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AP Biology Comprehensive Syllabus

April 12, 2023
AP - Comprehensive Syllabus
TYCHR

Table of Contents

1 Unit 1: Chemistry of Life
2 Unit 2: Cell Structure and Function
3 Unit 3: Cellular Energetics
4 Unit 4: Cell Communication and Cell Cycle
5 Unit 5: Heredity
6 Unit 6: Gene Expression and Regulation
7 Unit 7: Natural Selection
8 Unit 8: Ecology

Unit 1: Chemistry of Life

Subtopic Number	Subtopic Name	Key points
1.1	Structure of Water and Hydrogen Bonding	The structure of water is characterized by its bent shape and polar covalent bonds, which allow for hydrogen bonding and unique properties such as high surface tension and cohesion. Hydrogen bonding occurs between the positively charged hydrogen atoms of one water molecule and the negatively charged oxygen atoms of neighboring water molecules, resulting in a network of strong intermolecular attractions. The ability of water to form hydrogen bonds plays a crucial role in many biological processes, such as the stability of DNA structure, the folding of proteins, and the transport of nutrients and waste products in cells.
1.2	Elements of Life	Four elements, carbon, hydrogen, nitrogen, and oxygen, make up over 96% of the mass of living organisms, and are essential for the formation of biomolecules. Other elements, such as phosphorus and sulfur, are also important for life as they are key components of nucleic acids and amino acids, respectively. Trace elements, such as iron, zinc, and copper, are required in small amounts but are critical for enzyme function and metabolic processes in cells.
1.3	Introduction to Biological Macromolecules	Biological macromolecules are large, complex molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids. These macromolecules are composed of monomers, which are smaller building blocks that can be assembled into polymers through dehydration synthesis and broken down through hydrolysis. The unique properties and functions of each macromolecule are determined by its chemical structure and interactions with other molecules in the cellular environment.
1.4	Properties of Biological Macromolecules	The properties of biological macromolecules are determined by their chemical structure and functional groups, such as hydroxyl, carbonyl, and amino groups. Macromolecules can undergo various types of interactions, including covalent bonding, hydrogen bonding, and van der Waals interactions, which determine their stability and shape. Changes in environmental factors, such as pH, temperature, and salt concentration, can affect the properties of macromolecules and their ability to function properly in living organisms.
1.5	Structure and Function of Biological Macromolecules	The unique three-dimensional structure of biological macromolecules determines their function in the cell, such as the catalysis of chemical reactions or the transport of molecules across membranes. The primary structure of a macromolecule is the linear sequence of its monomers, while the secondary, tertiary, and quaternary structures are formed through various types of interactions between amino acids or nucleotides. Structural and functional differences between macromolecules can arise from variations in their primary structure, as well as post-translational modifications or alternative splicing of RNA.
1.6	Nucleic Acids	Nucleic acids are macromolecules that store and transmit genetic information in cells, including DNA and RNA. The structure of nucleic acids is based on a repeating unit called a nucleotide, which consists of a sugar, a phosphate group, and a nitrogenous base. The sequence of nucleotides in a nucleic acid determines the genetic code that is responsible for the synthesis of proteins, the regulation of gene expression, and the inheritance of traits from one generation to the next.

