Gametes (in Greek: γαμέτες) —also known as sex cells, or spores—are the specialized germ cells that come together during fertilization (conception) in organisms that reproduce sexually. The creation of gametes is called gametogenesis, in which gametocytes divide by meiosis into various gametes. In those species that produce two morphologically distinct types of gametes, and in which a particular individual produces only one type, "females" of the species produce the larger gamete called an ovum (or egg) and "males" produce the smaller gamete termed (in animals) a spermatozoon (or sperm cell). The equivalent "male" structure in higher plants is called a pollen grain. Organs that produce gametes are called gonads in animals, and archegonia or antheridia in plants. The term spore has several different meanings in biology. ... A germ cell is a kind of cell that is part of the germline, and is involved in the reproduction of organisms. ... Categories: Biology stubs ... In biology and ecology, an organism (in Greek organon = instrument) is a complex adaptive system of organs that influence each other in such a way that they function as a more or less stable whole and have properties of life. ... Sexual reproduction is a process of reproduction involving the merging of two gametes from the same species to produce a new organism. ... Gametogenesis is the creation of gametes by meiotic division of gametocytes into various gametes. ... A gametocyte is a eukaryotic germ cell that divides by mitosis into other gametocytes or by meiosis into gametes. ... In biology, meiosis is the process that transforms one diploid cell into four haploid cells in eukaryotes in order to redistribute the diploids cells genome. ... Female symbol Female is the sex of an organism, or a part of an organism, which produces egg cells. ... A human ovum An ovum (loosely, egg or egg cell) is a female sex cell or gamete. ... Male symbol Male is the sex of an organism, or a part of an organism, which produces sperm. ... A sperm cell, spermatozoon ( spermatozoa) (in Greek: sperma = semen and zoon = alive), or spermatozoan, is the haploid cell that is the male gamete. ... SEM image of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomea purpurea), hollyhock (Sildalcea malviflora), lily (Lilium auratum), primrose (Oenothera fruticosa), and castor bean (Ricinus communis). ... The gonad is the organ that makes gametes. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (flatworms, echinoderms, etc. ... An archegonium (pl: archegonia) (from the Greek arche = beginning and gonos = born) is a multicellular structure or organ of the gametophyte phase of certain plants producing and containing the ovum or female gamete. ... Diagram of antheridium anatomy An antheridium (plural: antheridia) is a structure or organ of the gametophyte phase of certain plants producing and containing the spermatids or male gametes. ... Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern...

Gametes are haploid cells; that is, they contain one complete set of chromosomes (the actual number varies from species to species). When two gametes unite (typically in animals, involving a sperm and an egg), they form a zygote—a cell having two complete sets of chromosomes and therefore diploid. The zygote cell receives one set of chromosomes from each of the two gametes involved in the union. After fusion of the two gamete nuclei, and after multiple cell divisions and cellular differentiation, a zygote develops, first into an embryo, and ultimately into a mature individual capable of producing gametes. Gametes from a mature diploid individual will be produced in the gonadal tissue through meiosis—a process of cellular division that reduces the number of sets of chromosomes from two to one (i.e., produces haploid gametes). Haploid (meaning simple in Greek) cells have only one copy of each chromosome. ... Figure 1: Chromosome. ... A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization. ... Diploid (meaning double in Greek) cells have two copies (homologs) of each chromosome (both sex- and non-sex determining chromosomes), usually one from the mother and one from the father. ... Nucleus can mean: The Nuclear Envelope The nucleus is enveloped by a pair of membranes enclosing a lumen that is continuous with that of the endoplasmic reticulum. ... Cell division is the process by which a cell (called the parent cell) divides into two cells (called daughter cells). ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ... Developmental biology is the study of the process by which organisms grow and develop. ... Embryos (and one tadpole) of the wrinkled frog (Rana rugosa). ... In biology, meiosis is the process that transforms one diploid cell into four haploid cells in eukaryotes in order to redistribute the diploids cells genome. ...

The diploid somatic cells of an individual will contain one copy of the chromosome set from the sperm and one copy of the chromosome set from the egg—that is, the cells of the offspring will have genes expressing characteristics of both the father and the mother. A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the somatic cells of the individual that produced the gametes. They can be hybrids produced through crossover (a form of genetic recombination) of chromosomes, something that takes place in meiosis. This hybridization has a random element, and the chromosomes tend to be a little different in every gamete that an individual produces. This recombination and the fact that the two chromosome sets ultimately have come from either a grandmother or a grandfather on each parental side account for the genetic dissimilarity of siblings. A somatic cell is a type of cell in an organism, such as the human body it also have [[homologous chromosomes, pairs of like chromosomes. ... Chromosomal crossover is the process by which two chromosomes, paired up during Prophase I of meiosis, exchange some distal portion of their DNA. Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but to the different end piece. ... Genetic recombination is the transmission-genetic process by which the combinations of alleles observed at different loci (plural of locus) in two parental individuals become shuffled in offspring individuals. ... Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... A family of Ouagadougou, Burkina Faso in 1997 A family is a domestic group of people, or a number of domestic groups, typically affiliated by birth or marriage, or by comparable legal relationships including domestic partnership, adoption, surname and in some cases ownership (as was the case in the Roman...

Gamete size and evolution

Isogamy occurs when gametes from both sexes are the same size. Anisogamy or heterogamy is the condition wherein females and males produce gametes of different sizes. Isogamy is considered to be the ancestral condition, the evolution of gametes of unequal size is a current area of evolutionary research.

Reference

• Randerson, J.P., and Hurst, L.D. 2001. The uncertain evolution of the sexes. Trends in Ecology & Evolution 16(10):571-579

External link

• Gametogenesis (spermatogenesis, oogenesis) & fertilization