Related Research Articles
The choanoflagellates are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals. Choanoflagellates are collared flagellates, having a funnel shaped collar of interconnected microvilli at the base of a flagellum. Choanoflagellates are capable of both asexual and sexual reproduction. They have a distinctive cell morphology characterized by an ovoid or spherical cell body 3–10 µm in diameter with a single apical flagellum surrounded by a collar of 30–40 microvilli. Movement of the flagellum creates water currents that can propel free-swimming choanoflagellates through the water column and trap bacteria and detritus against the collar of microvilli, where these foodstuffs are engulfed. This feeding provides a critical link within the global carbon cycle, linking trophic levels. In addition to their critical ecological roles, choanoflagellates are of particular interest to evolutionary biologists studying the origins of multicellularity in animals. As the closest living relatives of animals, choanoflagellates serve as a useful model for reconstructions of the last unicellular ancestor of animals.
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. 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.
Iphisa is a genus of the lizard family Gymnophthalmidae. The genus is monotypic, meaning that it has only one species, Iphisa elegans, and its common name is the glossy shade lizard. I. elegans is native to the Amazon and is typically found in regions of South America, centrally located in the Amazon Basin. The average body length of the glossy shade lizard is 55 mm. Relatively small, these lizards rely on running as their primary form of movement and, interestingly, exhibit death-feigning behavior, which aids in protection from potential predators.
In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each other, further blurring any distinctions. Terms that are sometimes used synonymously but have more precise meanings are cryptic species for two or more species hidden under one species name, sibling species for two species that are each other's closest relative, and species flock for a group of closely related species that live in the same habitat. As informal taxonomic ranks, species group, species aggregate, macrospecies, and superspecies are also in use.
Proterospongia is a genus of single-celled aquatic organisms which form colonies. It belongs to the choanoflagellate class. As a colony-forming choanoflagellate, Proterospongia is of interest to scientists studying the mechanisms of intercellular signaling and adhesion present before animals appeared.
Peripatoides is a genus of velvet worms in the family Peripatopsidae, whose species are found in New Zealand. Like all velvet worms, these animals are nocturnal predators that spit a sticky slime to trap their prey. Species of Peripatoides have 14, 15, or 16 pairs of legs.
The nematodes, roundworms or eelworms constitute the phylum Nematoda. They are a diverse animal phylum inhabiting a broad range of environments. Most species are free-living, feeding on microorganisms, but there are many that are parasitic. The parasitic worms (helminths) are the cause of soil-transmitted helminthiases.
Holozoa is a clade of organisms that includes animals and their closest single-celled relatives, but excludes fungi and all other organisms. Together they amount to more than 1.5 million species of purely heterotrophic organisms, including around 300 unicellular species. It consists of various subgroups, namely Metazoa and the protists Choanoflagellata, Filasterea, Pluriformea and Ichthyosporea. Along with fungi and some other groups, Holozoa is part of the Opisthokonta, a supergroup of eukaryotes. Choanofila was previously used as the name for a group similar in composition to Holozoa, but its usage is discouraged now because it excludes animals and is therefore paraphyletic.
Coniophora is a genus of fungi within the order Boletales. Basidiocarps are corticioid (patch-forming). There are 20 species in the genus, which has a widespread distribution. One notable member is the cellar fungus (C. puteana), which causes wet rot in wood. Molecular analysis has revealed that there are cryptic species in the fungal lineages Coniophora olivacea, C. arida, and C. puteana.
The evolution of nervous systems dates back to the first development of nervous systems in animals. Neurons developed as specialized electrical signaling cells in multicellular animals, adapting the mechanism of action potentials present in motile single-celled and colonial eukaryotes. Primitive systems, like those found in protists, use chemical signalling for movement and sensitivity; data suggests these were precursors to modern neural cell types and their synapses. When some animals started living a mobile lifestyle and eating larger food particles externally, they developed ciliated epithelia, contractile muscles and coordinating & sensitive neurons for it in their outer layer.
Bombus magnus is a species of bumblebee. It is native to Europe. It is known by the common name northern white-tailed bumblebee.
Apophysomyces variabilis is an emerging fungal pathogen that can cause serious and sometimes fatal infection in humans. This fungus is a soil-dwelling saprobe with tropical to subtropical distribution. It is a zygomycete that causes mucormycosis, an infection in humans brought about by fungi in the order Mucorales. Infectious cases have been reported globally in locations including the Americas, Southeast Asia, India, and Australia. Apophysomyces variabilis infections are not transmissible from person to person.
Amphipholis squamata, common names brooding snake star and dwarf brittle star, is a species complex of brittle stars in the family Amphiuridae.
Transversotrema elegans is a species of trematodes found from species of the labrid genus Choerodon on Heron Island and Lizard Island. It is characterised by its number of vitelline follicles enclosed by its cyclocoel and by the size of its testicle.
Choanozoa is a clade of opisthokont eukaryotes consisting of the choanoflagellates (Choanoflagellatea) and the animals. The sister-group relationship between the choanoflagellates and animals has important implications for the origin of the animals. The clade was identified in 2015 by Graham Budd and Sören Jensen, who used the name Apoikozoa. The 2018 revision of the classification first proposed by the International Society of Protistologists in 2012 recommends the use of the name Choanozoa.
Epiperipatus vespucci is a species of velvet worm in the Peripatidae family. This species is dark with a complex pattern on its dorsal surface. The male of this species has 30 pairs of legs; females have 33 or 34. The type locality is in Colombia.
Peripatopsis moseleyi is a species of velvet worm in the Peripatopsidae family. Males of this species have 20 to 24 pairs of legs with claws ; females have 19 to 23 pairs of legs with claws. Females range from 11 mm to 75 mm in length, whereas males range from 9 mm to 50 mm. The type locality is in South Africa.
Cladospongia is a genus of choanoflagellate. The type species is found in India (Madras).
Transversotrema is a genus of trematodes in the family Transversotrematidae.
When speciation is not driven by divergent natural selection, it can be said to be nonecological, so as to distinguish it from the typical definition of ecological speciation: "It is useful to consider ecological speciation as its own form of species formation because it focuses on an explicit mechanism of speciation: namely divergent natural selection. There are numerous ways other than via divergent natural selection in which populations might become genetically differentiated and reproductively isolated." It is likely that many instances of nonecological speciation are allopatric, especially when the organisms in question are poor dispersers, however sympatric nonecological speciation may also be possible, especially when accompanied by an "instant" loss of reproductive compatibility, as when polyploidization happens. Other potential mechanisms for nonecological speciation include mutation-order speciation and changes in chirality in gastropods.
References
- ↑ Notes de Protistologie. I. Craspédomonadines: Matériel systématique. H De Saedeleer - Ann. Soc. Roy. Belg, 1927
- ↑ Stoupin, D; Kiss, AK; Arndt, H; Shatilovich, AV; Gilichinsky, DA; Nitsche, F (November 2012). "Cryptic diversity within the choanoflagellate morphospecies complex Codosiga botrytis - phylogeny and morphology of ancient and modern isolates". European Journal of Protistology. 48 (4): 263–73. doi:10.1016/j.ejop.2012.01.004. PMID 22342133.
