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AP Bio exam vocab
A comprehensive list of all the vocab terms you need for the AP bio exam.
| Term | Definition |
|---|---|
| Cohesion | Water sticking to itself |
| Adhesion | Water sticking to other polar or charged surfaces |
| Surface tension | Water molecules hydrogen bond to neighbors beside and below them, but not above. This creates surface tension, a "film-like" effect that cans support small organisms. |
| Specific heat | The amount of energy required to raise 1 gram of a substance by 1ºC |
| Six essential elements of life | Carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur |
| Main macromolecules | Carbohydrates, lipids, proteins, nucleic acids |
| Carbohydrates main elements | C, H, O |
| Lipids main elements | C, H, O (and P in phospholipids) |
| Proteins main elements | C, H, O, N (sometimes S) |
| Nucleic Acids main elements | C, H, O, N, P |
| Why is carbon the backbone of life | Carbon has 4 valence electrons which means it can form 4 covalent bonds. This allows for long chains, branched chains, rings, and double and triple bonds. |
| Nitrogen | Found in amino groups of amino acids, present in nitrogenous bases of DNA and RNA, required to build proteins and nucleic acids. |
| Phosphorus | Found in phosphate groups, part of DNA and RNA backbone, phospholipids (cell membrane), and ATP (energy transfer) |
| Sulfer | Found in some amino acids (like cysteine), forms disulfide bonds that stabilize protein structure. |
| Functional groups | Hydroxyl (-OH), Carboxyl (-COOH), Amino (-NH2), Phosphate (-PO4), and Sulfhydryl (-SH) |
| Monomer | Small building block molecule |
| Polymer | Large molecule made of many monomers covalently bonded together |
| Carbohydrates macromolecules | Monomer: monosaccharides Polymer: Polysaccharides |
| Proteins macromolecules | Monomer: amino acid Polymer: polypeptide -> folds into a protein |
| Nucleic acids macromolecules | Monomer: nucleotide Polymer: DNA or RNA |
| Lipids macromolecules | built from glycerol + fatty acids. Not true polymers in the same repeating-chain sense |
| Dehydration synthesis | One monomer loses a hydrogen, another monomer loses a hydroxyl group, a new covalent bond forms between monomers. Water is removed, and the monomers become linked |
| Hydrolysis | Water is added, water molecule splits into H and OH, the covalent bond between monomers is broken, H attaches to one monomer, OH to the other. Breaks down polymers with the addition of water. |
| Carbohydrates function | Energy storage, structural support |
| Lipids function | Long term energy, membranes |
| Proteins function | Enzymes, structure, transport |
| Nucleic acids function | store and transmit genetic info |
| Monosaccharides | A single sugar molecule. Common examples include glucose, fructose, and galactose. Can form covalent bonds with other sugars |
| Polysaccharides | Long chains of monosaccharides. They can be either linear (straight chains) or branched (chains with side branches) |
| Starch | Made of glucose, found in plant cells, used to store energy, can be branched or unbranched. Plants store extra glucose as starch for later use |
| Glycogen | Made of glucose, stored in liver and muscle cells, highly branched. More branches = more ends = faster access to glucose |
| Cellulose | Made of glucose, found in plant cell walls, forms straight, unbranched chains, chains align side by side and hydrogen bond -> strong fibers |
| Lipids | All lipids share one big property: they are non-polar and hydrophobic. Made mostly of carbon and hydrogen, contain long hydrocarbon chains, do not mix with water, interact with each other through hydrophobic interactions. |
| Saturated fatty acids | Only single bonds between carbons, straight chains, pack tightly together, usually solid at room temperature. Examples: butter, animal fat. |
| Unsaturated fatty acids | At least 1 double bind. This double bond causes a kink in the hydrocarbon chain, cannot pack tightly, more likely liquid at room temperature. Examples: olive oil, plant oils |
| Fats | Fats (triglycerides) store long term energy, provide insulation, cushion organs, support cell function. |
| Phospholipids | Has 2 hydrophobic fatty acid tails and one hydrophilic phosphate head. That makes it Amphipathic (noth hydrophobic and hydrophilic parts) |
| Steroids | Steroids are lipids with 4 fused carbon rings. They function mostly in signaling and regulation. Examples: Estrogen, testosterone, and cortisol. These hormones regulate growth and development, energy metabolism, and homeostasis. |
| Cholesterol | Specific steroid that is embedded in animal cell membranes, provides structural stability, and helps regulate membrane fluidity. At higher temperatures, cholesterol stabilizes membranes. At lower temperatures, it prevents membranes from becoming too rigid |
| Nucleotide | The monomer of nucleic acids. Each nucleotide has a 5-carbon sugar, (deoxyribose in DNA, Ribose in RNA, a phosphate group, and a nitrogenous base (A, G, C, T (DNA only), U (RNA only) |
| DNA | Double stranded, antiparallel helix. A pairs with T (2 hydrogen bonds), C bonds with G (3 hydrogen bonds) One strand: 5` -> 3`, other strand: 3` -> 5` |
| Chargaff's rule | In double stranded DNA: %A = %T and %G = %C. Only applies to double stranded DNA, not single stranded RNA |
| DNA's job | Long term information storage |
| RNA's job | Information transfer and expression |
| Amino acid structure | Every amino acid has a central carbon (a-carbon), a hydrogen, an amino group (-NH2), a carboxyl group (-COOh), and a variable R group (side chain) |
| R- Group categories | Hydrophobic (nonpolar): repels water, folds inward, away from water. Hydrophilic (polar): Attracts water, often faces outward. Ionic (charged): positive or negative charge, forms ionic bonds (salt bridges) |
| Peptide bonds | A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of the next. Happens by dehydration synthesis |
| Primary protein structure | Linear sequence of amino acids. Example: Ala-Gly-Ser-Val. even one amino acid change can alter the final protein. |
| Sickle-cell disease | Results from a single amino acid substitution in hemoglobin |
| Secondary protein structure | Local folding caused by hydrogen bonds between backbone atoms. 2 main types include Alpha helix (α-helix) -> coiled structure, and Beta pleated sheet (β-sheet) -> folded sheet structure |
| Tertiary protein structure | Full 3D shape of one polypeptide. Tertiary structure is caused by R-group interactions, including: Hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges. Shape = function |
| Quaternary protein structure | Only exists if a protein has multiple polypeptide chains (subunits). These subunits interact using the same forces as tertiary structure. Examples: hemoglobin has 4 subunits |
| Ribosomes | Made of rRNA + proteins, found in all cells, not membrane bounds. Carry out translation, read mRNA sequences, build polypeptides (proteins). Free ribosomes -> make proteins that stay in cytosol. Bound ribosomes (attached to rough ER) |
| The Endomembrane System | Network of membranes that modify, package, and transport proteins, lipids, and polysaccharides. Includes the nuclear envelope, ER, golgi, lysosomes, vacuoles, transport vesicles, and plasma membrane. |
