AP Biology

• 1.1.A.1.i Water has polarity, because of the formation of polar covalent bonds between hydrogen and oxygen within water molecules. This polarity contributes to hydrogen bonding between and within biological molecules.
• 1.1.A.1.ii Water has a high specific heat capacity, which allows for the maintenance of homeostatic body temperature within living organisms.
• 1.1.A.1.iii Water has a high heat of vaporization, which allows for the evaporative cooling of the surrounding environment. In living organisms, this property allows for body temperature to be maintained.

• 1.2.A.1.i Sulfur is used in the building of proteins.
• 1.2.A.1.ii Phosphorus is used in the building of phospholipids (a type of lipid) and nucleic acids.
• 1.2.A.1.iii Nitrogen is used in the building of nucleic acids.

• Illustrative examples for 1.4.A.1:
  • Cellulose
  • Starch
  • Glycogen
• Exclusion statement: The molecular structure of specific carbohydrate polymers is beyond the scope of the AP Exam.

• 1.5.A.1.i Saturated fatty acids contain only single bonds between carbon atoms.
• 1.5.A.1.ii Unsaturated fatty acids contain at least one double bond between carbon atoms, which causes the carbon chain to kink.
• 1.5.A.1.iii The more double bonds in a fatty acid tail, the more unsaturated the lipid becomes.
• 1.5.A.1.iv The more unsaturated a lipid is, the more liquid it is at room temperature.

• 1.5.A.2.i Fats provide energy storage and support cell function. In some cases, they can also provide insulation to help keep mammals warm.
• 1.5.A.2.ii Steroids are hormones that support physiological functions including growth and development, energy metabolism, and homeostasis.
• 1.5.A.2.iii Cholesterol provides essential structural stability to animal cell membranes.
• 1.5.A.2.iv Phospholipids group together to form the lipid bilayers found in plasma and cell membranes.
• Exclusion statement: The molecular structure of specific lipids is beyond the scope of the AP Exam.

• Exclusion statement: The molecular structure of specific nucleotides is beyond the scope of the AP Exam.

• 1.6.A.4.i DNA contains the sugar deoxyribose, and RNA contains the sugar ribose.
• 1.6.A.4.ii DNA contains the nitrogenous base thymine, and RNA contains the nitrogenous base uracil.
• 1.6.A.4.iii DNA is typically double stranded, while RNA is typically single stranded.

• Exclusion statement: The molecular structure of amino acids is beyond the scope of the AP Exam.

• i. Rough ER is associated with membrane-bound ribosomes, allows for the compartmentalization of cells, and helps carry out protein synthesis.
• ii. Smooth ER functions include the detoxification of cells and lipid synthesis.
• Exclusion statement: Knowledge of the specific functions of smooth ER in specialized cells is beyond the scope of the AP Exam.

• i. Correctly folding and chemically modifying newly synthesized cellular products
• ii. Packaging proteins for trafficking
• Exclusion statement: Knowledge of the role of Golgi in the synthesis of specific phospholipids and packaging of specific enzymes for lysosomes, peroxisomes, and secretory vesicles is beyond the scope of the AP Exam.
• Illustrative examples for 2.1.A.4:
  • Glycosylation and other chemical modifications of proteins that take place within the Golgi and determine protein function or targeting

• i. In plant cells, a specialized large vacuole maintains turgor pressure through nutrient and water storage.
• ii. In animal cells, vacuoles are smaller in size, are more plentiful than in plant cells, and store cellular materials.

• Relevant equations:
  • Volume of a Sphere: $V = \dfrac{4}{3}\pi r^3$
  • Volume of a Cube: $V = s^3$
  • Volume of a Rectangular Solid: $V = lwh$
  • Volume of a Cylinder: $V = \pi r^2 h$
  • Surface Area of a Sphere: $SA = 4\pi r^2$
  • Surface Area of a Cube: $SA = 6s^2$
  • Surface Area of a Rectangular Solid: $SA = 2lh + 2lw + 2wh$
  • Surface Area of a Cylinder: $SA = 2\pi rh + 2\pi r^2$
  • $r$ = radius
  • $l$ = length
  • $h$ = height
  • $w$ = width
  • $s$ = length of one side of a cube
• Illustrative examples for 2.2.A.1:
  • SA/V Ratios and Exchanges
    • Root hairs
    • Guard cells
    • Gut epithelial cells
  • Cilia
  • Stomata

