AP Biology
In short
AP Biology has 8 units: Chemistry of Life, Cells, Cellular Energetics and 5 more. Each unit lists its topics in course framework order, with a self-check list and how each is tested on the exam. Start with Chemistry of Life or jump to the unit you are revising.
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What units are in AP Biology?
1.1 Structure of Water and Hydrogen Bonding
- I can describe how living systems depend on water's polarity, high specific heat capacity, and high heat of vaporization to sustain life and maintain homeostasis.
1.2 Elements of Life
- I can describe the elemental composition of the major macromolecules required by living organisms.
- I can identify that carbon, hydrogen, and oxygen are the most prevalent elements in carbohydrates, proteins, lipids, and nucleic acids.
- I can state that sulfur is used in the building of proteins.
- I can state that phosphorus is used in the building of phospholipids and nucleic acids.
- I can state that nitrogen is used in the building of nucleic acids.
1.3 Introduction to Macromolecules
- I can describe how hydrolysis reactions cleave covalent bonds and break down polymers into monomers by adding water.
- I can describe how dehydration synthesis joins monomers together through covalent bonding, resulting in the loss of a water molecule to form a polymer.
1.4 Carbohydrates
- I can explain that monosaccharides are connected by covalent bonds to form linear or branched polysaccharides.
1.5 Lipids
- I can describe how the structure of lipids, including saturated and unsaturated fatty acids, determines their properties.
- I can explain the biological functions of various lipids, including fats, steroids, cholesterol, and phospholipids.
1.6 Nucleic Acids
- I can identify the structural components of a nucleotide and describe how biological information is encoded in nucleic acids.
- I can explain the directionality of nucleic acids (3' and 5' ends) and describe how new nucleotides are added during synthesis.
- I can describe the antiparallel double helix structure of DNA and the specific hydrogen bonding between base pairs.
- I can compare and contrast the structural differences between DNA and RNA.
1.7 Proteins
- I can describe how proteins are formed by peptide bonds between the carboxyl group of one amino acid and the amine group of another.
- I can identify the components of an amino acid and categorize its R group as hydrophobic, hydrophilic, or ionic.
- I can explain how the sequence of amino acids determines a protein's primary structure and overall shape.
- I can describe how hydrogen bonding in the polypeptide backbone forms secondary structures like alpha-helices and beta-pleated sheets.
- I can explain how interactions between R groups form the tertiary structure of a protein.
- I can describe how quaternary structure arises from multiple polypeptides and how all structural levels determine protein function.
2.1 Cell Structure and Function
- I can describe the composition of ribosomes and explain their role in synthesizing proteins according to mRNA sequences.
- I can identify the components of the endomembrane system and describe how they work together to modify, package, and transport materials.
- I can explain the functions of the rough and smooth endoplasmic reticulum, including their roles in protein synthesis, compartmentalization, detoxification, and lipid synthesis.
- I can describe the structure of the Golgi complex and its functions in folding, chemically modifying, and packaging newly synthesized cellular products.
- I can explain how the double membrane structure of mitochondria, including the highly convoluted inner membrane, enables efficient ATP synthesis.
- I can describe the function of lysosomes in digesting material and their role in programmed cell death (apoptosis).
- I can compare the roles of vacuoles in plant and animal cells, including the maintenance of turgor pressure in plants.
- I can describe the structure of chloroplasts and their function as the location for photosynthesis.
2.2 Cell Size
- I can describe how surface area-to-volume ratios affect a biological system's ability to exchange nutrients, waste, and thermal energy with the environment.
2.3 Plasma Membrane
- I can describe how the hydrophilic phosphate heads and hydrophobic fatty acid tails of phospholipids orient themselves to form a membrane.
- I can explain how the hydrophilic and hydrophobic regions of embedded proteins dictate their position within or on the surface of the cell membrane.
- I can describe the fluid mosaic model and identify the structural framework of phospholipids, proteins, steroids, glycoproteins, and glycolipids.
2.4 Membrane Permeability
- I can state that plasma membranes separate internal and external environments and that selective permeability is due to the hydrophobic interior.
