Question

The correct sequence in the process of development of human embryo is

• A. fertilization—zygote—cleavage—morula—blastula— gastrula
• B. fertilization—cleavage—morula—zygote—blastula—gastrula
• C. fertilization—zygote—blastula—morula—cleavage—gastrula
• D. cleavage—zygote—fertilization—morula—blastula—gastrula

Answer 1

The Correct Option is A

The development of a human embryo is a complex process that begins with fertilization and progresses through several distinct stages. The correct sequence of these stages is important in understanding early human development. Let's go through each stage in detail:

1. Fertilization: This is the first step in the development of the embryo, where a sperm cell from the male and an egg cell from the female unite to form a zygote.
2. Zygote: After fertilization, the resultant single-celled structure is known as a zygote. It contains the combined genetic material from both parents.
3. Cleavage: The zygote undergoes a series of rapid mitotic divisions known as cleavage, leading to the formation of multiple smaller cells called blastomeres, without an increase in the overall size of the embryo.
4. Morula: Continued cleavage results in a solid ball of cells, known as the morula. This stage resembles a mulberry due to the appearance of the tightly packed cells.
5. Blastula: The morula develops a fluid-filled cavity called the blastocoel, transforming it into a blastula. This stage marks the formation of the blastocyst in mammals.
6. Gastrula: The blastula undergoes gastrulation, a process that reorganizes the blastula into a multi-layered structure called the gastrula. This stage leads to the formation of the three primary germ layers: ectoderm, mesoderm, and endoderm.

Based on this sequence, the correct order in the process of development of a human embryo is: fertilization—zygote—cleavage—morula—blastula—gastrula.