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

Essay topics:

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 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 truth is, we don't know what the main cause of extinction of Steller's sea cow was. There are problems with each of the theories that you read about.

First, these sea cows were massive creatures—they were up to nine meters long and could weigh over ten tons—just enormous. A couple of sea cows could feed a small Siberian village for months and the population of the native Siberian people wasn't very large. So while the Siberians certainly did hunt the sea cows, they didn't need to hunt a lot of them, so it's unlikely they were the ones who brought the sea cows to the point of extinction. Second, about a hypothetical decrease in kelp caused by ecological disturbances. Well, if something severe really happened in the ecosystem near Bering Island some time before 1768, it would have affected not just the kelp but also other parts of the ecosystem. For example, it would have caused a decline in other marine animals, like whales. But fishing ships in the area did not report a whale decline. Since there's no indication of broader ecosystem problems, the kelp was probably growing just fine, and the sea cows did not experience food shortage.

Third, it might seem like the European traders were responsible because the sea cows became extinct soon after the Europeans arrived. But actually, by the time the Europeans arrived, the sea cow population was already quite small. We have evidence that the sea cow population was at its largest hundreds of years before the 1700s. So something was causing a serious and ongoing decrease in the sea cow population long before Europeans arrived in the Bering Island area. Whatever this “something” was, it should be considered the main cause of the extinction, not the European traders who were just the last to arrive.

Summarize the points made in the lecture, being sure to explain how they challenge the specific theories presented in the reading passage.

In the regard to the issue of the reasons why sea cows became extinct. The reading passage points out three possible causes, whereas the lecturer puts forward three compelling arguments and efficaciously contradicts the theories of the writer.

Firstly, according to the author, the native Siberian overhunted the sea cows and made the population declined since sea cows were an ideal source of food for people who lived in a harsh environment. The speaker, however, disclaims the point of view and declares that the length of sea cows is nine meters and it weighs ten tons, overhunting was impossible since Siberian people did not need that much food to survive. Further, Siberian people only need one sea cow then they can feed a small village for a month, and the amount of the people was not large.

Secondly, the reading holds that ecosystem disturbance was the reason why sea cows died out. Additionally, sea cows relaid on kelp to living, while the amount of kelp decreased because of the ecological changes. By contrast, the professor disproves the claim of the reading, demonstrating that if there had been an ecosystem disturbance, it would not have only affected sea cows but also other marine animals, such as whale. However, there was nothing bother the ecosystem at that time, and the sea cows did not experience any food shortage as well.

Finally, the article asserts that the European fur traders may cause extinction since they possessed weapons that can kill lots of animals in a short time. On the other hand, the listening maintains an opposite opinion that there was evidence showed that the population of the sea cows had been already quite small before the fur traders arrived on the island. Thus, the fur traders were not the main reason to cause this extinction.

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Comments

Transition Words or Phrases used:
also, but, finally, first, firstly, however, if, may, second, secondly, so, then, thus, whereas, while, such as, 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: 6.0 5.04856512141 119% => OK
Conjunction : 7.0 7.30242825607 96% => OK
Relative clauses : 10.0 12.0772626932 83% => OK
Pronoun: 14.0 22.412803532 62% => OK
Preposition: 29.0 30.3222958057 96% => OK
Nominalization: 8.0 5.01324503311 160% => OK

Performance on vocabulary words:
No of characters: 1481.0 1373.03311258 108% => OK
No of words: 296.0 270.72406181 109% => OK
Chars per words: 5.00337837838 5.08290768461 98% => OK
Fourth root words length: 4.14784890444 4.04702891845 102% => OK
Word Length SD: 2.57495159769 2.5805825403 100% => OK
Unique words: 162.0 145.348785872 111% => OK
Unique words percentage: 0.547297297297 0.540411800872 101% => OK
syllable_count: 449.1 419.366225166 107% => OK
avg_syllables_per_word: 1.5 1.55342163355 97% => OK

A sentence (or a clause, phrase) starts by:
Pronoun: 1.0 3.25607064018 31% => OK
Article: 8.0 8.23620309051 97% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 2.0 1.51434878587 132% => OK
Preposition: 4.0 2.5761589404 155% => OK

Performance on sentences:
How many sentences: 12.0 13.0662251656 92% => OK
Sentence length: 24.0 21.2450331126 113% => OK
Sentence length SD: 50.784607795 49.2860985944 103% => OK
Chars per sentence: 123.416666667 110.228320801 112% => OK
Words per sentence: 24.6666666667 21.698381199 114% => OK
Discourse Markers: 10.8333333333 7.06452816374 153% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 0.0 4.19205298013 0% => OK
Sentences with positive sentiment : 3.0 4.33554083885 69% => OK
Sentences with negative sentiment : 4.0 4.45695364238 90% => OK
Sentences with neutral sentiment: 5.0 4.27373068433 117% => OK
What are sentences with positive/Negative/neutral sentiment?

Coherence and Cohesion:
Essay topic to essay body coherence: 0.175147234626 0.272083759551 64% => OK
Sentence topic coherence: 0.0662573099404 0.0996497079465 66% => OK
Sentence topic coherence SD: 0.0357693579583 0.0662205650399 54% => OK
Paragraph topic coherence: 0.0962163766861 0.162205337803 59% => OK
Paragraph topic coherence SD: 0.0397995816114 0.0443174109184 90% => OK

Essay readability:
automated_readability_index: 14.5 13.3589403974 109% => OK
flesch_reading_ease: 55.58 53.8541721854 103% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 11.5 11.0289183223 104% => OK
coleman_liau_index: 12.02 12.2367328918 98% => OK
dale_chall_readability_score: 8.61 8.42419426049 102% => OK
difficult_words: 71.0 63.6247240618 112% => OK
linsear_write_formula: 14.0 10.7273730684 131% => OK
gunning_fog: 11.6 10.498013245 110% => OK
text_standard: 12.0 11.2008830022 107% => OK
What are above readability scores?

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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.