Unit 2: Cell Structure and Function

Subtopic Number	Subtopic Name	Key points
2.1	Cell Structure: Subcellular Components	Cells contain several subcellular components, including organelles such as the nucleus, mitochondria, and endoplasmic reticulum, as well as non-membrane-bound structures such as ribosomes and the cytoskeleton. The function of these subcellular components varies, with the nucleus containing genetic material, the mitochondria producing energy, and the endoplasmic reticulum and ribosomes involved in protein synthesis and modification. The organization and interactions of subcellular components are critical for proper cellular function and contribute to the overall complexity and diversity of life.
2.2	Cell Structure and Function	The cell is the basic unit of life, with a highly organized structure and specialized organelles that enable it to carry out essential functions such as energy production, protein synthesis, and waste removal. The plasma membrane, composed of a phospholipid bilayer and various proteins, regulates the movement of molecules in and out of the cell and maintains cellular homeostasis. The diverse functions of cells are made possible by their ability to communicate and coordinate with other cells through chemical and physical signaling mechanisms.
2.3	Cell Size	Cells exhibit a wide range of sizes, from single-celled bacteria measuring just a few micrometers in diameter, to large, multinucleated cells in some plants and animals that can span several centimeters. The size of a cell is limited by its surface area-to-volume ratio, which affects the efficiency of nutrient uptake and waste removal, as well as the diffusion of molecules within the cell. To compensate for these limitations, some cells have evolved specialized structures, such as microvilli in the small intestine or branching filaments in fungal hyphae, to increase their surface area and facilitate absorption of nutrients.
2.4	Plasma Membranes	The plasma membrane is a selectively permeable barrier that surrounds the cell and separates the cytoplasm from the extracellular environment. Composed primarily of phospholipids, proteins, and cholesterol, the plasma membrane plays a critical role in maintaining cellular homeostasis and responding to external stimuli. Membrane proteins, including transporters, receptors, and enzymes, facilitate the movement of molecules across the membrane and enable communication between the cell and its environment.
2.5	Membrane Permeability	The permeability of a membrane is determined by the types of molecules that can cross it, with some membranes being more permeable to certain molecules than others. The phospholipid bilayer of a membrane is impermeable to charged ions and polar molecules, which require specialized transporters or channels to cross the membrane. Membrane permeability can be affected by various factors, such as temperature, pressure, and the presence of specific transport proteins or drugs.
2.6	Membrane Transport	Membrane transport refers to the movement of molecules across a membrane, which can occur via passive diffusion, facilitated diffusion, or active transport. Passive diffusion occurs when molecules move down their concentration gradient, from an area of high concentration to an area of low concentration, while facilitated diffusion requires the use of transport proteins to move molecules across the membrane. Active transport involves the movement of molecules against their concentration gradient and requires the input of energy, such as ATP, to power transport proteins.
2.7	Facilitated Diffusion	Facilitated diffusion is a form of passive transport that relies on the use of transport proteins to move molecules across a membrane. The movement of molecules in facilitated diffusion occurs down their concentration gradient, from an area of high concentration to an area of low concentration. Transport proteins used in facilitated diffusion include channels, which provide a hydrophilic pathway for molecules to cross the membrane, and carriers, which undergo conformational changes to move molecules across the membrane.
2.8	Tonicity and Osmoregulation	Tonicity refers to the relative concentration of solutes in two solutions separated by a selectively permeable membrane, which affects the movement of water across the membrane. Osmoregulation is the process by which organisms maintain the balance of water and solutes within their cells, typically through the use of specialized transporters and channels in the plasma membrane. The tonicity of a solution can be isotonic, hypotonic, or hypertonic relative to the cytoplasm of a cell, with different tonicity conditions affecting the shape and function of the cell.
2.9	Mechanisms of Transport	Mechanisms of transport refer to the various ways in which molecules and ions can move across biological membranes, including passive diffusion, facilitated diffusion, and active transport. Active transport involves the use of energy, typically in the form of ATP, to move molecules against their concentration gradient. Mechanisms of transport can be regulated by various factors, including the availability of transport proteins, changes in membrane potential, and the presence of signaling molecules such as hormones.
2.10	Cell Compartmentalisation	Cell compartmentalization is the division of cellular space into distinct membrane-bound compartments, allowing for separate and specialized functions to occur within the cell. Membrane-bound organelles, such as the nucleus, mitochondria, and endoplasmic reticulum, are examples of cellular compartments that enable specific biochemical processes to occur in isolation. Cell compartmentalization is critical for maintaining cellular homeostasis and ensuring that incompatible biochemical processes do not occur simultaneously.
2.11	Origins of Cell Compartmentalisation	Cell compartmentalization likely originated as a means to increase the efficiency and complexity of cellular processes. The first cells were likely prokaryotic and lacked membrane-bound organelles, but as cells evolved, compartmentalization provided a means to separate incompatible biochemical processes. The development of compartmentalization in eukaryotic cells is thought to have resulted from the incorporation of free-living prokaryotes into a host cell, leading to the development of endosymbiotic relationships and the formation of membrane-bound organelles.