• i. The surface area-to-volume ratio can restrict cell size and shape. Smaller cells typically have a higher surface area-to-volume ratio as well as a more efficient exchange of materials with the environment than do larger cells.
• ii. As cells increase in volume, the surface area-to-volume ratio decreases and the demand for internal resources increases.
• iii. More complex cellular structures (e.g., membrane folds) are necessary to adequately exchange materials with the environment.
• iv. As organisms increase in size, their surface area-to-volume ratio decreases, affecting properties like rate of heat exchange with the environment. Smaller amounts of mass exchange proportionally more heat with the ambient environment than do larger masses. As mass increases, both the surface area-to-volume ratio and the rate of heat exchange decrease.
• v. There is a relationship between metabolic rate per unit body mass and the size of multicellular organisms; typically, the smaller the organism, the higher the metabolic rate per unit body mass.

• i. Hydrophilic regions of the proteins are either inside the interior of the protein or exposed to the cytosol (cytoplasm).
• ii. Hydrophobic regions of proteins make up the protein surface that interacts with the fatty acids in the interior membrane.

• i. In endocytosis, the cell takes in large molecules and particulate matter by folding the plasma membrane in on itself and forming new (small) vesicles that engulf material from the external environment.
• ii. In exocytosis, internal vesicles release material from cells by fusing with the plasma membrane and secreting large molecules from the cell.

• i. Membranes may become polarized by the movement of ions across the membrane.
• ii. Charged ions, including $\mathrm{Na^+}$ (sodium) and $\mathrm{K^+}$ (potassium), require channel proteins to move through the membrane.

• Equation (Water Potential): $\psi = \psi_p + \psi_s$
  • where:
  • $\psi_p$ = pressure potential
  • $\psi_s$ = solute potential
• Illustrative examples for 2.7.A.1:
  • Contractile vacuole in protists
  • Central vacuole in plant cells

• Equation (Solute Potential of a Solution): $\psi_s = -iCRT$
  • where:
  • $i$ = ionization constant
  • $C$ = molar concentration
  • $R$ = pressure constant $\left(R = 0.0831 \dfrac{L \cdot bars}{mol \cdot K}\right)$
  • $T$ = temperature in Kelvin (°C + 273)

• i. Membrane proteins are necessary for active transport.
• ii. The $\mathrm{Na^+}/\mathrm{K^+}$ pump and ATPase contribute to the maintenance of the membrane potential.

• i. Denaturation of proteins, such as enzymes, occurs when the protein structure is disrupted by a change in temperature, pH, or chemical environment, eliminating the ability to catalyze reactions.
• ii. Environmental temperatures and pH outside the optimal range for a given enzyme will cause changes to its structure (by disrupting the hydrogen bonds), altering the efficiency with which it catalyzes reactions.

• i. Energy input must exceed energy loss to maintain order and to power cellular processes.
• ii. Cellular processes that release energy may be coupled with cellular processes that require energy.
• iii. Significant loss of order or energy flow results in death.
• Exclusion statement: Students will need to understand the concept of energy, but the equation for Gibbs free energy is beyond the scope of the AP Exam.

• i. Photosynthetic organisms capture energy from the sun and produce sugars that can be used in biological processes or stored.
• ii. Photosynthesis first evolved in prokaryotic organisms.
• iii. Scientific evidence supports the claim that prokaryotic (cyanobacterial) photosynthesis was responsible for the production of an oxygenated atmosphere.
• iv. Prokaryotic photosynthetic pathways were the foundation of eukaryotic photosynthesis.
• Exclusion statement: Memorization of the steps in the Calvin cycle, the structure of the molecules, and the names of the enzymes involved, with the exception of ATP synthase, is beyond the scope of the AP Exam.

