Biology
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Begin with Unit 1: The Study of Life and the Chemistry of Life. It sets the foundation for everything that follows.
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Unit 1: The Study of Life and the Chemistry of Life 79 lessons, 4 lecture parts
- 0001 What Biology Is
- 0003 Natural Science
- 0005 Basic Science
- 0007 Applied Science
- 0010 Observation and Question
- 0012 Hypothesis
- 0013 "A Hypothesis Is Just a Guess"
- 0015 Prediction
- 0017 Falsifiability
- 0019 Variable
- 0021 Control Group
- 0024 Designing a Controlled Experiment worked example
- 0027 Inductive Reasoning
- 0029 Deductive Reasoning
- 0031 Descriptive Science and Hypothesis-Based Science
- 0034 Scientific Theory
- 0035 "Evolution Is Just a Theory"
- 0037 Peer Review
- 0039 The Scientific Method, Applied review
- 0041 Order
- 0043 Response to Stimuli
- 0045 Reproduction
- 0047 Adaptation
- 0049 Growth and Development
- 0051 Homeostasis
- 0053 Energy Processing
- 0055 Evolution
- 0056 Natural Selection
- 0057 "Organisms Evolve Because They Need To"
- 0060 Levels of Organization: Atom to Cell
- 0062 Levels of Organization: Tissue to Organism
- 0064 Levels of Organization: Population to Biosphere
- 0067 Prokaryote and Eukaryote
- 0070 Is a Virus Alive?
- 0073 Three Domains of Life
- 0076 Phylogenetic Tree
- 0111 Matter and Elements
- 0113 Atomic Structure
- 0115 Atomic Number and Mass Number
- 0117 Isotopes
- 0119 Radioactive Isotopes and Half-Life
- 0122 Dating a Fossil by Isotope Decay worked example
- 0125 Electron Shells and the Octet Rule
- 0127 Ions
- 0129 Ionic Bonds
- 0131 Covalent Bonds
- 0133 Polar Covalent Bonds
- 0135 Nonpolar Covalent Bonds
- 0137 Hydrogen Bonds
- 0139 Van der Waals Interactions
- 0142 Water's Polarity
- 0144 Cohesion and Adhesion
- 0146 Water's High Heat Capacity
- 0148 Water's Heat of Vaporization
- 0150 Water as a Solvent
- 0152 Why Ice Floats
- 0155 The pH Scale
- 0157 Acids
- 0159 Bases
- 0161 Buffers
- 0164 Buffering Blood pH, Worked worked example
- 0185 Dehydration Synthesis
- 0187 Hydrolysis
- 0190 Monosaccharides
- 0192 Disaccharides and the Glycosidic Bond
- 0194 Polysaccharides: Starch and Glycogen
- 0196 Polysaccharides: Cellulose and Chitin
- 0199 Fatty Acids: Saturated and Unsaturated
- 0201 Triglycerides
- 0203 Phospholipids
- 0205 Steroids
- 0208 Amino Acids and the Peptide Bond
- 0210 Protein Primary Structure
- 0212 Protein Secondary Structure
- 0214 Protein Tertiary and Quaternary Structure
- 0216 Denaturation
- 0219 Nucleotide Structure
- 0221 DNA and RNA
- 0224 Identifying a Macromolecule from Its Monomer review
Unit 2: Cell Structure and the Plasma Membrane 71 lessons, 3 lecture parts
- 0241 Microscopy and Cell Size
- 0243 Light and Electron Microscopy
- 0245 Unified Cell Theory
- 0247 Four Components Every Cell Shares
- 0249 Structure of a Prokaryotic Cell
- 0251 Prokaryotic Surface Structures
- 0253 Why Cell Size Is Limited
- 0255 Structure of a Eukaryotic Cell
- 0257 The Plasma Membrane, Introduced
- 0259 Microvilli
- 0261 Cytoplasm and Cytosol
- 0263 The Nucleus and Nuclear Envelope
- 0265 Chromatin and Chromosomes
- 0267 The Nucleolus
- 0269 Ribosomes
- 0271 Mitochondria
- 0273 Chloroplasts
- 0274 Endosymbiosis
- 0275 Peroxisomes
- 0277 Vesicles and Vacuoles
- 0279 The Centrosome
- 0281 Lysosomes
- 0283 The Plant Cell Wall
- 0285 The Central Vacuole
- 0287 The Endomembrane System
- 0289 Rough Endoplasmic Reticulum
- 0291 Smooth Endoplasmic Reticulum
- 0293 The Golgi Apparatus
- 0295 Lysosome Formation within the Endomembrane System
- 0297 The Cytoskeleton, Introduced
- 0299 Microfilaments
- 0301 Intermediate Filaments
- 0303 Microtubules
- 0305 Flagella and Cilia
- 0307 The Extracellular Matrix
- 0309 Plasmodesmata
- 0311 Tight Junctions
- 0312 Desmosomes
- 0313 Gap Junctions
- 0316 Identifying a Cell from Its Organelles review
- 0321 The Fluid Mosaic Model
- 0323 Membrane Phospholipids, Oriented
- 0325 Integral and Peripheral Proteins
- 0327 The Glycocalyx
- 0328 How a Virus Exploits Membrane Receptors
- 0329 Membrane Fluidity
- 0330 Cholesterol's Role in the Membrane
- 0333 Selective Permeability
- 0335 Diffusion
- 0337 Dynamic Equilibrium
- 0339 Factors Affecting Diffusion Rate
- 0341 Facilitated Transport
- 0343 Channel Proteins
- 0345 Carrier Proteins
- 0347 Osmosis
- 0349 Osmolarity and Tonicity
- 0351 Hypotonic, Isotonic, and Hypertonic Solutions
- 0352 "Isotonic Means the Same for Every Cell"
- 0354 Osmotic Lysis and Crenation
- 0356 Turgor Pressure and Plasmolysis
- 0358 Active Transport
- 0360 Electrochemical Gradient
- 0362 The Sodium-Potassium Pump
- 0364 Primary and Secondary Active Transport
- 0366 Uniporters, Symporters, and Antiporters
- 0368 Endocytosis
- 0370 Phagocytosis
- 0372 Pinocytosis
- 0374 Receptor-Mediated Endocytosis
- 0376 Exocytosis
- 0473 Diagnosing a Membrane Transport Failure review
Unit 3: Metabolism, Respiration, and Photosynthesis 73 lessons, 5 lecture parts
- 0481 Metabolism and Bioenergetics
- 0483 Anabolic and Catabolic Pathways
- 0485 The Metabolic Pathway
- 0487 ATP versus Glucose: Currency and Storage
- 0489 Kinetic and Potential Energy
- 0491 Chemical Energy
- 0493 Gibbs Free Energy and Exergonic/Endergonic Reactions
- 0494 "Spontaneous Means Instantaneous"
- 0496 Chemical Equilibrium in an Open System
- 0498 Activation Energy
- 0500 Catalysis Lowers Activation Energy
- 0502 Systems: Open and Closed
- 0504 The First Law of Thermodynamics
- 0506 The Second Law of Thermodynamics and Entropy
- 0508 ATP Structure
- 0510 ATP Hydrolysis
- 0512 Energy Coupling and Phosphorylation
- 0514 Enzymes as Catalysts
- 0516 The Active Site and Substrate Specificity
- 0518 Induced Fit
- 0520 Temperature, pH, and Enzyme Activity
- 0522 Enzyme Denaturation
- 0524 Competitive Inhibition
- 0526 Noncompetitive and Allosteric Inhibition
- 0528 Cofactors and Coenzymes
- 0530 Enzyme Compartmentalization
- 0532 Feedback Inhibition
- 0534 Redox Reactions
- 0536 Electron Carriers: NAD+ and FAD
- 0538 Substrate-Level Phosphorylation
- 0540 Glycolysis, Overview
- 0542 The Steps of Glycolysis worked example
- 0544 Pyruvate Oxidation to Acetyl CoA
- 0546 The Citric Acid Cycle: A Closed Loop
