00:01
Problem number two for chapter 18 asks us to identify the pattern of embryonic development shown in each drawing, as well as name the phylum or phyla, that exited this pattern.
00:12
So on the left, for letter a, we can see that the embryo that's developing consists of only two cell layers.
00:19
We can also see that what was originally a sphere of cells is now developing a sort of indent, and what i'm referring to is this area right here.
00:29
All right, this part of development where this indent is being formed is called gastrolation because it's forming a gastrula, which is one of the first steps in becoming an organism.
00:48
Phylum that would only have two cell layers are going to include periphera or sponges and nideria.
00:57
In our next letter b, this next illustration here, we can see first of all, first and foremost, i think, that we have three cell layers.
01:08
All right, so we're no longer dealing with periphera, periphera or nideria...