• i. The stroma is the fluid within the inner chloroplast membrane and outside the thylakoid. The carbon fixation (Calvin cycle) reactions of photosynthesis occur in the stroma.
• ii. The thylakoid membranes contain chlorophyll pigments organized into two photosystems, as well as electron transport proteins.
• iii. Thylakoids are organized in stacks called grana. The light reactions of photosynthesis occur in the grana.

• Exclusion statement: The full names of the specific electron carriers in the electron transport chain are beyond the scope of the AP Exam.
• Exclusion statement: Specific steps, names of enzymes, and intermediates of the pathways for these processes are beyond the scope of this course and the AP Exam.

• i. In cellular respiration, electrons delivered by NADH and $\mathrm{FADH_2}$ are passed to a series of electron acceptors as they move toward the terminal electron acceptor, oxygen. Aerobic prokaryotes use oxygen as a terminal electron acceptor, while anaerobic prokaryotes use other molecules.
• ii. The transfer of electrons, through the ETC, is accompanied by the formation of a proton gradient across the inner mitochondrial membrane, with the membrane(s) separating a region of high proton concentration outside the membrane from a region of low proton concentration inside the membrane. The folding of the inner membrane increases the surface area, which allows for more ATP to be synthesized. In prokaryotes, the passage of electrons is accompanied by the movement of protons across the plasma membrane.
• iii. The flow of protons back through membrane-bound ATP synthase by chemiosmosis drives the formation of ATP from ADP and inorganic phosphate. This is known as oxidative phosphorylation in aerobic cellular respiration.
• iv. In aerobic cellular respiration, decoupling oxidative phosphorylation from electron transport generates heat. This heat can be used by endothermic organisms to regulate body temperature.
• Exclusion statement: The full names of the specific electron carriers in the electron transport chain are beyond the scope of the AP Exam.
• Exclusion statement: Specific steps, names of enzymes, and intermediates of the pathways for these processes are beyond the scope of this course and the AP Exam.

• Exclusion statement: Memorization of the steps in glycolysis and the Krebs cycle, and of the structures of the molecules and the names of the enzymes involved, is beyond the scope of this course and the AP Exam.

• Illustrative examples for 4.1.A.1:
  • Immune cells interact through cell-to-cell contact, antigen-presenting cells (APCs), helper T-cells, and killer T-cells.

• Illustrative examples for 4.1.B.1:
  • Neurotransmitters
  • Plant immune response
  • Quorum sensing in bacteria
  • Morphogens in embryonic development

• Illustrative examples for 4.1.B.2:
  • Insulin
  • Human growth hormone
  • Thyroid hormones
  • Testosterone
  • Estrogen

• i. The ligand-binding domain of a receptor recognizes a specific chemical messenger, which can be a peptide (protein) or a small molecule.
• ii. G protein-coupled receptors are an example of a receptor protein in eukaryotes.
• iii. Receptors may be located on the surface of a target cell or in the cytoplasm or nucleus of the target cell.

• i. After the ligand binds, the intracellular domain of a receptor protein changes shape, initiating transduction of the signal.
• ii. Enzymes and second messengers such as cyclic AMP (cAMP) relay and amplify the intracellular signal.
• iii. Hormones are an example of a signaling messenger that can travel long distances in the bloodstream.
• iv. The binding of ligands to ligand-gated channels can cause the channel to open or close.

• Illustrative examples for 4.3.A.1:
  • Use of chemical messengers by microbes to communicate with other nearby cells and to regulate specific pathways in response to population density (quorum sensing)
  • Epinephrine stimulation of glycogen breakdown in mammals

• Illustrative examples for 4.3.B.1:
  • Cytokines regulate gene expression to allow for cell replication and division.
  • Mating pheromones in yeast trigger mating gene expression.
  • Ethylene levels cause changes in the production of different enzymes allowing fruits to ripen.
  • HOX genes regulate animal body plans during embryonic development.

