The passage and lecture are both about Agnostids which were a group of marine animals that extinict about 450 million years ago The passages claims that there are several different theories about how agnostids may have lived The lecturer casts doubt on cl

The passage and lecture are both about Agnostids which were a group of marine animals that extinict about 450 million years ago. The passages claims that there are several different theories about how agnostids may have lived. The lecturer casts doubt on claim made in article, she states, these theories are weak to illustrate how these animals have lived.
First, the author says agnostids were free- swimming predators and can hunt smaller animals, because agnostids were a type of primitive arthropods which were a strong swimmers and active predators. This point challenged by lecturer, she states, the predators always have a large eyes to be abile to follow their preys and couch them, instead agnostids had a very small eyes and may be blind, therefore they could not be as a swimming – predators unless they might have a specific organ to detect their preys.
Second, the argues, agnostids may have dwelled on the seafloor, there are plenty of small organisms in the ocean for them to prey on. This argument is rebutted by professor, she posits, the animals which live in seafloor do not have ability to move fast and stay in localized area, but angostids do not stay in small area , they were found in large area and with long distance , that give a prove these animals move fast.
Finally the writer says, there is possibility that the agnostids were parasites, because many modern species of arthropods exist as parasites. The lecturer in the other hand suggests, parasites are small population which stay on a large animal to prey on it, the agnostids were very large population and many fossils found in many areas, therefore this role out the theory about agnostids may be parasits.