Search results
Results From The WOW.Com Content Network
Protists are a large group of diverse eukaryotic microorganisms, mainly unicellular animals and plants, that do not form tissues. [8] The earliest eukaryotes were likely protists. Mating and sexual reproduction are widespread among extant eukaryotes including protists such as Paramecium and Chlamydomonas.
Although protist flagella have a diversity of forms and functions, [11] two large families, flagellates and ciliates, can be distinguished by the shape and beating pattern of their flagella. [ 2 ] In the phylogenetic tree on the right, aquatic organisms (living in marine, brackish, or freshwater environments) have their branches drawn in blue ...
Again, however, this is not applicable to all sexual organisms. There are numerous species which are sexual but do not have a genetic-loss problem because they do not produce males or females. Yeast, for example, are isogamous sexual organisms which have two mating types which fuse and recombine their haploid genomes. Both sexes reproduce ...
[4] [5] Although most protists are unicellular, there is a considerable range of multicellularity amongst them; some form colonies or multicellular structures visible to the naked eye. The term 'protist' refers to all eukaryotes that are not animals, plants or fungi, the three traditional eukaryotic kingdoms.
The history of the study of protists has its origins in the 17th century. Since the beginning, the study of protists has been intimately linked to developments in microscopy , which have allowed important advances in the understanding of these organisms due to their generally microscopic nature.
Reproduction in Protozoa can be sexual or asexual. [38] Most Protozoa reproduce asexually through binary fission. [39] Many parasitic Protozoa reproduce both asexually and sexually. [38] However, sexual reproduction is rare among free-living protozoa and it usually occurs when food is scarce or the environment changes drastically. [40]
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. [43] Both abiotic and biotic factors may affect the frequency with which each phase occurs. [44] Coccolithophores reproduce asexually through binary fission.
Most of the segments move towards the anterior end of the cell, as do most of the enlarged micronuclei which position themselves between the macronuclei nodes. Then the micronuclei undergo meiosis first producing four daughter nuclei. Three of the daughter nuclei disappear while the fourth one undergoes mitosis and produces two haploid gametic ...