Subject: 5 - Make a cat!
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Posted on: 2009-09-14 14:49:00 UTC

To make a cat, you must first make a deuterostome.
Take an ovocyte, make it divide for a certain number of times, until you get a hollow sphere called a blastula.
Then, fold one half of the blastula inside the other and stretch it somewhat (the exact way depends on species). You'll obtain a gastrula, with a hole at one end which will become the anus. The ectoderm (outer layer), mesoderm (filling the former hole of the blastula) and endoderm (inner layer) are formed at this step. You have now a deuterostome.
Then, you'll have to get a chordate.
Development continues with neurulation: the neural tube is formed by folding the dorsal ectoderm along the notochord (structure existing in all chordate embryos, but which persists in only a few chordate species). Then, somites (corresponding to future vertebrae) form, one after the other. You have a chordate.
With a chordate, you then make a vertebrate, a gnathostome (jawed vertebrate, jaws form from branchial arcs), an osteichthyan (the name means bony fish, as opposed to cartilagenous fish (chondrichthyan), but it also includes tetrapods as well). Than you get a tetrapod, by forming the limbs. The tetrapod becomes then a mammal and then a cat.
Let the cat grow for a while, and you're done.

Well, in fact, it's a bit more complicated, but that's a rough outline.

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