Question

after several cycles of cell division, a fertilized cell develops into a hollow ball of cells called a(n)

amnion

fetus

blastocyst

follicle

Explanation:

🆕 New Concept Discovered: stages of early embryonic development
Early milestones from fertilization to implantation

Step 1: Understand the process of cleavage

After fertilization, the single-celled zygote undergoes rapid mitotic cell divisions called cleavage. This process increases the number of cells without increasing the overall size of the developing organism.

Step 2: Identify the stages of development

As division continues, the cells form different structures:

• Morula: A solid ball of cells (usually around 16 cells).
• Blastocyst (or blastula in non-mammals): As division continues, a fluid-filled cavity forms in the center, turning the solid ball into a hollow ball of cells.
• Fetus: A much later stage of prenatal development (in humans, starting from the 9th week of gestation).

Step 3: Evaluate the given options

• amnion: The innermost membrane that encloses the embryo/fetus in fluid.
• fetus: A later stage of development with recognizable features, not a simple hollow ball of cells.
• blastocyst: The hollow ball of cells formed after several rounds of cell division.
• follicle: A fluid-filled sac in the ovary that contains an immature egg.

Therefore, the correct term for the hollow ball of cells is the blastocyst.

Answer:

blastocyst