Fish are vertebrate animals, that is, they all have a vertebral column or âspineâ. There are two main groups of fish, bony fish (Teleosts) and cartilaginous fish (Elasmobranchs). As the common names imply, the skeletons of teleosts are made of bone while the elasmobranchs have cartilaginous skeletons.
Villard found a third type of radiation from pitchblende: gamma rays, which were much the same as X-rays. Then in 1896 Pierre and Marie Curie gave the name 'radioactivity' to this phenomenon, and in 1898 isolated polonium and radium from the pitchblende.
History. Radium was discovered in 1898 by Madame Curie in the pitchblende or uraninite of North Bohemia, where it occurs.There is about 1 g of radium in 7 tons of pitchblende. The element was isolated in 1911 by Mme.istory. Radium was discovered in 1898 by Madame Curie in the pitchblende or uraninite of North Bohemia, where it occurs.