• i. Negative feedback mechanisms maintain homeostasis by reducing the initial stimulus to regulate physiological processes. If a system is perturbed or disrupted, negative feedback mechanisms return the system back to its target set point. These processes operate at the molecular, cellular, and organismal levels.
  • Illustrative examples for 4.4.A.1.i:
    • Blood sugar regulation by insulin/glucagon
• ii. Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved further away from the initial set point. Amplification occurs when the stimulus is further intensified, which, in turn, initiates an additional response that produces system change.
  • Illustrative examples for 4.4.A.1.ii:
    • Lactation in mammals
    • Onset of labor in childbirth
    • Ripening of fruit

• i. The cell cycle consists of sequential stages of interphase (G1, S, G2), mitosis, and cytokinesis.
• ii. G1 phase: The cell is metabolically active, duplicating organelles and cytosolic components.
• iii. S phase: DNA is in the form of chromatin and replicates to form two sister chromatids connected at a centromere.
• iv. G2 phase: Protein synthesis occurs, ATP is produced in large quantities, and centrosomes replicate.
• v. A cell can enter a stage (G0) in which it no longer divides, but it can reenter the cell cycle in response to appropriate cues.
• vi. Nondividing cells may exit the cell cycle or be held at a particular stage in the cell cycle.

• i. Mitosis plays a role in growth, tissue repair, and asexual reproduction.
• ii. Mitosis occurs in sequential steps (prophase, metaphase, anaphase, telophase) and alternates with interphase in the cell cycle.
• iii. Prophase: Sister chromatids condense, mitotic spindle begins to form, and centrosomes move to opposite poles of the cell.
• iv. Metaphase: Spindle fibers align chromosomes along the equator of the cell.
• v. Anaphase: Paired sister chromatids separate as spindle fibers pull chromatids toward poles.
• vi. Telophase: Mitotic spindle breaks down, a new nuclear envelope develops, and then the cytoplasm divides.
• vii. Cytokinesis: A cleavage furrow forms in animal cells or a cell plate forms in plant cells, resulting in two new daughter cells.

• Exclusion statement: Knowledge of specific cyclin-CdK pairs or growth factors is beyond the scope of the AP Exam.

• i. Prophase I: Homologous chromosomes pair up and condense, synapsis occurs and then chiasmata may form, meiotic spindle begins to form, centrosomes move to opposite poles of the cell, and the nuclear envelope breaks down.
• ii. Metaphase I: Meiotic spindle fibers align homologous pairs of chromosomes along the equator of the cell at the metaphase plate.
• iii. Anaphase I: Homologous chromosomes separate, while sister chromatids remain attached, as meiotic spindle fibers pull chromosomes toward poles.
• iv. Telophase I: Meiotic spindle breaks down, a new nuclear envelope develops, a cleavage furrow (animal cell) or cell plate (plant cell) forms, and cytokinesis occurs. Two haploid daughter cells are formed (at the end of meiosis I).

• i. Prophase II: Meiotic spindle forms; sister chromatids connected at the centromere attach to meiotic spindle.
• ii. Metaphase II: Chromosomes align along the metaphase plate; the kinetochore of each chromatid is attached to a microtubule extending from the poles.
• iii. Anaphase II: Proteins at the centromeres break down, and sister chromatids are pulled apart and toward opposite poles in the cell.
• iv. Telophase II: Meiotic spindle breaks down, a new nuclear envelope develops, a cleavage furrow (animal cell) or a cell plate (plant cell) forms, chromatids begin to decondense, and cytokinesis occurs. Four haploid daughter cells are formed, each with an unduplicated chromatid.

• Exclusion statement: Knowledge of the details of sexual reproduction cycles in various plants and animals is beyond the scope of the AP Exam.

• i. Rules of probability can be applied to analyze the passing of single-gene traits from parent to offspring.
• ii. Monohybrid, dihybrid, and test crosses can be used to determine whether alleles are dominant or recessive.
• iii. An organism's genotype is the set of alleles inherited for one or more genes by an individual organism. An organism's genotype can be homozygous or heterozygous for each gene.
• iv. An organism's phenotype is the observable expression of the inherited traits.
• v. Patterns of inheritance (autosomal, genetically linked, sex-linked) and whether an allele is dominant or recessive can often be predicted from data, including pedigrees. Punnett squares can be used to predict the genotypes and phenotypes of parents and offspring.
• Equation (Laws of Probability): If $A$ and $B$ are mutually exclusive, then: $P(A \text{ or } B) = P(A) + P(B)$
• Equation (Laws of Probability): If $A$ and $B$ are independent, then: $P(A \text{ and } B) = P(A) \times P(B)$

• i. Genes located on the same chromosome are referred to as being genetically linked. The probability that these linked genes segregate together during meiosis can be used to calculate the map distance (or map units) between them on a chromosome. This calculation is called gene or genetic mapping.
• ii. Codominance occurs when the phenotype from both alleles is expressed such that the heterozygote would have a different phenotype than either homozygote.
• iii. Incomplete dominance occurs when neither allele of a gene can mask the other, so the phenotype of the heterozygote is a blended version of the dominant and recessive phenotypes.

• Illustrative examples for EK 5.4.A.2:
  • Sex-linked traits (X- or Y-linked) reside on sex chromosomes.
  • Sex-linked traits (X- or Y-linked) are inherited at higher rates in XY individuals than they are in XX individuals.
  • In certain species, the chromosomal basis of sex determination is not based on X and Y chromosomes (e.g., ZW in birds, haplodiploidy in bees).

• i. Chloroplasts and mitochondria are randomly assorted to gametes and daughter cells; thus, traits determined by chloroplast and mitochondrial DNA do not follow simple Mendelian rules.
• ii. In animals, mitochondria are usually transmitted by the egg and not by sperm; thus, traits determined by the mitochondrial DNA are typically maternally inherited.
• iii. In plants, mitochondria and chloroplasts are transmitted in the ovule and not in the pollen; as such, mitochondria-determined and chloroplast-determined traits are typically maternally inherited.

• Illustrative examples for EK 5.5.A.1:
  • Height and weight in humans
  • Flower color based on soil pH
  • Seasonal fur color in arctic animals
  • Sex determination in reptiles
  • Effect of increased UV on melanin production in animals
  • Presence of the opposite mating type on pheromone production in yeast and other fungi

• 6.1.A.1.i Prokaryotic organisms typically have circular chromosomes.
• 6.1.A.1.ii Eukaryotic organisms typically have multiple linear chromosomes that are comprised of DNA. These chromosomes are condensed using histones and associated proteins.

• 6.1.B.1.i Purines (guanine and adenine) have a double ring structure.
• 6.1.B.1.ii Pyrimidines (cytosine, thymine, and uracil) have a single ring structure.
• 6.1.B.1.iii Purines pair with pyrimidines: adenine with thymine (or uracil in RNA) and guanine with cytosine.

• 6.2.A.1.i DNA is synthesized in the 5' to 3' direction.
• 6.2.A.1.ii Replication is a semiconservative process, meaning one strand of DNA serves as the template for a new strand of complementary DNA.
• 6.2.A.1.iii Helicase unwinds the DNA strands.
• 6.2.A.1.iv Topoisomerase relaxes supercoiling in front of the replication fork.
• 6.2.A.1.v DNA polymerase requires RNA primers to initiate DNA synthesis.
• 6.2.A.1.vi DNA polymerase synthesizes new strands of DNA continuously on the leading strand and discontinuously on the lagging strand.
• 6.2.A.1.vii Ligase joins the fragments on the lagging strand.
• Exclusion statement: The names of the steps and particular enzymes involved, excluding DNA polymerase, ligase, RNA polymerase, helicase, and topoisomerase, are beyond the scope of the AP Exam.

• 6.3.A.1.i Messenger RNA (mRNA) molecules carry information from DNA in the nucleus to the ribosome in the cytoplasm.
• 6.3.A.1.ii Distinct transfer RNA (tRNA) molecules bind specific amino acids and have anticodon sequences that base pair with the codons of mRNA. tRNA is recruited to the ribosome during translation to generate the primary peptide sequence based on the mRNA sequence.
• 6.3.A.1.iii Ribosomal RNA (rRNA) molecules are functional building blocks of ribosomes.

• 6.3.A.4.i The addition of a poly-A tail makes mRNA more stable.
• 6.3.A.4.ii The addition of a GTP cap helps with ribosomal recognition.
• 6.3.A.4.iii The excision of introns, along with the splicing and retention of exons, generates different versions of the resulting mature mRNA molecule. This process is known as alternative splicing.

