COMPLETE BIOLOGY COURSE

Ninety-six ways into
the living world.

Begin with the easiest biological foundations, then rise through mechanisms, system-level reasoning and advanced integration.

96 units760 lessons4,200 challenges
1
FOUNDATIONLevel 1 Biology
2
MECHANISMLevel 2 Biology
3
SYSTEMSLevel 3 Biology
4
ADVANCEDLevel 4 Biology

COURSE CATALOG

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96 units
LEVEL 1 · UNIT 01

Characteristics and classification of living organisms

Covers the shared characteristics of life, species and scientific naming, construction and use of dichotomous keys, the diagnostic features of major groups, and the use of evolutionary and DNA evidence in classification.

5 lessons28 min
LEVEL 1 · UNIT 02

Organisation of the organism

Covers plant, animal, and bacterial cell structures and functions; specialised cells; levels of organisation; biological drawing; and magnification with millimetre-micrometre conversion.

5 lessons28 min
LEVEL 1 · UNIT 03

Movement into and out of cells

Covers diffusion, osmosis, active transport, concentration gradients, exchange surfaces, and investigations with plant tissue.

5 lessons28 min
LEVEL 1 · UNIT 04

Biological molecules

Covers the elemental composition and building blocks of carbohydrates, fats, proteins, and DNA; roles of water; and the standard food tests.

5 lessons28 min
LEVEL 1 · UNIT 05

Enzymes

Covers enzymes as biological catalysts, active-site specificity, effects of temperature and pH, and rate investigations.

5 lessons28 min
LEVEL 1 · UNIT 06

Plant nutrition

Covers photosynthesis, limiting factors, mineral nutrition, leaf structure, and standard investigations.

5 lessons28 min
LEVEL 1 · UNIT 07

Human nutrition

Covers balanced diet, alimentary-canal structure, physical and chemical digestion, digestive enzymes, absorption, assimilation, and egestion.

5 lessons28 min
LEVEL 1 · UNIT 08

Transport in plants

Covers xylem and phloem distribution and function, root water uptake, the transpiration stream, water-loss factors, and translocation between resources and sinks.

5 lessons28 min
LEVEL 1 · UNIT 09

Transport in animals

Covers the circulatory system, heart, blood vessels, blood components, lymph, and coronary heart disease.

5 lessons28 min
LEVEL 1 · UNIT 10

Diseases and immunity

Covers pathogens, transmissible disease, transmission control, body barriers, immune responses, vaccination, cholera, HIV, and public-health reasoning.

5 lessons28 min
LEVEL 1 · UNIT 11

Gas exchange in humans

Covers airway anatomy, alveolar exchange, ventilation mechanics, exercise effects, inspired-expired air, and airway protection.

5 lessons28 min
LEVEL 1 · UNIT 12

Respiration

Covers cellular respiration, uses of released energy, aerobic and anaerobic word and symbol equations, lactate and oxygen debt, and rate investigations.

5 lessons28 min
LEVEL 1 · UNIT 13

Excretion in humans

Covers metabolic waste, carbon dioxide and urea formation, urinary-system anatomy, kidney filtration and selective reabsorption, urine composition, and dialysis.

5 lessons28 min
LEVEL 1 · UNIT 14

Coordination and response

Covers nervous and hormonal coordination, reflexes and synapses, the eye, blood-glucose and temperature homeostasis, and plant tropisms with auxin.

5 lessons28 min
LEVEL 1 · UNIT 15

Drugs

For the 2026-2028 syllabus this focused topic defines drugs and covers antibiotics, bacterial resistance, and responsible antibiotic use.

5 lessons28 min
LEVEL 1 · UNIT 16

Reproduction

Covers asexual and sexual reproduction, flowering-plant reproduction, human reproductive anatomy and development, sex hormones, menstrual control, and sexually transmitted infections.

5 lessons28 min
LEVEL 1 · UNIT 17

Inheritance

Covers DNA, genes, alleles, proteins, sex determination, mitosis and meiosis, haploid and diploid nuclei, and genetic diagrams for monohybrid, test, codominant, and sex-linked crosses.

5 lessons28 min
LEVEL 1 · UNIT 18

Variation and selection

Covers continuous and discontinuous variation, mutation, adaptive features, natural selection, selective breeding, resistance, and hydrophyte/xerophyte adaptations.

5 lessons28 min
LEVEL 1 · UNIT 19

Organisms and their environment

Covers energy flow, food chains and webs, trophic levels, ecological pyramids, nutrient cycles, populations, communities, ecosystems, and sigmoid growth.

