Investigation 1: Artificial Selection provides an alternative for students to investigate artificial selection. Just as Darwin relied on artificial selection in domesticated farm animals to make his case in On the Origin of Species, students explore possible advantages or disadvantages that selected traits might confer on individuals in different environmental conditions. Because artificial selection experiments require a relatively large population with ample phenotypic variation, the first step of the investigation is conducted at the class level, and begins with questions that center on artificial selection in agricultural crops and well-known examples of natural selection T48 Big Idea 1 and evolution, such as antibiotic resistance in bacteria (big idea 3). Once students identify the common features of these events (selection, rapid changes in populations, and genetic variations), they design and conduct a selection experiment based on observable traits in Wisconsin Fast Plants growing in the classroom. These quantitative traits include number of trichomes (plant hairs) and plant height. Students may benefit from having an understanding of evolution and natural selection prior to beginning this investigation

Investigation 2: Mathematical Modeling: Hardy-Weinberg is a revision of Laboratory 8 (Population Genetics and Evolution) in the 2001 AP Biology Laboratory Manual. Students often find the study of population genetics challenging because most lab simulations in which students try to manipulate a population that is evolving are flawed, as the population is so small that genetic drift swamps any factors that promote evolution. Fortunately, the complexity of evolution in populations is illuminated by relatively simple mathematical equations, several of which are based on the Hardy-Weinberg (H-W) equilibrium formula. In this revised investigation, students manipulate data using a computer spreadsheet to build their own mathematical models derived from H-W to investigate allele inheritance patterns in a theoretically infinite population with inherent randomness. Students should begin this investigation after they have studied Mendelian genetics and have a solid

In Investigation 3: Comparing DNA Sequences to Understand Evolutionary Relationships with BLAST, students use BLAST (Basic Local Alignment Search Tool) to compare several genes from different organisms, and then use the information to construct a cladogram (i.e., phylogenetic tree) to visualize evolutionary relatedness among species. The field of bioinformatics merges statistics, mathematical modeling, and computer science to analyze biological data; entire genomes can be compared quickly to detect genetic similarities and differences. Identifying the precise location and sequences of genes not only allows us to better understand evolutionary relationships among organisms, but it also helps us to better understand human genetic diseases. The investigation covers concepts that pertain to genetics (big idea 3), as well as evolution.

In Investigation 4: Diffusion and Osmosis, students calculate surface area-to-volume ratios, and make predictions about which measurement — surface or volume — has the greater influence on the rate of diffusion. Next, students create artificial cells to model diffusion, followed by observation of osmosis in living cells and measurement of water potential in different types of plants. All sections of the investigation provide opportunities for students to design and conduct experiments to more deeply investigate questions that emerge from their observations and results. Students revisit the concepts of osmosis and water potential when they investigate transpiration in plants (big idea 4).

In Investigation 5: Photosynthesis, students learn how to measure the rate of photosynthesis indirectly by using the floating leaf disk procedure to gauge oxygen production. Photosynthesis is a strategy employed by autotrophs to capture light energy to build energy-rich carbohydrates. The process is summarized by the following reaction: 2H2 O + CO2 + light → carbohydrate (CH2 O) + O2 + H2 O To determine the rate of photosynthesis, one could measure the production of O2 or the consumption of CO2 . The difficulty related to measuring the production of oxygen gas is compounded by the complementary process of aerobic respiration consuming oxygen as it is produced. Therefore, the rate of photosynthesis generally is calculated by measuring the consumption of carbon dioxide, but this requires expensive equipment and complex procedures. Students are asked to consider variables that might affect the rate of photosynthesis and the floating disk procedure itself. A number of questions emerge about the process that leads to independent student investigations. The investigation also provides an opportunity for students to apply concepts that they have studied previously, including enzymatic activity, cell structure and function (big idea 4), and the evolution of conserved core processes in plants (big idea 1).

