Which of the following is the last stage of mammalian development to occur before implantation in the uterus?
A - Morula
B - Ovum
C - Blastocyst
D - Zygote
Answer: C - Blastocyst
The BLASTOCYST is the last stage of mammalian development before implantation. It is the specialized mammalian blastula (occurs after the trophoblast cells secrete fluid into the middle of the morula forming a hollow ball of cells) that contains the two different cell types (the trophoblast cells and the cells of the ICM).