- 0548 Steps of the Citric Acid Cycle worked example
- 0550 The Electron Transport Chain, Overview
- 0552 Steps of the Electron Transport Chain worked example
- 0554 Chemiosmosis and ATP Synthase
- 0556 Why ATP Yield from Glucose Varies
- 0558 Anaerobic Cellular Respiration
- 0560 Fermentation, Defined
- 0562 Lactic Acid Fermentation
- 0563 "Lactic Acid Causes Muscle Soreness"
- 0565 Alcohol Fermentation
- 0567 Glycogen and Other Sugars Feed Glycolysis
- 0569 Protein Catabolism Connects to Respiration
- 0571 Lipid Catabolism Connects to Respiration
- 0573 Regulation of Glycolysis by Phosphofructokinase
- 0575 Tracing Glucose Through Cellular Respiration review
- 0577 Photoautotrophs, Heterotrophs, and Chemoautotrophs
- 0579 The Overall Equation of Photosynthesis
- 0581 Leaf Structures: Mesophyll, Stomata, and Guard Cells
- 0583 Two Stages of Photosynthesis
- 0585 Wavelength and Light Energy
- 0587 Photosynthetic Pigments: Chlorophyll and Carotenoids
- 0589 The Absorption Spectrum
- 0591 Photosystem Structure
- 0593 Photosystem II and the Splitting of Water
- 0595 The Chloroplast Electron Transport Chain
- 0597 Photosystem I and NADPH Formation
- 0599 Chemiosmosis in the Thylakoid
- 0601 The Light-Dependent Reactions, Full Sequence worked example
- 0603 Carbon Fixation by RuBisCO
- 0604 Photorespiration: RuBisCO's Oxygenase Activity
- 0605 The Calvin Cycle: Three Stages worked example
- 0606 C4 Photosynthesis: Bundle Sheath Cells and PEP Carboxylase
- 0607 G3P as the Calvin Cycle's Export
- 0608 CAM: A Water-Conserving Adaptation
- 0609 C3, C4, and CAM Compared worked example
- 0610 Photosynthesis and Respiration Are Linked, Not Opposed
- 0612 Energy Flows and Degrades; Matter Cycles
- 0613 "Energy Is Recycled in an Ecosystem"
- 0616 Tracing Carbon and Energy Through Photosynthesis review
Unit 4: Cell Communication and Cell Reproduction 75 lessons, 4 lecture parts
- 0761 Intercellular and Intracellular Signaling
- 0763 Ligands and Receptors
- 0765 Paracrine Signaling
- 0767 Synaptic Signaling, a Paracrine Case
- 0769 Endocrine Signaling
- 0771 Autocrine Signaling
- 0773 Direct Signaling via Gap Junctions and Plasmodesmata
- 0775 Internal Receptors
- 0777 Cell-Surface Receptors: Three Domains
- 0779 Ion Channel-Linked Receptors
- 0781 G-Protein-Linked Receptors
- 0783 The G-Protein Activation Cycle worked example
- 0785 Enzyme-Linked Receptors and Receptor Tyrosine Kinases
- 0787 Small Hydrophobic Ligands: Steroid Hormones
- 0789 Water-Soluble Ligands
- 0791 Nitric Oxide as a Gaseous Ligand
- 0793 Signal Transduction and Receptor Dimerization
- 0795 Upstream and Downstream in a Signaling Cascade
- 0797 Signal Amplification
- 0799 Signal Integration
- 0801 Second Messengers, Defined
- 0803 Calcium as a Second Messenger
- 0805 Cyclic AMP as a Second Messenger
- 0807 The Phosphoinositide Pathway: PIP2 to DAG and IP3 worked example
- 0809 Signal Transduction Can Regulate Gene Expression
- 0811 Signal Transduction Can Alter Metabolism: the Epinephrine Case
- 0813 Signal Transduction Can Drive Cell Growth
- 0815 Apoptosis: Programmed Cell Death
- 0817 Terminating a Signal
- 0819 Tracing a Ligand from Binding to Cellular Response review
- 0821 Quorum Sensing in Bacteria
- 0823 Biofilms
- 0825 Signaling in Yeast
- 0827 Genome and Chromosome: Prokaryotic vs. Eukaryotic
- 0829 Gene and Allele, Locked Terms
- 0831 Locus and Homologous Chromosomes
- 0833 Diploid and Haploid
- 0835 Genes, Traits, and Variation
- 0837 Chromatin Compaction, Overview
- 0839 Chromatin Compaction: the Nucleosome
- 0841 Higher-Order Chromatin Packing
- 0843 Sister Chromatids and the Centromere
- 0845 The Cell Cycle: Interphase and the Mitotic Phase
- 0847 G1 Phase
- 0849 S Phase
- 0851 G2 Phase
- 0853 G0 Phase and Quiescence
- 0855 Mitosis, Overview
- 0857 Prophase
- 0859 Prometaphase and the Kinetochore
- 0861 Metaphase
- 0863 Anaphase
- 0865 Telophase
- 0867 Cytokinesis in Animal Cells
- 0869 Cytokinesis in Plant Cells
- 0871 Mitosis Is Not Meiosis
- 0873 Tracing One Cell Cycle from G1 through Cytokinesis review
- 0875 External Regulation of the Cell Cycle
- 0877 Cell-Cycle Checkpoints, Three Gates
- 0879 The G1 Checkpoint
- 0881 The G2 Checkpoint
- 0883 The M (Spindle) Checkpoint
- 0885 Cyclins and Cyclin-Dependent Kinases
- 0887 The Cyclin-Cdk Activation Cycle worked example
- 0889 Negative Regulation: Rb, p53, and p21
- 0891 p53 and the DNA-Damage Response
- 0893 Cancer as Uncontrolled Cell Division
- 0895 Proto-oncogenes and Oncogenes
- 0897 "An Oncogene Is a Foreign, Invading Gene"
- 0899 Tumor Suppressor Genes
- 0901 Cancer as a Multi-Hit, Multi-Generational Process
- 0903 Binary Fission
- 0905 The FtsZ Ring
- 0906 FtsZ and Tubulin: Homologous Structures
- 0907 Comparing Prokaryotic and Eukaryotic Cell Division review
Unit 5: Meiosis and Mendelian Genetics 60 lessons, 3 lecture parts
- 0961 Meiosis, Overview
- 0963 Interphase Before Meiosis
- 0965 Prophase I: Synapsis and the Synaptonemal Complex
- 0967 Crossing Over and the Chiasma
- 0969 The Tetrad
- 0971 Prometaphase I
- 0973 Metaphase I and Independent Orientation
- 0975 Anaphase I
- 0977 Telophase I and Cytokinesis I
- 0979 Meiosis II, Overview
- 0981 Prophase II Through Telophase II
- 0983 Tracing One Diploid Cell Through Meiosis I and II worked example
- 0985 Meiosis Compared to Mitosis: Homolog Pairing and Crossover
- 0987 Crossing Over as a Source of Genetic Variation
- 0989 Independent Assortment of Tetrads as a Source of Genetic Variation
- 0991 Random Fertilization as a Source of Genetic Variation
- 0993 Tracing Genetic Variation from Prophase I Through Fertilization review
- 0995 Sexual and Asexual Reproduction Compared
- 0997 The Diplontic Life Cycle
- 0999 The Haplontic Life Cycle
- 1001 The Haplodiplontic Life Cycle
- 1003 The Evolution of Meiosis, an Open Question
- 1005 Genetics and Mendel's Historical Context
- 1007 Mendel's Model System: the Garden Pea
- 1009 True-Breeding Lines and Controlled Pollination
- 1011 P0, F1, and F2 Generations
- 1013 The Monohybrid Cross
- 1015 Particulate Inheritance
- 1017 "Inherited Traits Blend Like Mixed Paint"
- 1019 Mendel's 3:1 Ratio, Observed
- 1021 The Rule of Addition
- 1023 The Rule of Multiplication
