Sexual reproduction - wikipedia Sexual reproduction This article is about sexual reproduction. For non-sexual reproduction, see Asexual reproduction. This article 's lead section may be too long for the length of the article. Please help by moving some material from it into the body of the article. Please read the layout guide and lead section guidelines to ensure the section will still be inclusive of all essential details. Please discuss this issue on the article 's talk page. ( March 2018 ) In the first stage of sexual reproduction, `` meiosis '', the number of chromosomes is reduced from a diploid number ( 2n ) to a haploid number ( n ). During `` fertilization '', haploid gametes come together to form a diploid zygote and the original number of chromosomes is restored. Sexual reproduction is a form of reproduction where two gametes fuse together. Each gamete contains half the number of chromosomes of normal cells. They are created by a specialized type of cell division, which only occurs in eukaryotic cells, known as meiosis. The two gametes fuse during fertilization to produce DNA replication and the creation of a single - celled zygote which includes genetic material from both gametes. In a process called genetic recombination, genetic material ( DNA ) joins up so that homologous chromosome sequences are aligned with each other, and this is followed by exchange of genetic information. Two rounds of cell division then produce four daughter cells with half the number of chromosomes from each original parent cell, and the same number of chromosomes as both parents. For instance, in human reproduction each human cell contains 46 chromosomes in 23 pairs. Meiosis in the parents ' gonads produce gamete cells which only contain 23 chromosomes each. When the gametes are combined via sexual intercourse to form a fertilized egg, the resulting child will have 23 chromosomes from each parent genetically recombined into 23 chromosome pairs or 46 total. Cell division mitosis then initiates the development of a new individual organism in multicellular organisms, including animals and plants, for the vast majority of whom this is the primary method of reproduction. The evolution of sexual reproduction is a major puzzle because asexual reproduction should be able to outcompete it as every young organism created can bear its own young. This implies that an asexual population has an intrinsic capacity to grow more rapidly with each generation. This 50 % cost is a fitness disadvantage of sexual reproduction. The two-fold cost of sex includes this cost and the fact that any organism can only pass on 50 % of its own genes to its offspring. One definite advantage of sexual reproduction is that it prevents the accumulation of genetic mutations. Sexual selection is a mode of natural selection in which some individuals out - reproduce others of a population because they are better at securing mates for sexual reproduction. It has been described as `` a powerful evolutionary force that does not exist in asexual populations. '' Prokaryotes, whose initial cell has additional or transformed genetic material, reproduce through asexual reproduction but may, in lateral gene transfer, display processes such as bacterial conjugation, transformation and transduction, which are similar to sexual reproduction although they do not lead to reproduction. Contents 1 Evolution 2 Sexual selection 3 Sex ratio 4 Animals 4.1 Insects 4.2 Birds 4.3 Mammals 4.4 Fish 4.5 Reptiles 4.6 Amphibians 4.7 Mollusks 5 Plants 5.1 Flowering plants 5.2 Ferns 5.3 Bryophytes 6 Fungi 7 Bacteria and archaea 8 See also 9 References 10 Further reading 11 External links Evolution Main article : Evolution of sexual reproduction The first fossilized evidence of sexual reproduction in eukaryotes is from the Stenian period, about 1 to 1.2 billion years ago. Biologists studying evolution propose several explanations for why sexual reproduction developed and why it is maintained. These reasons include reducing the likelihood of the accumulation of deleterious mutations, increasing rate of adaptation to changing environments, dealing with competition, and masking deleterious mutations. All of these