TPO 43

In this set of materials, both the reading and the lecturer discuss how agnostids, a group of marine animals that lived 450 million years ago, were lived. Although the passage claims some 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 become free-swimming predators because other arthropods were hunted smaller animals. The lecturer, in contrast, rejects this by claiming that the free-swimming predators live in the open ocean, and they need to have large, well-developed eyes that can see their prey easily because vision is an important ability for animals to be a predator. However, the agnostids' fossils show that the agnostids had small eyes, and sometimes they were blind. So, for becoming a predator, they must have other organisms which used to detective smaller animals. But, their fossil records rejects this.

Going through the next approach, the reading passage argues that the agnostids would have lived on the seafloor. Nevertheless, the professor believes that seafloor animals live in a small geographic area, and they cannot move fast or travel a far distance. He explains that the seafloor animals live in small colonies and move around this; however, the fossil records show that the agnostids lived in any area with a very far distance that animals need to travel long distance.

Finally, although the reading passage says that the agnostids may have parasites which animals live on larger animals, the speaker disagrees by mentioning that the population of parasites should be small because a large number of them can kill off the host animals. He adds that scientist found a lot of the agnostids' fossils that shows their population were large. So, they cannot become parasites.