• 6.4.A.3.i Translation is initiated when the rRNA in the ribosome interacts with the mRNA at the start codon (AUG, coding for the amino acid methionine).
• 6.4.A.3.ii The sequence of nucleotides on the mRNA is read in triplets, called codons.
• 6.4.A.3.iii Each codon encodes a specific amino acid, which can be deduced by using a genetic code chart. Many amino acids are encoded by more than one codon.
• 6.4.A.3.iv Nearly all living organisms use the same genetic code, which is evidence for the common ancestry of all living organisms.
• 6.4.A.3.v tRNA brings the correct amino acid to the place specified by the codon on the mRNA.
• 6.4.A.3.vi The amino acid is transferred to the growing polypeptide chain.
• 6.4.A.3.vii The process continues along the mRNA until a stop codon is reached.
• 6.4.A.3.viii Translation terminates with the release of the newly synthesized protein.
• Exclusion statement: The details and names of the enzymes and factors involved in each of these steps are beyond the scope of the AP Exam.
• Exclusion statement: Memorization of the genetic code, with the exception of the start codon AUG, is beyond the scope of the AP Exam.

• 6.5.A.3.i Observable cell differentiation results from the expression of genes for tissue-specific proteins.
• 6.5.A.3.ii Induction of transcription factors during development results in sequential gene expression.
• 6.5.A.3.iii The function and amount of gene products determine the phenotype of organisms.

• 6.5.B.1.i Prokaryotes regulate operons in an inducible or repressible system.
• 6.5.B.1.ii In eukaryotes, groups of genes may be influenced by the same transcription factors to coordinately regulate expression.

• 6.7.A.1.i Point mutations occur when one nucleotide has been substituted for a different nucleotide.
• 6.7.A.1.ii Frameshift mutations occur when one or more nucleotides are inserted or deleted, causing the reading frame to be shifted.
• 6.7.A.1.iii Nonsense mutations occur when there is a point mutation that causes a premature stop.
• 6.7.A.1.iv Silent mutations occur when the change in the nucleotide sequence has no effect on the amino acid sequence.
• Illustrative examples for 6.7.A.1:
  • Mutations in the CFTR gene disrupt ion transport and result in cystic fibrosis.
  • Mutations in the MC1R gene give adaptive melanism in pocket mice.
• Exclusion statement: Knowledge of specific mutations and their effects is beyond the scope of the AP Exam.

• 6.7.B.1.i Whether a mutation is beneficial, detrimental, or neutral depends on the environmental context.
• 6.7.B.1.ii Mutations are a source of genetic variation.

• 6.7.B.2.i Changes in chromosome number resulting from nondisjunction often result in new phenotypes caused by triploidy (aneuploidy).
• 6.7.B.2.ii Changes in chromosome number often result in disorders with developmental limitations.
• 6.7.B.2.iii Alterations in chromosome structure lead to genetic disorders.
• Exclusion statement: Knowledge of specific disorders related to changes in chromosome number is beyond the scope of the AP Exam.

• 6.7.C.1.i The horizontal acquisitions of genetic information in prokaryotes via transformation (uptake of DNA), transduction (viral transmission of genetic information), conjugation (cell-to-cell transfer of DNA), and transposition (movement of DNA segments within and between DNA molecules) increase genetic variation.
• 6.7.C.1.ii Related viruses can recombine genetic information if they infect the same host cell.
• 6.7.C.1.iii Reproductive processes that increase genetic variation are evolutionarily conserved and are shared by various organisms.
• Illustrative examples for 6.7.C.1: Sickle cell anemia

• 6.8.A.1.i Gel electrophoresis is a process that separates DNA fragments by size and charge.
• 6.8.A.1.ii During polymerase chain reaction (PCR), DNA fragments are amplified by denaturing DNA, annealing primers to the original strand, and extending the new DNA molecule.
• 6.8.A.1.iii Bacterial transformation introduces foreign DNA into bacterial cells.
• 6.8.A.1.iv DNA sequencing technology determines the order of nucleotides in a DNA molecule. Typically, these techniques result in a DNA fingerprint that allows for the comparison of DNA sequences from various samples.
• Illustrative examples for 6.8.A.1:
  • Amplified DNA fragments can be used to identify organisms and perform phylogenetic analysis.
  • Analysis of DNA can be used for forensic identification.
  • Genetically modified organisms include transgenic animals.
  • Gene cloning allows propagation of DNA fragments.
• Exclusion statement: Knowledge of the details of each of these genetic engineering techniques is beyond the scope of the AP Exam.

