Question

after the blastocyst undergoes implantation, it becomes a(n) ______.

a fetus
b zygote
c morula
d embryo

Explanation:

Identify the stages of early development

Using the Human Prenatal Development knowledge point, we trace the sequence of early human development:

1. Fertilization creates a single-celled zygote.
2. Cleavage divisions turn the zygote into a solid ball of cells called a morula.
3. Further division and fluid accumulation form a hollow ball of cells called a blastocyst.

Determine the post-implantation stage

Using the Embryonic Stage knowledge point, we identify the transition that occurs during implantation:

• The blastocyst embeds itself into the uterine lining (implantation).
• Once successfully implanted, the developing organism enters the embryonic period and is officially referred to as an embryo.
• The embryonic stage lasts until about the eighth week of development, after which it becomes a fetus.

Evaluate the given options

• a Fetus: This stage begins at week 9 of development, well after implantation.
• b Zygote: This is the single-celled stage immediately following fertilization.
• c Morula: This is an early pre-implantation stage consisting of a solid ball of cells.
• d Embryo: This is the correct term for the developing organism after implantation.

Answer:

• a Fetus
• b Zygote
• c Morula
• d Embryo (Correct answer)