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[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]
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]
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 .
The abbreviation is not always a short form of the word used in the clue. For example: "Knight" for N (the symbol used in chess notation) Taking this one stage further, the clue word can hint at the word or words to be abbreviated rather than giving the word itself. For example: "About" for C or CA (for "circa"), or RE.
The sperm released from the antheridia respond to chemicals released by ripe archegonia and swim to them in a film of water and fertilize the egg cells, thus producing zygotes that are diploid. The zygote divides repeatedly by mitotic division and grows into a diploid sporophyte.
A sequential hermaphrodite produces eggs (female gametes) and sperm (male gametes) at different stages in life. [2] Sequential hermaphroditism occurs in many fish , gastropods , and plants. Species that can undergo these changes do so as a normal event within their reproductive cycle, usually cued by either social structure or the achievement ...
Some proteins and other features that are key for sexual reproduction may have arisen in bacteria, but sexual reproduction is believed to have developed in an ancient eukaryotic ancestor. [10] In eukaryotes, diploid precursor cells divide to produce haploid cells in a process called meiosis. In meiosis, DNA is replicated to produce a total of ...
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]