I'm trying to teach myself the rest of my AP bio book before the exam, and i don't get this stuff on development and reproduction. my teacher said she didn't know because she hasn't had to teach this stuff before, so any help would be great!

1. hows the dorsal lip of the blastopore formed? i don't get it...
2. do only reptiles and amphibians have a gray crescent?
3. why does the second oocyte stay in metaphase 2 until its fertilized?
4. when and where does gastrulation usually take place?
5. whats the main function of the corpus luteum?
6. Is there a difference between an embryo and a proper embryo?
7. If humans have an embryonic disk(like the blastodisc of birds, right?) that cleaves, why are we holoblastic and not meroblastic?