Oogamy: Difference between revisions

'''Oogamy''' is an extremea form of [[anisogamy]] where the gametes differ in both size and form.

In oogamy the large [[female]] [[gamete]] (also known as [[Egg cell|ovum]]) is immobileimmotile, while the small [[male]] gamete (also known as [[sperm]]) is mobile.<ref>{{Cite book |last1=Fusco |first1=Giuseppe |url=https://wwwbooks.google.com/books/edition/The_Biology_of_Reproduction/AKGsDwAAQBAJ?hlid=en-us&kptab=editions&sa=X&ved=2ahUKEwj79o7IpP7wAhVKHs0KHXLTC0EQmBYwAHoECAIQCQAKGsDwAAQBAJ|title=The Biology of Reproduction |last2=Minelli |first2=Alessandro |date=2019-10-10 |publisher=Cambridge University Press |isbn=978-1-108-49985-9 |pages=111–112 |language=en |author-link2=Alessandro Minelli (biologist)|access-date=29 March 2021|url-status=live}}</ref> Oogamy is a common form of anisogamy, with almost all animals and land plants being oogamous.

Oogamy is found in mostalmost all animal species that [[Sexual reproduction|reproduce sexually]], all higher species being oogamous.<ref>{{Cite book|last=Bell|first=Graham|url=https://books.google.com/books?id=Xzv3DwAAQBAJ&q=the+evolution+of+sexual+reproduction+is+important+to+the+evolution+of+sex|title=The Masterpiece of Nature: The Evolution and Genetics of Sexuality|date=2019-11-28|publisher=Routledge|isbn=978-1-000-49744-1|pages=63|language=en|author-link=Graham Bell (biologist)}}</ref><ref name="Dusenbery-2009">{{Cite book|last=Dusenbery|first=David B.|url=https://books.google.com/books?id=9hgtEAAAQBAJ&dq=oogamy+and+internal+fertilization&pg=PA326|title=Living at Micro Scale: The Unexpected Physics of Being Small|date=2009|publisher=Harvard University Press|isbn=978-0-674-06021-0|pages=32|language=en}}</ref> There are exceptions, such as the [[opiliones]] that have immobile sperm.<ref>{{Cite book|last1=Leonard|first1=Janet|url=https://books.google.com/books?id=wmlnDAAAQBAJ&dq=oogamy+in+animals&pg=PA18|title=The Evolution of Primary Sexual Characters in Animals|last2=Cordoba-Aguilar|first2=Alex|date=2010-07-19|publisher=Oxford University Press, USA|isbn=978-0-19-532555-3|pages=18–19|language=en}}</ref>

Oogamy is found in all [[Embryophyte|land plants]],<ref>{{Cite book|last=Simpson|first=Michael G.|url=https://books.google.com/books?id=dj8KRImgyf4C&dq=oogamy+common+in+land+animals.&pg=PA58|title=Plant Systematics|date=2010-07-19|publisher=Academic Press|isbn=978-0-08-092208-9|pages=58|language=en}}</ref> and in some [[red algae]], [[brown algae]] and [[green algae]].<ref name=Raven>{{Cite book|last1=Raven|first1=Peter H.|url=https://books.google.com/books?id=8tz2aB1-jb4C&q=Oogamy|title=Biology of Plants|last2=Evert|first2=University Ray F.|last3=Evert|first3=Ray F.|last4=Eichhorn|first4=Susan E.|last5=Eichhorn|first5=University Susan E.|date=2005|publisher=W. H. Freeman|isbn=978-0-7167-1007-3|pages=309|language=en}}</ref>{{rp|309}} Oogamy is favored in land plants because only one gamete has to travel through harsh environments outside the plant.<ref>{{Cite book|last1name=Raven|first1=Peter H.|url=https://books.google.com/books?id=8tz2aB1-jb4C&q=Oogamy>{{rp|title=Biology of Plants|last2=Evert|first2=University Ray F.|last3=Evert|first3=Ray F.|last4=Eichhorn|first4=Susan E.|last5=Eichhorn|first5=University Susan E.|date=2005|publisher=W. H. Freeman|isbn=978-0-7167-1007-3|pages=376|language=en}}</ref> Oogamy is also present in [[oomycete]]s.<ref name=Buaya>{{cite journal |first1=Anthony T. |last1=Buaya |first2=Marco |last2=Thines |journal=Philippine Journal of Systematic Biology |volume=14 |issue=1 |page=1-20 |date=2020 |title=An overview on the biology and phylogeny of the early-diverging oomycetes |doi=10.26757/pjsb2020a14004 |doi-access=free }}</ref>

The term oogamy was first used in the year 1888.<ref>{{Cite web|title=Definition of OOGAMY|url=https://www.merriam-webster.com/dictionary/oogamy|access-date=2021-09-14|website=www.merriamMerriam-webster.comWebster |language=en}}</ref> It derives from the Greek noun "oon" (ΩΟΝ = egg) and the Greek verb "gameo" (ΓΑΜΕΩ -> ΓΑΜΩ = to have sex/to reproduce) and eventually means "reproduction through eggs".

It is generally accepted that [[isogamy]] is the ancestral state<ref>{{Cite book|last1=Pitnick|first1=Scott S.|url=https://books.google.com/books?id=kctYNbO1fE0C&q=evolution+of+anisogamy|title=Sperm Biology: An Evolutionary Perspective|last2=Hosken|first2=Dave J.|last3=Birkhead|first3=Tim R.|date=2008-11-21|publisher=Academic Press|isbn=978-0-08-091987-4|pages=43–44|language=en}}</ref> and that oogamy evolves from isogamy through anisogamy.<ref>{{Cite book|last=Kumar|first=Awasthi & Ashok|url=https://books.google.com/books?id=r0h1DwAAQBAJ&dq=isogamy+generally+accepted&pg=PA363|title=Textbook of Algae|publisher=Vikas Publishing House|isbn=978-93-259-9022-7|pages=363|language=en}}</ref><ref>{{Cite book|last1name="Dusenbery|first1=David-2009" B.|url=https://books.google.com/books?id=QCrimQJu1RAC>{{rp|title=Living at Micro Scale: The Unexpected Physics of Being Small|last2=Dusenbery|first2=Professor of Biology Emeritus David B.|date=2009|publisher=Harvard University Press|isbn=978-0-674-03116-6|pages=309|language=en}}</ref> However, transitions do exist between anisogamy and oogamy.<ref>{{Cite journal|last1=Hörandl|first1=Elvira|last2=Hadacek|first2=Franz|date=August 2020|title=Oxygen, life forms, and the evolution of sexes in multicellular eukaryotes|journal=Heredity|language=en|volume=125|issue=1|pages=1–14|doi=10.1038/s41437-020-0317-9|pmid=32415185|issn=1365-2540|pmc=7413252}}</ref> When oogamy has evolved, males and females typically differ in many aspects. Oogamy evolved before the transition from [[External fertilization|external]] to [[internal fertilization]].<ref name=Nozaki-2014 />{{rp|37}}<ref name="Dusenbery-2009" />{{rp|326}}

In [[Streptophyta|streptophyte]]s, oogamy likely first occurred before the split betweenfrom green algae and land plants.<ref>{{Cite journal|last1=Geng|first1=Sa|last2=De Hoff|first2=Peter|last3=Umen|first3=James G.|date=2014-07-08|title=Evolution of Sexes from an Ancestral Mating-Type Specification Pathway|journal=PLOS Biology|volume=12|issue=7|pages=e1001904|doi=10.1371/journal.pbio.1001904|issn=1544-9173|pmc=4086717|pmid=25003332 |doi-access=free }}</ref>