Comparative Anatomy - Chapter 2 Terms

Blastocyst

early stage of embryo described as a “ball of cells”

Cleavage

division of cells are aligned as they divide.

radial cleavage

cells are aligned as they divide

spiral cleavage

cells are offset from each other

Gastrulation

cells growing inward; these indented cells become the gut and continue until they reach the other wall, and then they usually break through and form a second ring

Blastopore

first opening into the indentation of gastrulation

ectoderm

outer layer

endodermla

inner layer that forms the lining of the gut

mesoderm

middle layer between the ectoderm and endoderm

coelom

internal body cavity

Schizocoelom

body cavity made form solid mass of mesodermal cells splitting

enterocoelom

body cavity forming from the outpocketing of the gut that pinches off

Chordate Characteristics

1. Notochord

2. Pharyngeal slits

3. Endostyle or thyroid gland

4. Dorsal hollow nerve cord

5. Postanal Tail

Myomeres

blocks of serially repeated muscles that run the length of the adult body and tail

Pelagic

residing in open water between the surface and the bottom

planktonic

riding from place to place primarily in currents and tides rather than their own efforts

benthic

living on or within a marine substrate

dioecious

two sex organs

monoecious

one sex organ

Patterning

specifying general regions of an embryo which determines where body parts are positioned