- 1025 Applying the Probability Rules to a Genetic Cross worked example
- 1027 Genotype and Phenotype, Locked Terms
- 1029 Homozygous and Heterozygous
- 1031 Dominant and Recessive Alleles
- 1033 "Dominant Means More Common"
- 1035 The Punnett Square
- 1037 The Testcross
- 1039 Incomplete Dominance
- 1041 Codominance
- 1043 Multiple Alleles: the ABO Blood Group
- 1045 Lethal Alleles
- 1047 X-Linked Inheritance
- 1049 The Law of Dominance
- 1051 The Law of Segregation
- 1053 The Physical Basis of Segregation in Meiosis I
- 1055 The Law of Independent Assortment
- 1057 The Physical Basis of Independent Assortment in Meiosis I
- 1059 The Dihybrid Cross
- 1061 The 9:3:3:1 Ratio
- 1063 The Forked-Line Method
- 1065 Solving a Trihybrid Cross with the Probability Method worked example
- 1067 Genetic Linkage
- 1069 Recombination Frequency
- 1071 Epistasis
- 1073 Full Dihybrid Cross: Genotype to Phenotype review
- 1075 Sex-Determination Systems
- 1077 X-Inactivation and the Barr Body
- 1079 Reading a Pedigree to Infer a Mode of Inheritance worked example
Unit 6: Modern Inheritance, DNA, and Gene Expression 83 lessons, 4 lecture parts
- 1181 The Chromosomal Theory of Inheritance
- 1183 Morgan's Drosophila Evidence for the Chromosomal Theory
- 1185 Genetic Maps from Recombination Frequency
- 1187 Nondisjunction
- 1189 Aneuploidy
- 1191 Human Trisomy as a Chromosomal-Disorder Example
- 1193 Griffith's Transformation Experiment (1928)
- 1195 Avery, MacLeod, and McCarty (1944)
- 1197 Hershey and Chase's Blender Experiment (1952)
- 1199 Franklin and Gosling's X-Ray Diffraction (1953)
- 1201 Watson and Crick's Double-Helix Model (1953)
- 1203 The Nucleotide
- 1205 Complementary Base Pairing
- 1207 Antiparallel Strand Orientation
- 1209 The Double Helix's Overall Structure
- 1211 Meselson and Stahl's Semiconservative-Replication Experiment (1958)
- 1213 "DNA Replication Keeps One Whole Original Helix Intact"
- 1215 Origins of Replication
- 1217 Helicase
- 1219 Primase and the RNA Primer
- 1221 DNA Polymerase's 5'-to-3' Directionality
- 1223 The Leading Strand
- 1225 The Lagging Strand and Okazaki Fragments
- 1227 DNA Ligase
- 1229 Tracing One Replication Fork from Origin to Ligation worked example
- 1231 Prokaryotic Replication's Single Circular Origin
- 1233 Eukaryotic Replication's Multiple Origins and Polymerases
- 1235 Telomeres and the End-Replication Problem
- 1237 Telomerase
- 1239 DNA Polymerase Proofreading
- 1241 Mismatch Repair
- 1243 Nucleotide Excision Repair
- 1245 Tracing DNA from Structure Through Replication and Repair review
- 1247 The Central Dogma
- 1249 The Genetic Code's Triplet Codons
- 1251 Codon Degeneracy
- 1253 The Wobble Hypothesis
- 1255 The Reading Frame
- 1257 Start and Stop Codons
- 1259 Prokaryotic RNA Polymerase and the Promoter
- 1261 Sigma Factor
- 1263 Prokaryotic Transcription Elongation and Termination
- 1265 Eukaryotic RNA Polymerases I, II, and III
- 1267 The Eukaryotic Promoter: the TATA Box
- 1269 Eukaryotic Transcription Factors Assembling the Initiation Complex
- 1271 The 5' Cap
- 1273 The Poly-A Tail
- 1275 Introns and Exons
- 1277 Splicing and the Spliceosome
- 1279 The 5' and 3' Untranslated Regions
- 1281 Tracing Pre-mRNA Processing from Transcription to a Mature mRNA worked example
- 1283 Ribosome Structure: Large and Small Subunits
- 1285 The Ribosome's A, P, and E Sites
- 1287 tRNA Structure and the Anticodon
- 1289 Translation Initiation
- 1291 Translation Elongation
- 1293 Translation Termination
- 1295 Tracing One Gene from Transcription Through a Finished Protein review
- 1297 Point Mutations: Silent
- 1299 Point Mutations: Missense
- 1301 Point Mutations: Nonsense
- 1303 Frameshift Mutations
- 1305 "A DNA Mutation Is Always Harmful"
- 1307 Trinucleotide Repeat Expansions
- 1309 Causes of Mutation
- 1311 Levels of Gene-Expression Regulation, Overview
- 1313 Operon Structure
- 1315 The trp Operon: Repressible, Negative Regulation
- 1317 The lac Operon: Inducible Regulation
- 1319 Chromatin Packing as Gene Regulation
- 1321 Histone Modification
- 1323 DNA Methylation
- 1325 The Central Dogma's One-Way Information Flow, Restated
- 1327 "Traits Acquired in Life Are Inherited"
- 1329 Eukaryotic Transcription Factors and Enhancers
- 1331 Post-Transcriptional Regulation: Alternative Splicing
- 1333 Translational Regulation
- 1334 Post-Translational Regulation
- 1335 Gene Expression Is Regulated, Not Automatic
- 1337 "Genes Are Blueprints Executed Literally"
- 1339 Proto-Oncogenes and Oncogenes, Extended
- 1341 Tumor Suppressor Genes, Extended
- 1343 Tracing a Regulatory Failure from Mutated Gene to Unchecked Cell Division review
Unit 7: Biotechnology and Genomics 43 lessons, 2 lecture parts
- 1521 Genomics Defined
- 1523 Gel Electrophoresis
- 1525 PCR: Amplifying a Target DNA Sequence
- 1527 RT-PCR: Amplifying from an RNA Template
- 1529 Southern and Northern Blotting
- 1531 Restriction Endonucleases and Sticky Ends
- 1533 The Plasmid Vector
- 1535 Constructing a Recombinant Plasmid worked example
- 1537 Recombinant Proteins
- 1539 Cellular Cloning
- 1541 Reproductive Cloning and Somatic Cell Nuclear Transfer
- 1543 "A Clone Is a Perfect Identical Copy"
- 1545 Genetic Engineering and Transgenic Organisms
- 1547 Gene Targeting and Reverse Genetics
- 1549 Recombinant Protein Production in Medicine
- 1551 Agrobacterium-Mediated Plant Transformation
- 1553 Bt Toxin as an Organic Insecticide
- 1555 Genetic Testing
- 1557 Gene Therapy
- 1559 The Physical Map
- 1561 Genetic Markers: RFLP, VNTR, and SNP
- 1563 Physical Mapping Methods: Cytogenetic, Radiation Hybrid, and Sequence Mapping
- 1565 Sequence-Tagged Sites
- 1567 Integrating Genetic and Physical Maps
- 1569 Sanger Chain-Termination Sequencing
- 1571 Shotgun Sequencing and Contigs
- 1573 Pairwise-End Sequencing
- 1575 Next-Generation Sequencing's Parallel Structure
- 1577 Whole-Genome versus Whole-Exome Sequencing
- 1579 Tracing Fragments to an Assembled, Annotated Genome Sequence worked example
- 1581 Sequence Alignment and BLAST
- 1583 Polygenic Disease Risk from Genome Analysis
- 1585 "A Genetic Risk Result Is a Diagnosis"
- 1587 Pharmacogenomics
- 1589 Metagenomics
- 1591 Mitochondrial Genomics
