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.
In this set of materials, the author strongly postulates that the fossils of one of the primitive extinct arthropods called agnostids do not show clear evidence about their behavior and provides three theories to endorse its idea of how agnostids may have lived. On the other hand, the professor states that hypotheses about the way of living of agnostids mentioned in the reading are very weak and gainsays each of the arguments.
First and foremost, the passage begins by asserting the first theory that agnostids were small and strong free-swimming predators. They fed off small animals in the ocean like other primitive arthropods. However, the professor states that in order to attack prey, the vision should be very strong. All predators have well-developed eyes and super strong vision to really focus on their prey but, agnostids had tiny eyes and some were even blind. So, there must be another sensory organ present in their body to observe their prey but there is no evidence to support this claim so they cannot be categorized as predators.
Next, the professor in the lecture further highlights the points that agnostids cannot be seafloor dwellers because not only the movement of seafloor dwellers is very slow but also limited to a localized area. In contrast, the agnostids have the ability to spread from one place to another very fast. Moreover, they occupied a large geological area which is something unusual for the species that inhabit the seafloor. These claims refute the writer's implication of agnostids survived on the seafloor by feeding off dead organisms or by grazing bacteria, hence, are seafloor dwellers like other arthropods.
Ultimately, the article wraps its theories by declaring that the agnostids may have lived on primitive fish or other larger arthropods. So, they might be parasites like many modern-day arthropods who depend on their host for survival. However, the speaker in the listening refutes this hypothesis by showing the inaccuracy of the author that parasites occurred in low population because otherwise, they would kill all of their hosts at once. Since the fossils of agnostids were found in large amounts, the population of agnostids must be large. Therefore, it cannot be concluded that they were parasites.
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| 2023-09-05 | YasamanEsml | 86 | view |
| 2023-06-19 | Vivian Chang | 76 | view |
| 2023-02-07 | reza_fattahi | 73 | view |
| 2023-01-30 | reza_fattahi | 86 | view |
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Grammar and spelling errors:
Line 5, column 444, Rule ID: POSSESIVE_APOSTROPHE[1]
Message: Possible typo: apostrophe is missing. Did you mean 'writers'' or 'writer's'?
Suggestion: writers'; writer's
...t the seafloor. These claims refute the writers implication of agnostids survived on th...
^^^^^^^
Transition Words or Phrases used:
also, but, first, hence, however, may, moreover, really, so, therefore, well, in contrast, on the other hand
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 16.0 10.4613686534 153% => OK
Auxiliary verbs: 10.0 5.04856512141 198% => OK
Conjunction : 11.0 7.30242825607 151% => OK
Relative clauses : 11.0 12.0772626932 91% => OK
Pronoun: 28.0 22.412803532 125% => Less pronouns wanted
Preposition: 51.0 30.3222958057 168% => OK
Nominalization: 6.0 5.01324503311 120% => OK
Performance on vocabulary words:
No of characters: 1909.0 1373.03311258 139% => OK
No of words: 367.0 270.72406181 136% => OK
Chars per words: 5.20163487738 5.08290768461 102% => OK
Fourth root words length: 4.37689890912 4.04702891845 108% => OK
Word Length SD: 2.64499212464 2.5805825403 102% => OK
Unique words: 197.0 145.348785872 136% => OK
Unique words percentage: 0.536784741144 0.540411800872 99% => OK
syllable_count: 593.1 419.366225166 141% => 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: 10.0 8.23620309051 121% => 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: 16.0 13.0662251656 122% => OK
Sentence length: 22.0 21.2450331126 104% => OK
Sentence length SD: 54.7128869646 49.2860985944 111% => OK
Chars per sentence: 119.3125 110.228320801 108% => OK
Words per sentence: 22.9375 21.698381199 106% => OK
Discourse Markers: 6.75 7.06452816374 96% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 1.0 4.19205298013 24% => OK
Sentences with positive sentiment : 9.0 4.33554083885 208% => Less positive sentences wanted.
Sentences with negative sentiment : 3.0 4.45695364238 67% => OK
Sentences with neutral sentiment: 4.0 4.27373068433 94% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.264115491172 0.272083759551 97% => OK
Sentence topic coherence: 0.0903132227936 0.0996497079465 91% => OK
Sentence topic coherence SD: 0.0751131498563 0.0662205650399 113% => OK
Paragraph topic coherence: 0.164436696588 0.162205337803 101% => OK
Paragraph topic coherence SD: 0.0513770642983 0.0443174109184 116% => OK
Essay readability:
automated_readability_index: 14.5 13.3589403974 109% => OK
flesch_reading_ease: 49.15 53.8541721854 91% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 11.9 11.0289183223 108% => OK
coleman_liau_index: 13.18 12.2367328918 108% => OK
dale_chall_readability_score: 8.43 8.42419426049 100% => OK
difficult_words: 86.0 63.6247240618 135% => OK
linsear_write_formula: 13.0 10.7273730684 121% => OK
gunning_fog: 10.8 10.498013245 103% => OK
text_standard: 13.0 11.2008830022 116% => OK
What are above readability scores?
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Write the essay in 20 minutes.
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.