- I can describe how small nonpolar molecules pass freely, while hydrophilic substances require embedded channels and transport proteins.
- I can explain that nonpolar hydrocarbon tails prevent the movement of ions and polar molecules, but small polar uncharged molecules can pass in small amounts.
- I can explain how cell walls in Bacteria, Archaea, Fungi, and plants provide a structural boundary, permeability barrier, and protection from osmotic lysis.
2.5 Membrane Transport
- I can describe passive transport as the movement of molecules from high to low concentration without metabolic energy.
- I can describe active transport as requiring direct energy input to move molecules, often against their concentration gradient.
- I can explain how endocytosis and exocytosis require energy to move large substances into and out of cells via vesicle formation and fusion.
2.6 Facilitated Diffusion
- I can describe how charged ions require transport or channel proteins to move across the membrane, and how this movement can lead to membrane polarization.
- I can explain that facilitated diffusion moves large polar molecules down their concentration gradient without the input of energy.
- I can identify aquaporins as the specific proteins that transport large quantities of water across membranes.
2.7 Tonicity and Osmoregulation
- I can describe the movement of water between hypotonic, hypertonic, and isotonic environments and explain osmosis in terms of water potential.
- I can calculate solute potential and explain how osmoregulation maintains water balance and internal solute composition.
2.8 Mechanisms of Transport
2.9 Cell Compartmentalization
- I can describe the membrane-bound structures found in eukaryotic cells.
- I can explain how membrane-bound organelles compartmentalize metabolic processes and enzymatic reactions.
- I can explain how internal membranes contribute to the compartmentalization of eukaryotic cell functions.
- I can describe how internal membranes minimize competing interactions and increase surface area for cellular reactions.
2.10 Origins of Cell Compartmentalization
3.1 Enzymes
- I can explain how enzymes act as biological catalysts by lowering the activation energy of chemical reactions.
- I can describe how the shape and charge of a substrate must be compatible with an enzyme's active site to form an enzyme-substrate complex.
3.2 Environmental Impacts on Enzyme Function
3.3 Cellular Energy
- I can state that all living systems require an input of energy.
- I can explain that life requires a highly ordered system, and that energy input must exceed energy loss to maintain order and power cellular processes.
- I can describe how energy-related pathways are sequential, allowing for controlled energy transfer where the product of one reaction is typically the reactant for the next.
- I can explain how core metabolic pathways, such as glycolysis and oxidative phosphorylation, are conserved across all domains of life and support the concept of common ancestry.
3.4 Photosynthesis
- I can explain that photosynthesis uses carbon dioxide, water, and light energy to make carbohydrates and oxygen, and describe its evolutionary origins in prokaryotes.
- I can identify the stroma and thylakoids within the chloroplast and describe their roles in the Calvin cycle and light reactions.
- I can describe how the light reactions capture energy to yield ATP and NADPH, which power the Calvin cycle.
- I can describe the role of the electron transport chain in chloroplasts and how electrons are transferred to NADP+ to form NADPH.
- I can explain how chlorophylls absorb light energy to boost electrons in photosystems I and II, and how water is split to replace electrons.
- I can describe how photosystems I and II are embedded in the thylakoid membrane and connected by an ETC.
- I can explain how the transfer of electrons through the ETC establishes an electrochemical gradient of protons across the thylakoid membrane.
- I can explain how the proton gradient drives the synthesis of ATP via ATP synthase through chemiosmosis (photophosphorylation).
- I can describe how the energy from ATP and NADPH is used in the Calvin cycle to produce carbohydrates from carbon dioxide in the stroma.
3.5 Cellular Respiration
- I can state that cellular respiration and fermentation use energy from biological macromolecules to synthesize ATP and are characteristic of all forms of life.
- I can describe how aerobic cellular respiration involves a series of coordinated enzyme-catalyzed reactions that capture energy.
- I can explain how the electron transport chain establishes an electrochemical gradient, how chemiosmosis drives ATP formation, and how decoupling generates heat.
- I can describe glycolysis as a pathway that releases energy from glucose to form ATP, NADH, and pyruvate.