• Illustrative examples for 7.2.A.2: Flowering time in relation to global climate change

• Illustrative examples for 7.2.A.3: Sickle cell anemia; DDT resistance in insects

• i. Mutation is a random process that adds new genetic variation to a population.
• ii. Genetic drift is a change in allele frequencies attributable to a nonselective process occurring in small populations.
• iii. The bottleneck effect is a type of genetic drift that occurs when a population size is reduced to a small number of individuals for at least one generation.
• iv. The founder effect is a type of genetic drift that occurs when a population is separated from other members of the population. The frequency of genes and traits will shift based on the genes in this new founder population.
• v. Migration can result in gene flow (the addition or removal of alleles from a population).

• i. Mutations result in genetic variation, which provides phenotypes on which natural selection acts.
• ii. Genetic drift can allow a small population to diverge from other populations of the same species.
• iii. Gene flow between two populations prevents them from diverging into separate species.

7.5.A.1 The Hardy–Weinberg Equilibrium is a model for describing and predicting allele frequencies in a non-evolving population. Conditions for a population or an allele to be in Hardy–Weinberg equilibrium are:

• i. A large population size
• ii. No migration
• iii. No new mutations
• iv. Random mating
• v. No natural selection

These conditions are never met, but they provide a valuable null hypothesis.

7.5.A.2 Allele frequencies in a nonevolving population can be calculated from genotype frequencies.

• Equation: Hardy–Weinberg Equation— $p^2 + 2pq + q^2 = 1$; $p + q = 1$, where: $p$ = frequency of allele 1 in the population; $q$ = frequency of allele 2 in the population
• Illustrative examples for 7.5.A.2: Graphic analysis of allele frequencies in a population

• i. Fossils can be dated by a variety of methods. These include 1) the age of the rocks where a fossil is found; 2) the rate of decay of isotopes including carbon-14; and 3) geographical data.
• ii. Morphological homologies, including vestigial structures, provide evidence of common ancestry.

• i. Membrane-bound organelles
• ii. Linear chromosomes
• iii. Genes that contain introns

• i. Genomic changes over time
• ii. Continuous change in the fossil record
• iii. Evolution of resistance to antibiotics, pesticides, herbicides, or chemotherapy drugs
• iv. Pathogens evolving and causing emergent diseases

• i. Shared derived characters can be present in more than one lineage and indicate common ancestry. These are informative for the construction of phylogenetic trees and cladograms.
• ii. Molecular data typically provide more accurate and reliable evidence than morphological traits in the construction of phylogenetic trees or cladograms.

• i. The ability of a population to respond to changes in the environment is influenced by genetic diversity. Species and populations with little genetic diversity are at risk of decline or extinction.
• ii. Genetically diverse populations are more resilient to environmental perturbation because they are more likely to contain individuals that can withstand the environmental pressure.
• iii. Alleles that are adaptive in one environmental condition may be deleterious in another because of different selective pressures.
• Illustrative examples for 7.11.A.1: California condors; Black-footed ferrets; Prairie chickens; Potato blight; Corn rust; Genetic diversity and selective pressures; Antibiotic resistance in bacteria (not all individuals in a diverse population are susceptible to a disease outbreak)

• i. Geological evidence reinforces models of the origin of life on Earth.
• ii. Earth formed approximately 4.6 billion years ago (bya). The environment was too hostile for life until about 3.9 bya, and the earliest fossil evidence for life dates to 3.5 bya. Taken together, this evidence provides a plausible range of dates for the origin of life.

• i. At some point in time, genetic continuity was assured by the replication of RNA.
• ii. Base-pairing is necessary for replication.
• iii. Genetically encoded proteins were not involved as catalysts.

