Use the Information to Answer the Question

question 4

Multiple Choice

Use the information to answer the question.
One small animal phylum (Placozoa) contains only two species, Trichoplax adhaerens (T. adhaerens) and T. reptans. T. adhaerens is the only species seen in over a century. Individuals are about 1 mm wide and only 27 μm high, are irregularly shaped, and consist of a total of about 2,000 cells, which are diploid (2n = 12) . There are four types of cells, none of which are nerve or muscle cells, and none of which have cell walls. Individual animals move using cilia, and any "edge" can lead. T. adhaerens feeds on marine microbes, mostly unicellular green algae, by crawling atop the algae and trapping it between its ventral surface and the substrate. Enzymes are then secreted onto the algae, and the resulting nutrients are absorbed. T. adhaerens sperm cells have never been observed. Embryos up to, but not past, the 64-cell (blastula) stage have been observed.
On the basis of information in the paragraph, which of these should be able to be observed in T. adhaerens?

• A) a coelom
• B) the process of gastrulation
• C) eggs
• D) a radially symmetric larval form

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Definitions:

Dissolution

The process of a solid substance becoming incorporated into a liquid to form a solution.

Limestone

A sedimentary rock composed mainly of calcium carbonate, often formed from the shells and skeletons of marine organisms.

Outer Weathered Zone

The top layer of the Earth's surface, altered by weathering processes, involving the physical and chemical breakdown of rocks and minerals.

Fractured Rocks

Rocks that have been broken or cracked through natural processes or human activity, often creating pathways for the movement of fluids or gases.