ideas about why sexual reproduction has been maintained are generally supported, but ultimately the size of the population determines if sexual reproduction is entirely beneficial. Larger populations appear to respond more quickly to benefits obtained through sexual reproduction than do smaller population sizes. Maintenance of sexual reproduction has been explained by theories that work at several levels of selection, though some of these models remain controversial. However, newer models presented in recent years suggest a basic advantage for sexual reproduction in slowly reproducing complex organisms. Sexual reproduction allows these species to exhibit characteristics that depend on the specific environment that they inhabit, and the particular survival strategies that they employ. Sexual selection Main article : Sexual selection In order to sexually reproduce, both males and females need to find a mate. Generally in animals mate choice is made by females while males compete to be chosen. This can lead organisms to extreme efforts in order to reproduce, such as combat and display, or produce extreme features caused by a positive feedback known as a Fisherian runaway. Thus sexual reproduction, as a form of natural selection, has an effect on evolution. Sexual dimorphism is where the basic phenotypic traits vary between males and females of the same species. Dimorphism is found in both sex organs and in secondary sex characteristics, body size, physical strength and morphology, biological ornamentation, behavior and other bodily traits. However, sexual selection is only implied over an extended period of time leading to sexual dimorphism. Sex ratio Apart from some eusocial wasps, organisms which reproduce sexually have a 1 : 1 sex ratio of male and female births. The English statistician and biologist Ronald Fisher outlined why this is so in what has come to be known as Fisher 's principle. This essentially says the following : Suppose male births are less common than female. A newborn male then has better mating prospects than a newborn female, and therefore can expect to have more offspring. Therefore parents genetically disposed to produce males tend to have more than average numbers of grandchildren born to them. Therefore the genes for male - producing tendencies spread, and male births become more common. As the 1 : 1 sex ratio is approached, the advantage associated with producing males dies away. The same reasoning holds if females are substituted for males throughout. Therefore 1 : 1 is the equilibrium ratio. Animals Further information : Reproductive system § Animals, Fertilization in animals, and Animal sexual behavior Insects Further information : Insect § Reproduction and development Australian emperor laying egg, guarded by the male Insect species make up more than two - thirds of all extant animal species. Most insect species reproduce sexually, though some species are facultatively parthenogenetic. Many insects species have sexual dimorphism, while in others the sexes look nearly identical. Typically they have two sexes with males producing spermatozoa and females ova. The ova develop into eggs that have a covering called the chorion, which forms before internal fertilization. Insects have very diverse mating and reproductive strategies most often resulting in the male depositing spermatophore within the female, which she stores until she is ready for egg fertilization. After fertilization, and the formation of a zygote, and varying degrees of development, in many species the eggs are deposited outside the female ; while in others, they develop further within the female and are born live. Birds Further information : Avian reproduction Mammals Main article : Mammalian reproduction See also : Human reproduction There are three extant kinds of mammals : monotremes, placentals and marsupials, all with internal fertilization. In placental mammals, offspring are born as juveniles : complete animals with the sex organs present although not reproductively functional. After several months or years, depending on the species, the sex organs develop further to maturity and the animal becomes sexually mature. Most female mammals