• Exclusion statement: Knowledge of specific behavioral or physiological mechanisms is beyond the scope of the AP Exam.
• Illustrative examples for 8.1.A.1:
  • Photoperiodism and phototropism in plants
  • Taxis and kinesis in animals
  • Nocturnal and diurnal activity

• Illustrative examples for 8.1.A.2:
  • Fight-or-flight response
  • Predator warnings
  • Plant responses to herbivory

• i. Organisms have a variety of signaling behaviors that produce changes in the behavior of other organisms and can result in differential reproductive success.
• ii. Animals use signals to indicate dominance, find food, establish territory, and ensure reproductive success.
• Exclusion statement: Knowledge of specific mechanisms of communication is beyond the scope of the AP Exam.
• Illustrative examples for 8.1.B.1:
  • Territorial marking in mammals
  • Coloration in flowering plants and animals
  • Bird songs
  • Pack behaviors in animals
  • Predatory warnings

• i. Fitness favors innate and learned behaviors that increase survival and reproductive success.
• ii. Cooperative behavior tends to increase the fitness of the individual and the survival of the population.
• Exclusion statement: The details of the various communications and community behavioral systems are beyond the scope of the AP Exam.
• Illustrative examples for 8.1.B.2.i:
  • Parent and offspring interactions
  • Courtship and mating behaviors
  • Foraging by bees and other animals
• Illustrative examples for 8.1.B.2.ii:
  • Pack behavior in animals
  • Herd, flock, and schooling behavior in animals
  • Predator warnings
  • Colony and swarming behavior in insects
  • Kin selection

• i. Organisms use different strategies to regulate body temperature and metabolism. Endotherms use thermal energy generated by metabolism to maintain homeostatic body temperatures. Ectotherms lack efficient internal mechanisms for maintaining body temperature, although they may regulate their temperature behaviorally by moving into the sun or shade or by aggregating with other individuals.
• ii. A net gain in energy results in energy storage, the growth of an organism, and increased reproductive output.
• iii. A net loss of energy results in loss of mass, a decrease in reproductive output, and, eventually, the death of an organism.

• Illustrative examples for 8.2.A:
  • Seasonal reproduction in animals and plants
  • Life-history strategy (biennial plants, reproductive diapause)

• i. A change in energy resources such as sunlight can affect the number and size of the trophic levels. Trophic levels include producers; primary, secondary, tertiary, and quaternary consumers; and decomposers.
• ii. A change in the biomass or number of producers in a given geographic area can affect the number and size of other trophic levels.

• i. Photosynthetic organisms capture energy present in sunlight contributing to primary productivity.
• ii. Chemosynthetic organisms capture energy from small inorganic molecules present in their environment, which can occur in the absence of oxygen.

• i. Population growth dynamics depend on birth rate, death rate, and population size.
  • Equation: Population Growth — $\dfrac{dN}{dt} = B - D$ where $dt$ = chage in time; $B$ = birth rate; $D$ = death rate; $N$ = population size; $dN$ = change in population size
• ii. Reproduction without constraints results in the exponential growth of a population.
  • Equation: Exponential Growth — $\dfrac{dN}{dt} = r_{max} N$ where $dt$ = change in time; $N$ = population size; $dN$ = change in population size; $r_{max}$ = maximum per capita growth rate of population

• Equation: Logistical Growth — $\dfrac{dN}{dt} = r_{max} N \left( \dfrac{K - N}{K} \right)$ where $dt$ = change in time; $N$ = population size; $dN$ = change in population size; $r_{max}$ = maximum per capita growth rate of population; $K$ = carrying capacity

• Equation: Simpson's Diversity Index — $\text{Diversity Index} = 1 - \sum \left( \dfrac{n}{N} \right)^2$ where $n$ = total number of organisms of a particular species; $N$ = total number of organisms of all species

• Illustrative examples for 8.7.B.1:
  • Kudzu
  • Zebra mussels

• i. Biomagnification
• ii. Eutrophication
• Illustrative examples for 8.7.C.1:
  • Dutch elm disease
  • Potato blight

• Illustrative examples for 8.7.D.1:
  • Global climate change
  • Logging
  • Urbanization
  • Monocropping
  • El Nino
  • Continental drift
  • Meteor impact on dinosaurs