Affects of Varying Salinity on Flatworm Dugesia dorotocephala

Affects of Varying Salinity on Flatworm Dugesia dorotocephala

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Affects of Varying Salinity on Flatworm Dugesia dorotocephala Courtney Williams TA: Stephanie Weldon Tuesday 10:10 May 1 st , 2011
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Abstract: The purpose of this experiment is to test how added concentrations of salt affect the movement and reaction time of the freshwater planarian flatworm Dugesia dorotocephala as the amount of salt added to their environment was increased the worms motility and respiration decreased at a quicker rate. The planarians were able to withstand the change in tonicity to their environments with concentrations of 1%-10% added salt but did not survive in concentrations of 15%-20% added salt. Our results supported our hypothesis; the more salt in the water the less movement there will be from the worms because their muscle cells cannot contract normally due to dehydration and affected breathing. Introduction: Approximately 600 million years ago simple animals began to evolve from multi-cellular life forms and from that time on organisms have continued to evolve, adapt and specialize to their surroundings. Various organisms had to each adapt differently to the specific environment their niche fit into, a necessity if that animal intended to survive and pass it’s genetic material on to future generations. With the correct genetic material and behaviors a species could adapt to ecological areas of very high or very low temperatures, acidic or basic environments and environments with high salinity (salt water) or little to no salinity (freshwater). However, for all other animals once an organism has adapted to a specific environment it is very difficult for that same organism to survive in a completely different set of surroundings without generations of adaptation in between, and an instantaneous change of surroundings will most likely result in death.
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Very few organisms can live in both fresh-water and salt-water environments, there are a few exceptions such as salmon and bull-sharks whom do in fact migrate from saltwater to freshwater environments, but for many other freshwater organism the addition of high amounts of salinity to their environment can be deadly. All freshwater organism’s cells have a specific solute concentration and membrane permeability which favors a freshwater environment so changes in the environment will result in changes in this solute concentration and membrane permeability and the overall tonicity of the organism’s cells. Tonicity is the ability of a cell to gain or lose water, tonicity depends on the concentration of solutes that cannot cross the membrane (salt) relative to that of the inside of a cell. There are different forms of tonicity; hypotonic solutions have a lesser solute concentration then the inside of the cell, isotonic solutions have equal solute concentrations both inside and outside of the cell and, hypertonic solutions have a higher solute concentration then the inside of the cell. The more salt you add to a solution the more hypertonic it will become as well as more deadly to un-
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This note was uploaded on 07/05/2011 for the course BIO NA taught by Professor Stanger-hall during the Spring '09 term at University of Georgia Athens.

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Affects of Varying Salinity on Flatworm Dugesia dorotocephala

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