2019 Ap Bio Frq Answers

Deconstructing the 2019 AP Biology Free Response Questions: A Comprehensive Guide

The 2019 AP Biology exam presented students with a challenging set of free-response questions (FRQs), testing their understanding of core concepts across various biological disciplines. This comprehensive guide will dissect each FRQ, providing detailed explanations of the correct approaches, common student errors, and valuable insights for future AP Biology students. Understanding the 2019 FRQs offers invaluable preparation for future exams and solidifies your grasp of fundamental biological principles. This analysis will cover the scoring rubrics implicitly, highlighting what earned points and what didn't.

Question 1: Enzyme Activity and Regulation

This question focused on the impact of environmental factors on enzyme activity and the mechanisms regulating enzyme function. Students were presented with a scenario involving an enzyme, its substrate, and the effect of different pH levels and temperature on the rate of reaction.

Part A: This section tested the understanding of enzyme kinetics. Students were asked to analyze a graph depicting enzyme activity at varying pH levels. The correct response involved identifying the optimal pH for the enzyme and explaining the observed decrease in activity at higher and lower pH values. Points were awarded for correctly identifying the optimal pH and providing a scientifically accurate explanation connecting pH changes to enzyme structure and function. Many students lost points by failing to clearly link altered pH to changes in enzyme conformation and subsequent substrate binding. Remember to always explicitly connect your observations to the underlying biochemical mechanisms.

Part B: Similar to Part A, this section involved analyzing a graph showing enzyme activity at different temperatures. Students needed to identify the optimal temperature and explain the decrease in activity at higher temperatures. This required understanding of enzyme denaturation at high temperatures – a critical concept in enzyme biology. Successful answers clearly explained how increased kinetic energy at higher temperatures disrupts the enzyme's three-dimensional structure, hindering its ability to bind substrate and catalyze the reaction. Weak answers lacked this crucial mechanistic explanation.

Part C: This section delved into enzyme regulation. Students needed to describe ONE mechanism of enzyme regulation, such as competitive or non-competitive inhibition, allosteric regulation, or feedback inhibition. A successful answer would not only name the mechanism but also clearly describe how it works at a molecular level, often involving diagrams to illustrate the interaction between the enzyme, substrate, and inhibitor. Many students provided vague descriptions or confused different regulatory mechanisms. Remember, clear and concise descriptions with appropriate terminology are crucial for earning full credit.

Part D: This final part of Question 1 asked for a prediction regarding the enzyme activity under specific conditions (a given temperature and pH). This required applying the knowledge gained from previous sections to predict the outcome. Successful responses correctly used the data provided earlier to make a reasonable prediction and justify it scientifically. A simple statement without a logical justification would not earn full credit.

Question 2: Cell Communication and Signal Transduction

This question examined cell communication and signal transduction pathways, focusing on the process by which a signal is received, transduced, and ultimately results in a cellular response.

Part A: This part described a scenario where a hormone binds to a receptor on the cell surface, initiating a signaling cascade. Students were asked to describe the steps involved in the transduction pathway, including the roles of second messengers and protein kinases. Correct responses accurately depicted the sequence of events, including receptor activation, signal amplification through second messengers (like cAMP), and the involvement of protein kinases in phosphorylating target proteins to elicit a cellular response. Students often struggled with providing sufficient detail about the cascade, lacking specificity in the roles of various components.

Part B: This section involved describing the difference between signal transduction pathways initiated by lipid-soluble versus water-soluble hormones. This required a firm understanding of cell membrane structure and the mechanisms of hormone action. Successful answers contrasted the different locations of hormone receptors (cell surface vs. intracellular) and explained how these differences lead to distinct downstream signaling pathways. Students often confused the mechanisms or provided overly generalized descriptions.

Part C: This section asked for an explanation of how a cellular response might be terminated. This required understanding of the mechanisms that actively shut down signaling pathways, such as enzyme deactivation, receptor internalization, and degradation of second messengers. Many responses lacked this level of detail, indicating a lack of comprehensive knowledge regarding the regulation of signal transduction. A full understanding of feedback mechanisms is crucial here.

Part D: This final part extended the scenario, introducing a mutation in a component of the signal transduction pathway. Students were asked to predict the effect of the mutation on the cellular response. This required applying the knowledge from previous parts to logically predict the consequences of the mutation. Successful responses accurately explained the predicted effect and logically linked the mutation to the disruption of the signaling pathway. Common errors included failing to provide a clear and logical connection between the mutation and the predicted consequences.

Question 3: Evolution and Natural Selection

This question assessed students' understanding of evolution, natural selection, and adaptation. It presented a scenario involving a population of organisms with varying traits and how these traits influence survival and reproduction in a changing environment.

Part A: This part involved describing the different types of natural selection (directional, stabilizing, disruptive) and their effects on the distribution of traits within a population. Successful responses clearly defined each type of selection with appropriate examples and accurately depicted how each type alters the phenotypic distribution. Students often confused the different types of selection or failed to provide clear examples. Using graphs to visually represent the changes in phenotypic distribution would have significantly enhanced these answers.