| Endoplasmic Reticulum (ER) | Has ribosomes attached, synthesizes proteins destined for export or membranes, helps with compartmentalization, provides mechanical support to help maintain cell shape. Structure -> flattened sacs with ribosomes attached |
| Smooth Endoplasmic reticulum | No ribosomes, lipid synthesis, detoxification, involved in intracellular transport |
| Golgi apparatus/body | Stack of flattened membrane sacs. Proteins from the rough ER enter on the cis face, move through stacked sacs, and exit from the trans face in transport vesicles. Modifies proteins, correctly folds products, packages and sorts into vesicles |
| Lysosomes | Membrane bound sacs that contain hydrolytic enzymes and an acidic interior. Digest macromolecules, recycle old organelles, involved in apoptosis (programmed cell death) |
| Apoptosis | Programmed cell death, a controlled process for removing cells. |
| Vacuoles | Membrane bound storage sacs. Plants have 1 large central vacuole for storing water and nutrients and maintaining turgor pressure. Animal cells have smaller, more numerous vacuoles for storage roles. |
| Mitochondria | site of aerobic cellular respiration. Double membrane, smooth outer membrane, highly folded inner membrane (cristae), inner space called the matrix. Folds increase surface area, more space for electron transport chain, and more efficient ATP production. |
| Chloroplasts | Found in plants and photosynthetic algae. Site of photosynthesis. Double membrane, internal membrane sacs called thylakoids, fuild filled space called stroma. |
| Surface area to volume ratio | SA to volume ratio effects the exchange of nutrients in, wastes out, gases (O2/CO2), and heat. Small organisms have high SA:V, large animals have low SA:V |
| Orientation in phospholipid bilayer | Heads face outward toward extracellular fluid, toward cytosol. Tails face inward away from water, interact with each other. This interior is the key to selective permeability. |
| Membrane proteins | Proteins are embedded in or attached to the membrane. Their structure matched the membrane's structure. |
| Integral (transmembrane) proteins | These span all the way across the membrane. Hydrophobic regions: interact with fatty acid tails, located in the middle portion of the membrane. Hydrophilic regions: Exposed to cytosol or extracellular fluid, often form channels or binding sites. |
| Peripheral proteins | Loosely attached to the membrane surface, often interact with integral proteins or phospholipid heads, frequently involved in signaling or maintaining cell shape. |
| Glycoproteins and Glycolipids | Glycoproteins = protein + carbohydrate. Glycolipids = lipid + carbohydrate. Found on the extracellular side of the membrane. Functions include cell recognition, cell-cell adhesion, and immune system identification |
| The fluid mosaic model | The fluid mosaic model describes the membrane as: Fluid: Phospholipids and many proteins move laterally within the layer. Mosaic: A patchwork of different components embedded in the bilayer. |
| Channel proteins | Membrane proteins that form hydrophilic openings for specific substances to pass through |
| Aquaporins | Specialized channel proteins that speed the movement of water across membranes. |
| Ions and large polar molecules interaction with cell membrane | They cannot pass through the hydrophobic core. Examples: Na+, K+, Cl-, glucose. The nonpolar fatty acid tails repel charged and polar substances. They have to cross through embedded membrane proteins, including channel and transport proteins |
| Who has cell walls? | Plants → cellulose Fungi → chitin Bacteria → peptidoglycan Archaea → other polymers (not peptidoglycan) Animal cells do not have cell walls |
| Cell wall function | Provides structural support, maintains cell shape, acts as an outer filter before materials reach the membrane, and prevents cells from bursting in hypotonic environments. |
| Passive transport | Net movement from high to low concentration, no ATP required. |
| Simple diffusion | Directly through the bilayer, only works for small non-polar molecules. Examples: O2 diffusing from alveoli into blood |
| Facilitated diffusion | Uses channel proteins or carrier proteins, used for ions and polar molecules like glucose. Moves from high to low concentration. |
| Osmosis | Diffusion of water across a selectively permeable membrane. Water moves toward the side with higher solute concentration (lower water concentration) |
| Hypotonic solution | water enters cell → cell swells. In animal cells, hypotonic conditions can lead to lysis. In plant cells, the cell wall prevents bursting and the cell becomes turgid instead. |
| Hypertonic solution | water leaves cell → cell shrinks. |
| Isotonic solution | No net water movement |
| Active transport | Requires energy, usually ATP. Moves substances against their concentration gradiant. Uses carrier proteins called pumps. Maintains ion gradients that cells depend on. Example: sodium potassium pump |
| sodium potassium pump | Pumps 3 Na⁺ out. Pumps 2 K⁺ in. Uses 1 ATP per cycle. |
| Endocytosis | Membrane folds inward → forms vesicle → brings material in. |
| Phagocytosis | “cell eating” (large particles, bacteria). |
| Pinocytosis | “cell drinking” (fluid, non-specific). |
| Receptor-mediated endocytosis | highly specific; receptors bind ligand before vesicle forms. |
| Exocytosis | Vesicle fuses with membrane → releases contents outside cell. Used for hormone secretion, neurotransmitter release, exporting proteins. |
| Tonicity | Compares the solute concentration of 2 solutions seperated by a membrane |
| Water potential | Water moves from higher water potential (Ψ) to lower water potential (Ψ). |
| Osmoregulation | Osmoregulation maintains internal solute concentration and water potential. |
| Electrochemical Gradients | has 2 parts: chemical gradient (difference in concentration), and electrical gradient ( difference in charge) |
| Compartmentalization | Dividing the cell into membrane-bound sections (organelles), each with a specific job. Prokaryotes lack membrane-bound organelles, so most processes occur in the same shared space |
| Nucleus | Surrounded by a double membrane (nuclear envelope), contains nuclear pores for controlled transport, stores DNA. This separates transcription (DNA -> RNA) from translation (RNA -> protein), protects genetic info and allows regulation of RNA export. |
| Peroxisomes | Break down fatty acids Detoxify harmful substances Produce hydrogen peroxide and then break it down |
| Prokaryotic Cells | Prokaryotes (bacteria and archaea): No membrane-bound organelles No nucleus DNA is in a region called the nucleoid Transcription and translation happen in the same space This means mRNA can be translated while its still being transcribed. |
| Endosymbiotic Theory | The theory that mitochondria and chloroplasts began as free-living prokaryotes inside a host cell. |
| Evidence of Endosymbiotic theory | Mitochondria and chloroplasts: Have double membranes Have their own circular DNA Have 70S ribosomes (prokaryotic type) Replicate independently via binary fission |
| Enzymes | An enzyme is a protein that acts as a catalyst. A catalyst speeds up a reaction without being consumed. Enzymes increase the reaction rate by lowering the activation energy. |
| Active site | The specific region of an enzyme where the substrate binds and the reaction occurs. Its shape, charge, and chemical properties are determined by the amino acids in that region. |
