Exam 40: Annelids, Molluscs, Nematodes and Arthropods

Molluscs that exhibit torsion have the unusual situation of dealing with their anus discharging directly over their head and mouth. Which of the following arguments can explain this phenomenon?

It would be correct to describe annelids as

The coelom probably evolved in the first annelids

Which of the following characteristics is true of a pseudocoelom?

Compared to other molluscan groups, cephalopods have a particularly well developed

Peristaltic locomotion is dependant on

A feature that distinguishes insects from crustaceans can be most easily seen in

Gastropods show major evolutionary changes relative to molluscs in that

Metameric segmentation

Both annelids and arthropods share the features

The group of arthropods that includes the insects is called the Uniramia because

In cephalopods, chromatophores

Insects are important to human activity because they are often

The coelom in arthropods

In pulmonate snails, gas exchange occurs

The Cuticulata, which includes diverse organisms such as arthropods and nematodes, is so called because

An entomologist is asked to examine an unknown organism from the Cuticulata that has a head plus four additional segments, 8 legs and is only around 1mm in length. However, it is late on a Friday afternoon and the scientist really wants to go to the pub, so he decides to leave the examination until the following week. He cleans up his bench and accidentally puts the unknown organism in a freezer over the weekend. Realising his mistake on the Monday, he removes the organism from the freezer and leaves it on his bench to defrost before deciding what to do. Distracted, he forgets about the organism again and in his absence a colleague sets up an experiment on his bench using a hot flame, which heats the organism to more than 80 $\degree$ C and desiccates it almost completely. Upon returning to his bench, the scientist is convinced that the organism must surely be dead, but to his surprise he discovers that once some moisture is added and it returns to ambient temperature, the organism shows signs of life. Ironically, this litany of errors has made the scientist's job much easier as to survive such conditions this organism must be a(n)

Metanephridia, which are open tubes with funnels,

Tagmata are

The modern molluscan class in which the visceral mass has undergone torsion contains