The zebra mussel, a freshwater shellfish native to Eastern Europe, has long been spreading out from its original habitats and has now reached parts of North America. There are reasons to believe that this invasion cannot be stopped and that it poses a serious threat to freshwater fish populations in all of North America.
First, the history of the zebra mussel's spread suggests that the invasion might be unstoppable. It is a prime example of an invasion made possible by human transportation. From the zebra mussel's original habitats in Eastern Europe, ships helped spread it out along new canals built to connect Europe's waterways. The mussel can attach itself to a ship's bottom or can survive in the water - called "ballast water" - that the ship needs to take on to properly balance its cargo. By the early nineteenth century, the mussel had spread to the whole of Europe. It was later carried to the east coast of North America in the ballast water of ships traveling from Europe. The way ships have spread the zebra mussel in the past strongly suggests that the species will soon colonize all of North America.
Moreover, once zebra mussels are carried to a new habitat, they can dominate it. They are a hardy species that does well under a variety of conditions, and they have a high rate of reproduction. Most important, however, zebra mussels often have no predators in their new habitats, and species without natural predators are likely to dominate their habitats.
Finally, zebra mussels are likely to cause a decline in the overall fish population in habitats where they become dominant. The mussels are plankton eaters, which means that they compete for food with many freshwater fish species.
The lecturer refutes all three claims made by the passage, which is about the causes for the spread of zebra mussels in their new habitat in North America. In fact, the mussels are originally from Eastern Europe, the author of the passage believes that ships that carry these mussels to its new environment through ballast water are non-stoppable can adversely affect the freshwater fish populations in the new region. However, the professor has counter-arguments for each assertion.
First, the reading posits that the transportation of zebra mussels through the ballast water- which is the freshwater at the bottom of the ship to balance the goods- is an ideal means of transfer of these species. In contrast, the professor thinks that the spread of these marine animals may probably unstoppable in the past because of the illiteracy of people. Moreover, the ballast water is converted to ocean water during the journey which can kill these freshwater mussels. In other words, the professor mentions the best way to control the spread of this animal.
Second, the reading states two important characteristics of zebra mussels in a new habitat. Their ability to withstand in the harsh environment from the predators as they have a hardy shell and a high success rate of reproduction. The professor challenges this argument. Although it seems like there are no predators at the beginning, the aquatic birds are a serious threat to them. In addition, these hunter birds switch their diet from small fishes to mussels also leads to zebra mussel decline in North America.
Finally, the professor contradicts the fact in the passage about the reduction of plankton eater fishes. Lecturer says that mussels produce a nutrition-rich substance that promotes the growth of bottom-feeding fishes.
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Transition Words or Phrases used:
also, finally, first, however, may, moreover, second, so, in addition, in contrast, in fact, in other words
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 8.0 10.4613686534 76% => OK
Auxiliary verbs: 3.0 5.04856512141 59% => OK
Conjunction : 1.0 7.30242825607 14% => More conjunction wanted.
Relative clauses : 9.0 12.0772626932 75% => More relative clauses wanted.
Pronoun: 20.0 22.412803532 89% => OK
Preposition: 47.0 30.3222958057 155% => OK
Nominalization: 11.0 5.01324503311 219% => Less nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1513.0 1373.03311258 110% => OK
No of words: 288.0 270.72406181 106% => OK
Chars per words: 5.25347222222 5.08290768461 103% => OK
Fourth root words length: 4.11953428781 4.04702891845 102% => OK
Word Length SD: 2.83561106363 2.5805825403 110% => OK
Unique words: 157.0 145.348785872 108% => OK
Unique words percentage: 0.545138888889 0.540411800872 101% => OK
syllable_count: 450.0 419.366225166 107% => OK
avg_syllables_per_word: 1.6 1.55342163355 103% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 2.0 3.25607064018 61% => OK
Article: 12.0 8.23620309051 146% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 0.0 1.51434878587 0% => OK
Preposition: 4.0 2.5761589404 155% => OK
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 20.0 21.2450331126 94% => OK
Sentence length SD: 55.1268018818 49.2860985944 112% => OK
Chars per sentence: 108.071428571 110.228320801 98% => OK
Words per sentence: 20.5714285714 21.698381199 95% => OK
Discourse Markers: 7.64285714286 7.06452816374 108% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 0.0 4.19205298013 0% => OK
Sentences with positive sentiment : 5.0 4.33554083885 115% => OK
Sentences with negative sentiment : 6.0 4.45695364238 135% => OK
Sentences with neutral sentiment: 3.0 4.27373068433 70% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.189744022661 0.272083759551 70% => OK
Sentence topic coherence: 0.0590927281435 0.0996497079465 59% => OK
Sentence topic coherence SD: 0.0540840062834 0.0662205650399 82% => OK
Paragraph topic coherence: 0.106778801737 0.162205337803 66% => OK
Paragraph topic coherence SD: 0.0643415918547 0.0443174109184 145% => OK
Essay readability:
automated_readability_index: 13.6 13.3589403974 102% => 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: 13.17 12.2367328918 108% => OK
dale_chall_readability_score: 8.8 8.42419426049 104% => OK
difficult_words: 76.0 63.6247240618 119% => OK
linsear_write_formula: 14.5 10.7273730684 135% => OK
gunning_fog: 10.0 10.498013245 95% => OK
text_standard: 9.0 11.2008830022 80% => 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.