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.
Both reading and lecture discuss extinction of Stellar's sea cow. The reading passage implies that there are three possibilities. However, the professor disagrees with the reading passage. Accordingly, he presents three refutations.
First of all, the reading mentions that the sea cows could have been over-hunted by native Siberian people. Yet, the lecturer challenging the theory by arguing that sea cows are massive and population of Siberian people is not large. In fact, he states Siberian people have no reason to over-hunt the sea cow because sea cow can feed them for months. As a result, being over-hunted by Siberian people cannot be a factor that cause extinction of sea cows.
Secondly, the passage suggests that sea cow population might have become extinct due to ecosystem disturbances which cause decline of food supplies. Nevertheless, the scholar seriously contradicts the hypothesis by asserting that other marine animals like whales did not been affected by ecosystem disturbances. Furthermore, he contends that kelp might just be fine and sea cows did not experience food shortage. Therefore, the second hypothesis is unconvincing.
Last but not least, the reading article indicates that European fur traders might responsible for extinction of sea cows. Once again, the speaker opposes evidence revealed in the reading by assuming that sea cow population were already quite small when European fur traders came to the island. Moreover, he points out that there must be something which caused sea cow to decline before European arrived. Thus, extinction of sea cows cannot attribute to European fur traders.
To conclude, the professor argues against the theories in the reading article. That is to say, he maintains that none of the explanations of extinction is achievable.
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Yet, the lecturer challenging the theory
Yet, the lecturer is challenging the theory
did not been affected by ecosystem disturbances
have not been affected by ecosystem disturbances
fur traders might responsible for
fur traders might be responsible for
flaws:
No. of Grammatical Errors: 3 2
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The correct pattern:
para 1: introduction
para 2: doubt 1
para 3: doubt 2
para 4: doubt 3
Don't need a conclusion paragraph.
Read sample essays from ETS:
http://www.testbig.com/users/toeflwritingmaster
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Attribute Value Ideal
Score: 20 in 30
Category: Satisfactory Excellent
No. of Grammatical Errors: 3 2
No. of Spelling Errors: 0 2
No. of Sentences: 18 12
No. of Words: 281 250
No. of Characters: 1478 1200
No. of Different Words: 150 150
Fourth Root of Number of Words: 4.094 4.2
Average Word Length: 5.26 4.6
Word Length SD: 2.752 2.4
No. of Words greater than 5 chars: 117 80
No. of Words greater than 6 chars: 95 60
No. of Words greater than 7 chars: 63 40
No. of Words greater than 8 chars: 40 20
Use of Passive Voice (%): 0 0
Avg. Sentence Length: 15.611 21.0
Sentence Length SD: 6.273 7.5
Use of Discourse Markers (%): 0.722 0.12
Sentence-Text Coherence: 0.347 0.35
Sentence-Para Coherence: 0.599 0.50
Sentence-Sentence Coherence: 0.15 0.07
Number of Paragraphs: 5 4