How does locomotion take place in leech?

Explanation

(a) Looping or crawling movement : Crawling movement is brought about by the contraction and relaxation of muscles . The two sukers serve for attachment during movement.
(b)Swimming movement : Leeches swim very actively and perform undulating movement in water.
(ii) Fossilization in plants : The process of formation of fossil in the rocks is called fossilization.
1. Petrifaction : Minerals like silica slowly penetrate in and replace the original organic tissue . This method can preserve hard and soft parts (e.g.) wood fossils .
2. Mold and Cast : A replica of a plant or animal is preserved in sedimentary rocks . when the organism get buried in sediment it is dissolved by underground water leaving a hollow depressin called Mold. It shows only the original shape and not the internal structure. Minerals or sediments fill the hollow depression and forms a cast .
3. Preservation : The entire plant may be preserved to protect from the orginism for decay . Ice or amber (tree sap) can be used for preservation.
4. Compression : When the organism dies , the hard parts settle at the bottom of the sea bed and are covered by sediment . The process goes on continuously and the fossils are formed.
5. Infiltration : The precipitation of minerals takes place which later on infiltrate the cell wall. The process is brought about by several mineral element such as silica, calcium carbonate and magnesium carbonate.