- I can explain the transport of pyruvate to the mitochondrion and its oxidation during the Krebs cycle to release CO2, NADH, and FADH2.
- I can describe the Krebs cycle's role in releasing carbon dioxide, synthesizing ATP, and transferring electrons to coenzymes.
- I can trace the transfer of electrons from glycolysis and the Krebs cycle to the ETC via NADH and FADH2.
- I can explain how electron transfer through the ETC establishes a proton gradient across the inner mitochondrial membrane.
- I can describe how fermentation allows glycolysis to continue in the absence of oxygen by producing organic molecules such as alcohol or lactic acid.
4.1 Cell Communication
- I can describe how cells communicate through direct contact or chemical signaling from a distance.
- I can explain how cells use local regulators to communicate over short distances.
- I can explain how signals released by one cell type travel long distances to target other cell types.
4.2 Introduction to Signal Transduction
- I can explain that signal transduction pathways often include protein modifications and phosphorylation cascades.
- I can describe how signaling begins with a ligand binding to a specific receptor protein, such as a G protein-coupled receptor, either on the cell surface or intracellularly.
- I can describe how signaling cascades relay and amplify signals using enzymes and second messengers like cAMP to produce cellular responses such as gene expression or cell growth.
4.3 Signal Transduction Pathways
4.4 Feedback
- I can describe how negative feedback mechanisms return a perturbed system back to its target set point by reducing the initial stimulus.
- I can explain how positive feedback mechanisms amplify responses by moving the variable further from the initial set point to produce system change.
4.5 Cell Cycle
- I can describe the sequential stages of the cell cycle (G1, S, G2, mitosis, cytokinesis) and explain the specific cellular events that occur in each phase, including the G0 stage.
- I can explain how mitosis ensures the transmission of a complete genome from a parent cell to two genetically identical daughter cells.
- I can describe the sequential steps of mitosis (prophase, metaphase, anaphase, telophase) and cytokinesis, detailing the movement of chromosomes and cellular structures in each step.
4.6 Regulation of Cell Cycle
5.1 Meiosis
5.2 Meiosis and Genetic Diversity
- I can explain how the correct separation of homologous chromosomes and sister chromatids results in haploid gametes with an assortment of maternal and paternal chromosomes, and describe the non-haploid results of nondisjunction.
- I can describe how crossing over during prophase I exchanges genetic material between non-sister chromatids to increase genetic diversity.
- I can explain how sexual reproduction, including crossing over, random assortment, and fertilization, increases genetic variation in eukaryotes.
5.3 Mendelian Genetics
- I can use rules of probability, Punnett squares, and pedigrees to analyze single-gene traits, determine allele dominance, and predict genotypes and phenotypes.
5.4 Non-Mendelian Genetics
- I can explain how linked genes, codominance, and incomplete dominance deviate from Mendelian ratios and calculate map distance between linked genes.
- I can predict the pattern of inheritance for sex-linked traits using data such as pedigrees.
- I can describe pleiotropy as a single gene resulting in multiple traits that do not segregate independently.
- I can explain how non-nuclear inheritance of chloroplast and mitochondrial DNA occurs maternally and does not follow Mendelian rules.
5.5 Environmental Effects on Phenotype
6.1 DNA and RNA Structure
- I can explain that genetic information is stored in DNA and sometimes RNA, and contrast prokaryotic circular chromosomes with eukaryotic linear chromosomes.
- I can describe plasmids as extra-chromosomal circular DNA molecules found in both prokaryotes and eukaryotes.
- I can identify purines and pyrimidines by their ring structures and describe their specific base pairing rules.
6.2 DNA Replication
- I can explain how DNA replication ensures continuity of hereditary information, including the roles of helicase, topoisomerase, DNA polymerase, and ligase.
6.3 Transcription and RNA Processing
- I can explain how the sequence and structure of RNA bases determine the functions of mRNA, tRNA, and rRNA.
- I can describe how RNA polymerases use a single template strand of DNA to synthesize a newly formed RNA molecule during transcription.
