TPO 43

In this set of materials, both the reading and the lecturer discuss the possible behavior and lifestyle of agnostids, a group of marine animals that become extinct 450 million years ago. Although the passage provides three theories about how agnostids may have lived, the speaker refutes all of the arguments described in this reporter.

To start off, the passage points out that the agnostids would have been free-swimming predators that hunted smaller animals. The lecturer, in contrast, rejects this by claiming that free-swimming predators that are good hunters have well-developed eyes because they need to see and detect preys. On the other hand, she adds that analyses of the agnostid's fossils show that they had poor eyesight, and in some cases, they were blind; hence, they must have another organism for finding and hunting prey. But, there is not any evidence of such abilities in the fossil records.

Going through the next approach, the reading passage states that the agnostids would become seafloor dwellers. However, the professor argues that the seafloor dwellers do not move fast or travel a far distance. They live and localize in a small geographic area that had originated. Nevertheless, the fossils of agnostids were discovered in multiple geographic areas, so they were able to swim pretty fast. Therefore, it is unlikely for the agnostids to be seafloor dwellers.

Finally, although the passage says that the agnostids may have been parasites that were living and feeding off larger animals, the speaker disagrees by mentioning that the population of parasites must be small and stay in a limited size. If their population become large, they may kill their host animals. She explains that the agnostid's fossils are founded in multiple areas that show they had a large population which could reject the theory of being parasites.