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 passage discusses three possible theories of how agnostids may have lived based on several reasons. Although these reasons appear to have considerable merits, the lecturer casts doubt on them due to the following reasons.
First of all, the passage claims that agnostids may have been free-swimming predators that hunted smaller animals. However, the lecture points out that a predator must have a clear vision to hunt for prey while the fossil records of agnostids show they only have tiny eyes and are possibly blind. Without a clear vision, agnostids may require sensory organs to sense for the outer world, yet the fossils do not record any.
The second theory assumes that agnostids may be seafloor dwellers. Nonetheless, the lecturer refutes this theory by pointing out seafloor dwellers typically can't move fast, they are usually localized while agnostids' habitats spread across large distances.
The third theory considers agnostids as parasites. Yet the lecturer repudiates the theory with the conception that the parasites' population can't be large, they need to stay off certain limits otherwise they may kill the host. The lecturer further supports her own position by mentioning that agnostids usually appear in a vast amount in fossils.
| Post date | Users | Rates | Link to Content |
|---|---|---|---|
| 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 5, column 158, Rule ID: CANT[1]
Message: Did you mean 'can't' or 'cannot'?
Suggestion: can't; cannot
...ointing out seafloor dwellers typically cant move fast, they are usually localized w...
^^^^
Line 7, column 120, Rule ID: POSSESIVE_APOSTROPHE[1]
Message: Possible typo: apostrophe is missing. Did you mean 'parasites'' or 'parasite's'?
Suggestion: parasites'; parasite's
...the theory with the conception that the parasites population cant be large, they need to ...
^^^^^^^^^
Line 7, column 141, Rule ID: CANT[1]
Message: Did you mean 'can't' or 'cannot'?
Suggestion: can't; cannot
...onception that the parasites population cant be large, they need to stay off certain...
^^^^
Transition Words or Phrases used:
first, however, may, nonetheless, second, so, third, well, while, first of all
Attributes: Values AverageValues Percentages(Values/AverageValues)% => Comments
Performance on Part of Speech:
To be verbs : 5.0 10.4613686534 48% => More to be verbs wanted.
Auxiliary verbs: 7.0 5.04856512141 139% => OK
Conjunction : 3.0 7.30242825607 41% => More conjunction wanted.
Relative clauses : 6.0 12.0772626932 50% => More relative clauses wanted.
Pronoun: 14.0 22.412803532 62% => OK
Preposition: 20.0 30.3222958057 66% => OK
Nominalization: 3.0 5.01324503311 60% => More nominalizations (nouns with a suffix like: tion ment ence ance) wanted.
Performance on vocabulary words:
No of characters: 1065.0 1373.03311258 78% => OK
No of words: 198.0 270.72406181 73% => More content wanted.
Chars per words: 5.37878787879 5.08290768461 106% => OK
Fourth root words length: 3.75116612262 4.04702891845 93% => OK
Word Length SD: 2.52157813485 2.5805825403 98% => OK
Unique words: 128.0 145.348785872 88% => More unique words wanted.
Unique words percentage: 0.646464646465 0.540411800872 120% => OK
syllable_count: 319.5 419.366225166 76% => 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: 8.0 8.23620309051 97% => OK
Subordination: 1.0 1.25165562914 80% => OK
Conjunction: 2.0 1.51434878587 132% => OK
Preposition: 1.0 2.5761589404 39% => More preposition wanted as sentence beginning.
Performance on sentences:
How many sentences: 10.0 13.0662251656 77% => Need more sentences. Double check the format of sentences, make sure there is a space between two sentences, or have enough periods. And also check the lengths of sentences, maybe they are too long.
Sentence length: 19.0 21.2450331126 89% => OK
Sentence length SD: 43.8872418819 49.2860985944 89% => OK
Chars per sentence: 106.5 110.228320801 97% => OK
Words per sentence: 19.8 21.698381199 91% => OK
Discourse Markers: 7.8 7.06452816374 110% => OK
Paragraphs: 4.0 4.09492273731 98% => OK
Language errors: 3.0 4.19205298013 72% => OK
Sentences with positive sentiment : 4.0 4.33554083885 92% => OK
Sentences with negative sentiment : 3.0 4.45695364238 67% => 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: 0.149048974666 0.272083759551 55% => OK
Sentence topic coherence: 0.0714276342189 0.0996497079465 72% => OK
Sentence topic coherence SD: 0.0402746908918 0.0662205650399 61% => OK
Paragraph topic coherence: 0.0894136932749 0.162205337803 55% => OK
Paragraph topic coherence SD: 0.0320290877193 0.0443174109184 72% => OK
Essay readability:
automated_readability_index: 13.8 13.3589403974 103% => OK
flesch_reading_ease: 52.19 53.8541721854 97% => OK
smog_index: 3.1 5.55761589404 56% => Smog_index is low.
flesch_kincaid_grade: 10.7 11.0289183223 97% => OK
coleman_liau_index: 13.92 12.2367328918 114% => OK
dale_chall_readability_score: 9.04 8.42419426049 107% => OK
difficult_words: 56.0 63.6247240618 88% => OK
linsear_write_formula: 9.0 10.7273730684 84% => OK
gunning_fog: 9.6 10.498013245 91% => OK
text_standard: 14.0 11.2008830022 125% => OK
What are above readability scores?
---------------------
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.