Unit 3: Cellular Energetics

Subtopic Number	Subtopic Name	Key points
3.1	Enzyme Structure	Enzyme structure refers to the three-dimensional arrangement of amino acid residues in an enzyme, which determines its function and specificity. Enzymes typically consist of a folded polypeptide chain, with specific regions or domains responsible for binding substrate molecules and catalyzing chemical reactions. The active site of an enzyme is a specific region within the enzyme structure where substrate molecules bind and undergo chemical transformation.
3.2	Enzyme Catalysis	Enzyme catalysis involves the acceleration of biochemical reactions by enzymes, which lower the activation energy required for the reaction to occur. Enzyme catalysis is highly specific, with enzymes catalyzing only a single reaction or a limited set of related reactions. Enzyme catalysis can be affected by various factors, including substrate concentration, pH, temperature, and the presence of inhibitors or activators.
3.3	Environmental Impacts on Enzyme Function	Enzyme function can be affected by environmental factors, such as temperature, pH, and salinity, which can cause changes in the enzyme’s structure and activity. Enzymes have optimal environmental conditions in which they function most efficiently, with deviations from these conditions resulting in decreased enzyme activity or denaturation. Environmental factors can also affect the expression and regulation of enzymes, with organisms adapting to changes in their environment by altering the types and levels of enzymes produced.
3.4	Cellular Energy	Cellular energy refers to the energy stored in chemical bonds within molecules, which can be harnessed by cells to power various biological processes. ATP is the primary energy currency of cells, with energy released during its hydrolysis used to drive cellular processes. Cellular energy is obtained through the breakdown of organic molecules, such as glucose, in a series of biochemical pathways, including glycolysis, the citric acid cycle, and oxidative phosphorylation.
3.5	Photosynthesis	Photosynthesis is the process by which autotrophic organisms convert light energy into chemical energy in the form of organic molecules, such as glucose. Photosynthesis occurs in chloroplasts, specialized organelles in plant cells that contain chlorophyll and other pigments involved in light absorption. The two stages of photosynthesis, the light-dependent reactions and the light-independent reactions (Calvin cycle), work together to produce organic molecules and release oxygen as a byproduct.
3.6	Cellular Respiration	Cellular respiration is the process by which cells convert organic molecules into ATP, the energy currency of the cell, through a series of biochemical pathways. Cellular respiration occurs in the mitochondria of eukaryotic cells and involves three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. Cellular respiration can be aerobic, requiring oxygen, or anaerobic, occurring in the absence of oxygen, with different types of organisms and cells utilizing different strategies for energy production.
3.7	Fitness	In evolutionary biology, fitness refers to an organism’s ability to survive and reproduce in a given environment. Fitness is determined by a combination of genetic factors and environmental pressures, with organisms possessing advantageous traits being more likely to survive and pass on their genes to the next generation. Fitness can be measured in various ways, including reproductive success, survival rate, and genetic diversity, and is central to understanding the process of natural selection.

Unit 4: Cell Communication and Cell Cycle

Subtopic Number	Subtopic Name	Key points
4.1	Cell Communication	Cell communication refers to the complex processes by which cells interact and exchange information with each other, both within an organism and between different organisms. Cell communication can occur through various mechanisms, including direct cell-to-cell contact, secretion of signaling molecules, and detection of external stimuli. The different types of cell communication, such as autocrine, paracrine, and endocrine signaling, play important roles in numerous biological processes, including development, immune response, and behavior.
4.2	Introduction to Signal Transduction	Signal transduction is the process by which cells convert signals from their environment into biochemical responses within the cell. Signal transduction can involve a series of steps, including reception of the signal, signal processing, and cellular response. Signal transduction pathways are critical for numerous cellular processes, including cell growth and division, immune response, and sensory perception.
4.3	Signal Transduction	Signal transduction pathways are complex networks of signaling molecules and proteins that relay information from the outside of a cell to the inside, triggering cellular responses. Signal transduction can occur through a variety of mechanisms, including receptor activation, second messenger cascades, and gene expression changes. Dysregulation of signal transduction pathways can lead to a range of diseases, including cancer, autoimmune disorders, and metabolic disorders.
4.4	Changes in Signal Transduction Pathways	Changes in signal transduction pathways can occur as a result of mutations in signaling molecules or downstream effectors, as well as changes in the expression of genes involved in the pathway. Dysregulation of signal transduction pathways can lead to altered cellular responses, including abnormal growth and differentiation, and can contribute to the development and progression of diseases. Understanding the mechanisms underlying changes in signal transduction pathways is important for developing targeted therapies for a wide range of diseases.
4.5	Feedback	Feedback is a process by which the output or response of a system affects its input or stimulus, either positively or negatively. Feedback mechanisms can be classified as positive or negative, depending on whether they amplify or dampen the initial stimulus, respectively. Feedback is a critical component of many biological processes, including homeostasis, regulation of gene expression, and control of cellular responses to external stimuli.
4.6	Cell Cycle	The cell cycle is the series of events that occur in a cell leading to its division and duplication. The cell cycle consists of two main stages: interphase and the mitotic phase, which includes mitosis and cytokinesis. The cell cycle is regulated by a complex network of checkpoints and control mechanisms, which ensure that cells divide only when necessary and that errors are minimized.
4.7	Regulation of Cell Cycle	The regulation of the cell cycle is critical for maintaining proper cell growth and development, as well as preventing the development of diseases such as cancer. The cell cycle is controlled by a variety of regulatory proteins and checkpoints, which monitor the cell’s progress through each phase and halt progression if errors are detected. Dysregulation of the cell cycle can lead to abnormal growth and division, which can result in tumor formation and cancer progression.