| change to enzyme structure | If the structure changes, the active site may change. If the active site changes, the substrate may not bind properly. If binding is disrupted, the reaction slows or stops. |
| Substrate | The substrate is the molecule the enzyme acts on. For a reaction to occur: the substrate must bind to the active site, and the shape and charge must be compatible. |
| Enzyme-substrate complex | The temporary complex formed when a substrate binds to an enzyme's active site. |
| Induced fit model | The active site is somewhat flexible. When the substrate binds, the enzyme changes shape slightly. This tighter fit improves catalysis. |
| Denaturation | Denaturation is the loss of normal protein shape due to environmental changes. When an enzyme denatures: its secondary/tertiary structure is disrupted, active site loses its shape, and the enzyme can no longer catalyze reactions effectively. |
| What causes denaturation | High temperature, extreme pH, and chemical changes in the environment. If the primary structure is intact, the protein may refold and renaturation can happen. Denaturation is often permanent, especially if bonds are severely disrupted. |
| Enzyme Inhibitors | Inhibitors reduce enzyme activity without necessarily denaturing the enzyme. |
| Competitive Inhibitors | Resemble the substrate, bind to the active site, compete directly with substrate. Reversible. Increasing substrate concentration can overcome inhibition |
| Noncompetitive inhibitors | Bind to an allosteric site (not the active site). Change the enzyme's shape, active site is altered. Substrate may still bind, but catalysis is reduced. |
| First law of thermodynamics | Energy cannot be created or destroyed, only transformed |
| Second Law of Thermodynamics | Every energy transfer increases entropy (disorder) in the universe |
| Entropy | A measure of disorder or energy spreading in a system. |
| Energy coupling | Linking an energy-releasing reaction to an energy-requiring reaction so both can occur together. |
| Exergonic reactions | Release energy. Example: breaking down glucose |
| Endergonic reactions | Require energy. Example: building a protein. |
| ATP | Adenosine triphosphate, the cell's main short-term energy carrier. |
| ATP hydrolysis | The splitting of ATP that releases energy and a phosphate group. |
| Metabolic pathway | A series of enzyme-controlled reactions where each product becomes the next reactant. |
| Glycolysis | A pathway that breaks glucose into smaller molecules and captures some energy as ATP. |
| Oxidative phosphorylation | A process that uses electron transport to make large amounts of ATP. |
| Photosynthesis | Captures light energy and stores it in the chemical bonds of carbs. In chloroplasts, light reactions convert solar energy into ATP and NADPH. Calvin cycles uses those molecules to build sugars from CO2. |
| Photosynthesis overall equation | 6CO2 + 6H2O + light –> C6H12O6 + 6O2 |
| Stroma | Fluid inside the inner membrane of the chloroplast that surrounds the thylakoids. Location of the Calvin cycle. |
| Thylakoid | Flattened membrane sacs that contain chlorophyll pigments. House photosystems II and I. Contain the electron transport chain (ETC) |
| Grana | Stacks of thylakoids. Increase surface area for light absorption. Site of the light reactions. |
| Oxidation | Loss of electrons |
| Reduction | Gain of electrons |
| Fermentation | Two types: Lactic acid fermentation Pyruvate → lactate Occurs in muscle cells. Alcoholic fermentation Pyruvate → ethanol + CO₂ Occurs in yeast. |
| 2 major ways of cell communication | Direct contact and chemical signaling |
| Direct Cell-to-Cell Contact | Cells physically touch each other and exchange information. This is common in the immune system, where specificity matters. |
| Chemical signaling | One cell releases a signaling molecule, and another cell with the correct receptor responds. |
| Short-Distance (Local) Signaling | Local regulators affect nearby cells only. Signal spreads through extracellular fluid, across synapses and within small tissue region. Examples: neurotransmitters, plant immune response, quorum sensing (bacteria), and morphogens |
| Long-Distance Signaling (Endocrine) | Hormones that are released into bloodstream, travel throughout the body, and only affect cells with the correct receptor. Examples: Insulin, human growth hormone, thyroid hormone, testostrone / estrogen. |
| Ligands | a signaling molecule (often a hormone, peptide, or small molecule). |
| Receptor protein | A protein that detects a specific signal by binding a matching ligand. The receptor changes shape. This conformational change is what starts the pathway. |
| G Protein-Coupled Receptors (GPCRs) | Spans membrane 7 times Works with a G protein inside the cell Ligand binding activates the G protein G protein activates downstream enzymes. Membrane receptor that triggers an internal signaling cascade |
| Transduction | Relaying and Amplifying the Signal |
| Cascade | A series of sequential molecular activations that passes a signal through the cell. |
| Phosphorylation Cascades | A protein kinase adds a phosphate group (phosphorylation). Phosphorylation usually changes a protein’s activity. One activated kinase activates the next. This continues through multiple steps. |
| Amplification | One activated molecule can activate many more. A small signal outside → large response inside. |
| Second Messengers | Small molecules that relay signals inside the cell. Example: cAMP (cyclic AMP) Receptor activation → enzyme produces many cAMP molecules. Each cAMP activates additional proteins. More amplification. |
| Ligand-Gated Ion Channels | Ligand binds. Channel opens or closes. Ions flow across membrane. Membrane potential changes |
| Hormones and Long-Distance Signaling | Hormones travel through the bloodstream. Only cells with the correct receptor respond. Specificity depends on receptor presence, not hormone location. |
| Signal response | The final step produces a cellular response, such as: Activation or inhibition of an enzyme (faster) Opening of an ion channel Gene expression changes (takes longer) Cell growth or division Secretion of molecules |
| Changes in Gene Expression | A transcription factor is activated Specific genes are expressed New proteins are made The cell’s phenotype can change |
| Changes in Cell Function (Without Changing Genes) | Enzyme activation Ion channel opening Metabolic shifts Structural changes |
| Programmed Cell Death (Apoptosis) | Some pathways trigger apoptosis, a controlled, organized cell death. Used for: Development (removing unnecessary cells) Removing damaged cells Preventing cancer |
| Homeostasis | The maintenance of stable internal conditions despite internal or external changes. |
| Feedback mechanisms | A regulatory process where a change triggers a response that affects that same condition. |
| 3 core parts of a feedback loop | Stimulus (a change in a variable) Sensor + control center (detects change, decides response) Effector (carries out response) |
| Negative Feedback | Negative feedback reduces the initial stimulus. It brings the system back toward a set point (target value). This is the main mechanism that maintains homeostasis. Example: Blood Glucose Regulation |
