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Some cells in other animals may be flagellate, for instance the spermatozoa of most animal phyla. Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, and some gymnosperms and closely related plants do so. [2] Likewise, most fungi do not produce cells with flagellae, but the primitive fungal chytrids do. [3]
[6] [7] [8] There are almost invariably only two gamete types, all analyses showing that intermediate gamete sizes are eliminated due to selection. [9] [10] Since intermediate sized gametes do not have the same advantages as small or large ones, [11] they do worse than small ones in mobility and numbers, and worse than large ones in supply. [12]
Two single-celled haploid gametes, each containing n unpaired chromosomes, fuse to form a single-celled diploid zygote, which now contains n pairs of chromosomes, i.e. 2n chromosomes in total. [ 17 ] The single-celled diploid zygote germinates, dividing by the normal process ( mitosis ), which maintains the number of chromosomes at 2 n .
Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes.Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis.
The tops of the gametophytes (2) can be discerned as well. Inset shows the surrounding, black poplars growing on sandy loam on the bank of a kolk , with the detail area marked. In biology , a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in ...
The mature spermatozoids of the fern Asplenium onopteris are 8 to 8.5 micrometers in length and contain 50 flagella. [16] The zoid of the cycad can be up to 300 to 500 micrometers long and can contain thousands of flagella. [5] The zoid of the ginkgo is approximately 86 micrometers long and also can contain thousands of flagella. [5]
Automixis [1] is the fusion of (typically haploid) nuclei or gametes derived from the same individual. [2] The term covers several reproductive mechanisms, some of which are parthenogenetic. [3] Diploidy might be restored by the doubling of the chromosomes without cell division before meiosis begins or after meiosis is completed.
A gonad, sex gland, or reproductive gland [1] is a mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. [2] The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells.