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All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium. [2] [3] Multicellular organisms arise in various ways, for example by cell division or by aggregation of many single ...
Animal – multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material , breathe oxygen , are able to move , reproduce sexually , and grow from a hollow sphere of cells, the blastula , during embryonic development .
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
The multicellular eukaryotes include the animals, plants, and fungi, but again, these groups too contain many unicellular species. [11] Eukaryotic cells are typically much larger than those of prokaryotes—the bacteria and the archaea—having a volume of around 10,000 times greater.
When first introduced by Georg Goldfuss, in 1818, the taxon Protozoa was erected as a class within the Animalia, [3] with the word 'protozoa' meaning "first animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae. [4] [5] [6]
The situation is quite different from that in animals, where the fundamental process is that a multicellular diploid (2n) individual directly produces haploid (n) gametes by meiosis. In animals, spores (i.e. haploid cells which are able to undergo mitosis) are not produced, so there is no asexual multicellular generation.
Microscopic organisms were increasingly constrained in the plant/animal dichotomy. In 1858, the palaeontolgist Richard Owen was the first to define Protozoa as a separate kingdom of eukaryotic organisms, with "nucleated cells" and the "common organic characters" of plants and animals, although he also included sponges within protozoa. [28]
In this system the multicellular animals are descended from the same ancestor as both the unicellular choanoflagellates and the fungi which form the Opisthokonta. [45] Plants are thought to be more distantly related to animals and fungi.