Investigation 6: Cellular Respiration is a revision of Laboratory 5 (Cell Respiration) in the 2001 AP Biology Laboratory Manual and reflects the shift toward more student-directed and inquiry-based laboratory experiences as students explore factors that might affect the rate of cellular respiration in multicellular organisms. Heterotrophic organisms harvest free energy stored in carbon compounds produced by other organisms. In cellular respiration, free energy becomes available to drive metabolic pathways primarily by the conversion of ADP to ATP. If sufficient oxygen is available, glucose may be oxidized completely, as summarized by the following reaction: C6 H12O6 + 6O2(g) → 6CO2(g) + 6H2 O + energy To determine the rate of cellular respiration, one could measure the consumption of O2 during the oxidation of glucose, or the production of CO2 . In this investigation, students assemble microrespirometers or use gas pressure sensors (probe system) to measure the relative volume (changes in pressure) as oxygen is consumed by germinating seeds. Once students learn how to measure the rate of cellular respiration, questions emerge about the process that leads to independent student investigations about factors that might affect the rate. This investigation can be conducted during the study of cellular processes, interactions (big idea 4), and even evolution (big idea 1) if students raise questions about cellular respiration as a conserved core process, or compare different processes such as C3 , C4 , and CAM plants and the environments in which they evolved.

In Investigation 7: Cell Division: Mitosis and Meiosis, students begin by thinking about how they developed from a single-celled zygote to an organism with trillions of cells. After students model mitosis and review chromosome duplication and movement, they set up an independent investigation using onion bulb squashes and lectins to explore what substances in the environment might increase or decrease the rate of mitosis, and then they statistically analyze their results by calculating chi-square values. This part of the investigation raises questions about mitosis, and students are asked to formulate hypotheses about how chromosomes of cancer cells, such as HeLa cells, might appear in comparison to normal cells, and how those differences are related to the mitotic behavior of the cancer cells. After modeling meiosis and crossing-over events to increase genetic variation, students mimic the phenomenon of nondisjunction and its relationship to genetic disorders. In a final experiment, students measure crossover frequencies and genetic outcomes in a fungus.

Investigation 8: Biotechnology: Bacterial Transformation is a revision of Laboratory 6A (Molecular Biology: Bacterial Transformation) in the 2001 AP Biology Lab Manual. The investigation begins with a question guaranteed to provoke student interest: Are genetically modified foods safe? One current argument is whether corn grown to express the Bt toxin (a pesticide) is safe for human consumption. Although genetic information can be changed through mutations in DNA or RNA and errors in information transfer, biotechnology makes it possible to engineer heritable changes to yield novel protein products, such as the Bt toxin. One technology, bacterial plasmid-based genetic transformation, enables students to manipulate genetic information in a laboratory setting to understand more fully how DNA operates. In this investigation, students will first acquire the tools to transform E. coli bacteria to express new genetic information using a plasmid system, and apply mathematical routines to calculate transformation efficiency. Students then have the opportunity to design and conduct an investigation to study transformation in more depth; for example, students can investigate whether bacteria take up more plasmids in some environmental conditions, and less in others. The investigation also provides students with the opportunity to review concepts that they have studied previously, including interactions between organisms and their environment (big idea 4), structure and function of cell membranes (big idea 2), and evolution and natural selection (big idea 1).

Investigation 9: Biotechnology: Restriction Enzyme Analysis of DNA, a revision of Laboratory 6B (Molecular Biology: Restriction Enzyme Cleavage of DNA and Electrophoresis) in the 2001 AP Biology Lab Manual, opens with two questions: Is that blood? and Are you sure that the hamburger you recently ate in the local fast-food restaurant was actually pure beef? Applications of DNA profiling extend beyond what we see on television crime shows; and in addition to confirming that often hamburger meat is a mixture of pork and other nonbeef products, DNA technology can be used to determine paternity and diagnose an inherited illness. To answer the question Whose blood is spattered on the floor? in the investigation’s crime scene scenario, students use restriction endonucleases and gel electrophoresis to create and analyze genetic “fingerprints.” By learning the fundamental skills involved in creating genetic profiles using gel electrophoresis, students acquire the tools to conduct more sophisticated biotechnology investigations. Because DNA testing makes it possible to profile ourselves genetically, the investigation raises questions about who owns our DNA and the information it carries.

