Algae are among the most abundant creatures on earth, growing rampantly in lakes, puddles, and even aquariums. The word algae usually brings to mind stagnant ponds covered with green sludge. Contrary to their foul reputation, algae are amazingly beautiful, diverse, and vital to life. They fill the seas, whether as solitary individuals or as gently swaying "kelp forests," which feed an immense variety of hungry ocean-going creatures. Under the microscope, algae populate a marvelous world of light-gathering, twirling, and spinning creatures. One of the most fascinating is Volvox. Just barely visible as a pale green dot to the human eye, under a microscope they appear like spherical, translucent spaceships, composed of thousands of dancing algae cells, sailing through the water.
A closer inspection shows a small biological wonder, a "colony" of up to thousands of individual "rowing" cells working together to move the floating ship. For decades microbiologists have been baffled how these cells cooperate without a brain or even a single nerve cell to guide them.
Even more puzzling, cells that are separated from the colony look just like any other single-celled algae, with two flagella (spinning whiplike propellers common in many one-celled organisms) and an eyespot (a basic "eye" which senses light). In a pond or the ocean, these single-celled algae would get lost in the crowd.
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