| Positive Feedback | Positive feedback amplifies the initial stimulus. It pushes the system farther from the original set point. Example: Childbirth (Labor) |
| Cell cycle | Interphase G1 S G2 Mitosis Cytokinesis |
| Interphase | Interphase prepares the cell for division. DNA is in chromatin form here, meaning it’s loosely packed and usable. |
| G1 Phase | Cell grows in size. Organelles duplicate (mitochondria, ER, etc.). Normal metabolism is happening. The cell decides whether to: Continue toward division Pause Enter G0 |
| G0 Phase | A non-dividing state. Some cells stay here long-term (like neurons). Others can re-enter the cycle if they receive proper signals. |
| S Phase (Synthesis) | This is where DNA replication happens. Each chromosome is copied. You now have two sister chromatids per chromosome. Sister chromatids are: Identical DNA copies Attached at a centromere |
| G2 Phase (Growth 2) | Final prep before mitosis. More growth Protein synthesis (especially for spindle fibers) Large ATP production Centrosomes replicate |
| Mitosis | Mitosis divides the nucleus. Its purpose is simple but critical: Ensure each daughter cell receives a complete, identical genome. Mitosis supports: Growth Tissue repair Asexual reproduction |
| Prophase | Chromatin condenses → visible chromosomes Mitotic spindle begins forming Centrosomes move to opposite poles |
| Metaphase | Chromosomes line up at the metaphase plate (cell equator). Spindle fibers attach to kinetochores at centromeres. |
| Anaphase | Sister chromatids separate. Spindle fibers pull them to opposite poles. Once separated, they are considered individual chromosomes. |
| Telophase | Chromosomes decondense. Nuclear envelopes reform. Spindle breaks down. |
| Cytokinesis | Cytokinesis divides the cytoplasm. It ensures each daughter cell gets: Organelles Cytoplasm Cellular machinery |
| Cell Cycle Checkpoints | A checkpoint is a control point where the cell either continues or stops. Think of it as a quality control inspection. |
| G1 Checkpoint (Restriction Point) | The cell checks: Is the cell large enough? Are nutrients available? Are growth signals present? Is the DNA undamaged? |
| G2 Checkpoint | This happens after DNA replication. The cell checks: Was DNA replicated completely? Is the DNA damaged? If problems are detected, repair enzymes attempt to fix them before mitosis begins. |
| M Checkpoint (Spindle Checkpoint) | The cell checks: Are all chromosomes attached to spindle fibers? Are they aligned properly? If even one chromosome is not properly attached, the cell does not proceed to anaphase. This prevents unequal chromosome separation. |
| Cyclins and CDKs | cyclins: A regulatory protein whose concentration rises and falls during the cell cycle. Cyclin-Dependent Kinase: An enzyme that helps control the cell cycle when activated by cyclins. Cyclin levels fluctuate CDK levels stay constant |
| Cancer | A disease caused by loss of normal control over cell division. What goes wrong: Checkpoints are bypassed Damaged DNA is not repaired Cells divide uncontrollably This leads to: Tumor formation Accumulation of mutations Possible metastasis |
| Diploid (2n) | 2 sets of chromosomes (one from each parent) |
| Haploid (n) | One set of chromosomes |
| Meiosis | Meiosis includes: One round of DNA replication (before meiosis begins, during S phase) Two rounds of division Meiosis I (reduction division) Meiosis II (like mitosis, but starting haploid) |
| Prophase I | Chromosomes condense Homologous chromosomes pair up → this pairing is called synapsis Paired chromosomes form a tetrad (4 chromatids total) Chiasmata form where crossing over occurs Spindle fibers form Nuclear envelope breaks down |
| Metaphase I | Homologous pairs (tetrads) line up at the metaphase plate. Each homolog is attached to spindle fibers from opposite poles. |
| Anaphase I | Homologous chromosomes separate Sister chromatids stay together This is the reduction step: Each pole gets one chromosome from each homologous pair. |
| Telophase I and Cytokinesis | Spindle breaks down. Nuclear envelopes may reform. Cytokinesis occurs. Result → Two haploid cells, but chromosomes are still duplicated (two sister chromatids each). |
| Prophase II | Spindle forms. Chromosomes (still made of sister chromatids) attach to spindle fibers. |
| Metaphase II | Chromosomes line up individually at the metaphase plate. Kinetochores attach to microtubules from opposite poles. |
| Anaphase II | Proteins at centromeres break down. Sister chromatids separate. |
| Telophase II and Cytokinesis | Nuclei reform. Chromosomes decondense. Cytokinesis occurs. |
| How Meiosis Creates Genetic Variation | Crossing over (Prophase I) Independent assortment (random alignment of homologous pairs in Metaphase I) Random fertilization |
| Independent Assortment | During metaphase I, homologous chromosome pairs line up in the middle of the cell. The orientation of each pair is random. That randomness determines which chromosomes move together into each daughter cell in anaphase I. |
| Crossing Over | During prophase I, homologous chromosomes pair up tightly. Non-sister chromatids exchange corresponding DNA segments. The exchange points are called chiasmata. |
| Random Fertilization | Random fertilization means any one sperm can fuse with any one egg. |
| Nondisjunction | Nondisjunction is the failure of chromosomes to separate properly. It can happen in: Meiosis I → homologous chromosomes fail to separate All four gametes are abnormal. Meiosis II → sister chromatids fail to separate 2 gametes normal 2 abnormal. |
| monosomy | A chromosome condition in which a cell is missing one chromosome, or 2n-1. |
| Trisomy | A chromosome condition in which a cell is missing one chromosome, or 2n-1. |
| Down syndrome | A genetic condition usually caused by an extra copy of chromosome 21. |
| Gene | A segment of DNA that helps determine a trait. |
| Alleles | different versions of the same gene (ex: T vs t). |
| Genotype | The allele combination an organism has for a gene. (TT, Tt, tt) |
| Phenotype | The observable trait produced by a genotype. |
| Homozygous | same alleles (TT or tt). |
| Heterozygous | different alleles (Tt). |
| Dominant | expressed in heterozygote |
| Recessive | only expressed when homozygous. |
| Law of Segregation | The two alleles for a gene separate during gamete formation. If a plant is Tt, it makes: 50% T gametes 50% t gametes |
| Law of Independent Assortment | Genes on different chromosomes assort independently into gametes. If genotype = AaBb, possible gametes are: AB Ab aB ab |
| Monohybrid Crosses | Tracking one gene. Example: Aa × Aa |
| Dihybrid Crosses | Tracking two genes. Example: AaBb × AaBb |
| Rules of Probability in Genetics | If events are mutually exclusive: P(A or B)=P(A)+P(B) If events are independent P(A and B)=P(A)×P(B) |
| Autosomal Recessive | Skips generations Affected individuals can have unaffected parents Males and females equally affected |
| Autosomal Dominant | Appears every generation Affected individuals usually have affected parent |
| Sex-Linked (usually X-linked recessive) | More males affected No father-to-son transmission Affected sons often have carrier mothers |
| Linked Genes | Genes on the same chromosome tend to be inherited together. They violate independent assortment. If offspring ratios do not match 9:3:3:1 and parental combinations appear more often than recombinants, think genetic linkage. |
