Evolution of sexual reproduction

The study of how sexual reproduction originated and diversified, including the evolution of meiosis, gamete fusion, and mating systems.

Meiosis: A cell division process that halves chromosome number and produces genetically varied haploid cells. Its ancient origin is central to explaining how sexual reproduction became possible.
Last universal common ancestor: The most recent ancestral population from which all living organisms descend. Evidence of ancient sexual machinery is often assessed against the biology of this ancestor.
Eukaryote: An organism whose cells contain a nucleus and membrane-bound organelles. Known sexual life cycles occur among eukaryotes, making their cell history essential context.
Fungal mating system: The genetic and cellular arrangements that regulate mating and sexual compatibility in fungi. Fungi display diverse mating types and life cycles that illuminate alternatives to animal sexes.
Twofold cost of sex: The potential disadvantage that sexual females produce fewer reproducing descendants than equivalent asexual females. Any account of sex’s origins must explain how its benefits could outweigh this demographic cost.
Syngamy: The fusion of two gametes to form a zygote. Gamete fusion is the defining event whose evolutionary emergence must be accounted for.
Eukaryogenesis: The evolutionary emergence of eukaryotic cells, with nuclei and complex internal organization. Sexual reproduction appears closely tied to the early history of eukaryotic cells.
Haploid and diploid: Haploid cells have one chromosome set; diploid cells have two. Alternation between these states defines the basic chromosome cycle of sex.
Sexual reproduction in plants: Plant reproduction involving meiosis, gametes, and fertilization, often with alternating generations. Plant life cycles show how sexual reproduction can diversify while retaining meiosis and syngamy.
Evolution of sex ratios: The study of how populations evolve proportions of males, females, or other mating classes. Sex allocation exposes conflicts between individual reproductive strategies and population-wide mating balance.

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Reproductive systemRelated: Evolution helps explain the diversity of reproductive structures and strategies.