are only fertile during certain periods during their estrous cycle, at which point they are ready to mate. Individual male and female mammals meet and carry out copulation. For most mammals, males and females exchange sexual partners throughout their adult lives. Fish Further information : Fish § Reproductive system The vast majority of fish species lay eggs that are then fertilized by the male, some species lay their eggs on a substrate like a rock or on plants, while others scatter their eggs and the eggs are fertilized as they drift or sink in the water column. Some fish species use internal fertilization and then disperse the developing eggs or give birth to live offspring. Fish that have live - bearing offspring include the guppy and mollies or Poecilia. Fishes that give birth to live young can be ovoviviparous, where the eggs are fertilized within the female and the eggs simply hatch within the female body, or in seahorses, the male carries the developing young within a pouch, and gives birth to live young. Fishes can also be viviparous, where the female supplies nourishment to the internally growing offspring. Some fish are hermaphrodites, where a single fish is both male and female and can produce eggs and sperm. In hermaphroditic fish, some are male and female at the same time while in other fish they are serially hermaphroditic ; starting as one sex and changing to the other. In at least one hermaphroditic species, self - fertilization occurs when the eggs and sperm are released together. Internal self - fertilization may occur in some other species. One fish species does not reproduce by sexual reproduction but uses sex to produce offspring ; Poecilia formosa is a unisex species that uses a form of parthenogenesis called gynogenesis, where unfertilized eggs develop into embryos that produce female offspring. Poecilia formosa mate with males of other fish species that use internal fertilization, the sperm does not fertilize the eggs but stimulates the growth of the eggs which develops into embryos. Reptiles Common house geckos ( Hemidactylus frenatus ) mating Further information : Reptiles § Reproduction Amphibians Further information : Amphibian § Reproduction Mollusks Further information : Mollusk § Reproduction Plants Main article : Plant reproduction Animals typically produce gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization follows immediately after meiosis. Plants on the other hand have mitosis occurring in spores, which are produced by meiosis. The spores germinate into the gametophyte phase. The gametophytes of different groups of plants vary in size ; angiosperms have as few as three cells in pollen, and mosses and other so called primitive plants may have several million cells. Plants have an alternation of generations where the sporophyte phase is succeeded by the gametophyte phase. The sporophyte phase produces spores within the sporangium by meiosis. Flowering plants Flowers are the sexual organs of flowering plants. Flowering plants are the dominant plant form on land and they reproduce either sexually or asexually. Often their most distinguishing feature is their reproductive organs, commonly called flowers. The anther produces pollen grains which contain the male gametophytes ( sperm ). For pollination to occur, pollen grains must attach to the stigma of the female reproductive structure ( carpel ), where the female gametophytes ( ovules ) are located inside the ovary. After the pollen tube grows through the carpel 's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization. The resulting zygote develops into an embryo, while the triploid endosperm ( one sperm cell plus two female cells ) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte ( s ), then grows into a fruit, which surrounds the seed ( s ). Plants may either self - pollinate or cross-pollinate. Nonflowering plants like ferns, moss and liverworts use other means of sexual reproduction. In 2013, flowers dating from the Cretaceous ( 100 million years before present ) were found encased in amber, the oldest evidence of sexual reproduction in a flowering plant. Microscopic images showed tubes growing out of pollen and penetrating