| Incomplete Dominance | The heterozygote shows a blended phenotype. Classic example: red × white flowers → pink offspring. RR = red rr = white Rr = pink Genotypic ratio from Rr × Rr = 1:2:1 Phenotypic ratio = 1 red : 2 pink : 1 white |
| Codominance | Both alleles are fully expressed in the heterozygote. Example: red cow × white cow → red-and-white spotted cow. RR = red WW = white RW = red and white (both visible) |
| Recombination Frequency | The percentage of offspring that are recombinants, used to estimate gene distance. Recombination frequency = recombinant offspring / total offspring X 100 |
| Map unit | A unit of chromosome distance equal to 1% recombination frequency. |
| X-Linked Traits | XY individuals have only one X. A single recessive allele on that X is expressed. This is why X-linked recessive disorders appear more often in males. |
| Y-Linked Traits | Only in males. Passed father → all sons. Rare in questions but easy to spot. |
| Phenotypic Plasticity | The ability of one genotype to produce different phenotypes in different environments. |
| Ribose | The five-carbon sugar found in RNA nucleotides. |
| Prokaryotic DNA | Usually one circular chromosome Located in the nucleoid region Not enclosed in a nucleus |
| Plasmids | Small, circular, extra-chromosomal DNA Replicate independently Often carry genes for antibiotic resistance |
| Eukaryotic DNA | Multiple linear chromosomes Located inside a nucleus DNA is tightly packaged |
| histone | A protein that DNA wraps around in eukaryotic cells. |
| Nucleosomes | A unit of DNA wrapped around histone proteins. |
| The Semiconservative Model | A replication model where each new DNA molecule has one old strand and one new strand. |
| Template strand | The original DNA strand used to build a new complementary strand. |
| DNA polymerase | The enzyme that adds DNA nucleotides to a growing strand and proofreads mistakes. Can only add nucleotides to the 3′ end Therefore, DNA is always synthesized 5′ → 3′ |
| Replication fork | The Y-shaped region where DNA is unwound and copied during replication. |
| Helicase | Unwinds the double helix Breaks hydrogen bonds between base pairs Creates the replication fork |
| Topoisomerase | Works ahead of helicase Prevents supercoiling (overwinding) Relieves torsional strain |
| Supercoiling | The extra twisting of DNA that builds up as the helix is unwound. |
| RNA Polymerase (Primase) | Builds short RNA primers DNA polymerase cannot start on its own Provides a free 3′ OH group |
| DNA Polymerase | Adds DNA nucleotides to the 3′ end Synthesizes DNA 5′ → 3′ Proofreads (removes mismatched bases) |
| Ligase | Joins DNA fragments together Forms phosphodiester bonds Especially important on the lagging strand |
| Leading Strand | Synthesized continuously Same direction as replication fork movement Requires only one primer |
| Lagging Strand | Synthesized discontinuously Made in short pieces called Okazaki fragments Each fragment requires its own RNA primer Ligase connects fragments |
| Okazaki fragments | Short DNA segments made separately on the lagging strand. |
| Replication big picture | Helicase unwinds DNA Topoisomerase relieves strain RNA primers are added DNA polymerase elongates (5′ → 3′) Leading strand continuous Lagging strand forms Okazaki fragments Ligase joins fragments |
| The Central Dogma of genetic information flow | DNA → RNA → Protein Transcription produces RNA. Translation uses RNA to build a protein. Different types of RNA have different jobs, and their sequence and structure determine their function. |
| Transcription | The process of copying a gene's DNA sequence into RNA. |
| Translation | The process of using an mRNA sequence to build a protein. |
| mRNA (messenger RNA) | Carries the genetic message from DNA in the nucleus to the ribosome in the cytoplasm. Its codon sequence (triplets of bases) determines the amino acid sequence of a protein. |
| Codon | A three-base mRNA sequence that specifies an amino acid or stop signal. |
| tRNA (transfer RNA) | Brings specific amino acids to the ribosome. Has: An anticodon that base-pairs with an mRNA codon. A binding site for a specific amino acid. Its L-shaped 3D structure allows it to interact with both mRNA and the ribosome. |
| Anti codon | A three-base sequence on tRNA that pairs with a complementary mRNA codon. |
| rRNA (ribosomal RNA) | Makes up the structural and catalytic core of the ribosome. Helps position mRNA and tRNA. Catalyzes peptide bond formation. |
| RNA polymerase. | The enzyme that builds an RNA strand using a DNA template. |
| Basic Steps of Transcription | Initiation, elongation, termination |
| initiation (transcription) | RNA polymerase binds to a promoter region upstream of the gene. DNA unwinds. |
| Elongation (transcription) | RNA polymerase moves along the template strand. Complementary RNA nucleotides are added. |
| Termination (transcription) | RNA polymerase reaches a termination sequence. RNA transcript is released. |
| 5′ Cap | A modified GTP is added to the 5′ end. Functions: Protects mRNA from degradation. Helps ribosomes recognize and bind to the mRNA. |
| Poly-A Tail | A long chain of adenines is added to the 3′ end. Functions: Increases stability. Helps with export from the nucleus. Affects how long the mRNA survives in the cytoplasm. |
| Splicing | Eukaryotic genes contain: Exons = coding regions (kept) Introns = noncoding regions (removed) A complex called the spliceosome: Cuts out introns. Joins exons together. |
| Exon | A gene segment that remains in the mature mRNA after splicing. |
| introns | A noncoding gene segment removed from pre-mRNA during splicing. |
| Spliceosome | A molecular complex that removes introns and joins exons together. |
| Alternative splicing | Different combinations of exons can be joined together. One gene → multiple mRNA versions → multiple proteins. This increases protein diversity without increasing the number of genes. |
| Where Translation Happens in prokaryotes | Ribosomes are in the cytoplasm Translation happens at the same time as transcription (no nucleus) |
| Where translation occurs in eukaryotes | Transcription happens in the nucleus mRNA travels to the cytoplasm Translation occurs: On free ribosomes (proteins stay in cytoplasm) On ribosomes attached to rough ER (proteins for secretion or membranes) |
| initiation (translation) | The small ribosomal subunit binds to mRNA rRNA recognizes the start codon (AUG) A tRNA carrying methionine binds via complementary base pairing The large subunit joins → full ribosome assembled |
| Elongation (translation) | A tRNA with a complementary anticodon enters ribosome at A site Ribosome forms a peptide bond between amino acids at the P site Ribosome moves one codon forward along the mRNA (5' → 3') Empty tRNA exits from the E site and growing polypeptide extends |
| Termination ((translation)) | A stop codon enters the ribosome No tRNA matches it A release factor binds The completed polypeptide is released Translation ends. The protein will then fold into its functional shape. |
| Silent mutation | A mutation that changes a codon but not the amino acid it encodes. |
| Missense mutation | A mutation that changes one codon so a different amino acid is added. |
| Nonsense mutation | A mutation that changes a codon into a stop codon. |
