CHANGING POPULATIONS CH 14 EXPLORE

IQ: How might we affect the growth of a population of yeast?? Basic yeast population set up*: 5 mL of H20 1 mL of yeast solution 2 mL of molasses solution Mix this in a clean beaker Put half of the solution in each small test tube Create a closed environment by covering test tube openings with tape *If you are manipulating the solution proportions (ex: more food, more yeast), you will need to make two separate solutions!

COUNTING YEAST – Making it Easier!!! Make sure the slides and cover slips are clean! Use lens paper to clean off the eye piece, objectives and stage light hole. Start on low and work your way up to high power to do your counts. A hint…count ¼ of the field of view and multiply by 4.

COUNTING YEAST!! Count on 4/11, 4/13 and 4/15 Before sampling, be sure to mix the contents of your test tube well as the yeast tend to settle to the bottom. Use 1 drop of yeast solution ONLY! Choose 3 areas of the slide where the yeast are evenly dispersed. Calculate the average.

MICROSCOPE PROTOCOL Use lens paper to clean the eye piece and objectives. Start on low power, work up to high power Go back to low power before removing the slide. Leave the microscope in low power. Unplug microscope and wrap up cord. Cover the microscope if you have a dust cover. Rinse and lay out slides and cover slips to dry Get replacement slides and coverslips, if necessary. Put slides and coverslip into the petri dish.

Monday, April 11 th : Set up your yeast populations with your manipulated variable. Record initial yeast counts for both your experimental and your experimental control test tubes. (On day 1 you only need to count the experimental control tube and record this number for both populations) Put your tubes in the appropriate location (as per your experimental design). Make sure they are clearly labeled so that they don’t get mixed up with another group’s yeast cultures. Work on your lab report (see next slide)

Wednesday, April 13 th : Record your yeast population data. Before sampling, be sure to mix the contents of your test tube well as the yeast tend to settle to the bottom. Use 1 drop of yeast solution ONLY! Count while on high power. Choose 3 areas of the slide where the yeast are evenly dispersed. Calculate the average. Record. Work on your lab report (see next slide) Do “Isle Royale” (See document and be self-directed. Will be stamped on Friday)

Friday, April 15 th : Record your yeast population data. Before sampling, be sure to mix the contents of your test tube well as the yeast tend to settle to the bottom. Use 1 drop of yeast solution ONLY! Count on high power. Choose 3 areas of the slide where the yeast are evenly dispersed. Calculate the average. Record Clean up as directed. Work on your lab report (see next slide) Do “Unsupervised” as instructed…will be stamped on Tuesday.

LAB REPORT GUIDELINES (due Thursday 4/21!!) You will each turn in a typed, formal lab write up at the conclusion of this activity. Your write up must include: Title Investigative Question Hypothesis (may differ within the lab group) Materials Detailed Procedure be sure to discuss MV, RV, CV’s (minimum of 3) and experimental control Data Table Graph of Data Original Conclusion (data is cited and referred to, trend is identified, a plausible explanation of results is included)