A prerequisite for the continuation of the species: Gametogenesis – Erakina

 Blossoming flower indicating gametogenesis

Gametogenesis:

• The blossoming of gametes from haploid precursor cells is called Gametogenesis. In animals and plants, two morphological unequivocal gametes are generated:  one male and one female via various differentiation events. 
• In animals, the Production of tissue takes place that is further dedicated to forming gametes (reproductive cells), which is called the germline (gametogonia). Discrete germline cells are called germ cells.
• During entire events of gametogenesis, A germ cell goes through meiosis which is an indispensable part of gametogenesis that led to the formation of haploid cells that mature into gametes. The haploid spores are evolved from diploid cells via meiosis which further propagates to a haploid generation known as ‘gametophyte’. Then the cells in the course of time develop into gametes, periodically via environmental or chemical stimuli.
• In many species like fungi, multicellular algae, and some protists the gametes are not morphologically distinct and are assigned as (+) or (-) rather than sperm or egg.
• Gametogenesis involves spermatogenesis as well as oogenesis.

Gametogenesis in animals:

• There are two forms of gametogenesis process that take place in animals: The process by which the production of male gametes takes place is called spermatogenesis, and the male gamete is known as sperm. Similarly, the process by which the generation of female gamete takes place is called oogenesis and the female gametes are known as ovum or egg. 
• Gonads are the primary reproductive organ where the gametogenesis process takes place. In females, the process of oogenesis takes place in the ovary and in males, the process of spermatogenesis takes place in the testis. That indicates that it is responsible for the production and storage of gametes and this can vary from one species to another.
• During embryonic development, undifferentiated cells are kept aside as primordial germ cells and with the development of gonads, these cells divide and proliferate to form a source of cells from which the generation of gametes takes place.
• The germline or gametogonia has exceptional ability to form gametes, summing it as discrete from other tissues of the developing organism, which is further called the soma which stands for “body” in Greek.

Spermatogenesis: (Fructification of sperms)

• The spermatogenesis takes place when the spermatogonium differentiates to become a primary spermatocyte and enters the reduction division called “meiosis”. 
• In simple words, “Meiosis” is a type of cell division in which the formation of four daughter cells takes place having half the number of chromosomes of the parent cell.
• Technically, the individual primary spermatocyte undergoes meiosis I (Ist meiotic division) generating two secondary spermatocytes. Further, a second meiotic division takes place known as meiosis II giving out a total of four haploid spermatids which eventually develop into mature sperm (also known as spermatozoa) via spermiogenesis.
• The process of spermatogenesis is highly dependent upon suitable conditions and plays a pivotal role in sexual reproduction. The process starts at puberty and remains undisrupted till death with a meager decrease in the quantity of produced sperm, as the personages.

Spermatogenesis

Oogenesis: (Fructification of ovum or egg)

• The generation of the ovum or the egg cell is called the oogenesis which is developed via the maturation process from the primary oocyte. The beginning of the oogenesis starts during the embryonic stage.
• The onset of the oogenesis begins with the transformation of oogonia into primary oocyte via maturation and this transformation of oogonia is called oocytogenesis. It gets completed either before or shortly after birth.
• The process starts initially within the 3 months of female embryonic life with the development of ovarian follicles and further these follicles consist of one oogonium which via the process of mitosis develop into 46 chromosomes containing primary oocyte. After that, the onset of the first meiotic reduction division takes place when the primary oocyte leads to the formation of a secondary oocyte and a polar body both consisting of 22 chromosomes. Then the secondary oocyte proceeds with meiosis II which take place after puberty and the continuous shedding of the ovum each month happens until it is been fertilized. Meiosis II gets completed on fertilization. The hormones that are involved in the growth and maturation of oocytes are Follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Oogenesis (Flowchart)

Importance of gametogenesis in reproduction or continuation of species:

• Gametogenesis: Reproduction plays a vital role in the continuation of life, and reproduction is not possible without gametes which are formed by the process of Gametogenesis. Production of haploid cells also known as “gametes” takes place via the process of Gametogenesis from the diploid germ cells in the gonads. 
• If by any means this process gets hampered, it will directly disturb the most vital process that is reproduction or offspring generation.

Notes: 

• In many species, up till the animal does not reach maturity there is no production of gametes takes place;
• However, in species like nematodes (roundworms), the generation of sperm takes place in the late larval development ahead of sexual maturity and is reserved for ulterior use; more sperms are produced in adulthood. High variability can be seen in the figures of germ cells that go through gametogenesis.
• Initially, the onset of gametogenesis in males takes place as they touch puberty but it’s completely different for the females as in females the process had already started before birth and continues with the dawn of puberty and ends with menopause.
• “Ovulation” is the term used for depicting the release of a secondary oocyte from the ovaries.
• Meiosis: It is the type of cell division in which the generation of four daughter cells takes place consisting of half the number of the parent cell that is parent cell (46 chromosomes) and daughter cell (23 chromosomes)
• Mitosis: This is that cell division in which the generation of two daughter cells takes place having the same number of chromosomes as that of the parent cell.