Unit 5: Heredity

Subtopic Number	Subtopic Name	Key points
5.1	Meiosis	Meiosis is a specialized type of cell division that occurs in sexually reproducing organisms, resulting in the production of haploid gametes. Meiosis involves two rounds of cell division, meiosis I and meiosis II, resulting in the production of four genetically unique daughter cells. The process of meiosis is regulated by a complex network of checkpoint mechanisms, which ensure proper chromosome alignment and segregation, as well as genetic diversity.
5.2	Meiosis and Genetic Diversity	Meiosis is essential for genetic diversity, as it results in the production of genetically unique haploid gametes. The random assortment of homologous chromosomes during meiosis I and the crossing over of genetic material during prophase I contribute to genetic diversity. Errors during meiosis, such as nondisjunction or failure of homologous chromosomes to separate properly, can result in chromosomal abnormalities and genetic disorders.
5.3	Mendelian Genetics	Mendelian genetics is the study of inheritance patterns in organisms based on the laws of segregation and independent assortment. The law of segregation states that each organism has two alleles for each trait, and they separate during gamete formation. The law of independent assortment states that different traits are inherited independently of each other, as long as they are located on different chromosomes.
5.4	Non-Mendelian Genetics	Non-Mendelian genetics refers to patterns of inheritance that do not follow the principles of segregation and independent assortment. Examples of non-Mendelian inheritance include incomplete dominance, codominance, and multiple alleles. Non-Mendelian inheritance can also involve the influence of environmental factors on gene expression, as in the case of epigenetics.
5.5	Environmental Effects on Phenotypes	Environmental effects on phenotypes can be caused by factors such as temperature, light, and nutrition. These effects can lead to phenotypic plasticity, where an organism can express different phenotypes in response to environmental cues. Environmental effects can also impact epigenetic modifications, which can influence gene expression and ultimately affect phenotype.
5.6	Chromosomal Inheritance	Chromosomal inheritance involves the transmission of genetic information from one generation to the next through chromosomes. Chromosomal abnormalities, such as nondisjunction, can lead to genetic disorders such as Down syndrome. Sex-linked inheritance involves the inheritance of genes located on the sex chromosomes and can lead to different patterns of inheritance compared to autosomal genes.

