Editing Fertilisation (section)

==== Humans ====
[[File:Human Fertilization.png|thumb|Fertilisation in humans. The sperm and ovum unite through fertilisation, creating a zygote that (over the course of 8-9 days) implants in the uterine wall, where it resides for nine months.]]
{{main|Human fertilisation}}

Fertilisation in humans is the union of a human [[ovum|egg]] and [[spermatozoon|sperm]], usually occurring in the [[ampulla of the fallopian tube]], producing a single celled [[zygote]], the first stage of life in the development of a genetically unique organism,<ref>{{Cite web |title=Zygote {{!}} Definition, Development, Example, & Facts {{!}} Britannica |url=https://www.britannica.com/science/zygote |access-date=2023-01-14 |website=www.britannica.com |language=en}}</ref> and initiating [[Human embryonic development|embryonic development]]. Scientists discovered the dynamics of [[human fertilisation]] in the nineteenth century.

The term ''conception'' commonly refers to "the process of becoming pregnant involving fertilisation or implantation or both".<ref>{{cite web |title=Conception |url=https://www.merriam-webster.com/dictionary/conception |website=Merriam-Webster |access-date=January 27, 2019}}</ref> Its use makes it a subject of [[beginning of pregnancy controversy|semantic arguments about the beginning of pregnancy]], typically in the context of the [[abortion]] debate.
<!-- In a statement by the [[American Association of Pro-Life Obstetricians & Gynecologists]] (AAPLOG), regarding the controversial [[morning-after pill]], AAPLOG claims:-->
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<!--:"[Again,] one must be careful of the terminology. Many now speak of "conception" as that moment when the human blastocyst, the early ball of approximately 100 cells, implants in the mother's uterus (womb).  The time from actual fertilisation (egg and sperm unite in the Fallopian Tube) until implantation, a period of about 7-10 days, is ignored, even though no genetic change occurs in the cells during this time period.  Many family planning specialists who have supported the terminology change can thus rationalize that the destruction of the human embryo between fertilisation and implantation should be labeled "contraception", rather than "early abortion".-->
Upon [[gastrulation]], which occurs around 16 days after fertilisation, the implanted blastocyst develops three germ layers, the endoderm, the ectoderm and the mesoderm, and the genetic code of the father becomes fully involved in the development of the embryo; later twinning is impossible.  Additionally, interspecies hybrids survive only until gastrulation and cannot further develop.
However, some human developmental biology literature refers to the ''[[conceptus]]'' and such medical literature refers to the "products of conception" as the post-implantation embryo and its surrounding membranes.<ref>{{cite book |author1=Moore, K. L. |author2=T. V. M. Persaud |year=2003 |title=The Developing Human: Clinically Oriented Embryology |publisher=W. B. Saunders Company |isbn=0-7216-6974-3 |url=https://archive.org/details/developinghumanc00moor_0 }}{{pn|date=August 2021}}</ref> The term "conception" is not usually used in scientific literature because of its variable definition and connotation.