The reading and lecture are both agnostids which existed 450 million years ago.

The reading and lecture are both agnostids which existed 450 million years ago. The fossil that in modern-day remains could not able to provide the characteristic of the agnostids. The author of the reading feels that there are several theories that they might exist. The lecturer challenges the claim made by the author. he expresses doubt about the explanation of the claim. To begin with, the author argues that agnostids were very small and free-swimming predator. The article also mentions that though it was a very small predator still it hunted plenty of smaller organism. The specific argument is challenged by the lecturer. He claims that for preying animals need very good vision for praying. But, it had very small eyes and moreover, for hunting other sensory organ is essential which is not specified in this theory properly. Secondly, the writer suggests that agnostids possibility habitat on the seafloor, by the way, primitive arthropods living there. In in the article, it is said that they fed the scavenging dead organisms or bacteria. The lecturer, however, rebut this by mentioning that seafloor dwellers are not able to move so fast. but, the agnostids fossile had found from different distance. Therefore they were able to travel from one place to another. So, the theory is clearly vague and incomplete. Thirdly, the author posits that it is possible that agnostids were lived as a parasite because many arthropods in modern days live as parasites. In contrast, the lecturer position is that too many parasites are harmful to the host animal and moreover it can kill the host organism. He notes that the researcher had found huge population of the agnostids. so, the third theory is not convincing.