edHelper.com Animal Themes Invertebrates Oceans

Sea Urchins

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Sea Urchins
Reading Level

	edHelper's suggested reading level:	grades 4 to 7
	Flesch-Kincaid grade level:	9.2

Vocabulary

challenging words:

assault, calcium, delicacy, internal, starfish, undeterred, urchin, rank, species, poisonous, reefs, underside, unique, fate, defense, pointy

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Sea Urchins

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¹     Sea urchins are like rolled-up hedgehogs. They have pointy spines projecting out of their spherically shaped bodies. These needle-sharp spikes, poisonous for some species, serve as sea urchins' best line of defense. Hiding among these spines are five paired rows of tube feet (often tipped with suckers) that sea urchins control through an internal water vascular system. By adjusting the amount of water inside, sea urchins can expand or contract their fluid-filled feet to move about, gather food, or keep a good grasp of rocks.
 
²     Beneath their intimidating assault weapons and means of transportation, sea urchins cover their bodies with a hard skeleton (also called a test). Upon a closer look, we can see that the skeleton is made up of ten fused calcium carbonate plates.
 
³     Sea urchins are grazers. As they travel along the ocean floor, they use their mouths, located at the center of their underside, to pick up scraps of food (such as algae and dead fish). Sea urchins have a unique dental apparatus called the Aristotle's lantern around their mouths. The lantern consists of five hard, tooth-like, inward-pointing plates. Sea urchins rely on this special structure to scratch edible particles off rocks.

Paragraphs 4 to 5:
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