| Frameshift mutation | A mutation caused by insertion or deletion that shifts the reading frame. |
| Retroviruses | An RNA virus that uses reverse transcriptase to make DNA from its RNA genome. |
| Reverse Transcriptase | An enzyme that synthesizes DNA using an RNA template. |
| Provirus | Viral DNA integrated into a host cell's genome. |
| Inducible | A gene turned on only when a specific signal or condition is present. |
| cell differentiation | The process by which cells become specialized in structure and function. |
| Constitutively expressed | Continuous gene expression that stays on under normal conditions. |
| Promoter | Located just upstream of a gene. Binding site for RNA polymerase. Required for transcription to start. |
| Enhancers | Increase transcription rate. Can be far away from the gene. Bind activator transcription factors. |
| Activator | A transcription factor that increases transcription by helping the transcription machinery bind. |
| Operator | A prokaryotic DNA control site where a repressor can bind. |
| Epigenetics | Changes in gene expression that do not alter the DNA sequence itself. |
| Acetylation | The addition of acetyl groups to histones, usually increasing transcription. |
| Histone Modification | DNA wraps around histone proteins to form nucleosomes. How tightly this DNA is packed determines whether genes are accessible for transcription. |
| DNA Methylation | Addition of methyl groups (-CH₃) to cytosine. Usually silences genes. Can block transcription factor binding. |
| Addition of methyl groups (-CH₃) to cytosine. Usually silences genes. Can block transcription factor binding. | Step-by-step activation of genes in a regulatory cascade during development. |
| Transcription factors | Step-by-step activation of genes in a regulatory cascade during development. |
| Silencer | A regulatory DNA sequence that lowers transcription when bound by certain proteins. |
| Repressors | Regulatory proteins that decrease transcription by blocking transcription machinery or tightening chromatin. |
| Mutation | a change in the DNA nucleotide sequence. That change can: Alter the type of protein made Alter the amount of protein made Have no effect at all |
| Point Mutations (Substitutions) | changes one nucleotide to another. Example: Original: AAG Mutated: AGG Effects depend on what happens to the codon |
| Silent Mutation | DNA changes Amino acid stays the same (due to genetic code redundancy) Protein unchanged |
| Insertions and Deletions | If nucleotides are added or removed: If the number is not a multiple of 3, it causes a frameshift mutation The reading frame shifts Every codon downstream changes |
| Biotechnology | The use of living systems or molecules to analyze DNA or make useful products. |
| Polymerase Chain Reaction (PCR) | PCR amplifies a specific DNA sequence. It turns a tiny amount of DNA into millions or billions of copies. This is critical when: Crime scene DNA is tiny A pathogen’s DNA must be detected A gene needs to be studied or sequenced |
| 3 steps of PCR | Denaturation Heat separates the double helix into single strands. Annealing Primers bind (base pair) to specific target sequences. Primers determine which region gets copied. Extension DNA polymerase adds nucleotides to build a new strand. |
| Gel Electrophoresis | A technique that separates DNA fragments by size using an electric field. DNA is negatively charged, so when placed in an electric field: It moves toward the positive electrode Smaller fragments move farther through the gel |
| Gel Electrophoresis things to know | Thicker band = more DNA Same band position in two lanes = same fragment size Used to compare samples (crime scene vs suspect) |
| DNA Sequencing | DNA sequencing determines the exact order of nucleotides (A, T, C, G). This allows scientists to: Identify mutations Compare species Diagnose genetic disorders Study evolutionary relationships |
| Bacterial Transformation | Bacterial transformation introduces foreign DNA into bacteria. |
| DNA Fingerprinting | This combines techniques: PCR → amplify DNA Gel electrophoresis → separate fragments Sometimes sequencing → confirm identity The result is a band pattern unique to an individual (except identical twins). Used in: Forensics Paternity testing |
| Phylogenetic Analysis | The use of genetic data to compare organisms and infer evolutionary relationships. |
| Evolution | A change in the genetic makeup of a population over time. It happens across generations, not within one individual’s lifetime. It involves changes in allele frequencies in a population. Natural selection is one major mechanism that causes those changes |
| Variation | Differences in traits among individuals in a population. |
| Heritable Traits | Traits that can be passed from parents to offspring through genes. |
| Environment | The living and nonliving conditions that influence survival and reproduction. |
| Fitness | An organism's reproductive success in its environment. |
| Biotic factors (living) | Predators Competitors Parasites and pathogens Mates (sexual selection) Food sources |
| Abiotic factors (nonliving) | Temperature Water availability pH Salinity Light intensity Natural disasters |
| Directional selection | One extreme is favored. The population mean shifts in one direction. |
| Stabilizing selection | Intermediate phenotype is favored. Variation decreases. |
| Disruptive selection | Both extremes are favored. Middle is selected against. |
| Natural Selection | The process where heritable traits that improve reproduction become more common over generations. |
| Selective pressures | An environmental factor that makes some traits more favorable than others. |
| Heterozygote Advantage | When individuals with two different alleles have higher fitness than either homozygote. |
| Malaria | A mosquito-borne disease that creates strong selection on human hemoglobin alleles. |
| Genetic diversity | The amount of genetic variation present within a population. |
| Artificial Selection | Evolution caused by humans choosing which organisms reproduce for desired traits. |
| Selective Breeding | The human practice of choosing parents with preferred traits to produce offspring. |
| Phenotypic Diversity | Variation in observable traits like size, color, or behavior within a species. |
| Domestication | The process of changing wild species over generations through human selection and use. |
| Gene pool | The total collection of all alleles in a population. |
| Genetic drift | Random changes in allele frequencies caused by chance events. |
| Bottleneck Effect | A bottleneck happens when population size is drastically reduced for at least one generation. |
| Founder Effect | A type of genetic drift that happens when a small group starts a new population. |
| Gene flow | The movement of alleles between populations through migration and interbreeding. |
| Hardy-Weinberg Equilibrium | A model showing when allele and genotype frequencies stay constant in a non-evolving population. |
| The Five Conditions for Hardy-Weinberg Equilibrium | Large population size No migration (no gene flow) No mutations Random mating No natural selection |
| The Hardy-Weinberg Equations | p + q = 1 p^2 + 2pq + q^2 = 1 Where: p = frequency of dominant allele q = frequency of recessive allele p^2= homozygous dominant genotype 2pq = heterozygous genotype q^2 = homozygous recessive genotype |