- 1593 Genomics in Agriculture
- 1595 The Proteome
- 1597 "The Genome Fully Predicts the Proteome"
- 1599 Techniques for Protein Analysis
- 1601 Systems Biology
- 1603 Metabolomics
- 1605 Tracing a Trait from a Sequenced Gene to Proteome-Level Function review
Unit 8: Evolutionary Processes 97 lessons, 4 lecture parts
- 1641 Evolution Defined as Change in Allele Frequency
- 1643 Natural Selection Defined
- 1645 Darwin, Wallace, and the Path to 1859
- 1647 Three Premises of Natural Selection
- 1649 Descent with Modification
- 1651 "Evolution Is Only a Theory"
- 1653 Scientific Theory, the Locked Term Reinforced
- 1655 Adaptation Defined
- 1657 Convergent and Divergent Evolution
- 1659 Homologous Structures
- 1661 Vestigial Structures
- 1663 Analogous Structures and Homoplasy
- 1665 Fossil Evidence for Evolution
- 1667 Comparative Embryology as Evidence
- 1669 Biogeography as Evidence
- 1671 Molecular Evidence: DNA Universality
- 1673 Genetic Variation from Mutation and Sexual Reproduction
- 1675 Neutral, Beneficial, and Deleterious Mutations
- 1677 "Organisms Evolve Because They Need To"
- 1679 Variation Precedes Selection
- 1681 "Humans Evolved from Monkeys"
- 1683 Common Ancestry, Not Common Descendant
- 1685 The Biological Species Concept
- 1687 Limits of the Biological Species Concept and Alternative Concepts
- 1689 The Gene Pool and Reproductive Isolation
- 1691 Speciation Defined
- 1693 Allopatric Speciation: Dispersal and Vicariance
- 1695 Adaptive Radiation
- 1697 Sympatric Speciation, Overview
- 1699 Polyploidy
- 1701 Autopolyploidy
- 1703 Alloploidy
- 1705 Nondisjunction as a Route to Polyploid Speciation
- 1707 Habitat and Behavioral Sympatric Speciation
- 1709 Prezygotic Reproductive Isolation, Overview
- 1711 Temporal Isolation
- 1713 Habitat Isolation
- 1715 Behavioral Isolation
- 1717 Mechanical Isolation
- 1719 Gametic Isolation
- 1721 Postzygotic Reproductive Isolation, Overview
- 1723 Hybrid Inviability and Hybrid Sterility
- 1725 Hybrid Breakdown
- 1727 Hybrid Zones
- 1729 Reinforcement, Fusion, and Stability
- 1731 Gradual Speciation and Punctuated Equilibrium
- 1733 Tracing One Allopatric Speciation Event worked example
- 1735 The Modern Synthesis
- 1737 Population Genetics Defined
- 1739 Allele Frequency
- 1741 Hardy-Weinberg Equilibrium
- 1743 Hardy-Weinberg's Five Assumptions
- 1745 The Hardy-Weinberg Equations
- 1747 Solving a Hardy-Weinberg Calculation worked example
- 1749 Polymorphism
- 1751 Heritability of Phenotypic Variation and Environmental Variation
- 1753 "Acquired Traits Are Inherited"
- 1755 Only Germline Variation Is Heritable
- 1757 Genetic Drift
- 1759 The Founder Effect
- 1761 The Bottleneck Effect
- 1763 Gene Flow and Clines
- 1765 Mutation as an Evolutionary Force, Population-Level
- 1767 Nonrandom Mating
- 1769 Fitness and Relative Fitness
- 1771 Stabilizing Selection
- 1773 Directional Selection
- 1775 Disruptive (Diversifying) Selection
- 1777 Frequency-Dependent Selection
- 1779 Sexual Selection and Sexual Dimorphism
- 1781 The Handicap Principle and the Good Genes Hypothesis
- 1783 Selection's Limits: No Perfect Organism, Not All Evolution Adaptive
- 1785 Tracing a Population's Adaptive Evolution from Mutation Through Fixation review
- 1787 Phylogeny Defined
- 1789 The Phylogenetic Tree as Hypothesis
- 1791 Rooted and Unrooted Trees
- 1793 Branch Points, Basal Taxa, Sister Taxa, and Polytomy
- 1795 Branch Length Does Not Default to Encoding Time
- 1797 The Linnaean Taxonomic Hierarchy
- 1799 Binomial Nomenclature
- 1801 Homology and Analogy, Applied to Phylogenetics
- 1803 Molecular Systematics
- 1805 Cladistics and Clades
- 1807 Monophyletic, Paraphyletic, and Polyphyletic Groups
- 1809 Shared Ancestral and Shared Derived Characters
- 1811 Maximum Parsimony
- 1813 Building a Phylogenetic Tree from Shared Derived Characters worked example
- 1815 Horizontal Gene Transfer, Defined
- 1817 HGT Mechanisms in Prokaryotes
- 1819 HGT in Eukaryotes
- 1821 Endosymbiosis, Revisited as Genome Fusion
- 1823 Competing Hypotheses for the Eukaryotic Nucleus's Origin
- 1825 The Web and Ring Models of Life
- 1827 Tracing Common-Descent Evidence Across One Clade review
- 1829 Prebiotic Earth Conditions and Abiotic Synthesis
- 1831 The Miller-Urey Experiment
- 1833 The RNA World Hypothesis
Unit 9: Microbial and Fungal Diversity 86 lessons, 4 lecture parts
- 1901 Virion Structure: Genome, Capsid, and Envelope
- 1903 Four Capsid Shape Classes
- 1905 Viral Receptors and Host Specificity
- 1907 Viral Genome Types: DNA and RNA
- 1909 The Baltimore Classification Logic
- 1911 Baltimore Groups I–III
- 1913 Baltimore Groups IV–VII and Retroviruses
- 1915 Three Hypotheses for Viral Origin
- 1917 "A Virus Is a Living Organism"
- 1919 Whether a Virus Is Alive, Revisited
- 1921 Steps of Viral Replication, Overview
- 1923 The Lytic Cycle
- 1925 The Lysogenic Cycle and Latency
- 1927 Plant Virus Transmission
- 1929 Animal Virus Entry and Exit
- 1931 Oncogenic Viruses
- 1933 Vaccines: Mechanism of Protection
- 1935 Antiviral Drug Mechanism
- 1937 Combination Therapy Against a Fast-Mutating Virus
- 1938 Subviral Agents: Prions and Viroids
- 1939 Tracing a Viral Infection from Attachment Through Immune Clearance and Treatment review
- 1941 Prokaryotic Cell Structure, Reused and Extended
- 1943 Three Prokaryotic Cell Shapes
- 1945 Bacteria versus Archaea: Membrane Lipid Differences
- 1947 The Peptidoglycan Cell Wall and the Gram Stain
- 1949 Gram-Positive versus Gram-Negative Wall Structure
- 1951 Archaeal Cell Walls
- 1953 Species Delimitation: Ribosomal RNA Sequencing
- 1955 Binary Fission and Horizontal Gene Transfer, Reused
- 1957 The Four Prokaryotic Nutritional Categories
- 1959 Prokaryotes and the Carbon Cycle
- 1961 Prokaryotes and the Nitrogen Cycle
- 1963 Extremophiles and Biofilms
- 1965 Bacterial Disease Mechanism, Overview
- 1967 Antibiotic Resistance Mechanism
- 1969 Nitrogen-Fixation Mutualism
- 1971 The Human Microbiome
- 1973 "Germs Are All Bad"
- 1975 Beneficial Prokaryotes, Correctly Weighted
- 1977 Bioremediation
- 1979 Classifying a Prokaryote by Its Nutritional Category worked example
- 1981 "Protist" as a Paraphyletic Wastebasket Grouping
- 1983 Eukaryotic Characteristics of the Last Common Ancestor