the flower 's stigma. The pollen was sticky, suggesting it was carried by insects. Ferns Ferns mostly produce large diploid sporophytes with rhizomes, roots and leaves ; and on fertile leaves called sporangium, spores are produced. The spores are released and germinate to produce short, thin gametophytes that are typically heart shaped, small and green in color. The gametophytes or thallus, produce both motile sperm in the antheridia and egg cells in separate archegonia. After rains or when dew deposits a film of water, the motile sperm are splashed away from the antheridia, which are normally produced on the top side of the thallus, and swim in the film of water to the archegonia where they fertilize the egg. To promote out crossing or cross fertilization the sperm are released before the eggs are receptive of the sperm, making it more likely that the sperm will fertilize the eggs of different thallus. A zygote is formed after fertilization, which grows into a new sporophytic plant. The condition of having separate sporephyte and gametophyte plants is called alternation of generations. Other plants with similar reproductive means include the Psilotum, Lycopodium, Selaginella and Equisetum. Bryophytes The bryophytes, which include liverworts, hornworts and mosses, reproduce both sexually and vegetatively. They are small plants found growing in moist locations and like ferns, have motile sperm with flagella and need water to facilitate sexual reproduction. These plants start as a haploid spore that grows into the dominate form, which is a multicellular haploid body with leaf - like structures that photosynthesize. Haploid gametes are produced in antherida and archegonia by mitosis. The sperm released from the antherida respond to chemicals released by ripe archegonia and swim to them in a film of water and fertilize the egg cells thus producing a zygote. The zygote divides by mitotic division and grows into a sporophyte that is diploid. The multicellular diploid sporophyte produces structures called spore capsules, which are connected by seta to the archegonia. The spore capsules produce spores by meiosis, when ripe the capsules burst open and the spores are released. Bryophytes show considerable variation in their breeding structures and the above is a basic outline. Also in some species each plant is one sex while other species produce both sexes on the same plant. Fungi Main article : Mating in fungi Further information : Fungus § Reproduction Puffballs emitting spores Fungi are classified by the methods of sexual reproduction they employ. The outcome of sexual reproduction most often is the production of resting spores that are used to survive inclement times and to spread. There are typically three phases in the sexual reproduction of fungi : plasmogamy, karyogamy and meiosis. The cytoplasm of two parent cells fuse during plasmogamy and the nuclei fuse during karyogamy. New haploid gametes are formed during meiosis and develop into spores. Bacteria and archaea Three distinct processes in prokaryotes are regarded as similar to eukaryotic sex : bacterial transformation, which involves the incorporation of foreign DNA into the bacterial chromosome ; bacterial conjugation, which is a transfer of plasmid DNA between bacteria, but the plasmids are rarely incorporated into the bacterial chromosome ; and gene transfer and genetic exchange in archaea. Bacterial transformation involves the recombination of genetic material and its function is mainly associated with DNA repair. Bacterial transformation is a complex process encoded by numerous bacterial genes, and is a bacterial adaptation for DNA transfer. This process occurs naturally in at least 40 bacterial species. For a bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must enter a special physiological state referred to as competence ( see Natural competence ). Sexual reproduction in early single - celled eukaryotes may have evolved from bacterial transformation, or from a similar process in archaea ( see below ). On the other hand, bacterial conjugation is a type of direct transfer of DNA between two bacteria through an external appendage called the conjugation pilus. Bacterial