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• Image Gallery
Worms, Chordates, and Algae
Worms
The term “worm” refers to several different groups of animals that have a similar body shape. Two groups of worms appeared in the Cambrian Period that still exist today.
Annelid (ANN-uh-lid) worms have segmented or “ringed” bodies and tiny bristles that help them move about.
Priapulid (pree-a-PEW-lid) worms have unusual spike-lined mouths they can turn inside out for feeding. The spikes snag prey, which the worms gulp down by pulling their mouths back inside their bodies.
Chordates
Chordates (CORE-dayts) include some very familiar animals: us. Although the first chordates look very different from us, all chordates share two features that run lengthwise along our backs: a nerve cord on top of a tough but flexible rod called a notochord.
Humans have a notochord only as embryos. As we develop, the backbone forms around it.
Algae
“Algae” (AL-jee) refers to several different groups of organisms that are photosynthetic—they have colored pigments that help turn the sun’s energy into food. Based on the colors of these pigments, scientists recognize different types of algae, such as red, brown, and green algae.
During the Cambrian and Ordovician Periods, algae were food and shelter for an increasing diversity of animals. Like algae living in today’s waters, some Ordovician algae were free-floating; others were attached to the seafloor or another surface.
Continue to Bryozoan and Graptolite Images. >>
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