TPO 43

The lecture and the reading passage discuss agnostids, a group of marine animals that became extinct 450 million years ago and were primitive anthropods-relatives of modern-day insects. Although the passage claims some theories about how agnostids may have lived, the speaker refutes these ideas through a number of reasons which I will describe in this report.
First and foremost, the passage points out that agnostids may have been free-swimming predators that hunted smaller animals. The lecturer, in contrast, rejects this by claiming that other arthropods which are good hunters have large well-developed eyes because vision is an important ability for animals to be a predator. On the other hand, agnostids were blind or had a poor eyesight, so they must had other abilities for finding and hunting preys, but there is not any evidence of such as these abilities in fossil records, and it is less probable that they were free-swimming predators.
Furthermore, unlike the passage which states that agnostids may have been seafloor dwellers like some other primitive arthropods, the professor argues that seafloor dwellers typically do not have the ability to move fast, and they usually live in a specific geographic area all of their living periods. Conversely, fossil records show that agnostids lived in multiple geographic areas, and they were able to move fast. Therefore, it is unlikely for agnostids to be seafloor dwellers.
Finally, although the passage says that agnostids may have been parasites because a large number of modern-day anthropods are parasites, the speaker disagrees by mentioning that the population of parasitic could not be very large because if they become expanded, their host animal may become extinct. But the fossil records shows that agnostids had a large population which could reject the theory of being parasites.