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ciało-człowieka: Alligator gar
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2 zapisanych źródełEvidence: 100 • authority: 72
The alligator gar (Atractosteus spatula) is a euryhaline ray-finned fish in the clade Ginglymodi of the infraclass Holostei , being most closely related to the bowfins. It is the largest species in the gar family (Lepisosteidae), and is among the largest freshwater fishes in North America. The fossil record traces its group's existence back to the Early Cretaceous over 100 million years ago. Gars are often referred to as "primitive fishes" or "living fossils", because they have retained some morphological characteristics of their early ancestors, such as a spiral valve intestine, which is also common to the digestive system of sharks, and the ability to breathe in both air and water. Their…
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Immunity: defense against infections essential for all living organisms.. All organisms need protection against infection. Bacteria are often primarily seen as infectious agents, but they also need protection against bacterial viruses, so-called bacteriophages. To this end, bacteria have developed very complex defense systems, including apoptosis-like mechanisms, restriction enzymes, and even adaptive-type mechanisms involving immunological memory of immune responses through a system called CRISPR-Cas. An earlier dominating view was that adaptive immunity in eukaryotes only exists in jawed vertebrates, as their immune system includes the classical and highly variable immunoglobulins (Igs) a…
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