Test: Fertilization and Implantation (NCERT) - NEET MCQ

After fertilisation, a single-celled zygote develops into a multicellular structure called blastocyst. This blastocyst then gets embedded in the endometrium of the uterus and the process is known as implantation.

Solution:

• Statement (i) is incorrect: Cleavage divisions do not increase the mass of protoplasm; they divide the existing protoplasm into smaller cells without growth in size.
• Statement (ii) is correct: With each cleavage division, the blastomeres do become smaller.
• Statement (iii) is incorrect: The blastomeres in the blastocyst are arranged into the trophoblast and the inner cell mass, not the endometrium.
• Statement (iv) is correct: Cleavage divisions result in a solid ball of cells called the morula.

Thus, the correct statements are (ii) and (iv).

let's analyze the terms:

• Cleavage refers to a series of rapid mitotic divisions.
• Morula is a stage in embryonic development, often described as a "little mulberry" due to its appearance.
• Polyspermy refers to the fertilization process involving multiple sperm.
• Implantation refers to the embedding of the embryo into the endometrium of the uterus.

Now let's match these terms:

• Cleavage - (ii) Mitotic divisions
• Morula - (iv) Little mulberry
• Polyspermy - (i) Fertilization
• Implantation - (iii) Endometric

Correct option is A. 

• Zygote undergoes cleavage producing an exponential increase in cell mass.
• These new daughter cells formed are called blastomeres.
• They form a blastula with a blastocoel cavity enclosed in between.

Insemination is the process of the release of semen by the penis into the vagina during copulation. The sperm is released into the female reproductive part. This sperm released travels through the cervix enters to the ureter and reached the junction of the isthmus and ampulla and this is the region of fertilization or fusion. the sperm and the ovum should be transported to this junction at the same time. Zona pellucida that contacts the sperm brings about changes in the egg membrane and blocks the entry of additional sperms as a result. The secretions of the acrosome a part of the head of the sperm that includes enzymes to penetrate the ovum helps the sperm enter into the cytoplasm of the ovum.

So, the correct option is '(i) - insemination, (ii) - ampullary isthmic junction, (iii) - fertilization, (iv) - additional sperms, (v) - acrosome'.

• Fertilization is one of the first processes that may result in pregnancy.
• Cleavage is the division of zygote that give rise to blastomeres.
• Lactation occurs to post-pregnancy. Implantation is the attachment of the developing embryo to the uterine wall.
• This is the last step that leads to pregnancy.

Implantation is embedding of the blastocyst into the endometrium of the uterus. Implantation begins about 7th day after fertilization of ovum and it takes about 3 days for the process to be completed.

During fertilization, the head of the sperm containing nucleus (DNA) enters the egg leading to formation of diploid zygote.