- 1985 Endosymbiosis Among Protists, Revisited
- 1987 Secondary Endosymbiosis
- 1989 Protist Cell Structure and Metabolic Diversity
- 1991 Protist Motility
- 1993 Protist Life Cycles
- 1995 The Five-Supergroup Classification Criterion
- 1997 Archaeplastida
- 1999 Amoebozoa and Slime Molds
- 2001 Opisthokonta and Choanoflagellates
- 2003 The SAR Supergroup: Stramenopiles, Alveolates, and Rhizaria
- 2005 Alveolates: Dinoflagellates and Ciliates
- 2007 Apicomplexans and Malaria Mechanism
- 2009 Stramenopiles: Diatoms and Brown Algae
- 2011 Rhizaria: Forams and Radiolarians
- 2013 Excavata
- 2015 Excavate Parasites: Giardia and Trypanosomes
- 2017 Protist Ecology: Producers, Decomposers, and Symbionts
- 2019 Classifying an Unfamiliar Protist by Supergroup-Defining Criteria worked example
- 2021 Tracing a Protist Lineage's Endosymbiotic Origin and Ecological Role review
- 2023 Fungal Characteristics: Heterotrophic Absorption and the Chitin Wall
- 2025 Hyphae and Mycelium
- 2027 Septate versus Coenocytic Hyphae
- 2029 Yeast: The Unicellular Fungal Form
- 2031 Asexual Fungal Reproduction
- 2033 Sexual Fungal Reproduction: Plasmogamy, Karyogamy, and Meiosis
- 2035 Fungal Classification: Reproductive Structure as the Criterion
- 2037 Chytridiomycota
- 2039 Zygomycota
- 2041 Glomeromycota
- 2043 Ascomycota
- 2045 Basidiomycota
- 2047 "Mold and Mushroom Are Unrelated Organisms"
- 2049 Growth Form versus Taxonomic Group
- 2051 Fungal Ecology: Decomposers and Nutrient Cycling
- 2053 Mycorrhizae Mechanism
- 2055 Lichens
- 2057 Fungal Plant Pathogens
- 2059 Fungal Human Pathogens: Mycosis Categories
- 2061 Antifungal Treatment Difficulty
- 2063 Fermentation and Food Uses of Fungi
- 2065 Fungi as Medical Compound Sources
- 2067 Fungi as Genetic Model Organisms
- 2069 Tracing a Mycorrhizal Symbiosis from Colonization Through Ecosystem Effect review
Unit 10: Plant and Animal Diversity 78 lessons, 4 lecture parts
- 2161 Land Plant Origin Among the Charophyte Green Algae
- 2163 Four Adaptations for Life on Land
- 2165 The Haplodiplontic Life Cycle in Land Plants
- 2167 "Seaweed Is a Plant"
- 2169 Algae versus Land Plants, the Defining Line
- 2171 Bryophyte Defining Traits: Nonvascular, Gametophyte-Dominant
- 2173 Bryophyte Diversity: Liverworts, Mosses, and Hornworts
- 2175 Moss Life Cycle, Worked worked example
- 2177 Seedless Vascular Plant Traits: Vascular Tissue, Sporophyte Dominance
- 2179 Lycophytes versus Monilophytes
- 2181 Homospory versus Heterospory
- 2183 Carboniferous Coal Forests
- 2185 Seed Evolution: Three Key Innovations
- 2187 Advantages of a Seed over a Spore
- 2189 Gymnosperm Defining Trait: the Naked Seed
- 2191 Four Gymnosperm Phyla
- 2193 Conifer Life Cycle Basics
- 2195 Angiosperm Defining Traits: Flower and Fruit
- 2197 Flower Structure
- 2199 Double Fertilization Mechanism
- 2201 Monocots versus Eudicots
- 2203 Angiosperm-Pollinator Coevolution
- 2205 Fruit Types and Seed Dispersal
- 2207 Ecological and Economic Role of Seed Plants
- 2209 Classifying a Plant Sample by Vascular, Seed, and Flower Criteria worked example
- 2211 Tracing One Lineage from Charophyte Ancestor to Angiosperm Flower review
- 2213 Animal Kingdom Defining Features
- 2215 Embryonic Development: Blastula and Gastrulation
- 2217 Diploblastic versus Triploblastic Body Plans
- 2219 Body Symmetry: Asymmetry, Radial, Bilateral
- 2221 Cephalization
- 2223 Coelom Types: Acoelomate, Pseudocoelomate, Coelomate
- 2225 Protostome versus Deuterostome Development
- 2227 "Plants Are Simpler Than Animals"
- 2229 Evolutionary Complexity Has No Direction
- 2231 Animal Phylogeny as Evidence-Based and Revisable
- 2233 Sponges' Contested Position at the Animal Root
- 2235 The Cambrian Explosion
- 2237 Phylum Porifera: Body Structure without True Tissues
- 2239 "Sponges Aren't Really Animals"
- 2241 Choanocytes and Positive Evidence for Sponge Ancestry
- 2243 Cnidarian Body Plan: Polyp and Medusa
- 2245 Cnidocytes and Nematocysts
- 2247 Four Cnidarian Classes
- 2249 Lophotrochozoa Defined
- 2251 Phylum Platyhelminthes: Flatworms
- 2253 Phylum Rotifera
- 2255 Phylum Nemertea: Ribbon Worms
- 2257 Mollusk Body Plan: Foot, Mantle, Visceral Mass
- 2259 Three Major Mollusk Classes
- 2261 Annelid Segmentation
- 2263 Ecdysozoa Defined: the Molting Cuticle
- 2265 Phylum Nematoda
- 2267 Phylum Tardigrada
- 2269 Arthropod Defining Traits
- 2271 Four Arthropod Subphyla
- 2273 "An Insect and a Spider Are Both Bugs"
- 2275 Insects versus Arachnids, Structurally Distinguished
- 2277 Deuterostomia Defined
- 2279 Echinoderm Body Plan: Water Vascular System
- 2281 Phylum Hemichordata
- 2283 Classifying an Unfamiliar Invertebrate by Body-Plan Criteria worked example
- 2285 Tracing the Protostome-Deuterostome Branch Point review
- 2287 Chordate Defining Traits
- 2289 Subphylum Vertebrata: the Vertebral Column
- 2291 Jawless versus Jawed Fishes
- 2293 Cartilaginous versus Bony Fishes
- 2295 Amphibian Traits: Dual Life and Permeable Skin
- 2297 Reptile Traits: the Amniotic Egg
- 2299 Birds as a Clade Nested within Reptilia
- 2301 Bird Flight Adaptations
- 2303 Mammal Traits: Hair and Mammary Glands
- 2305 Three Living Mammal Clades
- 2307 Primate Traits
- 2309 Human Lineage: Hominins, Not a Line
- 2311 "Humans Are the Most Evolved Animal"
- 2313 Evolution Has No Endpoint or Direction
- 2315 Tracing Tetrapod Evolution from Lobe-Finned Fish to Amniotes review
Unit 11: Plant Structure and Function 68 lessons, 4 lecture parts
- 2501 Plant Organ Systems: Shoot and Root
- 2503 Meristematic versus Permanent Tissue
- 2505 Three Meristem Locations: Apical, Lateral, Intercalary
- 2507 Dermal, Vascular, and Ground Tissue
- 2509 Simple versus Complex Tissue: Xylem and Phloem
- 2511 Stem Anatomy: Parenchyma, Collenchyma, Sclerenchyma
- 2513 Primary Growth: Apical Meristem Elongation
- 2515 "A Tree Grows Taller by Pushing Up From the Base"
- 2517 Why a Nail in a Trunk Never Rises
- 2519 Apical Dominance
- 2521 Secondary Growth: Vascular Cambium and Cork Cambium
- 2523 Annual Rings
- 2525 Stem Modifications
- 2527 Taproot versus Fibrous Root Systems
- 2529 Root Growth Zones
- 2531 Root Anatomy: Endodermis and Casparian Strip
- 2533 Root Modifications