5 lessons28 min
LEVEL 1 · UNIT 20

Human influences on ecosystems

Covers food production, habitat loss, pollution, eutrophication, greenhouse gases and climate change, sustainable resource use, endangered species, and conservation.

5 lessons28 min
LEVEL 1 · UNIT 21

Biotechnology and genetic modification

Covers useful microorganisms, yeast and enzyme applications, fermenters, genetic modification, recombinant plasmids, and benefits and risks of modified organisms.

5 lessons28 min
LEVEL 2 · UNIT 01

Cell structure

Covers light- and electron-microscope evidence, calibration and scale, eukaryotic and prokaryotic ultrastructure, specialised cells, and virus structure.

5 lessons28 min
LEVEL 2 · UNIT 02

Biological molecules

Covers water, monosaccharides, disaccharides, polysaccharides, lipids, amino acids, proteins, structure-function relationships, and biochemical tests.

5 lessons28 min
LEVEL 2 · UNIT 03

Enzymes

Covers activation energy, active-site models, collision and kinetic reasoning, rate measurement, temperature, pH, enzyme and substrate concentration, competitive and non-competitive inhibition, and immobilised enzymes.

5 lessons28 min
LEVEL 2 · UNIT 04

Cell membranes and transport

Covers phospholipid bilayers, membrane proteins, cholesterol and carbohydrates, cell signalling, diffusion, osmosis, facilitated diffusion, active transport, co-transport, endocytosis, and exocytosis.

5 lessons28 min
LEVEL 2 · UNIT 05

The mitotic cell cycle

Covers chromosome structure, DNA replication within interphase, mitosis, cytokinesis, cell-cycle significance, telomeres, stem cells, and cancer.

5 lessons28 min
LEVEL 2 · UNIT 06

Nucleic acids and protein synthesis

Covers nucleotide structure, DNA and RNA, semi-conservative replication, the genetic code, transcription, RNA processing at the required depth, translation, and gene mutation.

5 lessons28 min
LEVEL 2 · UNIT 07

Transport in plants

Covers vascular-tissue distribution, xylem structure, apoplast and symplast water movement, transpiration and stomatal control, cohesion-tension, phloem structure, and translocation by mass flow.

5 lessons28 min
LEVEL 2 · UNIT 08

Transport in mammals

Covers closed double circulation, heart and vessel structure, the cardiac cycle, tissue fluid, blood components, haemoglobin and oxygen dissociation, carbon dioxide transport, and fetal haemoglobin where required.

5 lessons28 min
LEVEL 2 · UNIT 09

Gas exchange

Covers mammalian gas-exchange surface histology, ventilation, gradient maintenance, and interpretation of respiratory-disease evidence within the current syllabus boundary.

5 lessons28 min
LEVEL 2 · UNIT 10

Infectious diseases

Covers pathogen classes, transmission, prevention, named disease mechanisms and control specified by the examination-year syllabus, antibiotics, and resistance.

5 lessons28 min
LEVEL 2 · UNIT 11

Immunity

Covers phagocytes, lymphocytes, antigens, clonal selection, antibody structure and action, primary and secondary responses, active and passive immunity, vaccination, autoimmune ideas where specified, and monoclonal antibodies.

5 lessons28 min
LEVEL 3 · UNIT 01

Energy and respiration

Covers ATP, redox and coenzymes, glycolysis, link reaction, Krebs cycle, oxidative phosphorylation and chemiosmosis, anaerobic pathways, respiratory substrates, respiratory quotient, and respirometry.

5 lessons28 min
LEVEL 3 · UNIT 02

Photosynthesis

Covers chloroplast structure, photosynthetic pigments, absorption and action spectra, light-dependent reactions, photophosphorylation, chemiosmosis, Calvin cycle, limiting factors, crop productivity, and adaptations of C4 plants where specified.

5 lessons28 min
LEVEL 3 · UNIT 03

Homeostasis

Covers homeostatic control systems, mammalian thermoregulation, kidney osmoregulation, ADH, blood-glucose control by insulin and glucagon, diabetes, and stomatal responses as plant homeostasis where specified.

5 lessons28 min
LEVEL 3 · UNIT 04

Control and coordination

Covers sensory neurones, resting and action potentials, saltatory conduction, synapses, neuromuscular junctions, skeletal-muscle contraction, endocrine coordination, and plant responses specified by the current syllabus.

5 lessons28 min
LEVEL 3 · UNIT 05

Inheritance

Covers meiosis, genetic variation, monohybrid and dihybrid crosses, codominance, multiple alleles, sex linkage, autosomal linkage, crossing over, epistasis where specified, test crosses, pedigrees, chi-squared testing, mutation, and gene control in prokaryotes and eukaryotes.

