Question

Write a short note on ovum and sperm.

Answer 1

Hint: Gametogenesis is the process of formation of gametes like spermatozoa and ovum. The spermatogenesis produces a male gamete called sperm. The oogenesis produces the female gamete called ovum or egg. Both of these gametes are haploid and fuse to form a diploid zygote. This results in fertilization, a key even in sexual reproduction.

Complete answer: Sexual reproduction is a complex type of reproduction in which the formation and fusion of gametes mark the key events. Two parents that are male and female produce their respective gametes called sperm and ovum. Both of these gametes are haploid meaning that they have half the set of normal chromosome sets in a diploid cell. Thus, these gametes fuse to recover their diploid state. This state is called the zygote which develops further to produce an individual.

Let us study each of the gametes individually.
Ovum – Ovum is the gamete which is produced by the female as a female sex gamete. The site of production for the ovum is the female ovaries. The ovum is also called an egg. It consists of a single set of unpaired chromosomes. The ovum is one of the biggest cells in the human female body. It can be seen without using a microscope. It is round in shape and consists of a large amount of cytoplasm. Ovum consists of cell fluid. It has a limited lifespan once released from ovaries after ovulation. It can stay alive for 12 to 24 hours in the fallopian tube. If not fertilized, the ovum dissolves and degenerates causing menstruation. The mature stage of the ovum consists of an outermost layer called corona radiata inner to which lies zona pellucida. The ovum requires warmer body temperature for sustenance. A special characteristic of the ovum is that these are made before the birth of the female. But they activate only after reaching puberty.
Sperm – Sperm is the gamete which is produced by the male as male sex gamete. The site of production of sperms is in the testis of the male present in the scrotum. The sperm also consists of a single set of unpaired chromosomes. The sperm is the smallest cell in the male body. A microscope is needed to see sperm. Sperm has a long tail attached to an oval head on the top. Also, the sperm has a rigid small portion in the middle of its body that encloses mitochondria. The mitochondria are present in abundance and thus provide the required energy to sperm to swim through the female reproductive tract. Millions of sperm cells are released during a single ejaculation as compared to the ovum which is only one in number at a time. The sperms require two degrees lower temperature than the body temperature to sustain. The acrosome present on the head of sperm helps to penetrate the protective layers of the ovum. Sperms can survive up to 3 to 5 days inside the female’s body. Sperms are produced daily in millions of numbers.

Note: The current stem cell research suggests that both the sperm and ovum can be made artificially for infertile couples. Stem cells are cells that are capable of forming any of the cells of the body. Scientists are working on skin cells to convert them into reproductive cells. Sperms have been made from skin cells by reversing them to become stem cells. But ovum is much more difficult to make.