Scenario Several Studies Involving Molecular Analyses of Comb Jellies, Also Known

question 22

Multiple Choice

Scenario
Several studies involving molecular analyses of Comb jellies, also known as sea gooseberries, cast doubt on the theory that sponges are the oldest animal phylum. Reported results of the studies suggested that Comb jellies, more complex animals having muscles and a nervous system, may actually be the true, first phylum of animals that diverged from a metazoan common ancestor. However, in 2015, a team of scientists re-analyzed the genetic data in the Comb jellies research with more specialized methods, and they determined that sponges were indeed the oldest animal phylum.
-Suppose that the re-analysis of the genetic data confirmed that Combjellies are the oldest animal phylum. It is therefore likely that their complex traits, such as organ systems, would probably have been present in the common ancestor as well. Therefore, any organisms that would have diverged from the common ancestor after the comb jellies, such as sponges, should likely have similar organ systems. What is the best hypothesis for why sponges do not have a nervous system?

• A)As sponges evolved over time, they lost the nervous system.
• B)The amoebocytes that make the fibers of a sponge skeleton were not strong enough to support a nervous system.
• C)As suspension feeders, sponges could not take in enough nutrients to support the development of a nervous system.
• D)As stationary animals, sponges could not move to avoid predators, so they don't live long enough to develop a nervous system.