| Nonrandom Mating | Mating patterns in which individuals do not pair by chance. |
| Fossils | Preserved remains or traces of past organisms that provide evidence about earlier life. |
| Transitional forms | Fossils that show traits shared by two different groups of organisms. |
| Law of Superposition | The rule that lower rock layers are older than layers above them. |
| Radiometric Dating | A method that uses radioactive decay to calculate the absolute age of materials. |
| Carbon-14 Dating | A radiometric dating method used to date once-living material up to about 50,000 years old. |
| Half-life | The time required for half of a radioactive isotope sample to decay. |
| isotopes | Forms of the same element that differ in neutron number and sometimes radioactivity. |
| Homologous Structures | Body parts with similar underlying anatomy because of shared ancestry. |
| Common Ancestry | The idea that different species descended from shared ancestors in the past. |
| Divergent Evolution | Evolution in which related species become increasingly different from a common ancestor. |
| Vestigial Structures | Reduced remnants of features that were more functional in ancestors. |
| Nucleotide Sequences | The order of bases in DNA that can be compared across species. |
| Molecular clock | A method that uses accumulated genetic differences to estimate evolutionary time. |
| Universal Genetic Code | All organisms use the same genetic code. That strongly supports a single common ancestor of life. If the code evolved separately, we would expect different codon systems. We don’t see that. |
| Phylogenetic Tree | A branching diagram that shows hypothesized evolutionary relationships among species. |
| Biogeography | The study of how species are distributed across different geographic locations. |
| Geographic Isolation | Physical separation of populations that limits gene exchange between them. |
| Stratigraphy | The study of rock layers and their order to determine relative ages. |
| Telomeres | Protective DNA sequences at the ends of linear chromosomes. |
| Pesticide Resistance | The evolution of insect populations that can survive exposure to a pesticide. |
| Herbicide Resistance | The evolution of weed populations that survive herbicide treatment. |
| Chemotherapy Resistance | The evolution of cancer cells that survive cancer drug treatment. |
| Transmissibility | How easily a pathogen spreads from one host to another. |
| Drug Resistance | The ability of pathogens or cells to survive treatment meant to kill them. |
| Basic Parts Of A Phylogenetic Tree You Must Recognize | Root = oldest common ancestor of all organisms in the tree Node = a speciation event; represents the most recent common ancestor Branches = evolving lineages Tips (terminal nodes) = living or extinct species Clade = one ancestor + all its descendants |
| Cladogram | Shows branching order only Branch lengths do not represent time or amount of change Focuses on shared derived characters |
| Phylogenetic Tree | Branch lengths represent amount of evolutionary change or time Often calibrated using fossils or a molecular clock Lets you compare how much change different lineages experienced |
| Homologous Structures | Body parts with a common ancestry, even if they now have different functions. |
| Outgroup | The least closely related lineage used for comparison in a phylogeny. |
| Analogous Structures | Structures with similar functions that evolved independently, not from a common ancestor. |
| Convergent Evolution | The independent evolution of similar traits in unrelated lineages. |
| Paraphyletic | Describing a group that includes an ancestor but not all of its descendants. |
| Speciation | The process by which new species arise from existing populations. |
| Species | A group of organisms that: Can interbreed in nature Produce viable, fertile offspring Are reproductively isolated from other such groups |
| Prezygotic Barriers (before fertilization) | They prevent mating or fertilization. |
| Habitat Isolation | A prezygotic barrier where populations live in different places and rarely meet to mate. |
| Temporal Isolation | A prezygotic barrier where populations reproduce at different times. |
| Behavioral Isolation | A prezygotic barrier caused by differences in courtship signals or mating behavior. |
| Mechanical Isolation | A prezygotic barrier where reproductive structures are physically incompatible. |
| Gametic Isolation | A prezygotic barrier where sperm and egg cannot fuse successfully. |
| Postzygotic Barriers (after fertilization) | They allow fertilization, but offspring have low fitness. |
| Hybrid Inviability | A postzygotic barrier where a hybrid embryo fails to develop or survive well. |
| Hybrid Sterility | A postzygotic barrier where hybrid offspring survive but cannot reproduce. |
| Hybrid Breakdown | A postzygotic barrier where first-generation hybrids are fertile, but later generations are weak or sterile. |
| Reproductive Isolation | A situation where populations can no longer successfully mate and produce fertile offspring. |
| Allopatric Speciation | Geographic separation splits a population. |
| Sympatric Speciation | Seperation that occurs without geographic separation |
| Founder Population | A small group that starts a new population separate from the original one. |
| Stasis | A long period in which a species shows little evolutionary change. |
| Gradualism | Slow, steady change over long time periods Many small accumulated changes |
| Punctuated Equilibrium | Long periods of little change (stasis) Short bursts of rapid speciation |
| Divergent Evolution | Populations become more different over time due to different environments. Often leads to speciation. |
| Adaptive Radiation | Rapid speciation when new habitats or niches open. After mass extinctions Colonizing new islands |
| Convergent Evolution | Unrelated species evolve similar traits due to similar selective pressures. Sharks and dolphins both streamlined Birds and bats both have wings |
| Inbreeding | Mating between closely related individuals, which increases genetic similarity. |
| Inbreeding Depression | Reduced survival or reproductive success caused by inbreeding. |
| Habitat Fragmentation | The breaking of a habitat into smaller, isolated pieces. |
| Clone | A genetically identical copy of an organism. |
| Extinction | The permanent loss of an entire species when no individuals remain. |
| Wildlife Corridor | A protected pathway that allows organisms to move between separated habitats. |
| Conservation | The protection and management of species, habitats, and genetic variation |
| Earth’s Early Timeline | 4.6 billion years ago (bya) → Earth forms ~3.9 bya → Earth becomes more stable ~3.5 bya → Earliest fossil evidence of life |
| Late Heavy Bombardment | An early period when Earth was hit frequently by asteroids and other space debris. |
| Microfossils | Tiny fossilized remains or traces of microscopic organisms preserved in rock. |
| Stromatolites | Layered rock-like structures built by ancient microbial communities, often cyanobacteria. |
| Behavioral responses | An action an organism takes after detecting a stimulus. |
| Taxis | Directed movement toward or away from a stimulus. |
| Kinesis | A change in movement rate or activity level in response to a stimulus. |
