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.
In this set of material, the reading provides some evidences that suppose some hypothesizes about extinction of Stellar's sea cow, but the lecturer refuse them by giving explanation.
First, the reading claims that native Siberian people may use sea cows as main resources of food and they overhunted them because they were a good and reliable source of food. So, due to overhunting, population of Stellar's sea cow decreased over the time. In contrast, the lecturer rejects this idea by describing size and weight of sea cow; 90 meters long and 900 kilograms! He claimed that native people didn't need to hunt these creatures in a large scale because they could alive by just haunting couple of them for long period of time. So, some other reasons except of this idea can be the main reason of extinction.
Second, as reading says, population of kelp, which was the main food source of sea cows, were decreased enormously because of ecological fluctuations. But, the lecturer gave explanations against to the claim. He believes that if kelps' population was affected by ecological changes, why these changes didn't impacted other creatures like whales too? As he told, reports from fish hunting ships didn't mentioned any shortages in quantity of fishes. So, this hypothesis could not be true.
Third, reading believes that the main reason for sea cow' disappearance could be European fur traders who hunted sea cows to obtain their fur and sell them in market. They usually used weapons and guns that able them to hunt many Stellar's sea cow in a short period of time. On the contrary, the lecturer rejected this viewpoint too. Based on his speeches, population of Stellar's sea cow were reduced before European fur trades arrive to Bering Island. So, European fur trades were not able to access and hunt many sea cows because their population was already diminished.
In conclusion, maybe there is some other reasons exist that can explain Stellar's sea cows extinction.
Grammar and spelling errors:
Line 3, column 407, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: didn't
...ilograms! He claimed that native people didnt need to hunt these creatures in a large...
^^^^^
Line 3, column 525, Rule ID: PERIOD_OF_TIME[1]
Message: Use simply 'period'.
Suggestion: period
...y just haunting couple of them for long period of time. So, some other reasons except of this ...
^^^^^^^^^^^^^^
Line 5, column 301, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: didn't
...y ecological changes, why these changes didnt impacted other creatures like whales to...
^^^^^
Line 5, column 393, Rule ID: EN_CONTRACTION_SPELLING
Message: Possible spelling mistake found
Suggestion: didn't
...e told, reports from fish hunting ships didnt mentioned any shortages in quantity of ...
^^^^^
Line 7, column 258, Rule ID: PERIOD_OF_TIME[1]
Message: Use simply 'period'.
Suggestion: period
...o hunt many Stellars sea cow in a short period of time. On the contrary, the lecturer rejected...
^^^^^^^^^^^^^^
Transition Words or Phrases used:
but, first, if, may, second, so, third, in conclusion, in contrast, on the contrary
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 : 8.0 7.30242825607 110% => OK
Relative clauses : 9.0 12.0772626932 75% => More relative clauses wanted.
Pronoun: 29.0 22.412803532 129% => Less pronouns wanted
Preposition: 43.0 30.3222958057 142% => OK
Nominalization: 10.0 5.01324503311 199% => OK
Performance on vocabulary words:
No of characters: 1650.0 1373.03311258 120% => OK
No of words: 328.0 270.72406181 121% => OK
Chars per words: 5.03048780488 5.08290768461 99% => OK
Fourth root words length: 4.25567506705 4.04702891845 105% => OK
Word Length SD: 2.55178373652 2.5805825403 99% => OK
Unique words: 171.0 145.348785872 118% => OK
Unique words percentage: 0.521341463415 0.540411800872 96% => OK
syllable_count: 501.3 419.366225166 120% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Interrogative: 1.0 0.116997792494 855% => Less interrogative sentences wanted.
Article: 5.0 8.23620309051 61% => 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: 16.0 13.0662251656 122% => OK
Sentence length: 20.0 21.2450331126 94% => OK
Sentence length SD: 58.8876048078 49.2860985944 119% => OK
Chars per sentence: 103.125 110.228320801 94% => OK
Words per sentence: 20.5 21.698381199 94% => OK
Discourse Markers: 5.1875 7.06452816374 73% => OK
Paragraphs: 5.0 4.09492273731 122% => OK
Language errors: 5.0 4.19205298013 119% => OK
Sentences with positive sentiment : 4.0 4.33554083885 92% => OK
Sentences with negative sentiment : 4.0 4.45695364238 90% => OK
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: 0.12200831124 0.272083759551 45% => OK
Sentence topic coherence: 0.0441448791614 0.0996497079465 44% => OK
Sentence topic coherence SD: 0.0380364642966 0.0662205650399 57% => OK
Paragraph topic coherence: 0.068010327578 0.162205337803 42% => OK
Paragraph topic coherence SD: 0.03726155409 0.0443174109184 84% => OK
Essay readability:
automated_readability_index: 12.5 13.3589403974 94% => Automated_readability_index is low.
flesch_reading_ease: 59.64 53.8541721854 111% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 9.9 11.0289183223 90% => OK
coleman_liau_index: 11.89 12.2367328918 97% => OK
dale_chall_readability_score: 7.9 8.42419426049 94% => OK
difficult_words: 68.0 63.6247240618 107% => OK
linsear_write_formula: 14.0 10.7273730684 131% => OK
gunning_fog: 10.0 10.498013245 95% => 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: 83.3333333333 out of 100
Scores by essay e-grader: 25.0 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.