- I can describe the enzyme-mediated modifications that eukaryotic mRNA transcripts undergo, including the addition of a poly-A tail, a GTP cap, and alternative splicing.
6.4 Translation
- I can describe where translation occurs in prokaryotic and eukaryotic cells.
- I can explain that translation occurs simultaneously with transcription in prokaryotes.
- I can describe the steps of translation (initiation, elongation, termination) and the roles of mRNA, tRNA, rRNA, and codons.
- I can explain how retroviruses use reverse transcriptase to flow genetic information from RNA to DNA.
6.5 Regulation of Gene Expression
6.6 Gene Expression and Cell Specialization
6.7 Mutations
- I can describe how alterations in a DNA sequence (point, frameshift, nonsense, silent mutations) can change the type or amount of protein produced and the resulting phenotype.
- I can explain how errors in DNA replication, DNA repair, or external factors can cause random mutations, and how their effect depends on the environmental context.
- I can explain how errors in mitosis or meiosis, such as nondisjunction, can result in changes in chromosome number (e.g., aneuploidy) and lead to developmental limitations or genetic disorders.
- I can explain how changes in genotype, including horizontal gene transfer in prokaryotes and viral recombination, contribute to genetic variation that is subject to natural selection.
6.8 Biotechnology
- I can describe the basic principles and applications of gel electrophoresis, PCR, bacterial transformation, and DNA sequencing.
7.1 Introduction to Natural Selection
- I can state that natural selection is a major mechanism of evolution.
- I can explain that competition for limited resources results in differential survival, and individuals with favorable phenotypes are more likely to survive and reproduce.
- I can describe how evolutionary fitness is measured by reproductive success.
- I can explain how fluctuating biotic and abiotic environments affect the rate and direction of evolution by selecting different genetic variations.
7.2 Natural Selection
7.3 Artificial Selection
- I can describe data from a table or graph, including identifying specific data points, trends, patterns, and relationships between variables.
7.4 Population Genetics
- I can describe how mutation, genetic drift (including bottleneck and founder effects), and migration drive evolution through random occurrences.
- I can explain how mutations, genetic drift, and gene flow lead to changes in allele frequencies and affect population divergence.
7.5 Hardy–Weinberg Equilibrium
- I can list the five conditions required for a population to be in Hardy-Weinberg equilibrium and explain how it serves as a null hypothesis.
- I can calculate allele and genotype frequencies in a nonevolving population using the Hardy-Weinberg equations.
7.6 Evidence of Evolution
- I can describe the geographical, geological, physical, biochemical, and mathematical data that provide evidence for evolution.
- I can explain how fossils are dated and how morphological homologies, including vestigial structures, provide evidence of common ancestry.
7.7 Common Ancestry
- I can identify membrane-bound organelles, linear chromosomes, and genes that contain introns as evidence for the common ancestry of all eukaryotes.
7.8 Continuing Evolution
- I can provide examples of ongoing evolution, such as genomic changes, continuous fossil record changes, resistance to drugs or chemicals, and emergent diseases.
7.9 Phylogeny
- I can explain how traits gained or lost during evolution, including shared derived characters and molecular data, are used to construct phylogenetic trees and cladograms, and identify the out-group.
- I can use phylogenetic trees and cladograms to illustrate speciation and identify the most recent common ancestor at the nodes.
- I can construct phylogenetic trees and cladograms from morphological similarities and from DNA and protein sequence similarities.
7.10 Speciation
- I can explain that speciation occurs when two populations become reproductively isolated from each other.
- I can define a species using the biological species concept as a group capable of interbreeding and exchanging genetic information to produce viable, fertile offspring.
- I can distinguish between punctuated equilibrium and gradualism as different rates of evolution.
- I can describe how divergent evolution and adaptive radiation lead to rapid speciation when new habitats become available.
- I can explain how convergent evolution results in similar phenotypic adaptations in different populations due to similar selective pressures.
- I can differentiate between sympatric speciation (geographic overlap) and allopatric speciation (geographic isolation).
