How many lab experiments did you complete this year? Episode 23 recAPs the lab manual published by the College Board.
How many lab experiments did you complete this year? Episode 23 recAPs the lab manual published by the College Board. Each lab is reviewed with the guiding question, procedure rundown, and quantitative skills. Labs 1-3 focus on Big Idea #1: Evolution(1:30). Labs 4-6 focus on Big Idea #2: Energetics (3:30). Labs 7-9 focus on Big Idea #3: Information Storage and Transmission (6:18). Labs 10-13 focus on Big Idea #4: Systems Interactions (9:12).
The Question of the Day asks (12:24) “What do error bars represent?”
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Hi and welcome to the APsolute Recap: Biology Edition. Today’s episode will recap Lab Experiments
Lets Zoom out:
The College Board has a published manual titled AP Biology Investigative Labs - An Inquiry Based Approach. This 13 lab document was created by higher ed faculty, AP teachers, and inquiry experters so that students can develop understanding through investigative techniques. You can google it, answer keys too no doubt. But knowing the answers or how to perform the experiments is not the same as understanding the purpose and connecting to the big ideas. You must practice scientific inquiry, work through reasoning, and develop critical thinking. This episode will recAP the labs in the manual as they correlate to the Big Ideas and the enduring understanding behind each. Some of these investigations are less applicable to the modified 2020 exam. Buckle up, this episode is a little longer than normal.
Lets Zoom in:
Big Idea 1 is Evolution - Evolution takes far longer than a 45 minute class period, so it's common to use computer simulations that mimic generations. The three labs included in the manual review artificial selection, mathematical modeling, and comparing DNA sequences.
Investigation 1 is Artificial Selection. The guiding question is: Can extreme selection change expression of a quantitative trait in a population in one generation? This lab will likely first have you look at farming, then antibiotic resistance, and lastly Wisconsin Fast plants - those really small seeds you may have grown in petri dishes for a few weeks (also commonly used when practicing genetic crosses). The quantitative skills are counting, measuring, graphing, and statistical analysis with frequency distribution.
Investigation 2 is Mathematical Modeling of the Hardy-Weinberg Equation. The guiding question is: How can mathematical models be used to investigate the relationship between allele frequencies in populations of organisms and evolutionary change?
In this lab, students manipulate data in a computer spreadsheet to design their own mathematical model of allele patterns in a population. The emphasized quantitative skills are Mendelian genetics equations, the Hardy-Weinberg equation, and Excel and spreadsheet operations.
Investigation 3 invites students to compare DNA sequences with BLAST (which stands for Basic Local Alignment Search tool). The guiding question is: How can bioinformatics be used as a tool to determine evolutionary relationships and to better understand genetic diseases? Once you have the genetic data from several organisms, you can investigate evolutionary relationships by designing a cladogram. The quantitative skills are statistical analysis, mathematical modeling, and computer science with bioinformatics.
Big idea 2 is Energetics. Materials, like solutes and water, must move through cell membranes to maintain dynamic homeostasis. The three labs included review diffusion and osmosis, photosynthesis, and cellular respiration.
Lab 4 is Diffusion and Osmosis. The guiding question is what causes my plants to wilt if I forget to water them? This investigation begins with calculating surface area to volume ratios, perhaps through agar cubes and phenolphthalein or potato cubes and iodine. You let them sit, cut them open, and measure the depth of diffusion. Then, artificial cells are made using dialysis tubing, knotted on either end and submerged in different solutions (salt, glucose, sucrose). You may have measured change in mass or tested extracellular fluid for the presence of diffused solutes. The quantitative skills are measuring volumes, calculating surface area-to-volume ratios, calculating rate, calculating water potential, and graphing.
Lab 5 is Photosynthesis - the process by which autotrophs capture light energy and assemble energy rich carbohydrates. The guiding question is: What factors affect the rate of photosynthesis in living leaves? Ironically, this lab tends to follow the gases, not the water or the sugars. The rate of photosynthesis can be calculated with the floating leaf disk method (enter hole punching and syringe frustrations - why won't the leaves just sink!) or with CO2 or O2 sensors. Once comfortable with rate calculations, other variables can be investigated - like light intensity, light color, temperature, pH, leaf size, plant species, and bicarbonate concentration. The quantitative skills are calculating rate, preparing solutions and dilutions, measuring light intensity, developing and applying indices to represent the relationship between two quantitative values, using reciprocals to modify graphical representations, utilizing medians, and graphing.
Lab 6 is Cellular Respiration. The guiding question is: what factors affect the rate of cellular respiration in multicellular organisms? Just like with the photosynthesis lab, we tend to follow the gases - not the sugar or the energy. The old school version of this lab involves making a respirometer, adding germinating peas or beans to vials, submerging them in water and watching for volumetric changes. Students need to have a healthy respect for the gas laws (PV = nRT) when analyzing lab data. This lab can also be done with probeware, measuring CO2 consumption or O2 production. The quantitative skills are calculating rate, measuring temperature and volume, and graphing.