| Physiological Response | An internal body change involving hormones, gene expression, or metabolism |
| Phototropism | Plant growth in response to the direction of light |
| Fight-or-Flight Response | A rapid stress response that prepares the body for immediate action. |
| Pheromones | Chemical signals released by one individual that affect others of the same species. |
| Territory | An area an organism defends because it contains resources it needs. |
| Innate Behavior | A behavior that is genetically programmed rather than learned from experience. |
| Learned Behavior | A behavior acquired or modified through experience. |
| Cooperative behavior | Pack hunting Herding, flocking, schooling Colony behavior in insects |
| Inclusive fitness | Total genetic success from both personal reproduction and helping relatives reproduce. |
| Energy Budget | The balance between energy an organism takes in and energy it uses. |
| Net Gain | A state where energy intake is greater than energy expenditure. |
| Net loss | A state where an organism uses more energy than it takes in. |
| Primary Productivity | The rate at which producers capture energy and store it as biomass. |
| Endotherms | Animals that generate most of their body heat through internal metabolism. |
| Ectotherms | Animals that rely mainly on external environmental heat to regulate body temperature. |
| Seasonal Reproduction | A reproductive pattern where organisms breed during favorable times of year. |
| Biennial Plants | Plants that complete their life cycle over two growing seasons. |
| Reproductive Diapause | A temporary pause in reproduction or development during unfavorable conditions. |
| Asexual Reproduction | Reproduction by one parent without fusion of gametes. |
| Sexual Reproduction | Reproduction that combines genetic material from two parents. |
| Trophic Levels | The feeding positions organisms occupy in a food chain or food web. |
| Producers (autotrophs) | Organisms that make organic molecules using an external energy source. Capture energy from: Sunlight (photosynthesis) Inorganic chemicals (chemosynthesis) |
| Primary consumers (herbivores) | Organisms that eat producers directly. |
| Decomposers | Organisms that break down dead organic matter and waste. |
| The 10% Rule | Only about 10% of energy transfers to the next trophic level. Each level has less available energy and less biomass. |
| Biomass | The total mass of living organic material in a given area or trophic level. |
| Bottom-Up Effect | A change that starts at lower trophic levels and affects the levels above them. |
| Reservoirs | Places where matter is stored within a biogeochemical cycle. |
| Population | A group of individuals of the same species living in one area. |
| Community | All the populations of different species living and interacting in one area. |
| Ecosystem | A biological community plus its nonliving environment. |
| Biome | A large region defined by its climate and characteristic life forms. |
| Water Cycle | Evaporation Condensation Precipitation Transpiration |
| Carbon Cycle | Photosynthesis (CO₂ → organic carbon) Cellular respiration (organic carbon → CO₂) Decomposition Combustion |
| Nitrogen Cycle | Nitrogen fixation Nitrification Assimilation Ammonification Denitrification |
| Phosphorus Cycle | Released by weathering of rocks Taken up as PO4 3- Moves through food web Returned via decomposition No major atmospheric phase |
| Changes in Energy Availability | If sunlight decreases: ↓ Photosynthesis ↓ Producer biomass ↓ Consumer populations If producers increase: Larger energy base More trophic levels possible |
| Predation | An interaction in which one organism kills and eats another. |
| Competition | An interaction in which organisms use the same limited resources. |
| Disease | An illness-causing condition that reduces survival or reproduction in organisms. |
| Intraspecific Competition | Competition among individuals of the same species. |
| Interspecific Competition | Competition between individuals of different species. |
| limiting factors | Environmental factors that restrict population growth. |
| Invasive Species | A nonnative species that spreads and disrupts its new environment. |
| Population Density | The number of individuals living in a given area or volume. |
| Carrying Capacity | The largest population size an environment can support over the long term. |
| Density-Dependent Factors | Competition (less food per individual) Disease transmission (spreads faster in crowded populations) Predation (more prey supports more predators) Territoriality (more conflict in limited space) |
| Density-Independent Factors | Their effect is unrelated to population density. Examples: Hurricanes Wildfires Drought Extreme temperature Human habitat destruction |
| logistic growth | Population growth that slows and levels off as it approaches carrying capacity. |
| Exponential growth | Population growth that increases rapidly when resources are abundant and unrestricted. |
| Species Composition | Which species are present in a community. |
| Species Diversity | A measure that combines how many species there are and how evenly they are represented. |
| Commensalism | A symbiotic relationship in which one species benefits and the other is unaffected. |
| Top-Down Control | When predators strongly influence the size of populations at lower trophic levels. |
| Competitive Exclusion | The principle that two species competing for the same niche cannot coexist indefinitely. |
| Niche Partitioning | When species divide resources to reduce competition and coexist more easily. |
| Symbiosis | A close, long-term relationship between organisms of different species. |
| Parasitism | Parasite benefits, host harmed. Parasites usually don’t kill host immediately. Smaller than host. Long-term interaction. |
| Community Structure | The overall pattern of species present, their abundance, and how they interact. |
| Biodiversity | The variety of life in an ecosystem, including different genes and species. |
| Functional Redundancy | When multiple species perform similar ecological roles in an ecosystem. |
| Resistance | An ecosystem's ability to remain stable during a disturbance |
| Resilience | An ecosystem's ability to recover after a disturbance |
| Food Web | A network of feeding relationships showing how energy moves through an ecosystem. |
| Keystone Species | A species with a much larger ecological effect than its abundance suggests. |
| Trophic Cascade | A chain reaction in a food web caused by changes at one trophic level. |
| Nutrient Cycling | The movement and reuse of nutrients through organisms and the environment. |
| Random Variation | Differences in traits arise by chance, not because organisms need them. |
| Nonrandom Selection | Environmental conditions consistently favor some traits over others. |
| Ecological Niche | An ecological niche is a species' role and resource use in an ecosystem. |
| Biomagnification | Biomagnification is the increase in toxin concentration at higher trophic levels. |
| Bioaccumulation | Bioaccumulation is the buildup of a toxin within a single organism over time. |
| Hypoxia or dead zones | Hypoxia is dangerously low dissolved oxygen in water. |
Created by:
Mohamed Kulla
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