One of the most primitive creatures with a body, placazoans were discovered when they developed on the walls of an aquarium in the 1880s. Though they are flat plate shaped disks that only have four different types of cells, placazoans show the division of labor between cells to qualify as an actual multi-cellular body. Some cells take care of movement while others handle digestion of food. Placazoans have never been observed in a natural habitat.
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Placazoan Term Timeline in Your Inner Fish
The timeline below shows where the term Placazoan appears in Your Inner Fish. The colored dots and icons indicate which themes are associated with that appearance.
Chapter 7: Adventures in Bodybuilding
...on the glass walls of the fish tanks. This blob is now known as a placazoan, a very simple creature with only four different types of cells in its plate-shaped body....
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Going even further back, sponges have bodies that are simpler than placazoans. The “body” of a sponge is actually a non-living silica complex with collagen interspersed. In...
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Placazoans and sponges are as simple as bodies can get. To find out anything more, Shubin...
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