5 lessons28 min
LEVEL 3 · UNIT 06

Selection and evolution

Covers resources of variation, natural and artificial selection, antibiotic resistance, directional, stabilising and disruptive selection, evolution, genetic drift where specified, speciation, molecular evidence, and extinction.

5 lessons28 min
LEVEL 3 · UNIT 07

Classification, biodiversity and conservation

Covers taxonomy and domains, phylogeny, molecular classification, species and ecosystem biodiversity, sampling design, Simpson's index, mark-release-recapture, correlation and selected statistics, threats, conservation methods, and international or local strategies.

5 lessons28 min
LEVEL 3 · UNIT 08

Genetic technology

Covers recombinant DNA, restriction enzymes and ligase, vectors and markers, PCR, gel electrophoresis, DNA profiling, sequencing, microarrays and bioinformatics where specified, medical and agricultural applications, gene therapy, and ethical evaluation.

5 lessons28 min
LEVEL 4 · UNIT 01

Evolution, the Themes of Biology, and Scientific Inquiry

This is the gold-standard expansion of Level 4 unit, Evolution, the Themes of Biology, and Scientific Inquiry. It turns the unit's organizing ideas into an original, resource-backed course of study. The course remains the primary reading; this deep dive supplies explanation, reasoning practice, evidence analysis, and modern research connections.

10 lessons70 min
LEVEL 4 · UNIT 02

The Chemical Context of Life

This is the deep expansion of Level 4 unit, The Chemical Context of Life. It connects introductory atomic and bonding models to quantitative chemistry, biological mechanisms, experimental evidence, and modern research.

10 lessons70 min
LEVEL 4 · UNIT 03

Water and Life

This is the deep expansion of Level 4 unit, Water and Life. It connects molecular polarity to hydrogen-bond networks, organismal physiology, solution chemistry, environmental change, quantitative reasoning, and primary evidence.

10 lessons70 min
LEVEL 4 · UNIT 04

Carbon and the Molecular Diversity of Life

This is the deep expansion of Level 4 unit, Carbon and the Molecular Diversity of Life. It follows carbon from prebiotic synthesis through molecular geometry, isomerism, functional groups, chemical reactivity, biological recognition, and ATP-coupled work.

10 lessons70 min
LEVEL 4 · UNIT 05

The Structure and Function of Large Biological Molecules

This is the deep expansion of Level 4 unit, The Structure and Function of Large Biological Molecules. It connects covalent assembly to molecular sequence, three-dimensional structure, biological function, experimental evidence, genomic scale, and evolutionary comparison.

10 lessons70 min
LEVEL 4 · UNIT 06

A Tour of the Cell

This is the deep expansion of Level 4 unit, A Tour of the Cell. It treats the cell as a measured, dynamic, compartmentalized system whose structures are inferred through microscopy, biochemical separation, molecular perturbation, and quantitative modeling.

10 lessons70 min
LEVEL 4 · UNIT 07

Membrane Structure and Function

This is the deep expansion of Level 4 unit, Membrane Structure and Function. It treats membranes as dynamic physical systems whose composition, topology, transport pathways, energy coupling, and vesicle traffic can be measured and tested.

10 lessons70 min
LEVEL 4 · UNIT 08

An Introduction to Metabolism

This is the deep expansion of Level 4 unit, An Introduction to Metabolism. It treats metabolism as a measurable network governed simultaneously by conservation, thermodynamic direction, kinetic barriers, energy coupling, enzyme mechanism, spatial organization, and feedback control.

10 lessons70 min
LEVEL 4 · UNIT 09

Cellular Respiration and Fermentation

This is the deep expansion of Level 4 unit, Cellular Respiration and Fermentation. It follows carbon atoms, electrons, protons, ATP equivalents, compartments, and regulatory signals from fuel entry through glycolysis, pyruvate oxidation, the citric acid cycle, respiratory electron transport, ATP synthase, fermentation, and metabolic integration.

10 lessons70 min
LEVEL 4 · UNIT 10

Photosynthesis

This is the deep expansion of Level 4 unit, Photosynthesis. It follows photons, excitation, electrons, protons, ATP, NADPH, carbon atoms, gases, compartments, and regulatory tradeoffs from light interception through the thylakoid reactions, Calvin cycle, photorespiration, C4 and CAM carbon concentration, biosynthesis, whole-plant integration, and planetary consequences.

10 lessons70 min
LEVEL 4 · UNIT 11

Cell Communication

This advanced study deep dive reconstructs Level 4 unit as a causal, quantitative, and experimental system. It covers the complete course unit span, pages 212-233, while keeping every claim tied to a compartment, measurement, perturbation, and interpretation boundary.

