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Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
In humans, the vermiform appendix is sometimes called a vestigial structure as it has lost much of its ancestral digestive function.. Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. [1]
Bichirs as a whole may more closely resemble the common ancestor of lobe-finned fish and bony fish as a whole than coelacanths due to their deepwater adaptations. Acipenseriformes including sturgeons and paddlefish have small seemingly vestigial spiracles much like coelacanths [ 11 ] further reduced in Holostei [ 12 ] and completely absent in ...
In fish, the arches support the gills and are known as the branchial arches, or gill arches. In the human embryo , the arches are first seen during the fourth week of development . They appear as a series of outpouchings of mesoderm on both sides of the developing pharynx .
Branchial arches or gill arches are a series of paired bony/cartilaginous "loops" behind the throat (pharyngeal cavity) of fish, which support the fish gills. As chordates , all vertebrate embryos develop pharyngeal arches , though the eventual fate of these arches varies between taxa .
Thus the zoologist Newman stated in the Scopes Trial: "There are, according to Wiedersheim, no less than 180 vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities." Some of the vestigial organs or organs containing evolutionary vestigial structures, as listed on the article about him: Adenoids
The hermaphroditic adults are oviparous and produce eggs into the water which hatch prior to attaching to the gills of a fish host and developing into an oncomiracidium. [7] Adult Dactylogyrus lay about 4-10 eggs per day. [8] After the eggs hatch, water currents aid the free-swimming ciliated larva in reaching its host.
Gills or gill-like organs, located in different parts of the body, are found in various groups of aquatic animals, including mollusks, crustaceans, insects, fish, and amphibians. Semiterrestrial marine animals such as crabs and mudskippers have gill chambers in which they store water, enabling them to use the dissolved oxygen when they are on land.