- 2535 Leaf Structure: Mesophyll, Stomata, Veins
- 2537 Simple versus Compound Leaves
- 2539 Leaf Arrangement: Phyllotaxy
- 2541 Water Potential: Solute, Pressure, Gravity, Matric Components
- 2543 Cohesion-Tension Theory of Sap Ascent
- 2545 Transpiration and Stomatal Regulation
- 2547 Translocation: Pressure-Flow in Phloem
- 2549 Tracing Water and Photosynthate Transport, Worked worked example
- 2551 Phototropism: the Phytochrome and Blue-Light Systems
- 2553 Photoperiodism
- 2555 Gravitropism
- 2557 Thigmotropism and Thigmonasty
- 2559 Auxin
- 2561 The Darwin and Boysen-Jensen Phototropism Experiments, Worked worked example
- 2563 Cytokinins
- 2565 Gibberellins
- 2567 Ethylene
- 2569 Abscisic Acid
- 2571 Tracing Apical Dominance Through Auxin-Cytokinin Balance, Worked Capstone review
- 2573 Essential Nutrients: Macronutrients and Micronutrients
- 2575 Deficiency Symptoms as Diagnostic Method
- 2577 Soil Composition: Four Major Components
- 2579 Soil Horizons: O, A, B, C
- 2581 "Plants Get Most of Their Mass From the Soil"
- 2583 Photosynthesis Supplies a Plant's Mass, Not Soil
- 2585 Nitrogen Fixation and the Legume-Rhizobia Symbiosis
- 2587 Ectomycorrhizae and Endomycorrhizae
- 2589 Parasitic Plants: Holoparasites and Hemiparasites
- 2591 Carnivorous Plants as a Nutrient Adaptation
- 2593 "Carnivorous Plants Eat Insects Instead of Photosynthesizing"
- 2595 Insect Prey Supplements Nitrogen, Not Energy
- 2597 Epiphytes
- 2599 Classifying a Plant's Nutritional Strategy, Worked worked example
- 2601 Male Gametophyte Development: Microsporogenesis and the Pollen Grain
- 2603 Female Gametophyte Development: Megasporogenesis and the Embryo Sac
- 2605 Complete versus Incomplete Flowers
- 2606 Monoecious versus Dioecious Species
- 2607 Pollination Mechanisms and Pollinator Syndromes
- 2609 Self-Pollination versus Cross-Pollination
- 2611 Self-Incompatibility Mechanisms
- 2613 "Self-Pollination and Asexual Reproduction Are the Same Thing"
- 2615 Self-Pollination Still Requires Meiosis and Fertilization
- 2617 Double Fertilization Detail: Endosperm and Seed Coat Development
- 2619 Seed Structure and Monocot/Dicot Storage Strategy
- 2621 Seed Dormancy and Germination Cues
- 2623 Fruit Types Revisited: Simple, Aggregate, Multiple, Accessory
- 2625 Asexual/Vegetative Reproduction: Natural Methods
- 2627 Asexual/Vegetative Reproduction: Artificial Methods
- 2629 Evolutionary Tradeoffs: Sexual versus Asexual Reproduction
- 2631 Plant Life Spans and Flowering Frequency
- 2633 Tracing a Flower From Pollination to Seed Dispersal, Worked Capstone review
Unit 12: Animal Form, Nutrition, and Control Systems 121 lessons, 5 lecture parts
- 2721 Body Plans and the Symmetry Constraint
- 2723 Body Planes
- 2724 Body Cavities: Dorsal and Ventral
- 2725 Exoskeleton and Endoskeleton Size Limits
- 2727 Surface-to-Volume Ratio Limits Size
- 2729 Endotherms and Ectotherms
- 2731 Metabolic Rate: BMR and SMR
- 2733 Torpor, Hibernation, and Estivation
- 2735 Four Primary Animal Tissue Types
- 2737 Epithelial Tissue: Simple and Stratified
- 2739 Connective Tissue: Matrix and Fiber Types
- 2741 Bone Remodeling: Osteoblasts, Osteocytes, Osteoclasts
- 2743 Three Muscle Tissue Types
- 2745 Nervous Tissue: Neurons and Glia, Introduced
- 2747 The Set Point and Feedback Control
- 2749 Negative Feedback Loop
- 2751 Positive Feedback Loop
- 2753 "Positive Feedback Means Something Has Gone Wrong"
- 2755 Positive Feedback Is Self-Limiting by Design
- 2757 Thermoregulation: Four Heat-Exchange Mechanisms
- 2758 Thermoregulatory Responses: Insulation, Vasodilation, Vasoconstriction, Behavior
- 2759 Classifying an Animal's Thermoregulatory Strategy, Worked worked example
- 2763 Herbivore, Carnivore, Omnivore Diet Classification
- 2765 Gastrovascular Cavity versus Alimentary Canal
- 2767 Monogastric versus Ruminant Digestive Systems
- 2769 Avian Digestive Adaptations
- 2771 Oral Cavity: Mastication and Salivary Enzymes
- 2773 Esophagus and Peristalsis
- 2775 Stomach: Acid Environment and Pepsin
- 2777 Small Intestine: Villi and Microvilli
- 2779 Duodenum, Jejunum, Ileum
- 2781 Large Intestine: Water Reabsorption
- 2783 Accessory Organs: Liver, Pancreas, Gallbladder
- 2785 Essential Nutrients
- 2787 Macronutrient Caloric Density
- 2789 Four-Step Nutritional Process: Ingestion to Elimination
- 2791 Carbohydrate Digestion
- 2793 Protein Digestion
- 2795 Lipid Digestion: Emulsification
- 2797 Glycogen Storage and Mobilization
- 2799 Neural Control: Three Digestive Phases
- 2801 Hormonal Control: Gastrin, Secretin, CCK
- 2803 "Skipping a Meal Immediately Starves the Body"
- 2805 Glycogen Reserves Buffer Short-Term Fasting
- 2807 Obesity as an Energy-Balance Imbalance
- 2809 Eating Disorders as Disrupted Energy-Intake Regulation
- 2811 Tracing a Meal Through the Digestive Tract, Worked review
- 2815 Neuron Structure: Dendrites, Soma, Axon
- 2817 Four Neuron Types
- 2819 Glial Cell Types
- 2821 Resting Membrane Potential
- 2823 Action Potential
- 2825 Myelin and Saltatory Conduction
- 2827 Chemical Synapse: Neurotransmitter Release
- 2829 Electrical Synapse: Gap Junctions
- 2831 EPSP, IPSP, and Summation
- 2833 Long-Term Potentiation and Long-Term Depression
- 2835 "Addiction Is a Failure of Willpower"
- 2837 Addiction as Hijacked Synaptic Plasticity
- 2839 Meninges and Cerebrospinal Fluid
- 2841 Cerebral Cortex: Hemispheres and Lobes
- 2843 Frontal, Parietal, Occipital, Temporal Lobe Functions
- 2845 Basal Ganglia, Thalamus, and Hypothalamus
- 2847 Limbic System and the Amygdala
- 2849 Cerebellum and Brainstem
- 2851 Spinal Cord: Gray and White Matter
- 2853 The Spinal Reflex Arc
- 2855 Autonomic Nervous System: Two-Synapse Relay
- 2857 Sympathetic Nervous System
- 2859 Parasympathetic Nervous System
- 2861 Sensory-Somatic Nervous System
- 2863 Neurodegenerative Disorders as Neuron Loss
- 2865 Neurodevelopmental Disorders as Atypical Wiring
- 2867 Tracing a Reflex Arc Signal Path, Worked worked example
- 2871 Sensory Transduction
- 2873 Receptive Field and Receptor Specificity
- 2875 Sensation versus Perception
- 2877 Stimulus Intensity Encoding
- 2879 Somatosensory Mechanoreceptors
- 2881 Two-Point Discrimination and Receptor Density
