Embryonic Development and Body Symmetry

GAMETE

sex cell

ZYGOTE

fertilized egg

MORULA

solid ball of 32 cells

BLASTULA

hollow ball of cells

BLASTOPORE

indentation that forms on a blastula

BLASTOCOEL

the fluid-filled cavity of a blastula

GASTRULA

an embryo at the stage following the blastula, when it is a hollow cup-shaped structure having three layers of cells.

ECTODERM

outermost germ layer

MESODERM

middle germ layer

ENDODERM

the inner germ layer

ECTODERM

germ layer that produces sense organs, nerves, and outer layer of skin

ENDODERM

germ layer that develops into the linings of the digestive tract and much of the respiratory system

MESODERM

germ layer that develops into muscles, and much of the circulatory, reproductive, and excretory systems

DIGESTIVE

1st body system to form in development

ARCHENTERON

The endoderm-lined cavity, formed during gastrulation, that develops into the digestive tract of an animal.

ANTERIOR

the head end of a frog

POSTERIOR

the end of the frog with the anus

DORSAL

the back surface of the frog

VENTRAL

the surface with the "belly" of the frog

RADIAL SYMMETRY

body plan in which body parts repeat around the center of the body; can be cut many ways to get two identical halves

BILATERAL SYMMETRY

Body plan in which only a single, imaginary line can divide the body into two equal halves.

ASYMMETRICAL

no symmetry