conjugation is controlled by plasmid genes that are adapted for spreading copies of the plasmid between bacteria. The infrequent integration of a plasmid into a host bacterial chromosome, and the subsequent transfer of a part of the host chromosome to another cell do not appear to be bacterial adaptations. Exposure of hyperthermophilic archaeal Sulfolobus species to DNA damaging conditions induces cellular aggregation accompanied by high frequency genetic marker exchange. Ajon et al. hypothesized that this cellular aggregation enhances species - specific DNA repair by homologous recombination. DNA transfer in Sulfolobus may be an early form of sexual interaction similar to the more well - studied bacterial transformation systems that also involve species - specific DNA transfer leading to homologous recombinational repair of DNA damage. See also Book : Sex Amphimixis ( psychology ) Anisogamy Biological reproduction Hermaphroditism Isogamy Mate choice Mating in fungi Operational sex ratio Outcrossing Allogamy Self - incompatibility Sex Sexual intercourse Transformation ( genetics ) References Jump up ^ `` Fertilization ''. Merriam - Webster. Retrieved 2013 - 11 - 03. Jump up ^ Otto, Sarah P. ; Lenormand, Thomas ( 1 April 2002 ). `` EVOLUTION OF SEX : RESOLVING THE PARADOX OF SEX AND RECOMBINATION ''. Nature Reviews Genetics. 3 ( 4 ) : 252 -- 261. doi : 10.1038 / nrg761. PMID 11967550. Jump up ^ John Maynard Smith The Evolution of Sex 1978. Jump up ^ Ridley M ( 2004 ) Evolution, 3rd edition. Blackwell Publishing, p. 314. Jump up ^ Hussin, Julie G ; Hodgkinson, Alan ; Idaghdour, Youssef ; Grenier, Jean - Christophe ; Goulet, Jean - Philippe ; Gbeha, Elias ; Hip - Ki, Elodie ; Awadalla, Philip ( 2015 ). `` Recombination affects accumulation of damaging and disease - associated mutations in human populations ''. Nature Genetics. 47 ( 4 ) : 400 -- 404. doi : 10.1038 / ng. 3216. PMID 25685891. Lay summary ( 4 March 2015 ). Jump up ^ Cecie Starr ( 2013 ). Biology : The Unity & Diversity of Life ( Ralph Taggart, Christine Evers, Lisa Starr ed. ). Cengage Learning. p. 281. Jump up ^ Vogt, Yngve ( January 29, 2014 ). `` Large testicles are linked to infidelity ''. Phys.org. Retrieved January 31, 2014. Jump up ^ Agrawal, A.F. ( 2001 ). `` Sexual selection and the maintenance of sexual reproduction ''. Nature. 411 ( 6838 ) : 692 -- 5. doi : 10.1038 / 35079590. PMID 11395771. Jump up ^ N.J. Buttefield ( 2000 ). `` Bangiomorpha pubescens n. gen., n. sp. : implications for the evolution of sex, multicellularity, and the Mesoproterozoic / Neoproterozoic radiation of eukaryotes ''. Paleobiology. 26 ( 3 ) : 386 -- 404. doi : 10.1666 / 0094 - 8373 ( 2000 ) 026 < 0386 : BPNGNS > 2.0.CO ; 2. Jump up ^ Gray, J.C. ; Goddard, M.R. ( 2012 ). Bonsall, Michael, ed. `` Gene - flow between niches facilitates local adaptation in sexual populations ''. Ecology Letters. 15 ( 9 ) : 955 -- 962. doi : 10.1111 / j. 1461 - 0248.2012. 01814. x. ^ Jump up to : Michod RE, Bernstein H, Nedelcu AM ; Bernstein ; Nedelcu ( May 2008 ). `` Adaptive value of sex in microbial pathogens '' ( PDF ). Infect. Genet. Evol. 8 ( 3 ) : 267 -- 85. doi : 10.1016 / j. meegid. 2008.01. 002. PMID 18295550. CS1 maint : Multiple names : authors list ( link ) ^ Jump up to : Bernstein, Harris ; Bernstein, Carol ( 2010 ). `` Evolutionary Origin of Recombination during Meiosis ''. BioScience. 60 ( 7 ) : 498 -- 505. doi : 10.1525 / bio. 2010.60. 7.5. ^ Jump up to : Bernstein H, Bernstein C, Michod RE. ( 2012 ) `` DNA Repair as the Primary Adaptive Function of Sex in Bacteria and Eukaryotes ''. Chapter 1, pp. 1 -- 50, in DNA Repair : New Research, Editors S. Kimura and Shimizu S. Nova Sci. Publ., Hauppauge, New York. Open access for reading only. ISBN 978 - 1 - 62100 - 756 - 2 Jump up ^ Colegrave, N ( 2002 ). `` Sex releases the speed limit on evolution ''. Nature. 420 ( 6916 ) : 664 -- 6. Bibcode : 2002Natur. 420... 664C. doi : 10.1038 / nature01191. PMID 12478292. Jump up ^ Kleiman, Maya ; Tannenbaum, Emmanuel ( 2009 ). `` Diploidy and the selective advantage for sexual reproduction in unicellular organisms ''. Theory in Biosciences. 