- 2883 Thermoreception
- 2885 Nociception and the Subjectivity of Pain
- 2887 Taste: Five Primary Tastants
- 2889 Olfaction: Receptor Diversity and Odor Coding
- 2891 "Humans Have Only Five Senses"
- 2893 Somatosensation Splits Into Several Distinct Modalities
- 2895 Sound Wave Properties: Frequency and Amplitude
- 2897 Outer and Middle Ear: Ossicle Amplification
- 2899 Cochlea and the Organ of Corti
- 2901 Place Theory of Pitch Perception
- 2903 Vestibular System: Utricle, Saccule, Semicircular Canals
- 2905 Eye Anatomy: Cornea, Lens, Iris
- 2907 Rods versus Cones
- 2909 Phototransduction: Rhodopsin and Hyperpolarization
- 2911 Trichromatic Color Coding
- 2913 Retinal Processing: Lateral Inhibition
- 2915 Tracing a Sound Wave From Air to Auditory Cortex, Worked worked example
- 2919 Three Hormone Chemical Classes
- 2921 Lipid-Soluble versus Water-Soluble Receptor Location
- 2923 Intracellular Hormone Receptors and Gene Transcription
- 2925 Plasma Membrane Receptors and cAMP Second Messenger
- 2927 "Hormones and Neurotransmitters Are Entirely Different Things"
- 2929 One Molecule Can Signal as Both Hormone and Neurotransmitter
- 2931 Hypothalamic-Pituitary Axis
- 2933 Anterior versus Posterior Pituitary
- 2935 ADH and Water Balance
- 2937 Aldosterone and the Renin-Angiotensin-Aldosterone System
- 2939 Thyroid Hormones and Metabolic Rate
- 2941 Parathyroid Hormone and Calcitonin: Opposing Calcium Control
- 2943 Insulin and Glucagon: Opposing Glucose Control
- 2945 Growth Hormone: Direct and Indirect Mechanisms
- 2947 Adrenal Cortex versus Adrenal Medulla
- 2949 Short-Term versus Long-Term Stress Response
- 2951 Negative Feedback in Hormone Regulation
- 2953 Three Stimuli Triggering Hormone Release
- 2955 Gonadal Hormones and Reproductive Regulation
- 2957 "Steroid Hormones Are Only a Bodybuilding Drug"
- 2959 Anabolic Steroids Disrupt the Body's Own Endocrine Feedback
- 2961 Endocrine Glands With Secondary Function
- 2963 Tracing the Hypothalamic-Pituitary-Thyroid Feedback Loop, Worked worked example
- 2965 Tracing a Stress Response From Stimulus to Hormone Cascade, Worked Capstone review
Unit 13: Animal Support, Transport, Defense, and Reproduction 119 lessons, 5 lecture parts
- 3081 Hydrostatic Skeleton Mechanism
- 3083 Exoskeleton Structure and Molting
- 3085 Endoskeleton Structure Overview
- 3087 Axial Skeleton
- 3089 Appendicular Skeleton
- 3091 Bone Classification by Shape
- 3093 Compact versus Spongy Bone
- 3095 Bone Marrow: Red and Yellow
- 3097 Bone Growth: Ossification and the Epiphyseal Plate
- 3099 Cartilage Types
- 3101 Tendons versus Ligaments
- 3103 Fibrous Joints
- 3105 Cartilaginous Joints
- 3107 Synovial Joints and Synovial Fluid
- 3109 Synovial Movement Types
- 3111 Skeletal Muscle Organization: Fascicle to Sarcomere
- 3113 Sarcomere Structure
- 3115 Sliding Filament Mechanism
- 3117 Neuromuscular Junction and Excitation-Contraction Coupling
- 3119 Calcium, Troponin, and Tropomyosin
- 3121 ATP's Three Roles in Muscle Contraction
- 3123 Slow-Twitch and Fast-Twitch Muscle Fibers
- 3125 "Muscles Only Pull, Never Push"
- 3127 Antagonistic Muscle Pairs Produce Both Directions of Movement
- 3131 Tracing a Single Muscle Contraction Cycle, Worked worked example
- 3141 Partial Pressure and the Diffusion Gradient
- 3143 Gas Exchange Surface Requirements
- 3145 Integumentary Gas Exchange
- 3147 Gills and Countercurrent Exchange
- 3149 Tracheal System in Insects
- 3151 Mammalian Lung Structure
- 3153 Avian Flow-Through Lungs and Air Sacs
- 3155 Negative-Pressure Breathing Mechanics
- 3157 Compliance and Resistance in the Lungs
- 3159 V/Q Mismatch Mechanism
- 3161 Hemoglobin Structure and Cooperative Binding
- 3163 The Oxygen-Hemoglobin Dissociation Curve
- 3165 The Bohr Effect
- 3167 CO2 Transport: Bicarbonate and Carbaminohemoglobin
- 3169 "Breathing Is Driven by Low Oxygen"
- 3171 Rising CO2 and Falling pH Drive the Breathing Reflex
- 3175 Tracing Gas Exchange Across the Pulmonary-Systemic Loop, Worked worked example
- 3185 Open versus Closed Circulatory Systems
- 3187 Single versus Double Circulation
- 3189 Blood Plasma Composition
- 3191 Erythrocyte Structure and Function
- 3193 Leukocyte Types, Introduced
- 3195 Platelets and the Clotting Cascade
- 3197 Heart Chambers and Valves
- 3199 Cardiac Cycle: Systole and Diastole
- 3201 SA Node and the Cardiac Conduction System
- 3203 Artery Structure
- 3205 Vein Structure
- 3207 Capillary Structure and Exchange
- 3209 "Arteries Carry Oxygenated Blood, Veins Carry Deoxygenated Blood"
- 3211 Vessel Direction, Not Oxygen Content, Defines Artery and Vein
- 3215 Baroreceptor Reflex and Blood Pressure Regulation
- 3217 The Lymphatic System's Role Alongside Circulation
- 3221 Tracing Blood Through Double Circulation, Worked worked example
- 3231 Osmoconformers versus Osmoregulators
- 3233 Osmotic Balance Challenges by Habitat
- 3235 Nephron Structure
- 3237 Filtration, Reabsorption, Secretion: the Three-Step Mechanism
- 3239 The Loop of Henle and the Countercurrent Multiplier
- 3241 ADH and Aquaporin Insertion in the Collecting Duct
- 3243 Excretory Organs Across Taxa: Flame Cells, Malpighian Tubules, Nephridia
- 3245 Nitrogenous Waste Forms and Tradeoffs
- 3249 Tracing Filtrate Through the Nephron, Worked worked example
- 3259 Innate Immunity: Physical and Chemical Barriers
- 3261 Phagocytes: Neutrophils and Macrophages
- 3263 Inflammation Mechanism
- 3265 Fever as a Systemic Innate Response
- 3267 The Complement System
- 3269 Interferons and Viral Defense
- 3271 Natural Killer Cells
- 3273 Adaptive Immunity: Humoral versus Cell-Mediated
- 3275 Antigen Specificity and Receptor Diversity
- 3277 B Cell Activation and Clonal Selection
- 3279 T Cell Types: Helper and Cytotoxic
- 3281 MHC Class I and II Antigen Presentation
- 3283 Antibody Structure
- 3285 Antibody Classes and Functions
- 3287 Immunological Memory
- 3289 "Vaccines Give You the Disease"
- 3291 A Vaccine Trains Memory Without Causing Disease
- 3295 "Antibiotics Work on Viruses"
- 3297 Antibiotics Target Bacterial Structures a Virus Lacks
- 3301 Autoimmune Disease Mechanism
- 3303 Immunodeficiency Mechanism
- 3305 Hypersensitivity and Allergy Mechanism
- 3307 Cancer Immune Evasion Mechanism