- I can describe how various pre-zygotic and post-zygotic mechanisms maintain reproductive isolation and prevent gene flow.
7.11 Variations in Populations
- I can describe how the level of variation in a population affects its ability to respond to environmental changes, and why populations with little diversity are at risk of extinction.
- I can explain why genetically diverse populations are more resilient to environmental perturbations.
- I can explain how an allele that is adaptive in one environment may be deleterious in another due to different selective pressures.
7.12 Origins of Life on Earth
- I can explain the geological timeline of early Earth and how it provides a plausible range of dates for the origin of life.
- I can describe the RNA world hypothesis and list its three key assumptions regarding early genetic material.
8.1 Responses to the Environment
- I can describe how organisms communicate through various mechanisms and how signaling behaviors can result in differential reproductive success.
- I can explain how responses to information are vital to natural selection, and how innate, learned, and cooperative behaviors increase survival and reproductive success.
8.2 Energy Flow Through Ecosystems
- I can explain how organisms use energy to maintain homeostasis, including the differences between endotherms and ectotherms.
- I can describe how reproductive strategies change in response to energy availability.
- I can list the ecological levels of organization.
- I can describe the components of biogeochemical cycles, including abiotic and biotic reservoirs.
- I can describe the processes and reservoirs involved in the hydrologic cycle.
- I can explain the four main parts of the carbon cycle.
- I can describe the steps and microorganisms involved in the nitrogen cycle.
- I can explain how phosphorus cycles through the environment and living organisms.
- I can link changes in energy availability to changes in population size.
- I can describe how changes in energy resources or producer biomass affect trophic levels.
- I can distinguish between photosynthetic and chemosynthetic autotrophs.
- I can explain how heterotrophs capture energy by consuming organic matter.
8.3 Population Ecology
- I can describe how populations consist of individuals of the same species that interact with each other and their environment.
- I can explain how an organism's adaptations relate to how it obtains and uses energy and matter.
- I can explain how population growth dynamics depend on birth rate, death rate, and population size, and calculate population growth.
- I can describe how reproduction without constraints leads to exponential growth and calculate exponential growth rates.
8.4 Effect of Density on Populations
8.5 Community Ecology
- I understand that communities change over time based on the interactions between populations of different species.
- I can describe how competition, predation, and symbioses (parasitism, mutualism, commensalism) drive population dynamics.
8.6 Biodiversity
- I can describe the relationship between the diversity of an ecosystem and its resilience to environmental changes.
- I can explain why natural and artificial ecosystems with fewer components and less diversity are less resilient.
- I can identify the roles of keystone species, producers, and essential abiotic and biotic factors in maintaining ecosystem diversity.
- I can explain how adding or removing a component affects an ecosystem's short-term and long-term structure.
- I can describe the disproportionate impact of keystone species and predict the likelihood of ecosystem collapse if they are removed.
8.7 Disruptions in Ecosystems
- I can describe how an adaptation is a genetic variation favored by selection that provides an advantage in a particular environment.
- I can explain heterozygote advantage, where the heterozygous genotype has a higher relative fitness than homozygous genotypes.
- I can describe how the introduction of invasive species allows them to exploit new niches and outcompete native species.
- I can explain how human impacts like biomagnification and eutrophication drive changes in ecosystems and can cause extinctions.
How should you use these resources?
Revise
Work through your course unit by unit, in the order it is taught, so nothing gets missed.
Test yourself
Check each topic against what you should be able to do, and practise on exam-style questions as they are added.
Improve
Go back to what you could not do, or work with a tutor to close the gaps before your exams.
AP Biology: common questions
What units are in AP Biology?
AP Biology has 8 units: Unit 1: Chemistry of Life; Unit 2: Cells; Unit 3: Cellular Energetics; Unit 4: Cell Communication and Cell Cycle; Unit 5: Heredity; Unit 6: Gene Expression and Regulation; Unit 7: Natural Selection; Unit 8: Ecology.
How should I revise AP Biology?
Work through one unit at a time in order, since later units build on earlier ones. For each topic, check you can do everything on its list before moving on, and go back to the ones you could not.
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