Isogamy Explained

Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), and is found in most unicellular eukaryotes.[1] Because both gametes look alike, they generally cannot be classified as male or female.[2] Instead, organisms undergoing isogamy are said to have different mating types, most commonly noted as "+" and "-" strains.[3]

Etymology

The etymology of isogamy derives from the Greek adjective isos (meaning equal) and the Greek verb gameo (meaning to have sex/to reproduce), eventually meaning "equal reproduction" which refers to a hypothetical initial model of equal contribution of resources by both gametes to a zygote in contrast to a later evolutional stage of anisogamy.[4] The term isogamous was first used in the year 1887.[5]

Characteristics of isogamous species

Isogamous species often have two mating types. Some isogamous species have more than two mating types, but the number is usually lower than ten. In some extremely rare cases a species can have thousands of mating types. In all cases, fertilization occurs when gametes of two different mating types fuse to form a zygote.[6]

Evolution

It is generally accepted that isogamy is an ancestral state for anisogamy[1] [7] and that isogamy was the first stage in the evolution of sexual reproduction. Isogamous reproduction evolved independently in several lineages of plants and animals to anisogamous species with gametes of male and female types and subsequently to oogamous species in which the female gamete is much larger than the male and has no ability to move. This pattern may have been driven by the physical constraints on the mechanisms by which two gametes get together as required for sexual reproduction.[8]

Isogamy is the norm in unicellular eukaryote species, although it is possible that isogamy is evolutionarily stable in multicellular species.[1]

Occurrence

Almost all unicellular eukaryotes are isogamous.[9] Among multicellular organisms, isogamy is restricted to fungi and algae.[10] Many species of green algae are isogamous. It is typical in the genera Ulva, Hydrodictyon, Tetraspora, Zygnema, Spirogyra, Ulothrix, and Chlamydomonas.[1] [11] Many fungi are isogamous.[1] [12]

See also

Biology

Social anthropology

Notes and references

Notes and References

  1. Lehtonen. Jussi. Kokko. Hanna. Parker. Geoff A.. 2016-10-19. What do isogamous organisms teach us about sex and the two sexes?. Philosophical Transactions of the Royal Society B: Biological Sciences. 371. 1706. 10.1098/rstb.2015.0532. 0962-8436. 5031617. 27619696.
  2. Book: Sawada. Hitoshi. Sexual Reproduction in Animals and Plants. Inoue. Naokazu. Iwano. Megumi. 2014. Springer. 978-4-431-54589-7. 216. en. 2021-07-24. 2024-04-04. https://web.archive.org/web/20240404062136/https://books.google.com/books?id=Adm6BQAAQBAJ&q=isogamy+mating+types#v=snippet&q=isogamy%20mating%20types&f=false. live.
  3. Encyclopedia: Anisogamy . Anisogamy . Encyclopedia of Animal Cognition and Behavior . Springer International Publishing . Cham . 2019 . 1–5 . 10.1007/978-3-319-47829-6_340-1 . 978-3-319-47829-6 . Kumar R, Meena M, Swapnil P . Vonk J, Shackelford T.
  4. Book: Encyclopedia of Evolutionary Biology. 2016-04-14. Academic Press. 978-0-12-800426-5. 2. 212. en. 2021-08-14. 2023-10-06. https://web.archive.org/web/20231006173122/https://books.google.com/books?id=_r4OCAAAQBAJ&q=isogamy+encyclopedia&pg=RA1-PA212. live.
  5. Web site: Definition of ISOGAMOUS. 2021-09-14. www.merriam-webster.com. en. 2021-09-14. https://web.archive.org/web/20210914002001/https://www.merriam-webster.com/dictionary/isogamous. live.
  6. Krumbeck. Yvonne. Constable. George W. A.. Rogers. Tim. 2020-02-26. Fitness differences suppress the number of mating types in evolving isogamous species. Royal Society Open Science. 7. 2. 192126. 1906.07117. 2020RSOS....792126K. 10.1098/rsos.192126. 2054-5703. 7062084. 32257356.
  7. Book: Pitnick. Scott S.. Sperm Biology: An Evolutionary Perspective. Hosken. Dave J.. Birkhead. Tim R.. 2008-11-21. Academic Press. 978-0-08-091987-4. 43–45. en. 2021-07-24. 2023-10-06. https://web.archive.org/web/20231006173121/https://books.google.com/books?id=kctYNbO1fE0C&q=anisogamy+defines+the+sexes. live.
  8. Dusenbery, David B. (2009). Living at Micro Scale, Chapter 20. Harvard University Press, Cambridge, Massachusetts .
  9. Book: Bell, Graham. Selection: The Mechanism of Evolution. 2008. OUP Oxford. 978-0-19-856972-5. 439. en. Graham Bell (biologist). 2023-03-19. 2023-10-06. https://web.archive.org/web/20231006173121/https://books.google.com/books?id=jS0TDAAAQBAJ. live.
  10. Book: Togashi. Tatsuya. The Evolution of Anisogamy: A Fundamental Phenomenon Underlying Sexual Selection. Cox. Paul Alan. 2011-04-14. Cambridge University Press. 978-1-139-50082-1. 96. en. 2021-07-24. 2023-10-06. https://web.archive.org/web/20231006173122/https://books.google.com/books?id=5eOvRTIuLXMC&q=isogamy+in+fungi. live.
  11. Book: Sharma, O. P.. Textbook of Algae. 1986-01-01. Tata McGraw-Hill Education. 978-0-07-451928-8. 130. en. 2021-07-24. 2023-10-06. https://web.archive.org/web/20231006173123/https://books.google.com/books?id=hOa74Hm4zDIC&q=isogamy&pg=PA130. live.
  12. Book: Heitman. Joseph. The Fungal Kingdom. Howlett. Barbara J.. Crous. Pedro W.. Stukenbrock. Eva H.. James. Timothy Yong. Gow. Neil A. R.. 2020-07-10. John Wiley & Sons. 978-1-55581-958-3. 149. en. 2021-07-24. 2023-10-06. https://web.archive.org/web/20231006173122/https://books.google.com/books?id=VILwDwAAQBAJ&q=most+fungi+are+isogamous&pg=PA149. live.

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