NEET BIOLOGY

Detailed explanation-1: -The early stages of embryonic development, such as fertilization, cleavage, blastula formation, gastrulation, and neurulation, are crucial for ensuring the fitness of the organism. Fertilization is the process in which gametes (an egg and sperm) fuse to form a zygote.

Detailed explanation-2: -The early stages of embryonic development begin with fertilization. The process of fertilization is tightly controlled to ensure that only one sperm fuses with one egg. After fertilization, the zygote undergoes cleavage to form the blastula.

Detailed explanation-3: -After fertilization, the development of a multicellular organism proceeds by a process called cleavage, a series of mitotic divisions whereby the enormous volume of egg cytoplasm is divided into numerous smaller, nucleated cells. These cleavage-stage cells are called blastomeres.

Detailed explanation-4: -The first two weeks after conception are known as the germinal stage, the third through the eighth week is known as the embryonic period, and the time from the ninth week until birth is known as the fetal period.

Detailed explanation-5: -Each layer gives rise to specific tissues and organs in the developing embryo thus, the correct sequence is: Zygote–> Morula–> Blastula–> Gastrula–> Embryo.