128 ( 4 ) : 249 -- 85. arXiv : 0901.1320. doi : 10.1007 / s12064 - 009 - 0077 - 9. PMID 19902285. Jump up ^ Dimijian, G.G. ( 2005 ). Evolution of sexuality : biology and behavior. Proceedings ( Baylor University. Medical Center ), 18, 244 -- 258. Jump up ^ Hamilton, W.D. ( 1967 ). `` Extraordinary sex ratios ''. Science. 156 ( 3774 ) : 477 -- 488. Bibcode : 1967Sci... 156... 477H. doi : 10.1126 / science. 156.3774. 477. PMID 6021675. Jump up ^ Reichard, U.H. ( 2002 ). `` Monogamy -- A variable relationship '' ( PDF ). Max Planck Research. 3 : 62 -- 7. Archived from the original ( PDF ) on 24 May 2013. Retrieved 24 April 2013. Jump up ^ Lipton, Judith Eve ; Barash, David P. ( 2001 ). The Myth of Monogamy : Fidelity and Infidelity in Animals and People. San Francisco : W.H. Freeman and Company. ISBN 0 - 7167 - 4004 - 4. Jump up ^ Research conducted by Patricia Adair Gowaty. Reported by Morell, V. ( 1998 ). `` Evolution of sex : A new look at monogamy ''. Science. 281 ( 5385 ) : 1982 -- 1983. doi : 10.1126 / science. 281.5385. 1982. PMID 9767050. Jump up ^ BONY FISHES - Reproduction Jump up ^ M. Cavendish ( 2001 ). Endangered Wildlife and Plants of the World. Marshall Cavendish. p. 1252. ISBN 978 - 0 - 7614 - 7194 - 3. Retrieved 2013 - 11 - 03. Jump up ^ Orlando EF, Katsu Y, Miyagawa S, Iguchi T ; Katsu ; Miyagawa ; Iguchi ( 2006 ). `` Cloning and differential expression of estrogen receptor and aromatase genes in the self - fertilizing hermaphrodite and male mangrove rivulus, Kryptolebias marmoratus ''. Journal of Molecular Endocrinology. 37 ( 2 ) : 353 -- 365. doi : 10.1677 / jme. 1.02101. PMID 17032750. CS1 maint : Multiple names : authors list ( link ) Jump up ^ I. Schlupp, J. Parzefall, J.T. Epplen, M. Schartl ; Parzefall ; Epplen ; Schartl ( 2006 ). `` Limia vittata as host species for the Amazon molly : no evidence for sexual reproduction ''. Journal of Fish Biology. 48 ( 4 ) : 792 -- 795. doi : 10.1111 / j. 1095 - 8649.1996. tb01472. x. CS1 maint : Multiple names : authors list ( link ) Jump up ^ Poinar Jr., George O ; Chambers, Kenton L ; Wunderlich, Joerg ( 10 December 2013 ). `` Micropetasos, a new genus of angiosperms from mid-Cretaceous Burmese amber ''. J. Bot. Res. Inst. Texas. 7 ( 2 ) : 745 -- 750. Archived from the original ( PDF ) on 5 January 2014. Lay summary ( 3 January 2014 ). Jump up ^ Jon Lovett Doust ; Lesley Lovett Doust ( 1988 ). Plant Reproductive Ecology : Patterns and Strategies. Oxford University Press. p. 290. ISBN 9780195063943. Jump up ^ Lorenz, MG ; Wackernagel, W ( 1994 ). `` Bacterial gene transfer by natural genetic transformation in the environment ''. Microbiological Reviews. 58 ( 3 ) : 563 -- 602. PMC 372978. PMID 7968924. Jump up ^ Lodé, T ( 2012 ). `` Have Sex or Not ? Lessons from Bacteria ''. Sexual development : genetics, molecular biology, evolution, endocrinology, embryology, and pathology of sex determination and differentiation. 6 ( 6 ) : 325 -- 8. doi : 10.1159 / 000342879. PMID 22986519. Jump up ^ Krebs, JE ; Goldstein, ES ; Kilpatrick, ST ( 2011 ). Lewin 's GENES X. Boston : Jones and Bartlett Publishers. pp. 289 -- 292. ISBN 9780763766320. Jump up ^ Fröls S, Ajon M, Wagner M, Teichmann D, Zolghadr B, Folea M, Boekema EJ, Driessen AJ, Schleper C, Albers SV ( 2008 ). `` UV - inducible cellular aggregation of the hyperthermophilic archaeon Sulfolobus solfataricus is mediated by pili formation ''. Mol Microbiol. 70 ( 4 ) : 938 -- 952. doi : 10.1111 / j. 1365 - 2958.2008. 06459. x. PMID 18990182. ^ Jump up to : Ajon M, Fröls S, van Wolferen M, Stoecker K, Teichmann D, Driessen AJ, Grogan DW, Albers SV, Schleper C ; Fröls ; Van Wolferen ; Stoecker ; Teichmann ; Driessen ; Grogan ; Albers ; Schleper ( November 2011 ). `` UV - inducible DNA exchange in hyperthermophilic archaea mediated by type IV pili ''. Mol. Microbiol. 82 ( 4 ) : 807 -- 17. doi : 10.1111 / j. 1365 - 2958.2011. 