2019 ap biology frq answers

Daniel Parker

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27-02-2025

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2019 AP Biology FRQ Answers: A Comprehensive Guide

The 2019 AP Biology Free Response Questions (FRQs) challenged students' understanding of core biological concepts. This guide provides detailed answers and explanations for each question, helping you understand the reasoning behind the scoring and improve your future performance. Remember, these are example answers; the AP graders look for specific points, and your wording may vary while still earning full credit.

Question 1: Enzyme Activity and Cellular Respiration

This question explored the effect of temperature and pH on enzyme activity within the context of cellular respiration.

(a) Graph Interpretation and Analysis: Students were presented with a graph depicting enzyme activity at varying temperatures and pH levels. The task was to interpret the graph, identifying optimal conditions and explaining the observed trends.

• Answer: A successful response would accurately describe the optimal temperature and pH for the enzyme based on the graph. It would explain the decrease in activity at temperatures and pH levels outside the optimum, citing denaturation at high temperatures and disruption of enzyme structure at extreme pH values. Understanding of enzyme-substrate complex formation was key.

(b) Cellular Respiration and Enzyme Activity: This part connected enzyme activity to the specific processes of cellular respiration.

• Answer: A strong answer clearly linked specific enzymes (e.g., those involved in glycolysis, Krebs cycle, or oxidative phosphorylation) to their roles in cellular respiration. It described how changes in temperature and pH would affect the rate of these processes and, consequently, ATP production. This required knowledge of the locations and functions of these enzymes.

Question 2: Population Genetics and Evolution

This question focused on population genetics principles and evolutionary mechanisms.

(a) Hardy-Weinberg Equilibrium: Students had to apply the Hardy-Weinberg equilibrium principle to analyze allele and genotype frequencies in a population.

• Answer: Successful responses accurately calculated allele frequencies (p and q) and used the Hardy-Weinberg equation (p² + 2pq + q² = 1) to determine expected genotype frequencies. The explanation should clearly state the conditions necessary for Hardy-Weinberg equilibrium and identify deviations from these conditions that might affect allele frequencies in the given scenario.

(b) Evolutionary Mechanisms: This part required an understanding of various evolutionary mechanisms and their impact on allele frequencies.

• Answer: Students needed to explain how mechanisms such as natural selection, genetic drift, gene flow, and mutation could alter allele frequencies within a population. Connecting specific examples from the given scenario to these mechanisms was crucial for earning full credit. A clear understanding of the difference between these mechanisms was necessary.

Question 3: Plant Responses and Environmental Stimuli

This question delved into plant responses to environmental stimuli.

(a) Plant Hormones: Students needed to discuss the roles of plant hormones in mediating plant responses to environmental changes.

• Answer: This required knowledge of auxins, gibberellins, cytokinins, abscisic acid, and ethylene. The answer should discuss the specific roles of these hormones in growth, development, and responses to light, gravity, or water stress.

(b) Mechanism of Action: Students had to explain the mechanisms by which these plant hormones elicit their effects on plant cells.

• Answer: A complete answer explained the signaling pathways involved, including receptor binding, signal transduction, and resulting changes in gene expression or cellular processes. The response should correctly identify the cellular level at which these hormones act.

Question 4: Animal Systems and Homeostasis

This question focused on animal physiology and homeostasis.

(a) Physiological Processes: This part examined the relationship between different organ systems in maintaining homeostasis.

• Answer: This required explaining how organ systems like the nervous, endocrine, and excretory systems work together to regulate internal conditions such as body temperature, blood glucose levels, or water balance. The response should explicitly show the connection between different systems.

(b) Feedback Mechanisms: Students needed to explain the role of feedback mechanisms (positive and negative) in maintaining homeostasis.

• Answer: A successful response differentiated between positive and negative feedback mechanisms, providing examples of each within the context of animal physiology. It should clearly explain how feedback mechanisms help maintain a stable internal environment despite external changes.

Question 5: Molecular Genetics and Gene Expression

This question dealt with molecular genetics and gene expression.

(a) Gene Regulation: This part addressed the mechanisms by which gene expression is regulated in eukaryotic cells.

• Answer: Students should have discussed various regulatory mechanisms, including transcription factors, enhancers, silencers, and epigenetic modifications. The response needed to relate these mechanisms to controlling the amount of protein produced from a specific gene.

(b) Gene Mutations: The second part examined the impact of gene mutations on protein structure and function.

• Answer: A good response accurately described different types of mutations (e.g., point mutations, frameshift mutations) and their potential effects on protein structure, function, and phenotype. The connection between the genotype and resulting phenotype needed to be explicitly stated.

Conclusion:

The 2019 AP Biology FRQs tested a wide range of topics. Mastering these questions requires a thorough understanding of core concepts, the ability to apply those concepts to novel situations, and clear communication skills. By reviewing these example answers and focusing on the key points emphasized, you can significantly improve your performance on future AP Biology exams. Remember to consult the official AP Biology scoring guidelines for a definitive assessment of what constitutes a complete and correct answer.