A certain small fish isproving to be very helpful in answering the questions about evolution. The Gasterosteus Aculeatus commonly rferred to as the three spine stickleback was usually found in the sea. However, after around 10,000 passed, and there were changes in the environment, the glaciers melted and these fish found their way into freshwater bodies, mainly streams and lakes.Since they were not used to fresh water environments,the fish lost some of their original traits. They lost their bony plates and spines and gained new characteristics. Their phsicological and behavioral characteriostics changed. Many studies have shown that these changes are not as a result of gene mutation, but are due to the changing of gene activities. This observation should then help in paying more atention on the importance and the role of gene in the process of evolution of every organism, most inportantly the the human being.
The reoccuringi of evolution of fresh water characteristics in marine sticklebacks has for a long time amazed biologist dealing with evolution. In these fish, the changes have copied themselves very many times, from the time the first fish migrated from the sea into the fresh water bodies in different parts of the nothern region . These include regions like Alaska, California, Europe and Japan.It has been discovered that all the fish that have been found in all these different regiions have gone through the same evolution in all parts, including the kidneys, the shape of the body, the sizes of the eyes, and a number of bony plates on their bodies. An evolutionary biologist from Stanford University on Palo Alto california, David Kingsley has used this evolution to look at and try and explain how these changes occure as a result of the genome.
David and the Broad Institute in Cambridge Massachusetts Kerstin Lindblad-Toh and their collegues began by externining the DNA of a stickleback fish from an Alaska lake to a very high degree of accuracey. With this as the reference sequence guide,the biologists have been able to sequence ten other addittional pairs or stickleback genomes from around the world with a lot of ease. Every pair consisted of a marine stickleback and its fresh water counterpart.
Usually,a gane should be simillar among fish of the same location. Hawerever,if theerre was a recurrence of evolution at a particular area of the genome, then that region should be simillar in all the freshwater fish,no matter the distance from each other. Lingsley’s group examined all the genomes from regions where evolution has taken place repeatedly and found 147 of them, hence conferming that evolution had taken place repeatedly in these fish.
From there, the reaserchers then estgablished the number of regiions that contained the gene. Atfer that they compared the sequences of the different fish. If the gene was the same in all the fish found in fresh water but not the same with the marine fish, the biologist made an assumption that the gene was the one responsible for the adaptation in fresh water. This occured in 17 percent of the regions the group visited. However, 41 percent of the region had no gene, giving a clear indication that the changes that were responsible for the adaptation were regulating the activity of the genes elsewhere in the genome. The other 43 percent consisted of a gene a a regulatory DNA, but since the regulatory DNA was similar among the fresh water fish, the biologist made an assumption that the regulatory changes were at the heart of these adaptations as well.
Many researchers have documented the reoccuring of evolution in other organisms, but the stickleback are different and one of a kind in that this freshwatwer transition has taken place time and again. Erica Bree Rosenblum of the University of California says that the sticklebacks have been a phenomenal system for the understanding of rapid evolution. Berkeley who wasnt involved in the reseach notes that the repeated evolution can occure as a result of reusing the same genetic mechanism repeatedly. As for now, Kingsley has a wide accounting of the reused genetic changes involved in the change from marine to fresh water.He and other reaserchers are trying to find out what traits these changes control.