Question

In humans, the process of fertilization occurs when
A. The sperms are transported into vagina just after the release of ovum in fallopian tube
B. The ovum and sperms are transported simultaneously to ampullary-isthmic junction of the fallopian tube
C. The ovum and sperms are transported simultaneously to the ampullary-isthmic junction of the cervix.
D. The sperms are transported into the cervix within 48 hrs of release of ovum in the uterus.

Answer 1

Hint: Fertilization is described as the fusion of haploid male and female gametes to form a diploid zygote. The zygote undergoes cleavage and forms 2, 4, 8 and 16-celled stages. The 16- celled stage is known as the morula, which divides and converts into a blastocyst. It implants into the uterus and begins gastrulation.

Complete answer:
- The fertilization process is described as the fusion of haploid male and female gametes to form a diploid zygote. The fertilization takes place in the fallopian tube, especially at the ampullary-isthmic junction.
- The motile sperms swim rapidly, pass through the cervix, enter into the uterus, and finally reach the junction of the isthmus and ampulla of the fallopian tube. The ovum released from the ovary is also transferred to the ampullary-isthmic junction because fertilization takes place here.
- The fertilization can occur if both the gametes are transported simultaneously. This is the reason why not all copulations lead to fertilization and pregnancy.
- In flowering plants, the pollen grains are known as male gamete. The pollen tube arises from the stigma and reaches to the ovary where fertilization takes place.

Hence, the correct answer is option (B). The ovum and sperms are transported simultaneously to the ampullary-isthmic junction of the fallopian tube.

Additional information:
The process of formation of a mature female gamete is known as oogenesis. This process includes three phases. These are the multiplication phase, growth phase and maturation phase.

Note: The secretions of the female genital tract make the sperms capable of fertilizing the ovum. This phenomenon of sperm activation is known as capacitation. Due to this phenomenon, the sperm remain viable and motile even in the female genital tract and can fertilize the ovum.