10 lessons70 min
LEVEL 4 · UNIT 12

The Cell Cycle

This advanced deep dive reconstructs Level 4 unit as a timed, mechanical, quantitative, and experimentally testable system. It covers course pages 234-252 and all three concepts while separating chromosome count from DNA content, phase accumulation from transition mechanism, and cultured-cell results from organismal or clinical claims.

10 lessons70 min
LEVEL 4 · UNIT 13

Meiosis and Sexual Life Cycles

This advanced deep dive reconstructs Level 4 unit as a chromosome-accounting, life-cycle, mechanical, quantitative, and evolutionary system. It covers course pages 254-268 and all four concepts while separating ploidy from DNA content, homologs from sisters, nuclear products from functional gametes, and the origin of variants from their meiotic reshuffling and later selection.

10 lessons70 min
LEVEL 4 · UNIT 14

Mendel and the Gene Idea

This advanced deep dive reconstructs Level 4 unit as an experimental, probabilistic, molecular, clinical, and ethical system. It covers course pages 269-293 and all four concepts while separating allele transmission from phenotype mapping, a probability from a realized family, dominance from fitness, and screening from diagnosis.

10 lessons70 min
LEVEL 4 · UNIT 15

The Chromosomal Basis of Inheritance

This advanced deep dive reconstructs Level 4 unit as a chromosome-state, crossing, mapping, cytogenetic, epigenetic, and extranuclear inheritance system. It covers course pages 294-313 and all five concepts while separating physical linkage from sex linkage, recombination fraction from physical distance, constitutional from somatic alterations, and imprinting from organelle inheritance.

10 lessons70 min
LEVEL 4 · UNIT 16

The Molecular Basis of Inheritance

This advanced deep dive reconstructs Level 4 unit as an information-storage, molecular-structure, replication, repair, chromosome-end, and chromatin-organization system. It covers course pages 314-334 and all three concepts while separating observation from inference, parental strands from parental molecules, DNA damage from fixed mutation, and chromatin packing models from direct measurements.

10 lessons70 min
LEVEL 4 · UNIT 17

Gene Expression: From Gene to Protein

This advanced deep dive reconstructs Level 4 unit as an oriented information-conversion system. It covers course pages 335-364 and all five concepts while separating transcription from translation, template from coding strand, primary from mature RNA, codon from anticodon, tRNA charging from ribosomal energy use, sequence change from molecular consequence, and intended editing from verified function.

10 lessons70 min
LEVEL 4 · UNIT 18

Regulation of Gene Expression

This advanced deep dive reconstructs Level 4 unit as a multiscale control system. It covers course pages 365-397 and all five concepts while separating DNA sequence from chromatin state, regulator binding from productive expression, transcription from RNA and protein turnover, determination from differentiation, and cancer predisposition from deterministic disease.

10 lessons70 min
LEVEL 4 · UNIT 19

Viruses

This advanced deep dive reconstructs Level 4 unit as a host-dependent information and transmission system. It covers course pages 398-414 and all three concepts while separating genome copies from particles and infectious units, attachment from entry, entry from productive infection, lytic growth from lysogeny and latency, mutation from reassortment, outbreak detection from viral origin, and protein requirement from a complete prion mechanism.

10 lessons70 min
LEVEL 4 · UNIT 20

DNA Tools and Biotechnology

This advanced deep dive reconstructs Level 4 unit as a measurement-to-intervention pipeline. It covers course pages 415-441 and all four concepts while separating sequence signal from base call, physical DNA from cloned cells, amplification from quantification, expression from function, an edit from its repair outcome, nuclear-genome identity from phenotype, analytical validity from clinical utility, and technical feasibility from ethical authorization.

10 lessons70 min
LEVEL 4 · UNIT 21

Genomes and Their Evolution

This advanced deep dive reconstructs Level 4 unit as a sequence-to-history inference pipeline. It covers course pages 442-466 and all six concepts while separating reads from assemblies, annotation from function, genome size from complexity, repetition from activity, duplication from innovation, similarity from homology, lineage specificity from adaptation, and a comparative association from a causal developmental mechanism.

10 lessons70 min
LEVEL 4 · UNIT 22

Descent with Modification: A Darwinian View of Life

This advanced deep dive reconstructs Level 4 unit as a pattern-to-process evidence system. It covers course pages 468-485 and all three concepts while separating evolution as an observed pattern from natural selection as a mechanism, development from population change, usefulness from adaptation, survival from reproductive success, homology from analogy, a tree from a ladder, historical inference from speculation, and scientific theory from an unsupported guess.

