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Phylogenetic inertia or phylogenetic constraint refers to the limitations on the future evolutionary pathways that have been imposed by previous adaptations. [ 1 ] Charles Darwin first recognized this phenomenon, though the term was later coined by Huber in 1939. [ 2 ]
The phyllosoma larva of spiny lobsters has a long planktonic life before metamorphosing into the puerulus stage, which is the transitional stage from planktonic to a benthic existence. [ 3 ] [ 4 ] Despite the importance of larval survival to predict recruitment, not much is known about the biology of phyllosoma larvae. [ 5 ]
A phyllosoma larva of the spiny lobster Palinurus elephas, from Ernst Haeckel's Kunstformen der Natur. The larvae of the Achelata (slipper lobsters, spiny lobsters and furry lobsters) are unlike any other crustacean larvae. The larvae are known as phyllosoma, after the genus Phyllosoma erected by William Elford Leach in 1817. They are flattened ...
[12] [13] The sequence of the 16S ribosomal RNA gene, a vital gene encoding a part of the ribosome, was used to find the broad phylogenetic relationships between all extant life. The analysis by Carl Woese resulted in the three-domain system , arguing for two major splits in the early evolution of life.
However, as found by Rebecci et al. in their 2020 study, desiccation is a major selective force in only terrestrial environments, which the larva will combat by dauer dormancy. [19] Phylogenetic analysis of nematodes suggests that parasitic lineages are derived overwhelmingly from terrestrial ancestors, even with lineages that reside in water.
The basic annelid form consists of multiple segments. Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion . Septa separate the segments of many species, but are poorly defined or absent in others, and Echiura and Sipuncula show no obvious signs of segmentation.
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).
A few species from other phyla; the nemertean pilidium larva, the larva of the phoronid species Phoronopsis harmeri and the acorn worm larva Schizocardium californicum, do not depend on Hox genes in their larval development either, but need them during metamorphosis to reach their adult form.