Agnostids were a group of marine animals that became extinct about 450 million years ago. Agnostid fossils can be found in rocks in many areas around the world. From the fossil remains, we know that agnostids were primitive arthropods-relatives of modern-day insects. However, the fossil information does not allow paleontologists to determine with certainty what agnostids ate or how they behaved. There are several different theories about how agnostids may have lived.
Free-Swimming Predators
First, the agnostids may have been free-swimming predators that hunted smaller animals. It is known that other types of primitive arthropods were strong swimmers and active predators, so it is reasonable that the agnostids may have lived that way as well And while the agnostids were small, sometimes just six millimeters long, there were plenty of smaller organisms in the ancient ocean for them to prey on.
Seafloor Dwellers
Second, they may have dwelled on the seafloor. Again, there are examples of other types of primitive arthropods living this way, so it is possible that agnostids did too. On the seafloor they would have survived by scavenging dead organisms or by grazing on bacteria.
Parasites
Third, there is the possibility that the agnostids were parasites, living on and feeding off larger organisms. One reason that this seems possible is that there are many species of modern-day arthropods that exist as parasites, such as fleas, ticks, and mites. The agnostids might have lived on primitive fish or even on other, larger arthropods.
The reading passage and the lecture both discuss how agnostids, small sea creatures, could have lived. The author presents three theories about how their lifestyle could have looked like. However, the lecturer call the arguments in the article into question. She mentions that the proposals have serious weaknesses.
First of all, the author claims that these organisms could have been free-swimming predators feeding on smaller animals since other primitive arthropods have lived this way. Nevertheless, the lecturer challenges this hypothesis. She assumes that agnostids lacked large well-developed eyes or any other sensory organs that could help them find and track the prey. According to the lecture, they only had tiny eyes and sometimes they were blind, which disproves this theory about hunting.
Secondly, the author holds that this species could have been seafloor dwellers getting their nutrition through eating dead corpses and bacteria. Conversely, the lecturer brings up the fact that seafloor occupiers usually move slowly and stay in their local environment. On the other hand, agnostids were found to have spread over multiple geographic areas, which supports the idea that they were highly mobile and this casts doubt on the theory that they were actually seafloor inhabitants.
Lastly, the writer maintains that those animals could have lived as parasites on other primitive fish and even other larger arthropods. The speaker in the lecture illustrates some flaws in this position. She explains that the population of agnostids was so large that if they were parasites, they would have killed off the host. Hence, this great population size rules out the possibility that their way of living was through parasitism
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| 2020-01-24 | jewel | 76 | view |
| 2020-01-03 | jason_linnil | 76 | view |
| 2019-12-20 | jewel | 80 | view |
| 2019-12-04 | shatealabo1110 | 70 | view |
| 2019-11-04 | p0uya | 85 | view |
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Grammar and spelling errors:
Line 13, column 437, Rule ID: WHITESPACE_RULE
Message: Possible typo: you repeated a whitespace
Suggestion:
...eir way of living was through parasitism
^^^^^^^^
Transition Words or Phrases used:
actually, conversely, first, hence, however, if, lastly, look, nevertheless, second, secondly, so, well, first of all, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 9.0 10.4613686534 86% => OK
Auxiliary verbs: 7.0 5.04856512141 139% => OK
Conjunction : 8.0 7.30242825607 110% => OK
Relative clauses : 14.0 12.0772626932 116% => OK
Pronoun: 35.0 22.412803532 156% => Less pronouns wanted
Preposition: 24.0 30.3222958057 79% => OK
Nominalization: 6.0 5.01324503311 120% => OK
Performance on vocabulary words:
No of characters: 1483.0 1373.03311258 108% => OK
No of words: 269.0 270.72406181 99% => OK
Chars per words: 5.51301115242 5.08290768461 108% => OK
Fourth root words length: 4.0498419064 4.04702891845 100% => OK
Word Length SD: 2.50657983496 2.5805825403 97% => OK
Unique words: 162.0 145.348785872 111% => OK
Unique words percentage: 0.602230483271 0.540411800872 111% => OK
syllable_count: 432.9 419.366225166 103% => OK
avg_syllables_per_word: 1.6 1.55342163355 103% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 6.0 3.25607064018 184% => OK
Article: 9.0 8.23620309051 109% => OK
Subordination: 0.0 1.25165562914 0% => More adverbial clause wanted.
Conjunction: 0.0 1.51434878587 0% => OK
Preposition: 2.0 2.5761589404 78% => OK
Performance on sentences:
How many sentences: 15.0 13.0662251656 115% => OK
Sentence length: 17.0 21.2450331126 80% => The Avg. Sentence Length is relatively short.
Sentence length SD: 43.8935074926 49.2860985944 89% => OK
Chars per sentence: 98.8666666667 110.228320801 90% => OK
Words per sentence: 17.9333333333 21.698381199 83% => OK
Discourse Markers: 9.06666666667 7.06452816374 128% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 5.0 4.33554083885 115% => OK
Sentences with negative sentiment : 5.0 4.45695364238 112% => 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: 0.104733806226 0.272083759551 38% => The similarity between the topic and the content is low.
Sentence topic coherence: 0.0320314536381 0.0996497079465 32% => Sentence topic similarity is low.
Sentence topic coherence SD: 0.0445867815328 0.0662205650399 67% => OK
Paragraph topic coherence: 0.0673784435762 0.162205337803 42% => OK
Paragraph topic coherence SD: 0.0337871928699 0.0443174109184 76% => OK
Essay readability:
automated_readability_index: 13.5 13.3589403974 101% => OK
flesch_reading_ease: 54.22 53.8541721854 101% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 9.9 11.0289183223 90% => OK
coleman_liau_index: 14.38 12.2367328918 118% => OK
dale_chall_readability_score: 9.0 8.42419426049 107% => OK
difficult_words: 77.0 63.6247240618 121% => OK
linsear_write_formula: 6.5 10.7273730684 61% => OK
gunning_fog: 8.8 10.498013245 84% => OK
text_standard: 9.0 11.2008830022 80% => OK
What are above readability scores?
---------------------
Rates: 90.0 out of 100
Scores by essay e-grader: 27.0 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.