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 author discusses how agnostids lived by mentioning three different theories, such as being free-swimming predators, seafloor dwellers and parasites. However, the lecturer refutes there theories by giving further explanations.
First of all, it is impossible for agnostids to be a free-swimming predators. Generally speaking, the free-swimming predators have large well-developed eyes, which enable them to hunt for other animals. Nevertheless, agnostids have poorly developed eyes, or even blind. In addition, they do not have other sensor organism found in the fossils. As a result. it is flawed to predict that agnostids are free-swimming predators.
Second, the seafloor dwellers usually move slowly and stay in local area, but agnostids move fast and long distance. So the character of agnostids does not meet the expectation of being seafloor dwellers. The original assumption does not make sense.
Third, agnostids are not parasites since they exist in large amount, while parasites do not. To be more specific, the larger the population of parasites have on the host organism, the higher the possibility of killing the host. That is why it is not reasonable to assume them as parasites.
| Post date | Users | Rates | Link to Content |
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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 |
| 2023-01-30 | reza_fattahi | 75 | view |
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Grammar and spelling errors:
Line 3, column 68, Rule ID: A_PLURAL[2]
Message: Don't use indefinite articles with plural words. Did you mean 'predator'?
Suggestion: predator
...ble for agnostids to be a free-swimming predators. Generally speaking, the free-swimming ...
^^^^^^^^^
Line 3, column 345, Rule ID: SENTENCE_FRAGMENT[1]
Message: “As” at the beginning of a sentence requires a 2nd clause. Maybe a comma, question or exclamation mark is missing, or the sentence is incomplete and should be joined with the following sentence.
...r sensor organism found in the fossils. As a result. it is flawed to predict that ...
^^
Line 3, column 358, Rule ID: UPPERCASE_SENTENCE_START
Message: This sentence does not start with an uppercase letter
Suggestion: It
...nism found in the fossils. As a result. it is flawed to predict that agnostids are...
^^
Transition Words or Phrases used:
but, first, however, if, nevertheless, second, so, third, well, while, in addition, such as, as a result, first of all
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 10.0 10.4613686534 96% => OK
Auxiliary verbs: 0.0 5.04856512141 0% => OK
Conjunction : 5.0 7.30242825607 68% => OK
Relative clauses : 3.0 12.0772626932 25% => More relative clauses wanted.
Pronoun: 9.0 22.412803532 40% => OK
Preposition: 18.0 30.3222958057 59% => More preposition wanted.
Nominalization: 5.0 5.01324503311 100% => OK
Performance on vocabulary words:
No of characters: 1022.0 1373.03311258 74% => OK
No of words: 185.0 270.72406181 68% => More content wanted.
Chars per words: 5.52432432432 5.08290768461 109% => OK
Fourth root words length: 3.68801715136 4.04702891845 91% => OK
Word Length SD: 3.06677570444 2.5805825403 119% => OK
Unique words: 114.0 145.348785872 78% => More unique words wanted.
Unique words percentage: 0.616216216216 0.540411800872 114% => OK
syllable_count: 311.4 419.366225166 74% => OK
avg_syllables_per_word: 1.7 1.55342163355 109% => OK
A sentence (or a clause, phrase) starts by:
Pronoun: 4.0 3.25607064018 123% => OK
Article: 7.0 8.23620309051 85% => OK
Subordination: 2.0 1.25165562914 160% => OK
Conjunction: 2.0 1.51434878587 132% => OK
Preposition: 2.0 2.5761589404 78% => OK
Performance on sentences:
How many sentences: 14.0 13.0662251656 107% => OK
Sentence length: 13.0 21.2450331126 61% => The Avg. Sentence Length is relatively short.
Sentence length SD: 35.8361492328 49.2860985944 73% => OK
Chars per sentence: 73.0 110.228320801 66% => OK
Words per sentence: 13.2142857143 21.698381199 61% => OK
Discourse Markers: 8.42857142857 7.06452816374 119% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 2.0 4.33554083885 46% => More positive sentences wanted.
Sentences with negative sentiment : 5.0 4.45695364238 112% => OK
Sentences with neutral sentiment: 7.0 4.27373068433 164% => OK
What are sentences with positive/Negative/neutral sentiment?
Coherence and Cohesion:
Essay topic to essay body coherence: 0.145145052044 0.272083759551 53% => OK
Sentence topic coherence: 0.0497663012334 0.0996497079465 50% => OK
Sentence topic coherence SD: 0.0453960249356 0.0662205650399 69% => OK
Paragraph topic coherence: 0.0838530172809 0.162205337803 52% => OK
Paragraph topic coherence SD: 0.0243835522786 0.0443174109184 55% => OK
Essay readability:
automated_readability_index: 11.2 13.3589403974 84% => Automated_readability_index is low.
flesch_reading_ease: 49.82 53.8541721854 93% => OK
smog_index: 8.8 5.55761589404 158% => OK
flesch_kincaid_grade: 9.5 11.0289183223 86% => OK
coleman_liau_index: 13.85 12.2367328918 113% => OK
dale_chall_readability_score: 8.89 8.42419426049 106% => OK
difficult_words: 54.0 63.6247240618 85% => More difficult words wanted.
linsear_write_formula: 5.0 10.7273730684 47% => Linsear_write_formula is low.
gunning_fog: 7.2 10.498013245 69% => OK
text_standard: 9.0 11.2008830022 80% => OK
What are above readability scores?
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Rates: 85.0 out of 100
Scores by essay e-grader: 25.5 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.