Unit 6: Gene Expression and Regulation

Subtopic Number	Subtopic Name	Key points
6.1	DNA and RNA Structure	DNA and RNA are both nucleic acids made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base. The sugar in DNA is deoxyribose, while RNA contains ribose, which has an additional hydroxyl group. The nitrogenous bases in DNA are adenine, thymine, cytosine, and guanine, while RNA contains uracil instead of thymine.
6.2	Replication	Replication is the process by which DNA makes an exact copy of itself, ensuring the genetic information is accurately passed from cell to cell. DNA replication requires enzymes like helicase, DNA polymerase, and ligase to unwind, synthesize, and repair the DNA strands. Replication is semiconservative, meaning that each daughter cell contains one original strand and one newly synthesized strand of DNA.
6.3	Transcription and RNA Processing	Transcription is the process of making an RNA copy of a DNA sequence, using the enzyme RNA polymerase. RNA processing includes modifications like capping, splicing, and polyadenylation to produce a mature mRNA transcript that can be used in translation. Alternative splicing can create multiple different mRNA transcripts from a single gene, leading to increased protein diversity.
6.4	Translation	Translation is the process by which mRNA is used to synthesize a protein on ribosomes. Translation involves initiation, elongation, and termination stages, with tRNA molecules bringing amino acids to the ribosome to be incorporated into the growing protein chain. The genetic code is universal, meaning that the same codons (three-base sequences on mRNA) code for the same amino acids in all living organisms
6.5	Regulation of Gene Expression	Gene expression can be regulated at various levels, including transcriptional, post-transcriptional, translational, and post-translational. Gene regulation allows cells to respond to changes in their environment and to perform specific functions during development and differentiation. Regulatory elements, such as enhancers and repressors, bind to DNA and control the rate and timing of gene expression.
6.6	Gene Expression and Specialisation	Cells can differentiate into specialized cell types by expressing specific sets of genes. Gene expression is influenced by environmental cues and signals from other cells in the organism. Epigenetic modifications, such as DNA methylation and histone modification, play a crucial role in regulating gene expression during development and cell differentiation.
6.7	Mutations	Mutations can be caused by errors in DNA replication or by exposure to mutagens, such as chemicals or radiation. Mutations can have various effects on gene expression, including loss of function, gain of function, or altered regulation. Some mutations are heritable and can be passed on to offspring, leading to genetic disorders or variations in phenotype.
6.8	Biotechnology	Biotechnology uses techniques such as genetic engineering and recombinant DNA technology to manipulate and modify genetic material. Applications of biotechnology include the production of pharmaceuticals, genetically modified crops, and gene therapy for genetic diseases. Ethical and social concerns surrounding biotechnology include issues of safety, accessibility, and equity in the distribution of benefits and risks.

Unit 7: Natural Selection

Subtopic Number	Subtopic Name	Key points
7.1	Introduction to Natural Selection	Natural selection is the process by which organisms with advantageous traits are more likely to survive and reproduce. The principles of natural selection were first proposed by Charles Darwin and Alfred Russel Wallace in the 19th century. Natural selection operates on heritable variations within a population.
7.2	Natural Selection	Natural selection can lead to changes in allele frequencies and the evolution of new species. Selection can be directional, stabilizing, or disruptive depending on environmental pressures. Adaptations that increase an organism’s fitness in its environment are key outcomes of natural selection.
7.3	Artificial Selection	Artificial selection is the selective breeding of plants and animals by humans for specific traits. Domesticated crops and animals are products of artificial selection over thousands of years. Artificial selection can lead to rapid changes in traits compared to natural selection.
7.4	Population Genetics	Population genetics is the study of genetic variation within and between populations. The Hardy-Weinberg equilibrium describes a theoretical population in which allele frequencies remain constant over time. Genetic drift and gene flow are important mechanisms that can alter allele frequencies in populations.
7.5	Hardy-Weinburg Equilibrium	The Hardy-Weinberg equilibrium is a mathematical model used to describe the relationship between allele frequencies and genotype frequencies in a population that is not evolving. The model assumes certain conditions, including a large population size, random mating, no mutations, no migration, and no natural selection. Deviations from the Hardy-Weinberg equilibrium can indicate that the population is evolving and can provide insights into the evolutionary processes that are occurring.
7.6	Evidence of Evolution	Evidence of evolution includes fossil records, comparative anatomy, embryology, molecular biology, and biogeography. Fossil records provide evidence of changes in species over time, while comparative anatomy and embryology reveal similarities in the anatomical structures and developmental processes of different organisms. Molecular biology techniques such as DNA sequencing and phylogenetic analysis can reveal genetic similarities between different species, and biogeography can reveal how species have evolved and spread across different geographical regions.
7.7	Common Ancestry	The concept of common ancestry suggests that all living organisms share a common ancestor, and that the diversity of life on Earth has arisen through a process of descent with modification. Evidence supporting the idea of common ancestry includes the presence of homologous structures and shared genetic sequences among different species. Phylogenetic trees, which are diagrams showing the evolutionary relationships between different species, provide a visual representation of the idea of common ancestry.
7.8	Continuing Evolution	Evolution is an ongoing process, and populations are constantly evolving through mechanisms such as natural selection, genetic drift, and gene flow. Factors such as environmental changes, genetic mutations, and the movement of individuals between populations can drive evolutionary change over time. Evolution can lead to the development of new species, the extinction of existing species, and the diversification of life on Earth.
7.9	Phylogeny	Phylogeny is the study of the evolutionary relationships between different organisms, based on shared ancestry and genetic relatedness. Phylogenetic trees are used to represent the branching patterns of evolutionary relationships between different species or groups of species. The development of molecular biology techniques such as DNA sequencing has revolutionized the field of phylogeny, allowing for more accurate reconstructions of evolutionary relationships.
7.10	Speciation	Speciation is the process by which one species splits into two or more distinct species. This process can occur through mechanisms such as geographic isolation, reproductive isolation, and genetic divergence. Speciation is an important driver of biodiversity and can lead to the development of new species with unique adaptations to their environments.
7.11	Extinction	Extinction is the permanent loss of a species or group of organisms from the Earth. Factors that can contribute to extinction include habitat destruction, climate change, overexploitation, and the introduction of invasive species. Mass extinctions, which have occurred at various points in Earth’s history, can have profound impacts on the diversity and evolution of life on Earth.
7.12	Variations in Populations	Genetic variation within populations is an important driver of evolutionary change, as it provides the raw material for natural selection to act upon. Variations in phenotype can be caused by genetic mutations, environmental factors, or a combination of both. The study of variations in populations can provide insights into the evolutionary processes that have shaped the diversity of life on Earth.
7.13	Origin of Life on Earth	The origin of life on Earth is still a topic of scientific debate, but it is generally believed to have occurred around 3.5 billion years ago. One proposed hypothesis is the RNA world hypothesis, which suggests that RNA molecules played a key role in the development of early life forms.

