"And when the seasons change again then I will too
But I just wanna be closer to you"
Brandi Carlile - Closer to You
Happy Darwin Day! How have you advanced the values of inquisitiveness and intellectual integrity today?
Let's see... what would make a good evolutionary topic? Aha!
Compare Exhibit A to Exhibit B, ignoring color for the moment. Do they seem like the same organism to you? Both are actually groups and not a single critter. Both are funnel-shaped and elongated with a narrow point of attachment at their base. Both grow in roughly spherical colonies, orienting themselves with a flattened "mouth" part outward to slurp in their prey. Both might be perfectly at home in your nearest stream or lake, depending on where you live. Both are even roughly the same size, from one-tenth to just under half a millimeter in length.
Yet A is a rotifer, an animal composed of a thousand or more cells. B is a single-celled eukaryote, a ciliated protist, called Ophrydium. Its green color comes from hundreds of smaller intracellular symbiotic Chlorella algae. The two organisms are separated by several hundred million years of evolution. They haven't shared a common grandma since before most instructional videos even bother measuring continental drift. In fact, according to modern classifications, ciliates along with the other alveolates are more closely related to the grass in your back yard than to you, me, rotifers, all other animals or even the mold under your toenails. Aside from bacteria, there are few things in the world less related than those two hungry-hungry specks of life.
But hey, at that size and in that environment and with those nutritional capabilities, that shape and organization just... works! And that's what life does: whatever works. I guess we can chalk up yet another of the endless examples of convergent evolution along with fins and wings and the various filamentous photosynthesizers we so naively lump together as "algae" at first glance.
Now, call me petty but for me it's not a Darwin Day without a jab at brain-dead creationists, so ask yourself the usual question: why the mind screw? Why the ever-loving fuck would any "intelligent designer" go to the trouble of separating these two organisms 600,000,000 laps around the sun ago only to re-mold them to almost exactly the same size, shape and function just to confuse biology students straining their eyes through a microscope in 2019?
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P.S. Though I can barely guess my way around a few words of Portuguese, I must say the Brazilian website Planeta Invertebrados boasts a very impressive collection of photographs on the topic of... well, invertebrados.
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