🧬AP Biology AP Cram Sessions 2021

Key Concepts and Themes

• Evolution serves as the foundation for modern biology and explains the diversity of life on Earth
  • Includes mechanisms such as natural selection, genetic drift, and gene flow
  • Leads to adaptations that enhance survival and reproductive success in specific environments
• Structure and function are closely related in biological systems at all levels of organization (molecules, cells, tissues, organs, organisms)
• Information flow, exchange, and storage are essential for life
  • Includes genetic information (DNA), cell communication, and signal transduction
• Pathways and transformations of energy and matter are critical for maintaining life
  • Includes photosynthesis, cellular respiration, and nutrient cycling in ecosystems
• Biological systems interact and are interconnected, from the molecular level to ecosystems
• Homeostasis maintains internal stability and enables organisms to respond to environmental changes
• Science practices and the scientific method guide the study of biology and the development of new knowledge

Biological Processes and Systems

• Cell structure and function
  • Prokaryotic and eukaryotic cells have distinct features and organelles
  • Cell membranes regulate the movement of substances in and out of cells
  • Cellular respiration (aerobic and anaerobic) generates ATP for cellular processes
• Gene expression and regulation
  • DNA replication, transcription, and translation are key processes in the central dogma of molecular biology
  • Gene regulation (e.g., transcription factors, epigenetic modifications) controls the timing and level of gene expression
• Photosynthesis converts light energy into chemical energy, producing glucose and oxygen
  • Light-dependent reactions occur in the thylakoid membranes and produce ATP and NADPH
  • Light-independent reactions (Calvin cycle) use ATP and NADPH to fix carbon dioxide into glucose
• Cellular communication and signal transduction
  • Cells communicate through direct contact (juxtacrine signaling) or by releasing signaling molecules (paracrine and endocrine signaling)
  • Signal transduction pathways convert extracellular signals into intracellular responses
• Feedback mechanisms maintain homeostasis
  • Negative feedback loops reduce deviations from the set point (e.g., thermoregulation, blood glucose regulation)
  • Positive feedback loops amplify responses and drive processes to completion (e.g., blood clotting, childbirth)

Important Theories and Models

• Cell theory states that all living organisms are composed of one or more cells, the cell is the basic unit of life, and cells arise from pre-existing cells
• Gene theory explains the inheritance of traits through the transmission of genes from parents to offspring
  • Mendel's laws of inheritance (law of segregation, law of independent assortment) form the foundation of classical genetics
• Chromosomal theory of inheritance states that genes are located on chromosomes and that the behavior of chromosomes during meiosis explains Mendel's laws
• Endosymbiotic theory proposes that mitochondria and chloroplasts originated as independent prokaryotic organisms that were engulfed by ancestral eukaryotic cells
• Hardy-Weinberg equilibrium model describes the relationship between allele frequencies and genotype frequencies in a non-evolving population
  • Assumes no mutation, no migration, no natural selection, random mating, and large population size
• Phylogenetic trees depict evolutionary relationships among organisms based on shared derived characteristics
• Fluid mosaic model describes the structure of cell membranes as a fluid phospholipid bilayer with embedded proteins

Lab Techniques and Experiments

• Microscopy techniques allow the visualization of cells and cellular components
  • Light microscopy is used to observe living cells and stained specimens
  • Electron microscopy (scanning and transmission) provides higher resolution images of cell ultrastructure
• Gel electrophoresis separates DNA, RNA, or proteins based on size and charge
  • Agarose gel electrophoresis is used for DNA and RNA
  • SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) is used for proteins
• Polymerase chain reaction (PCR) amplifies specific DNA sequences using primers, DNA polymerase, and thermal cycling
• Spectrophotometry measures the absorption of light by a sample, which can be used to quantify the concentration of a substance (e.g., DNA, proteins)
• Chromatography techniques separate mixtures based on the differential affinities of substances for a mobile phase and a stationary phase
  • Paper chromatography and thin-layer chromatography (TLC) are simple chromatography methods
  • High-performance liquid chromatography (HPLC) and gas chromatography (GC) are more advanced techniques
• Enzyme kinetics experiments measure the rate of enzyme-catalyzed reactions and the effects of substrate concentration, temperature, and pH on enzyme activity
• Transformation experiments introduce foreign DNA into bacterial cells, allowing for the expression of new genetic traits

