What are gill slits used for?
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks, and rays, as well as primitive fish such as lampreys.
Pharyngeal slits resembling gill slits are transiently present during the embryonic stages of tetrapod development. However, it is now accepted that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates.
- Pharyngeal slits are a third chordate feature; these are openings between the pharynx, or throat, and the outside. They have been modified extensively in the course of evolution. In primitive chordates, these slits are used to filter food particles from the water.
- A notochord is a primitive beginning to the backbone. It appears in embryos as a small flexible rod made from cells from the mesoderm, which is one of the three layers of cells of embryos. Notochords are only found in the phylum chordata, a group of animals that includes humans.
- In chordates, four common features appear at some point during development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.
Charles Darwin listed a number of putative human vestigial features, which he termed rudimentary, in The Descent of Man (1890). These included the muscles of the ear, wisdom teeth, the appendix, the tail bone, body hair, and the semilunar fold in the corner of the eye.
- So here are ten vestigial traits and behaviors that you may still be clinging to.
- 10) The Appendix. The appendix is probably the most widely known vestigial human organ.
- 9) Sinuses.
- 8) Wisdom Teeth.
- 7) Coccyx.
- 6) The Ear.
- 5) Arrector Pili.
- 4) Tonsils.
- 3) Male Nipples.
- Vestigial organs are organs of the body which are smaller and simpler than those in related species. They have lost, or almost lost their original function. But one type of snake – the boas – have vestigial rear legs and pelvis. The human vermiform appendix is another example.
- In some cases, life in the developed world—rather than insufficient medical technology—has obscured important functions of vestigial organs. The appendix, a narrow tube that hangs off one end of the colon, is probably the most famous "junk" organ. But it's turned out to be important even today—in certain circumstances.
Updated: 26th October 2019