Unit 8: Ecology

Subtopic Number	Subtopic Name	Key points
8.1	Responses to the Environment	Organisms exhibit a variety of responses to environmental stimuli, including behavioral, physiological, and morphological adaptations. Sensory receptors detect environmental cues and transmit signals through sensory neurons to the central nervous system, which coordinates an appropriate response. Responses can be innate or learned, and can be shaped by natural selection over time.
8.2	Energy Flow through Ecosystems	Energy enters ecosystems as sunlight and is captured by primary producers through photosynthesis. Energy is transferred between trophic levels through consumption and is lost as heat through metabolic processes. Energy flow through ecosystems is limited by the second law of thermodynamics, which states that energy is lost as it is transferred from one level to the next.
8.3	Population Ecology	Population ecology is the study of how populations of organisms interact with their environment. Population size is influenced by birth and death rates, immigration, and emigration. Population growth is limited by environmental factors such as resource availability, predation, disease, and competition.
8.4	Effect of Density on Populations	As population density increases, competition for resources and mating opportunities also increases. Density-dependent factors such as predation, disease, and food availability can regulate population growth. Density-independent factors such as weather events and natural disasters can also affect population size.
8.5	Community Ecology	Community ecology is the study of how groups of species interact with each other in a given area. Interactions between species can be categorized as mutualism, commensalism, predation, parasitism, and competition. The complexity and stability of communities are influenced by the number and strength of these interactions.
8.6	Biodiversity	Biodiversity refers to the variety of life on Earth, including genetic, species, and ecosystem diversity. Biodiversity provides important ecosystem services such as nutrient cycling, soil formation, and climate regulation. Human activities such as habitat destruction, pollution, and climate change are leading to a decline in global biodiversity.
8.7	Disruptions to Ecosystems	Ecosystems can be disrupted by natural events such as fires, floods, and volcanic eruptions, as well as by human activities such as deforestation, pollution, and overfishing. Disruptions can lead to changes in species composition, loss of biodiversity, and decreased ecosystem services. Ecosystems can exhibit resilience, the ability to recover from disturbances, but can also reach a tipping point beyond which recovery is unlikely.