AP EXAM REVIEW SESSION III Be prepared, not scared!  Experimental Design 12 AP Labs

EXPERIMENTAL DESIGN Clearly state a hypothesis using the “If…,then” format. Set up a control group and indicate its purpose. Use a large sample size. Identify the independent & dependent variables. Indicate which variables you will hold constant. Indicate how you will manipulate the variable you will test; in other words, how will you conduct your experiment? Describe how the function you are testing is affected by the change in the variable; in other words, how is the dependent variable changing in response to the independent variable? Describe how you will measure the change in the variable . . . titration, measuring temp every 2 minutes, etc Describe how you will verify your experiment (repeat the experiment many times). Describe how you will analyze your data (run a Chi square test, graph the data) Relate possible results to the hypothesis; in other words, what results support or reject your hypothesis?

The AP Labs . . . A Walk Down Memory Lane 

AP Lab 1 – Diffusion & Osmosis Cell Transport Tonicity Movement of water determined by water potential Ψ = Ψ S + Ψ P

AP Lab 1 – Diffusion & Osmosis, cont Part A Diffusion across a semipermeable membrane Set-up = glucose + starch in dialysis tubing; iodine in beaker Part B Determined % change in mass of known molarities of sucrose solutions (dH2O, 0.2 M → 1.0M) placed in distilled water Increase or decrease in mass of bags following incubation?

AP Lab 1 – Diffusion & Osmosis, cont Part C Set up potato cubes in different molarities of sucrose, then calculated, graphed % change in mass Some gained mass, some lost mass Molarity of potato = ?? Part D Plasmolysis

AP Lab 2 – Enzyme Catalysis

AP Lab 2 – Enzyme Catalysis, cont Purpose: To develop a better understanding of enzyme function by working with the enzyme catalase Reaction: KMnO4 used for titration – deep purple color. If H2O2 is present, it reacts with KMnO4 to form clear product – provides way to measure H2O2 Procedure Determined actual concentration of H2O2 in 1.5% solution of H2O2 Determined the 24-hour uncatalyzed reaction rate by performing a titration on the hydrogen peroxide left sitting overnight without the addition of catalase. Catalase was allowed to react with H2O2 for varying amounts of time. H2SO4 was added to stop the reaction, then amount of H2O2 remaining was titrated using KMnO4. Data was graphed and reaction rate was calculated to determine the effect of time on reaction rate.

AP Lab 3 – Mitosis & Meiosis Purpose: To observe stages of cell cycle in apical meristem tissue of root tip.

AP Lab 3 – Mitosis & Meiosis, cont

AP Lab 3 – Mitosis & Meiosis, cont To observe crossing over in asci of Sordaria by looking at the pattern & colors of ascospores

AP Lab 4 – Plant Pigments & Photosynthesis

AP Lab 4 – Plant Pigments & Photosynthesis Part A Purpose: To separate plant pigments using chromatography Different plant pigments vary in their affinity for the chromatography paper and their solubility in the solvent, therefore will travel different distances along chromatography paper

AP Lab 4 – Plant Pigments & Photosynthesis

AP Lab 4 – Plant Pigments & Photosynthesis

AP Lab 4 – Plant Pigments & Photosynthesis Part B Purpose: To measure the rate of photosynthesis in (1) an unboiled chloroplast solution kept in the dark, (2) an unboiled chloroplast solution exposed to light, and (3) a solution containing boiled chloroplasts exposed to light. A dye reduction technique was used. DPIP acts as electron acceptor. It is normally a blue color but becomes colorless when it is reduced. Color change measured as % transmittance by spectrophotometer or % absorbance by colorimeter. Provides a means to measure electron excitation

AP Lab 5 – Cell Respiration Purpose: To determine the effect of factors on the rate of cellular respiration by measuring oxygen consumption/carbon dioxide production by yeast

AP Lab 5 – Cell Respiration

AP Lab 5 – Cell Respiration

AP Lab 6 – Molecular Genetics Part A – Transformation First, two suspensions of bacteria in log phase of growth were made competent by heat shock and treatment with CaCl2 One tube exposed to plasmid containing gene for ampicillin resistance, one tube not exposed to plasmid Each tube is plated on 2 agar plates, one with ampicillin, one without, incubated, then checked for growth Expected results?

AP Lab 6 – Molecular Genetics Part B – Restriction Enzyme Cleavage Identical DNA samples cut with 2 different restriction enzymes HindIII fragments measured, base pairs per fragment provided, data graphed EcoRI bands measured, then graph used to interpolate number of base pairs per fragment

AP Lab 7 – Genetics of Organisms Determined phenotypes of P x P by looking at representative flies Analysis of F1 provided information about cross Predictions made for F2 Null hypothesis: F2 offspring counted; results evaluated using Chi square Chi-square “Goodness of Fit” Test Degrees of freedom = If the calculated Chi square value is greater than or equal to the p value listed for 0.05, null hypothesis is rejected. This means you are 95% certain that the data does not fit the expected value.

AP Lab 8 – Population Genetics & Evolution Purpose: To become familiar with the Hardy-Weinberg equation and to use H-W to calculate the number of alleles in a population Five criteria for H-W equilibrium Having a widow’s peak is dominant to lacking a widow’s peak. In a population of 920 people, 510 show the dominant phenotype. How many individuals would you expect of each of the three possible genotypes for this trait?

AP Lab 9 – Transpiration Part A Transpiration = Measured transpiration rate in plants exposed to light, fan, darkness, and ambient conditions

AP Lab 9 – Transpiration Part B Cross section of dicot stem structure prepared by using a microtome to slice thin sections, staining them, fixing them to a slide, and examining the slide under the microscope

AP Lab 10 – Physiology of the Circulatory System Purpose To become familiar with taking blood pressure readings, To determine the effect of exercise on pulse rate, and to determine fitness by comparing pulse rate when standing, reclining, after exercising, and calculating the amount of time required for pulse rate to return to normal after exercise. To determine the effect of temperature on heart rate is determined using a test organism.

AP Lab 11 – Animal Behavior Purpose: To observe animal behavior and to design an experiment testing the response of an organism to a stimulus. Taxis vs kinesis

AP Lab 12 – Dissolved Oxygen & Aquatic Primary Productivity Part A Purpose: To determine the relationship between dissolved O2 concentration and temperature

AP Lab 12 – Dissolved Oxygen & Aquatic Primary Productivity Part B Primary productivity = rate of photosynthesis Net productivity = (Primary productivity) – (Respiration) Set up bottles with varying amounts of light to calculate effect of light on net productivity Measured O2 concentration using Winkler method [dO2 ] fixed Iodine concentration measured by titrating with sodium thiosulfate, starch indicator