Investigation 10: Energy Dynamics guides students in the exploration of energy in a model ecosystem by estimating (1) net primary productivity of Wisconsin Fast Plants growing under lights, and (2) the flow of energy from the plants to cabbage white butterflies as the larvae consume cabbage-family plants. These two exercises describe methods for estimating energy flow in a terrestrial ecosystem, and students are asked to apply the skills they acquire, including converting biomass measurements to energy units. Students record their questions and observations as they work through the investigation. Questions might include What is the role of energy in ecosystems? What factors affect plant productivity, the growth of cabbage white larvae, and the interactions of the organisms? How can energy be tracked in the model system? and Can the data collecting techniques be improved? The study of these model organisms and methods for estimating energy flow create a rich, accessible environment that facilitates student exploration of basic ecological concepts with respect to energy flow, the roles of producers and consumers, and the complex interactions between organisms in a community.

Investigation 11: Transpiration is a revision of Laboratory 9 (Transpiration) in the 2001 AP Biology Lab Manual. The revision reflects the changes in the overall AP Biology program, moving from a teacher-directed investigation to a guided, inquiry-based exploration of transpiration in plants. With a new twist, students begin by calculating leaf surface area, and then determine the average number of stomata per square millimeter of leaf. Their data should generate several questions, including Are surface area and the number of stomata related to the rate of transpiration? Do all parts of a plant transpire? Do all plants transpire at the same rate? and Is there a relationship between habitats in which plants evolved to their rates of transpiration? Students design and conduct their own experiments to investigate answers to questions they generate about factors — such as environmental variables — that affect the rate of transpiration. The investigation provides an opportunity for students to review and apply concepts and science practices they have studied previously, including cell structure and function, the movement of molecules across membranes, and the exchange of matter between biological systems and with their environment.

In Investigation 12: Fruit Fly Behavior, students use Drosophila melanogaster as a model organism to explore chemotaxis and other observed behaviors. The fruit fly has been studied in depth by the scientific community; its genome has been sequenced, its physical characteristics charted, and its meiotic and developmental processes carefully researched. Although students typically become familiar with Drosophila while studying genetics, the fly also has been the source for many historical experiments in animal behavior. In this investigation, students begin by listing when and where they notice fruit flies — in a bowl of fruit, on a picnic table, and during the spring and summer — and then construct a choice chamber from a plastic water bottle to conduct a series of experiments to gather information about negative and positive responses to chemical stimuli. Students note patterns and ratios, and then design and conduct additional experiments based on unanswered questions from their initial series of experiments. The investigation provides students an opportunity to explore more deeply behaviors that underlie chemotaxis.

Investigation 13: Enzyme Activity provides new twists for Laboratory 2 (Enzyme Catalysis) in the 2001 AP Biology Lab Manual by taking students through a guided inquiry exploration of biotic and abiotic factors that influence the rates of enzymatic reactions. Students explore the catalytic activity of peroxidase, an enzyme that breaks down hydrogen peroxide, a toxic metabolic waste product of aerobic respiration, converting peroxide into water and oxygen gas. Guaiacol, an indicator, is used to measure the amount of oxygen released in the reaction. As students work through the investigation, they acquire skills to explore their own questions about enzymatic activity. Questions raised might include How will different pH buffers or temperatures affect reaction rates? and Which has a greater effect on the rate of reaction: changing the concentration of enzyme or the concentration of substrate? The investigation also provides students an opportunity to apply and review concepts they have studied previously, such as energy transfer, the levels of protein structure, and the role of enzymes in maintaining homeostasis.