Question

A zygote is a/an
A. Implanted fertilized egg
B. Fertilized egg
C. Ovulated egg
D. Blastocyst

Answer 1

Hint: A zygote is the cell formed when two distinct gametes fuse together. These two gametes are the male gamete, the sperm, and the female gamete, the ovum. These gametes have genetic information within them in the form of DNA.

Complete answer: Ovulation is the process of liberation of an egg from the ovaries (almond-shaped bodies). Therefore, an ovulated egg is the unfertilized female gamete. The female gamete i.e., ova or egg, and the male gamete i.e., spermatozoa or sperm fuse together and form the zygote by a process called fertilization. Hence the fertilized egg is the zygote only. After the formation of the zygote, the mitotic division which is called cleavage takes place. Cleavage divisions are the slowest in the animal kingdom. Cleavage divisions result in the complete division of the zygote and the subsequent daughter cells are called blastomeres. The embryo at 16 celled stages is called morula (resemblance with a mulberry fruit). After passing through certain more stages a fluid is secreted in the morula which forms a fluid-filled cavity called blastocoel and the resulting structure is called blastocyst. Approximately after one week, the blastocyst embeds itself in the thickened wall of the uterus, a process called implantation. Therefore, an implanted fertilized egg is an implanted blastocyst.
Hence, the correct answer is option B.

Note: We should not get confused between a fertilized egg and an implanted fertilized egg. A fertilized egg is simply the zygote but an implanted fertilized egg is then implanted blastocyst when pregnancy is actually established.