How could a paleontologist distinguish between a bryozoan fossil and a brachiopod fossil?

Question

A.  Bryozoans are large and solitary.
B.  Zoecia are always found in aggregates.
C.  You can only distinguish the two by examining the lophophore.
D.  Bryozoans often look like bivalves.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?

Gather Content
· What do you already know about lophophorates?
 Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  Zoecia are always found in aggregates.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses lophophorates.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.

Gather Content
· What do you already know about lophophorates?
        o Both Bryozoa and Brachiopoda are phyla of marine organisms with a lophophore, a circular or U-shaped ridge around the mouth with one or two rows of ciliated tentacles. The lophophore functions for gas exchange, and the cilia of the lophophore help bring food to the mouth.
        o Because of the lophophore, bryozoans and brachiopods have been considered related to one another, but some recent data indicate that the structures may have evolved convergently.
        o Bryozoans are tiny and live in colonies that look like patches of moss on the surfaces of submerged objects. Bryozoans are the only exclusively colonial animals. Each individual bryozoan—a zooid—secretes a tiny chitinous chamber called a zoecium (plural, zoecia) that is attached to rocks or other substrates such as the leaves of marine plants and algae.
        o Calcium carbonate is deposited in the wall of a zoecium in many marine bryozoans, and in early geological times, bryozoans formed reefs just as corals do today. A zooid can divide or bud to create asexually another zooid beside the existing one so one wall of the new zooid’s zoecium is shared with that of the existing one; this expanding group of zoecia constitutes a colony. Individuals in the colony communicate chemically through pores between the zoecia. Not all zoecia of a colony may be identical; some are specialized for functions such as feeding, reproduction, or defense.
        o Brachiopods and phoronids are solitary lophophorates.
        o Brachiopods, or lamp shells, superficially resemble clams, but in brachiopods, the valves are dorsal and ventral. Many species attach to rocks or sand by the pedicle (a stalk) that protrudes through an opening in one shell, whereas in others one valve is cemented to the substrate and the animal lacks a pedicle.
        o The gut in some brachiopods is U-shaped, as in bryozoans, whereas in others there is no anus at all.
 Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o The Bryozoa are always colonial, whereas the brachiopods are solitary. In other words, the zoecia (the shell-like chambers secreted by each bryozoan zooid) are always found in aggregates.
 Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that bryozoans are always colonial, but brachiopods are solitary?