutes all three theories and presents counter-arguments for each of the assertions.
To begin with, the professor notes that the Stellar sea cows are enormous marine animals weighing up to 10 tons and a length of about 9 meters. He elaborates the point by adding that a couple of sea cows can feed the small Siberian village since the population is dramatically very low. Therefore, Siberians are the prime factor for the decrease of sea-cows that are not feasible. This specific point contradicts the reading. According to the passage, sea cows were the food source in the harsh environment of Bering Island.
Next, the hypothetical decline of kelp that causes upset in the ecological balance is rejected by the lecturer by contending that if there is a critical decrease in this sea plant, it would have affected other marine organisms as well. Nevertheless, fishing ships never noticed a reduction of sea whales or other marine animals. Hence, this theory is precisely challenged by the tutor and argues that there was no broader destruction of kelp and there was enough food source for sea cows to flourish.
Next, as per reading, the European fur traders could have caught the Stellar Sea cows with their sophisticated weapons can be a plausible explanation for the marine animal extinction. On the other hand, the tutor says the decline of sea cows was noted 100 years before the Europeans advent. Moreover, By the time the fur traders approached the island the population of sea cows was already at the brim of extinction. As a result, the original cause of extinction is still unclear.
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Grammar and spelling errors:
Line 1, column 261, Rule ID: POSSESIVE_APOSTROPHE[2]
Message: Possible typo: apostrophe is missing. Did you mean 'traders'' or 'trader's'?
Suggestion: traders'; trader's
...al disturbance theory, and the European traders theory. However, the lecturer refutes a...
^^^^^^^
Transition Words or Phrases used:
hence, however, if, moreover, nevertheless, so, still, therefore, well, as a result, to begin with, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 14.0 10.4613686534 134% => OK
Auxiliary verbs: 4.0 5.04856512141 79% => OK
Conjunction : 7.0 7.30242825607 96% => OK
Relative clauses : 6.0 12.0772626932 50% => More relative clauses wanted.
Pronoun: 12.0 22.412803532 54% => OK
Preposition: 35.0 30.3222958057 115% => OK
Nominalization: 13.0 5.01324503311 259% => Less nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1594.0 1373.03311258 116% => OK
No of words: 309.0 270.72406181 114% => OK
Chars per words: 5.15857605178 5.08290768461 101% => OK
Fourth root words length: 4.1926597562 4.04702891845 104% => OK
Word Length SD: 2.79537851342 2.5805825403 108% => OK
Unique words: 171.0 145.348785872 118% => OK
Unique words percentage: 0.553398058252 0.540411800872 102% => OK
syllable_count: 488.7 419.366225166 117% => OK
avg_syllables_per_word: 1.6 1.55342163355 103% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Article: 9.0 8.23620309051 109% => OK
Subordination: 2.0 1.25165562914 160% => OK
Conjunction: 1.0 1.51434878587 66% => OK
Preposition: 4.0 2.5761589404 155% => OK
Performance on sentences:
How many sentences: 15.0 13.0662251656 115% => OK
Sentence length: 20.0 21.2450331126 94% => OK
Sentence length SD: 49.3037749287 49.2860985944 100% => OK
Chars per sentence: 106.266666667 110.228320801 96% => OK
Words per sentence: 20.6 21.698381199 95% => OK
Discourse Markers: 7.8 7.06452816374 110% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 3.0 4.33554083885 69% => OK
Sentences with negative sentiment : 6.0 4.45695364238 135% => OK
Sentences with neutral sentiment: 6.0 4.27373068433 140% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.215161763529 0.272083759551 79% => OK
Sentence topic coherence: 0.0755631908322 0.0996497079465 76% => OK
Sentence topic coherence SD: 0.0453499664571 0.0662205650399 68% => OK
Paragraph topic coherence: 0.134448407548 0.162205337803 83% => OK
Paragraph topic coherence SD: 0.0259437589548 0.0443174109184 59% => OK
Essay readability:
automated_readability_index: 13.2 13.3589403974 99% => OK
flesch_reading_ease: 51.18 53.8541721854 95% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 11.1 11.0289183223 101% => OK
coleman_liau_index: 12.65 12.2367328918 103% => OK
dale_chall_readability_score: 9.13 8.42419426049 108% => OK
difficult_words: 88.0 63.6247240618 138% => OK
linsear_write_formula: 11.0 10.7273730684 103% => OK
gunning_fog: 10.0 10.498013245 95% => 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.