Size of gametes

In species that produce two morphologically distinct forms of gametes and in which each individual produces just one type, a female is any individual who produces the bigger type of gamete, known as an ovum, and a male produces the smaller type, known as a sperm. Sperm cells, also known as spermatozoa, are tiny and motile thanks to the flagellum, which is a tail-shaped feature that allows the cell to propel and move. Each egg cell or ovum, on the other hand, is rather big and non-motile. A gamete is either an egg cell (female gamete) or a sperm (male gamete). In animals, ova mature in female ovaries while sperm develops in male testes. A spermatozoon and an ovum combine during fertilisation to generate a new diploid organism.  Gametes contain half of an individual’s genetic information, one ploidy of each type, and are produced by meiosis, in which a germ cell undergoes two fissions, culminating in the generation of four gametes. In biology, the type of gamete produced by an organism defines its sex. 

Size of Gametes:

This is an example of anisogamy or heterogamy, a condition in which females and males generate varied sizes of gametes (this is the case in humans; the human ovum has approximately 100,000 times the volume of a single human sperm cell). Isogamy, on the other hand, is the condition in which gametes from both sexes are the same size and form and have arbitrary designators for mating type. Eduard Strasburger, a German cytologist, coined the term “gamete.” Male and female gametes establish the foundation for sexual roles and sexual selection. A gamete (biology definition) is a mature haploid reproductive cell produced by gametogenesis that combines with another of the opposite sex during fertilisation to form a zygote that develops into a new individual. Etymology: from the Ancient Greek (gamet), which means “woman.” Synonyms include sex cell and reproductive cell.

Types of Gametes based on Size:

Another technique to categorise gametes is based on their size. Gametes are classified into two types based on their size:

Microgametes are smaller-sized gametes. These are motile, produced in enormous numbers, and do not have nutrition storage. Consider sperm cells.

Macrogametes are gametes that are greater in size. These are non-motile, produced in small quantities, and contain a great number of nutrients. As an example, consider egg cells or ova.

Differences in the sizes of the gametes:

Typically, one of the gametes is bigger in size and non-motile. It is referred to as a female gamete, ovum, or egg cell. The other gamete cell is smaller and motile. It is referred to as a male gamete or sperm cell. In humans, each gamete contains 23 chromosomes, and their fusion produces a diploid zygote with 46 chromosomes. These reproductive cells are formed in the male and female gonads, or reproductive organs, of animals. Male gametes are pollen in seed-bearing plants, while female gametes are encased in the plant’s ovules. In plants, however, the gamete may or may not necessarily be a haploid cell.

The gametes involved in fertilisation can be identical (referred to as isogamy) or they can be distinct (referred to as anisogamy).

Isogamy refers to gametes that have identical morphology, such as size and form. This is also referred to as ‘heterogamy.’ These gametes are not classified as male or ‘female.’ These gametes are denoted by a ‘+’ or a ‘-‘. Unicellular algae gametes, Chlamydomonas reinhardtii, and Carteria palmitate are two examples.

Anisogamy refers to gametes that have dissimilar morphology, i.e. size and shape. These gametes are classified as ‘female’ or male.’ The smaller gamete is known as sperm or male gamete, whereas the larger gamete is known as ova or egg or female gamete. Furthermore, these gametes can be both motile and nonmotile.

In the instance of Polysiphonia, red algae, both gametes are non-motile. A zygote is formed when non-motile sperm unites with a non-motile egg. Spermatia is a non-motile male gamete or sperm. This is also seen in certain blooming plants when both non-motile gametes are present in the gametophyte. Pollen is the non-motile male gamete of plants.

Oogamy occurs when one of the gametes, male gamete or sperm, is motile and the other gamete, egg or female gamete, is non-motile in humans and mammals. This is known as oogamy, and it occurs when a giant non-motile egg is fertilised or fuses with a small motile sperm to produce the zygote.

Conclusion

Gametes are reproductive cells or sex cells as they are more popularly known, that are designed to combine during the act of sexual reproduction. These reproductive cells, also known as gametes, are crucial to the process because they aid in the creation of a completely new cell known as the zygote.

Anisogamy relates to gametes with morphological differences, such as size and shape. Female and male gametes are distinguished.

Each human gamete has 23 chromosomes, and when they fuse, a diploid zygote containing 46 chromosomes is formed.