After ovulation, the remaining parts of the Graafian follicle transform into the corpus luteum, which secretes large amounts of progesterone. Progesterone is crucial for maintaining the endometrium, preparing it for the potential implantation of a fertilized ovum. If fertilization does not occur, the corpus luteum degenerates, leading to a decrease in progesterone and subsequent disintegration of the endometrium, resulting in menstruation.

Polyspermy is prevented by Depolarization of membranes due to entry of sperm leading  to influx of Ca+ ions and then cortical granules release to prevent further fusion of sperms.

• The secondary oocyte released from the ovary has finished first round of meiosis.
• The second round of meiosis occurs in ampulla after the egg encounters the sperm.
• This leads to formation of large ovum and a tiny second polar body.

The fusion of sperm and egg restores the chromosome number.

The new cell is called zygote having the potential to develop into a new organism.

• Sperm and egg are haploid cells hence have only one set of chromosomes.
• Zygote on the other hand is diploid thus has 46 chromosomes.

Acrosome contains an enzyme hyaluronidase which breaks the covering of the ovum.

Polyspermy

- Polyspermy occurs when more than one sperm cell successfully fertilizes an egg.
- This can lead to abnormalities in the resulting embryo, as multiple sets of chromosomes from different sperm can cause genetic complications.
- In most cases, polyspermy is prevented by the egg 's zona pellucida, which only allows one sperm to penetrate and fertilize the egg.
- If polyspermy does occur, it can result in failed fertilization or the development of an embryo with too many chromosomes.
- Polyspermy is usually considered a detrimental outcome in fertilization, as it can lead to miscarriage or developmental issues in the resulting offspring.

Fertilization is defined as a process of fusion of male and female gametes. The gametes are special haploid cells. The most widely accepted definition of species is the biological species- according to which members of same species alone can carry on the process of sexual reproduction (including fertilization) and produce fertile  offspring.

Image showing fertilization

The fertilization of the ovum with only one sperm is termed as monospermy and causes the fertilization membrane to  prevent  the entry of other sperm. So, the correct answer is, 'Formation of fertilization membrane. '.

Answer: C.

Solution: Medical Termination of Pregnancy (MTP) or induced abortion is carried out to terminate an unwanted pregnancy. This procedure is legal under certain conditions to ensure it is performed safely and ethically, helping to avoid complications that can arise from unsafe abortions.