- 3311 Tracing the Innate Response to a Skin Wound, Worked worked example
- 3321 Asexual Reproduction Methods
- 3323 Sexual Reproduction's Genetic-Diversity Advantage
- 3325 External versus Internal Fertilization
- 3327 Oviparity, Ovoviviparity, Viviparity
- 3329 Male Reproductive Anatomy
- 3331 Female Reproductive Anatomy
- 3333 Spermatogenesis Mechanism
- 3335 Oogenesis Mechanism
- 3337 The HPG Axis and Hormonal Control of Male Reproduction
- 3339 Hormonal Control of the Menstrual Cycle
- 3341 "Fertilization Takes Many Sperm to Break Through the Egg"
- 3343 One Sperm Fertilizes the Egg; Polyspermy Is Actively Blocked
- 3347 Placenta Structure and Function
- 3349 Human Gestation: a Structural Mechanism
- 3351 Hormonal Signaling for Labor
- 3353 Cleavage and Blastula Formation
- 3355 Gastrulation and the Three Germ Layers
- 3357 Organogenesis Overview
- 3359 Vertebrate Axis Formation
- 3361 "Identical Twins Are 100% Genetically Identical"
- 3363 Somatic Mutation Breaks Perfect Genetic Identity After Twinning
- 3367 Tracing Fertilization Through Early Embryonic Development, Worked worked example
- 3369 Determination and Differentiation
- 3371 Induction and Morphogen Gradients
- 3373 Hox Genes and Body-Plan Specification
- 3375 Stem Cell Potency
- 3401 Tracing Fluid, Gas, and Waste Balance During Exercise, Worked Capstone review
Unit 14: Ecology, Ecosystems, and Conservation 80 lessons, 4 lecture parts
- 3481 Ecology's Levels of Organization
- 3483 Biogeography and Abiotic Distribution Factors
- 3485 Endemic versus Generalist Species
- 3489 Light and Nutrient Availability Across Habitats
- 3491 Temperature as a Distribution Constraint
- 3493 Biome Definition and Classification Basis
- 3495 Desert and Tropical Wet Forest Contrast
- 3497 Grassland and the Role of Fire Disturbance
- 3499 Tundra and the Permafrost Constraint
- 3501 Aquatic Biome Classification by Salinity and Zone
- 3505 Classifying a Biome from Climate and Vegetation Data, Worked worked example
- 3521 The Greenhouse Effect Mechanism
- 3523 How Atmospheric Greenhouse-Gas Concentration Is Measured
- 3525 How Global Mean Temperature Change Is Measured and Reported
- 3541 Population Size and Population Density
- 3545 Quadrat and Mark-Recapture Sampling Methods
- 3547 Uniform, Random, and Clumped Dispersion Patterns
- 3549 Life Tables and Age-Specific Mortality
- 3553 The Three Survivorship Curve Types
- 3555 Life History Strategy Shaped by Natural Selection
- 3557 Exponential Population Growth
- 3559 Logistic Growth and Carrying Capacity
- 3563 Density-Dependent Limiting Factors
- 3565 Density-Independent Limiting Factors
- 3569 Human Population Growth as a Case of the Same Models
- 3573 Tracing a Population from Exponential Onset Through Logistic Leveling, Worked worked example
- 3591 Community Interactions: Competition
- 3593 Predation and Herbivory
- 3595 Symbiosis: Mutualism, Commensalism, and Parasitism
- 3599 "Any Close Species Relationship Is Parasitic"
- 3601 Fitness Outcome, Not Closeness Alone, Classifies a Symbiosis
- 3605 Competitive Exclusion and the Ecological Niche
- 3607 Resource Partitioning
- 3609 Primary and Secondary Ecological Succession
- 3613 Pioneer Species and Facilitation
- 3615 Proximate versus Ultimate Causation in Behavior
- 3617 Interpreting a Population Change Through Community Interactions, Worked worked example
- 3619 Innate Behavior and Fixed Action Patterns
- 3621 Habituation
- 3623 Imprinting
- 3625 Classical Conditioning
- 3627 Operant Conditioning
- 3629 Foraging and Optimality
- 3631 Communication and Pheromones
- 3633 Mating Systems
- 3635 Eusociality and Kin Selection
- 3641 Trophic Levels and Food Chains
- 3645 Food Webs versus Food Chains
- 3649 Energy Flow and the Ten-Percent Rule
- 3653 "Ecosystems Recycle Their Energy the Way They Recycle Matter"
- 3655 Biogeochemical Cycling Applies to Matter, Not Energy
- 3659 The Carbon Cycle
- 3663 The Nitrogen Cycle
- 3667 The Phosphorus Cycle
- 3671 The Water Cycle
- 3675 Tracing Energy Loss and Nutrient Cycling Through a Food Chain, Worked worked example
- 3677 Keystone Species
- 3681 Defensive Adaptations and Mimicry
- 3685 Character Displacement
- 3689 Gross and Net Primary Productivity and Ecological Pyramids
- 3693 Eutrophication and Acid Rain as Nutrient-Cycle Disruptions
- 3701 Species Richness and Species Diversity
- 3705 Background Extinction Rate versus Mass Extinction
- 3709 How the IUCN Red List Classifies Extinction Risk
- 3713 How an Extinction-Risk Assessment Is Constructed
- 3717 Instrumental Value of Biodiversity
- 3721 Intrinsic Value of Biodiversity
- 3725 Applying Red List Criteria to Classify a Described Species, Worked worked example
- 3741 Habitat Loss and Fragmentation
- 3745 Invasive Species
- 3749 Overexploitation
- 3753 Climate Change as a Biodiversity Threat
- 3757 In Situ Conservation: Protected Areas
- 3761 Ex Situ Conservation: Captive Breeding and Seed Banks
- 3765 "An Extinct Species Can Be Fully Restored"
- 3767 De-Extinction Restores Genome, Not the Original Ecological Context
- 3771 Conservation Status Is a Reassessed Classification, Not a Fixed Fact
- 3775 "A Species' Conservation Status Never Changes Once Assigned"
- 3781 Applying Threat Categories and Conservation Strategy to a Described Case, Worked worked example
- 3891 Tracing a Species from Population Decline to Conservation Response, Worked Capstone review
Who this subject is for
- Students preparing for the CLEP Biology exam
- Nursing and allied health students
- Pre-med and life science majors
- Adult learners finishing a degree
- Homeschool students
- Anyone who wants a structured tour of the life sciences
Why Biology matters
Biology is the science of living things, and most health and life-science study builds on it. It is the foundation for:
- Anatomy and physiology
- Microbiology
- Genetics
- Nursing and allied health
- Ecology
Time to complete
- of lessons (1,133, measured)
- 8.1 h
- of lectures (55)
- 26.0 h
- learning hours on the certificate, with quizzes and the final
- 40 h
Times are measured from the recordings and the exam time limits. Go at your own pace; nothing expires.

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