TPO 43

The article and the lecture are both about Agnostids, which were a group of marine animals that became extinct. The author of the reading believes that there are three theories that explain how agnostids may have lived. However, the professor casts doubt on the claims made in the article. She explains that each of these theories have serious problems.

First, the reading claims that the agnostids may have been free-swimming predators. This theory is challenged by the professor. She says that all the other types of swimming predators had large, well-developed eyes and agnostids had tiny, poor-developed eyes. She believes that agnostids couldn't have been swimming predators because of this characteristic.

Second, the articles posits that agnostids may have been seafloor dwellers. However, the professor challenges this point by saying that all seafloor dwellers move very slowly and stay in their local area. Furthermore, she points out that each of the seafloor dwellers occupy only a small area. She mentions that this is not true about agnostids. She explains that agnostids have inhabitted multiple areas and they must have been able to move quickly and easily.

Third, the reading says that agnostids may have been parasites. The professor opposes this point by explaining that the population of parasites couldn’t be large, because the large number of parasites would kill the host enviroment. She explains that the great population of agnostids rules out this theory.