Data Analysis and Interpretation

• Quantitative data is numerical and can be analyzed using statistical methods
  • Measures of central tendency (mean, median, mode) describe the typical value in a dataset
  • Measures of dispersion (range, variance, standard deviation) describe the spread of data points
• Qualitative data is descriptive and can be categorized based on shared characteristics
• Graphical representations (e.g., line graphs, bar graphs, scatter plots) visually display data and help identify trends or relationships
  • Independent variables are plotted on the x-axis, while dependent variables are plotted on the y-axis
• Correlation analysis assesses the relationship between two variables
  • Positive correlation: variables increase or decrease together
  • Negative correlation: one variable increases as the other decreases
  • Correlation does not imply causation
• Statistical significance tests (e.g., t-test, chi-square test) determine the likelihood that observed differences between groups are due to chance
• Error bars (e.g., standard error, standard deviation) indicate the variability or uncertainty in a dataset
• Interpreting results involves drawing conclusions based on the data, considering the limitations of the study, and proposing future research questions

Exam Strategies and Tips

• Read each question carefully and identify the key concepts being tested
• Eliminate incorrect answer choices to narrow down the options
• Use process of elimination when unsure of the correct answer
• Manage your time effectively by not spending too much time on any one question
• Answer all questions, as there is no penalty for incorrect answers on the AP Biology exam
• Support your answers with specific examples and evidence from the course content
• Use diagrams and illustrations to your advantage, as they often contain important information
• Be familiar with the format of the exam, including the types of questions (multiple-choice, grid-in, free-response) and the time allotted for each section
• Practice with released AP Biology exams and questions to familiarize yourself with the content and format
• Review key concepts, themes, and connections across different topics in biology

Common Misconceptions

• "Survival of the fittest" does not mean that only the strongest or most aggressive individuals survive; rather, it refers to the survival and reproduction of individuals best adapted to their environment
• Dominant traits are not always the most common in a population; allele frequencies determine the prevalence of traits
• Evolution is not a linear progression from "simple" to "complex" organisms; it is a branching process that results in a diversity of life forms
• Genes do not solely determine an organism's characteristics; environmental factors also play a role in shaping phenotypes
• Cells do not "want" or "try" to maintain homeostasis; instead, feedback mechanisms and regulatory processes maintain stable internal conditions
• The term "theory" in science does not mean a guess or hypothesis; scientific theories are well-supported explanations based on evidence
• Humans did not evolve from chimpanzees or other modern apes; rather, humans and apes share a common ancestor
• Acquired characteristics (e.g., learned behaviors, physical changes due to environmental factors) are not inherited by offspring

Real-World Applications

• Understanding evolution and natural selection informs strategies for managing antibiotic resistance in bacteria and pesticide resistance in insects
• Genetic engineering techniques (e.g., recombinant DNA technology, CRISPR-Cas9) are used to develop genetically modified organisms (GMOs) with desired traits, such as increased crop yield or disease resistance
• Knowledge of cell signaling pathways and molecular targets is essential for drug discovery and development in the pharmaceutical industry
• Forensic science relies on DNA profiling and other biological techniques to identify individuals and solve crimes
• Conservation biology applies ecological principles to protect and restore biodiversity, manage endangered species, and mitigate human impacts on ecosystems
• Bioremediation uses microorganisms to break down and remove pollutants from contaminated environments (e.g., oil spills, industrial waste)
• Personalized medicine tailors treatments to an individual's genetic profile, enabling more targeted and effective therapies for diseases such as cancer
• Synthetic biology combines principles from biology and engineering to design and construct novel biological systems or organisms with specific functions (e.g., producing biofuels, biosensors)