The Things They Carried Essay

Brine Shrimp Lab

Abstract: In our lab, we observed the adaptation of brine shrimp eggs when they are exposed to different salt concentrations. Brine shrimp are greatly influenced by environmental factors and their relatively short development time makes them great candidates for an experiment for observing adaptation. We tested populations of brine shrimp by exposing them to different concentrations of salt solution (NaCl). The lab was spaced out over three days and each day we collected data after we exposed the shrimp. On the first day we set up the lab by counting the amount of shrimp we were exposing to each concentration of NaCl. We used 5 different concentrations: 0%, 0.5%, 1%, 1.5%, and 2%. We let the population sit for 24 hours before counting the number of eggs that hatched and the number of eggs that died or partially hatched. We then let them sit for another 24 hours and collected the same data. Using this data we could calculate the hatching viability which would tell us which concentration of NaCl was easier for the brine shrimp to adapt to and survive in. We recorded this data in our data tables and made a graph showing the relationship between the salt concentrations and the hatching viability for the brine shrimp.

Introduction: In this lab we observed the effects that the environment had on a population of brine shrimp eggs. Since brine shrimp take a relatively short amount of time to develop, we used them in our lab to observe how some individuals in a population are better adapted to survive in different conditions. We tested the population of brine shrimp with different percentages of salt solutions using sodium chloride (NaCl) and observed to see how many eggs either survived, hatched, or died. This lab was exercised over a period of three days. On the first day we prepared five beakers of 30 mL salt solutions of different percentages NaCl. We then labeled five petri dishes 0%, 0.5%, 1%, 1.5%, and 2%. We then poured 30 mL of the appropriate percentage salt solution into the five different petri dishes. Then using double sided tape we placed a small amount of brine shrimp eggs on each slide and examined them under a steromicroscope. We counted the number of eggs on the slides and recorded the data under “0 hours” in Table 1. We allowed the dishes to sit at room temperature for 24 hours. On the second day we examined each petri dish with a microscope and counted the number of swimming, dead or partially hatched, and unhatched eggs and recorded that under “24 hours” in Table 1. On the third day we reexamined each petri dish and again counted the number of swimming, dead or partially hatched, and unhatched eggs and recorded that data under “48 hours” in Table 1. We hypothesized that more brine shrimp eggs would adapt to the 0.5% NaCl and more would die in the 2% NaCl.

Pre-Lab questions:
The adjustment of an organism’s behavior or structure to become better suited to survive in a different environment. The finches on the Galapagos Islands that adapted their beak shapes in order to catch different foods.
Some will adapt to the environment and hatch and others will not be able to adapt and will die or partially hatch.

Methods:
Day 1: 1. Prepare and label five beakers of 30-ml salt solutions, using sodium chloride and dechlorinated water. The solutions should be 0%, 0.5%, 1%, 1.5%, and 2% NaCI. Use the space in the Analysis section that follows to determine what mass of sodium chloride to add to each solution. 2. Label five petri dishes, 0%, 0.5%, 1%, 1.5%, 2%. 3. Use a graduated cylinder to measure 30 ml of 0% salt solution and pour it into the petri dish labeled 0%. 4. Likewise measure and pour 30 ml of each of the remaining concentrations into their corresponding petri dishes. 5. Measure and cut 1.5 em of double-sided tape. 6. Stick the double-sided tape to a microscope slide. 7. Lightly touch the paintbrush to the side of the bag containing the brine shrimp

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