07861. x. PMID 21999488. CS1 maint : Multiple names : authors list ( link ) Further reading Pang, K. `` Certificate Biology : New Mastering Basic Concepts '', Hong Kong, 2004 Journal of Biology of Reproduction, accessed in August 2005. `` Sperm Use Heat Sensors To Find The Egg ; Weizmann Institute Research Contributes To Understanding Of Human Fertilization '', Science Daily, 3 February 2003 Michod, RE ; Levin, BE, eds. ( 1987 ). The Evolution of sex : An examination of current ideas. Sunderland, Massachusetts : Sinauer Associates. ISBN 978 - 0878934584. Michod, RE ( 1994 ). Eros and Evolution : A Natural Philosophy of Sex. Perseus Books. ISBN 978 - 0201407549. External links Khan Academy, video lecture Sex Biological terms Sexual dimorphism Male Female Sexual differentiation Feminization Virilization Sex - determination system XY ZW XO Temperature - dependent Haplodiploidy Heterogametic sex Homogametic sex Sex chromosome X chromosome Y chromosome Testis - determining factor Hermaphrodite Sequential hermaphroditism Intersex parasexuality Sexual reproduction Evolution of sexual reproduction Anisogamy Isogamy Germ cell Reproductive system Sex organ Meiosis Gametogenesis Spermatogenesis Oogenesis Gamete spermatozoon ovum Fertilization External Internal Sexual selection Plant reproduction Fungal reproduction Sexual reproduction in animals Sexual intercourse Copulation Human reproduction Sexuality Plant sexuality Animal sexuality Human sexuality Mechanics Differentiation Activity Sex portal Biology portal Animal sexual behaviour General Sexual selection Sexual reproduction evolution reproductive system Courtship display sexual ornamentation handicap principle sexy son hypothesis Fisherian runaway Mating systems mate choice mating call mating plug lek mating Copulation pseudocopulation Fertilisation internal external sperm competition traumatic insemination penile spines Modes monogamy promiscuity polyandry polygyny polygynandry semelparity and iteroparity opportunistic hermaphroditism cuckoldry seasonal synchrony synchronous spawning Sexual dimorphism anisogamy oogamy Bateman 's principle bimaturism cannibalism coercion Sexual conflict interlocus intralocus Interspecies breeding Non-reproductive behavior Fisher 's principle Invertebrates Arthropods crab spider scorpion beetle insect butterfly Cephalopods octopus Cnidaria sea anemone jellyfish coral Echinoderms Gastropods apophallation love dart Sponge Worms earthworm penis fencing Fish Fish reproduction Spawning strategies Polyandry in fish Eels Salmon run Seahorse Sharks Amphibians Sexual selection frogs Frog reproduction Salamanders Reptiles Sexual selection in scaled reptiles lizards snakes side - blotched lizard Crocodilians Tuatara Birds Sexual selection Breeding behaviour golden eagle seabirds Homosexual behavior Mammals Sexual selection rut Lordosis behavior Homosexual behavior Canid African wild dog coyote dingo domestic dog gray wolf red fox spotted hyena Dolphin Elephant European badger Felid lion tiger cheetah domestic cat Fossa Hippopotamus Marsupial kangaroo Pinnipeds walrus Primates human bonobo gorilla olive baboon mandrill ringtailed lemur sexual swelling Raccoon Rodent Short - beaked echidna Biology portal evolutionary biology portal Science portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Sexual_reproduction&oldid=850338008 '' Categories : Sexual reproduction Developmental biology Fertility Reproduction Sexuality Hidden categories : CS1 maint : Multiple names : authors list Wikipedia introduction cleanup from March 2018 All pages needing cleanup Articles covered by WikiProject Wikify from March 2018 All articles covered by WikiProject Wikify All articles with unsourced statements Articles with unsourced statements from September 2017 Articles with unsourced statements from April 2013 Talk Contents About Wikipedia Alemannisch Asturianu বাংলা Bân - lâm - gú Беларуская Български Bosanski Català Čeština Dansk Deutsch Eesti Ελληνικά Español Esperanto فارسی Fiji Hindi Français Galego 한국어 Հայերեն हिन्दी Íslenska Italiano Қазақша Kreyòl ayisyen Magyar മലയാളം Bahasa Melayu မြန်မာဘာသာ Nederlands 日本 語 Norsk Norsk nynorsk Polski Português Română Русский Scots Simple English Slovenčina Slovenščina Српски / srpski Suomi Svenska Tagalog தமிழ் Татарча / tatarça ไทย Türkçe Українська اردو Tiếng Việt Võro 中文 47 more Edit links This page was last edited on 15 July 2018, at 07 : 08 ( UTC ). 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Question: name the single cell from where life begins in all sexually reproducing organisms
Answer: zygote