Key Difference – Anisogamy vs Isogamy vs Oogamy
Sexual reproduction is a form of reproduction in which two different haploid cells called gametes are fused to produce a diploid zygote which further develops into the offspring. The fusion of male and female gametes during the sexual reproduction is known as syngamy. Syngamy differs among organisms according to the nature of gametes and their mode of fusion. There are three types of syngamy named anisogamy, isogamy and oogamy. Isogamy is the fusion of two motile gametes which are morphologically identical and physiologically different. Anisogamy is the fusion of morphologically dissimilar male and female gametes which can be motile or immotile. Oogamy is a form of anisogamy in which fusion of immotile, large female gamete (egg) occurs with motile, small male gamete (sperm). This is the key difference between anisogamy isogamy and oogamy.
CONTENTS
1. Overview and Key Difference
2. What is Anisogamy
3. What is Isogamy
4. What is Oogamy
5. Side by Side Comparison – Anisogamy vs Isogamy vs Oogamy
6. Summary
What is Anisogamy?
If syngamy occurs between two dissimilar male and female gametes, it is known as anisogamy or heterogamy. In anisogamy, male and female gametes can be differentiated as sperms and eggs. Both gametes are motile in some species while only the male gamete is motile in some organisms. Female gamete is larger in size than the male gamete. In certain organisms, the female gamete does not have flagella to move. Hence, male gamete moves towards the female gamete for syngamy. Anisogamy is shown by lower plants such as certain green algae and red algae.
Figure 01: Anisogamy
What is Isogamy?
The fusion of morphologically similar but physiologically dissimilar two gametes is called isogamy. There is no differentiation between female gametes and male gametes in isogamy. They are referred to as positive (+) and negative (-) mating types. Both gametes are absolutely identical in size, shape, and appearance. They can be rounded or pear-shaped cells. Gametes have flagella to move towards their destinations. Once they fuse, a zygote is produced, resulting in a new organism. This type of syngamy is shown by unicellular organisms like protozoans, lower plants like algae and some fungi.
Figure 01: Isogamy
What is Oogamy?
Oogamy is a type of anisogamous sexual process. It can be defined as the fusion of large, immotile egg cell with small and motile sperm cell to produce a zygote. Male and female gametes are largely different in size, shape, appearance and motility. Male gamete bears a flagellum; hence, it is highly mobile. The egg cell is comprised of a lot of nutrients for future use during the development of the offspring.
Oogamy is shown by all higher plants and animals.
Figure 03: Oogamy
What is the difference between Anisogamy Isogamy and Oogamy?
Anisogamy vs Isogamy vs Oogamy |
|
| Definition | |
| Anisogamy | Anisogamy is a type of syngamy in which morphologically dissimilar male and female gamete fuse with each other to produce a zygote. |
| Isogamy | Isogamy is a type of syngamy in which morphologically similar two motile gametes are fused together in sexual reproduction. |
| Oogamy | Oogamy is a type of syngamy and also a form of anisogamy which occurs between large immotile egg cell and small motile sperm cell to produce a zygote. |
| Differentiation of Gametes | |
| Anisogamy | Female and male gametes are differentiated. |
| Isogamy | Two gametes are not differentiated as male and female gametes. |
| Oogamy | Male gamete and female gamete are highly differentiated. |
| Size of the Gametes | |
| Anisogamy | Female gamete is larger than male gamete. |
| Isogamy | Male and female gametes are identical in size. |
| Oogamy | Female gamete is larger than male gamete. |
| Specialization of Gametes | |
| Anisogamy | Cells are specialized. They are physiologically different. |
| Isogamy | Cells are unspecialized, but they are physiologically different. |
| Oogamy | Cells are specialized, and they are physiologically different. |
| Flagella | |
| Anisogamy | In some organisms, both gametes are motile while in some species, only the male gamete is motile. |
| Isogamy | Both gametes have flagella. |
| Oogamy | Male gamete is motile while female gamete is immotile. |
| Offsprings | |
| Anisogamy | This produces a less number of offspring. |
| Isogamy | This produces more offspring. |
| Oogamy | This produces a limited number of offspring with higher fitness. |
Summary – Anisogamy vs Isogamy vs Oogamy
Male and female gametes are fused together to produce diploid zygote during the sexual reproduction which is known as syngamy. This process differs among organisms, based on the nature of the gametes and the mode of the fusion. Hence, there are three types of syngamy named isogamy, anisogamy, and oogamy. Isogamy occurs between two identical motile gametes which are not differentiated as male and female gametes. Anisogamy occurs between two dissimilar male and female gametes which are motile or immotile. Oogamy is a form of anisogamy which occurs between immotile large female gamete and small motile male gamete. This is the difference between anisogamy isogamy and oogamy.
Reference:
1. Kodric-Brown, Astrid, and James H. Brown. “Anisogamy, sexual selection, and the evolution and maintenance of sex.” SpringerLink. Kluwer Academic Publishers, n.d. Web. 23 May 2017
2. “Sexual reproduction in plants (isogamy, anisogamy, oogamy) [Types, Forms, morphology].” Sexual reproduction in plants (isogamy, anisogamy, oogamy) [Types, Forms, morphology] – WORLD OF SCHOOL. N.p., n.d. Web. 23 May 2017. <http://worldofschool.org/Sexual_reproduction_in_plants_(isogamy,_anisogamy,_oogamy)>.
Image Courtesy:
1. “Anisogamy” By Original uploader was Tameeria at en.wikipediaLater versions were uploaded by Helix84 at en.wikipedia. – Anisogamy.png (Public Domain) via Commons Wikimedia
2. “Isogamy diagram” by BlueRidgeKitties (CC BY 2.0) via Flickr
3. “Human gametes: ovum & spermatozoon. Approximately 50% of the floating sperms contain the y-chromosome (–> fertilization leads to a male child), the other 50% encompass the x-chromosome” by Karl-Ludwig Poggemann (CC BY 2.0) via Flickr