Part B: This section asked students to explain how the environment can drive natural selection. This required a thorough understanding of the relationship between environmental factors, selective pressures, and the adaptation of populations. Strong answers explicitly linked specific environmental changes to the selective pressures they create, and how those pressures lead to shifts in allele frequencies within a population. Weak answers lacked this connection, often providing general descriptions without specific examples.

Part C: This part introduced a new environmental factor and asked students to predict how the frequency of a specific trait within the population would change over time due to natural selection. This tested the ability to apply knowledge of natural selection to a new scenario and make a well-reasoned prediction. Successful responses provided a clear prediction and a logical justification based on the selective pressures imposed by the new environmental factor. Students who did not explicitly link the environmental change to the changes in allele frequencies lost points.

Part D: This final section delved into the concept of genetic drift, contrasting it with natural selection. This required understanding the difference between these two evolutionary mechanisms. Successful answers clearly outlined how natural selection is driven by differential reproductive success based on advantageous traits, while genetic drift results from random fluctuations in allele frequencies, particularly in small populations. Many answers lacked clarity in differentiating between these two significant concepts.

Question 4: Plant Biology and Transpiration

This question assessed students' understanding of plant structure and function, specifically focusing on the process of transpiration and its regulation.

Part A: This section asked students to describe the structures involved in water transport in plants, from the roots to the leaves. This tested knowledge of xylem, phloem, and the various tissues involved in water uptake and transport. Strong answers included detailed descriptions of the structures and their functions, including the role of cohesion-tension theory. Students often lacked detail in their descriptions, not clearly differentiating between xylem and phloem.

Part B: This part addressed the process of transpiration, including the forces driving water movement through the plant. This required understanding of water potential, osmosis, and the cohesive and adhesive properties of water molecules. Successful responses clearly explained how these forces contribute to the movement of water from the roots to the leaves. Students frequently struggled with explaining the underlying physical principles involved.

Part C: This section examined the regulation of transpiration, focusing on the role of stomata. This required knowledge of guard cell function and the factors affecting stomatal opening and closing. Successful answers clearly explained the role of guard cells in regulating gas exchange and water loss, mentioning environmental factors such as light intensity, humidity, and CO2 concentration. Many students lacked a comprehensive understanding of how environmental conditions influence stomatal behavior.

Part D: This final part involved a scenario involving environmental changes and asked students to predict the effect on transpiration rate. This tested the ability to apply knowledge of transpiration to a new scenario. Successful responses correctly predicted the impact of the environmental change on transpiration and provided a logical justification based on the principles discussed in earlier parts.

Question 5: Animal Behavior and Ecology

This question covered animal behavior and its ecological context. It presented a scenario involving animal behavior and the interplay between genetics and the environment in shaping behavior.

Part A: This part focused on innate versus learned behaviors. Students needed to provide examples of each and describe the mechanisms underlying these behavioral patterns. Successful answers included clear examples and accurate descriptions of the genetic and environmental influences on behavior. Many responses provided vague examples or confused the definitions of innate and learned behaviors. A clear differentiation between genetic predisposition and environmental influence was crucial for earning full points.

Part B: This section addressed the concept of altruistic behavior, focusing on how such behaviors can be explained in an evolutionary context. This tested the understanding of inclusive fitness and kin selection. Successful responses clearly defined altruism and explained how behaviors that appear self-sacrificing can still enhance the overall fitness of an individual's genes through the survival and reproduction of relatives. Students often lacked a full grasp of inclusive fitness and kin selection.

Part C: This section explored the ecological consequences of animal behavior, focusing on the interaction between animals and their environment. This required understanding of concepts like niche partitioning and resource competition. Successful responses clearly linked specific behaviors to ecological outcomes, such as resource acquisition, predator avoidance, or mate selection. Students often failed to provide specific examples or lacked a clear understanding of the ecological implications of animal behavior.

Part D: The final part presented a scenario involving a change in the environment and asked students to predict how a specific behavior might change over time due to natural selection. This tested the ability to apply the understanding of behavior and evolution to predict future changes. Successful responses made accurate predictions and provided well-reasoned justifications based on principles of natural selection.

Conclusion: Mastering the AP Biology FRQs

The 2019 AP Biology FRQs highlight the importance of a deep understanding of core biological concepts, the ability to apply that knowledge to new scenarios, and the skill of providing clear, concise, and well-supported explanations. By analyzing these questions and understanding the reasoning behind the scoring, you can significantly improve your performance on future AP Biology exams. Remember to always connect observations to underlying mechanisms, provide specific examples, and clearly explain your reasoning. Practice is key; reviewing past FRQs and practicing your writing skills are crucial for success. Focus on the underlying biological principles, and the application of that knowledge will become more intuitive.