Big idea 3 is Information Storage and Transmission. The three labs review cell division and biotechnology.
Lab 7 is Cell Division: Mitosis and Meiosis. The guiding question is: How do eukaryotic cells divide to produce genetically identical cells or to produce gametes with half the normal DNA? This investigation begins with modeling mitosis and chromosome duplication with pop beads, sockosomes, or clay before exploring the environmental effect of onion bulb squashes and producing your own slides. Maybe you looked at the effect of caffeine on root growth? Students then model and mimic nondisjunction before looking at crossover frequencies and genetic outcomes in the fungus Sordaria. There is a lot of microscope work in Lab 7. The quantitative skills are measuring volume, counting, chi-square statistical analysis, and calculating crossover frequency.
Lab 8 is Biotechnology: Bacterial Transformation! The guiding question is: How can we use genetic engineering techniques to manipulate heritable information? Students begin by reflecting on genetically modified foods and whether corn can express the Bt toxin from pesticides. Next, E.coli and plasmids. Give your teachers a round of applause - because while these lab results are super cool (we will make bacteria glow with a jellyfish gene!) it takes a lot of tedious and timely preparation. You will have to be very focused on sterile techniques and keep track of your petri dishes. Hint - you should have the most glowing bacterial growth on the +/LB/Amp/Ara plate. Once comfortable with the process of transformation, you can investigate whether bacteria take up more plasmid in certain environmental conditions. The quantitative skills focused on in this lab are measuring volume and temperature and calculating transformation efficiency.
Lab 9 is Biotechnology: Restriction Enzyme Analysis of DNA. The guiding question is:How can we use genetic information to identify and profile individuals? In a mimicked crime lab scenario, students use restriction enzyme exonucleases and gel electrophoresis to create and analyze genetic fingerprints. Your teacher likely had you practice pipetting before working with the gels - it's not easy to fit the right amount of sample into such a small well! DNA fragments travel through the gel with the electric current based on size, and through comparison with a known sample, a culprit can be determined. The quantitative skills focused on in this lab are measuring volume and distance, graphing data using log scale, and extrapolating from a standard curve.
Big idea 4 is Systems Interactions. The four labs included review energy and enzymes, transpiration, and animal behavior.
Lab 10 is Energy Dynamics. The guiding question is:
What factors govern energy capture, allocation, storage, and transfer between producers and consumers in a terrestrial ecosystem? Students explore energy movement in model ecosystems through the net primary productivity of Wisconsin Fast plants and energy flow from fast plant producers to cabbage white butterfly larvae. The quantitative skills focused on in this lab are estimating productivity and efficiency of energy transfer, accounting and budgeting, measuring biomass, and calculating unit conversions in simple equations.
Lab 11 is Transpiration. The guiding question is: what factors, including environmental variables, affect the rate of transpiration in plants? Students begin by calculating stomata density on leaves with a nail polish peel and wet mount. The remainder of the lab is very open ended, with students investigating different environmental factors that influence the rate of transpiration. One common tool is to assemble a potometer with a gas pressure sensor. The quantitative skills are measuring distance, volume, and mass; estimating surface area; calculating surface area; graphing; and calculating rate.
Lab 12 is Fruit Fly Behavior. The guiding question is: What environmental factors trigger a fruit fly response? Good ‘ol Drosophila Melanogaster. You may have first studied these organisms as part of genetics, but now chemotaxis can be observed with choice chambers. Students will make note of patterns and ratios as they design their own investigations. The emphasized quantitative skills are preparing solutions, counting and graphing.
Lastly - Lab 13 - Enzyme Activity. The guiding question is: How do abiotic or biotic factors influence the rates of enzymatic reactions? In this lab investigation, students explore the activity of peroxidase, an enzyme that breaks down hydrogen peroxide. This might be done simply, with a potato slurry and gas displacement setup or with guaiacol, an oxygen indicator. Through extension, other variables, like pH and temperature, can be investigated. The quantitative skills focused on in this lab are measuring volume and mass, measuring color change, graphing, and calculating rates of enzymatic reactions.
What? Your class never did any of these labs? Its OK - You can watch many of them performed and explained on YouTube - or better yet, head over to Bozeman Science with Paul Anderson. These labs are suggested, and do not represent an absolute necessity when preparing for the AP Exam.
To recap….
The thirteen lab investigations published by the College Board are designed for students to think critically and develop scientific skills. Focus on the big ideas and data analysis, as these are the lasting impressions of the scientific process.
Today’s Question of the day is about statistical analysis.
Question: What do error bars represent?