Cnidarian Worksheet: Fill & Download for Free

I hate questions like this. It’s not the fact that this question is coming from someone who wants help with his or her homework; I can live with that. But it’s that the question’s so dull—so un-representative of what biological diversity is freakin’ about.Somebody who writes Educational Materials thought something like “OK, we have to make these kids regurgitate some canned answer that their teacher can quickly grade, so let’s pull some number out of our posteriors and make the kids look up that many number of invertebrates.” I’m sorry if I sound ranty, but I see so many questions like this on Quora, and I get peeved at whoever’s giving assignments like this, because I’m just not convinced that this is any way to learn something that will be retained.So whoever wrote this question, if I’m right and you asked this question because it’s part of a school assignment, I want you to tell your teacher the following:“Invertebrates make up 97% of all animal species. There are roughly thirty ‘major types’ of invertebrates—or phyla, as scientists call them. Just rattling off five names of them is a crime against biodiversity education, and a stultifying exercise of dubious pedagogical value that will bring down the wrath of Aldo Leopold upon us all. Instead, I’ve brought you a single bucketful of mucky water from a nearby lake, including some of the mud on the bottom, a few plants growing on the bottom, and some green gloppy stuff floating on top. If you look at samples of it under a microscope, you will almost certainly spot rotifers and nematodes. Rotifers swim with cilia on their “heads”; nematodes thrash their bodies back and forth.“The water will also probably have lots of microscopic arthropods—animals with a firm outer cuticle and jointed legs—such as this copepod. This one’s called Cyclops because it has only one eye in the center of its head. You can tell this is a female because she’s carrying around two masses of eggs. Oh, and we might also spot larvae of crawfish, “water fleas” or Daphnia, and diverse insect larvae, all of which are also arthropods.“Finally, let’s leave this bucket undisturbed in a quiet place for 24 hours. We’ll almost certainly see flatworms crawling up the sides of the bucket. As the water down deeper in the bucket runs out of oxygen, the flatworms crawl up to the air-water line. The kind we’ll find are probably a type called “planaria”. Some planarians (Dugesia) are large and often used in biology classes. But the last time that this dashingly handsome and brilliant scientist who writes on Quora made his students do this exercise with water and muck from a local lake, what they actually found were worms more like this Polycoelis worm.“And we may also spot cnidarians, a group that includes jellyfish and corals. There is in fact a jellyfish species that lives in freshwater lakes, good ol’ Craspedacusta sowerbyi, but actually spotting that one can be hit or miss. But we’ve got a good chance of finding Hydra attached to the sides of the bucket. Those tentacles contain ‘stinging cells’ that inject venomous barbed threads into an unsuspecting small arthropod, like Cyclops—and then the whole animal contracts, pulling the prey down to the mouth within the center of the ring of tentacles.“So we can find five major types of invertebrates in a typical pond or lake, without even really trying hard. We can learn far more by looking for ourselves than by doing crappy worksheets that we try to cheat on by posting questions on Quora. So why don’t you just junk the lesson plan for the week, get the school board to buy us a few inexpensive microscopes when they’re done paying for the Jumbotron on the football stadium—and then let’s all learn by actually looking at what we’re studying?”