TPO 43 Integrated Writing Task

The reading passage explores several theories regarding how agnostids, extinct arthropods-relatives, survived in ancient times. Although these points seem reasonable, the lecturer casts doubt on them, pointing out some cons for the following reasons.
To begin with, even though the author suggests that agnostids could be predators that hunted small prey by swimming in the ocean and there were several primitive arthropods exhibiting similar behavior, the lecturer argues that it is a misconception. This is because most free-swimming arthropods have well-developed eyes that help them detect their prey. Nonetheless, it was discovered that agnostids only had tiny and poor eyes. Furthermore, there wasn’t fossil evidence of agnostids that had other sensory organs. Thereby, without good sensory systems, the lecturer believes that agnostids were unlikely to be predators.
Second, the author points out that agnostids could also dwell on the seafloor where they could feed on dead organisms or bacteria. On the other hand, the lecturer illustrates that, because of the poor ability to move fast and far, most similar seafloor dwellers could only live in certain fixed areas without moving around. Nevertheless, the agnostids inhabited widely scattered areas, indicating that agnostids were able to move across long distances. Accordingly, the lecturer dismisses the idea that agnostids could be seafloor dwellers.
Last but not least, the lecturer acutely identifies the weakness in the reading passage that agnostids were parasites. The lecturer points out that most normal parasites have low populations so as not to pose fatal impacts on the host species that they live on. In contrast, agnostids were discovered in large populations, which ruled out the possibility that they were parasites.