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===Life history strategy===
The life cycle of coccolithophores is complex and is characterized by an alternation of both asexual and sexual phases. The asexual phase is known as the [[diploidhaploid]] andphase, while the sexual phase is known as the [[haploiddiploid]] phasesphase. They alternate fromDuring the haploid tophase, diploidcoccolithophores phaseproduce haploid cells through [[syngamymitosis]]. andThese fromhaploid diploidcells tocan then divide further through mitosis or undergo sexual reproduction with other haploid cells. The resulting diploid cell goes through [[meiosis]]. Into contrastproduce withhaploid mostcells organismsagain, withstarting alternatingthe lifecycle cyclesover. With coccolithophores, asexual reproduction by mitosis is possible in both phases of the life cycle, which is a contrast with most other organisms that have alternating life cycles.<ref name="Young2003"/> Both [[abiotic]] and [[biotic factors]] may affect the frequency with which each phase occurs.<ref name=Vardi2012>{{citation |journal=Proceedings of the National Academy of Sciences |volume=109 |issue=47 |year=2012 |pages=19327–19332 |title=Host–virus dynamics and subcellular controls of cell fate in a natural coccolithophore population |first=A. |last=Vardi |doi=10.1073/pnas.1208895109 |pmid=23134731 |display-authors=etal |bibcode = 2012PNAS..10919327V |pmc=3511156 |doi-access=free }}</ref>
 
Coccolithophores [[asexual reproduction|reproduce asexually]] through [[Fission (biology)|binary fission.]] In this process the coccoliths from the parent cell are divided between the two daughter cells. There have been suggestions stating the possible presence of a sexual reproduction process due to the diploid stages of the coccolithophores, but this process has never been observed.<ref name=Houdan2006>{{citation |journal=Aquatic Microbial Ecology |volume=44 |year=2006 |pages=291–301 |title=. Ecology of oceanic coccolithophores. I. Nutritional preferences of the two stages in the life cycle of Coccolithus braarudii and Calcidiscus leptoporus |last1=Houdan |doi=10.3354/ame044291|last2=Probert |first2=I |last3=Zatylny |first3=C |last4=Véron |first4=B |last5=Billard |first5=C |display-authors=etal|doi-access=free }}</ref>
 
K or r- selected strategies of coccolithophores depend on their life cycle stage. When coccolithophores are diploid, they are r-selected. In this phase they tolerate a wider range of nutrient compositions. When they are haploid they are K- selected and are often more competitive in stable low nutrient environments.<ref name=Houdan2006 /> Most coccolithophores are K strategist and are usually found on nutrient-poor surface waters. They are poor competitors when compared to other phytoplankton and thrive in habitats where other phytoplankton would not survive.<ref name=Hogan2009 />
[[R/K selection theory|K or r- selected strategies]] of coccolithophores depend on their life cycle stage. When coccolithophores are diploid, they are r-selected. In this phase they tolerate a wider range of nutrient compositions. When they are haploid they are K- selected and are often more competitive in stable low nutrient environments.<ref name=Houdan2006 /> Most coccolithophores are K strategist and are usually found on nutrient-poor surface waters. They are poor competitors when compared to other phytoplankton and thrive in habitats where other phytoplankton would not survive.<ref name=Hogan2009 /> These two stages in the life cycle of coccolithophores occur seasonally, where more nutrition is available in warmer seasons and less is available in cooler seasons. This type of life cycle is known as a complex heteromorphic life cycle.<ref name=Houdan2006 />
 
===Global distribution===
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