Answer
After fertilization ovum and sperm unite to for a single cell (2n chromosomes0 which divides mitotically over and over for about 72 hours . At about 72 hours this ball of cells ( mulberry-looking) consists of 16 solidly bound cells. This is the morula.
Work Step by Step
Thirty six hours after fertilization, the zygote divides to give 2 blastomeres. Repeated cell divisions ( cleavages) continue in these blastomeres and their derivatives, so that by 72 hours after fertilization the ball of blastomers has about 16 cells.
The word "morula" come from the Latin which means mulberry . At 72 hours the morula is still in the distal uterine ( Fallopian) tube--trying to get to the uterus.
