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Photo essays are an increasingly popular medium for journalists, bloggers, and advertisers alike. Whether you’re trying to show the emotional impact of a current news story or share your hobby with friends and family, images can capture your topic in a personal, emotional, and interesting way. Creating a photo essay can be as easy as choosing a topic, getting your images, and organizing the essay.
Symmetry has a variety of causes. Radial symmetry suits organisms like sea anemones whose adults do not move: food and threats may arrive from any direction. But animals that move in one direction necessarily have upper and lower sides, head and tail ends, and therefore a left and a right. The head becomes specialised with a mouth and sense organs ( cephalisation ), and the body becomes bilaterally symmetric (though internal organs need not be).  More puzzling is the reason for the fivefold (pentaradiate) symmetry of the echinoderms. Early echinoderms were bilaterally symmetrical, as their larvae still are. Sumrall and Wray argue that the loss of the old symmetry had both developmental and ecological causes.