10 lessons70 min
LEVEL 4 · UNIT 23

The Evolution of Populations

This advanced deep dive reconstructs Level 4 unit as a population-genetic accounting system. It connects the origin and reshuffling of variation to allele counting, Hardy-Weinberg expectations, selection, drift, founder events, bottlenecks, gene flow, relative fitness, sexual selection, balancing selection, and the constraints that prevent perfect adaptation.

10 lessons70 min
LEVEL 4 · UNIT 24

The Origin of Species

This advanced deep dive reconstructs Level 4 unit as a gene-flow and reproductive-barrier evidence system. It covers species concepts, prezygotic and postzygotic isolation, allopatric and sympatric routes, polyploidy, ecological and sexual divergence, hybrid-zone dynamics, reinforcement, fusion, stability, speciation tempo, and the genetics of reproductive isolation.

10 lessons70 min
LEVEL 4 · UNIT 25

The History of Life on Earth

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 26

Phylogeny and the Tree of Life

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 27

Bacteria and Archaea

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 28

Protists

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 29

Plant Diversity I: How Plants Colonized Land

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 30

Plant Diversity II: The Evolution of Seed Plants

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 31

Fungi

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 32

An Overview of Animal Diversity

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 33

An Introduction to Invertebrates

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 34

The Origin and Evolution of Vertebrates

This is an original study artifact: no course prose, figures, answer keys, or PDF content is reproduced. Page numbers are navigation markers. Questions, answers, calculations, diagrams in words, and explanations were independently written. The assessment bank contains original prompts, not course questions or an answer-key reconstruction.

10 lessons70 min
LEVEL 4 · UNIT 35

Vascular Plant Structure, Growth, and Development

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers; all explanations, prompts, diagrams in words, calculations, and solutions were independently written.

10 lessons70 min
LEVEL 4 · UNIT 36

Resource Acquisition and Transport in Vascular Plants

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers; all explanations, prompts, diagrams in words, calculations, and solutions were independently written.

10 lessons70 min
LEVEL 4 · UNIT 37

Soil and Plant Nutrition

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers; all explanations, prompts, diagrams in words, calculations, and solutions were independently written.## Purpose

10 lessons70 min
LEVEL 4 · UNIT 38

Angiosperm Reproduction and Biotechnology

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers; all explanations, prompts, diagrams in words, calculations, and solutions were independently written.## Purpose

10 lessons70 min
LEVEL 4 · UNIT 39

Plant Responses to Internal and External Signals

An original, evidence-bounded learning system for plant sensing, signaling, development, stress physiology, and defense.

10 lessons70 min
LEVEL 4 · UNIT 40

Basic Principles of Animal Form and Function

A advanced learning system for animal structure, homeostasis, thermoregulation, and bioenergetics.

10 lessons70 min
LEVEL 4 · UNIT 41

Animal Nutrition

A advanced learning system for animal nutrition, digestion, absorption, dietary adaptation, microbiomes, fuel regulation, and appetite.

10 lessons70 min
LEVEL 4 · UNIT 42

Circulation and Gas Exchange

A advanced learning system for circulation, blood, respiratory surfaces, ventilation, gas transport, quantitative physiology, and evidence reasoning.

10 lessons70 min
LEVEL 4 · UNIT 43

The Immune System

A advanced learning system for innate recognition, adaptive specificity, immune effector routes, memory, disruption, quantitative reasoning, and evidence.

10 lessons70 min
LEVEL 4 · UNIT 44

Osmoregulation and Excretion

A advanced learning system for osmotic strategy, nitrogen disposal, excretory architectures, nephron transport, countercurrent gradients, endocrine control, quantitative reasoning, and evidence.

10 lessons70 min
LEVEL 4 · UNIT 45

Hormones and the Endocrine System

A advanced learning system for hormone signaling, receptor logic, feedback, neuroendocrine architecture, endocrine glands, rhythms, development, evolution, quantitative reasoning, and evidence.

10 lessons70 min
LEVEL 4 · UNIT 46

Animal Reproduction

A advanced learning system for reproductive modes, fertilization, anatomy, gametogenesis, endocrine cycles, pregnancy, birth, reproductive technology, quantitative reasoning, ethics, and evidence.

10 lessons70 min
LEVEL 4 · UNIT 47

Animal Development

This original learning layer turns Level 4 unit into a advanced map of fertilization, cleavage, morphogenesis, cell fate, and evidence. It is written for Level 3 Biology through advanced study while keeping the first assessment tier genuinely accessible.

10 lessons70 min
LEVEL 4 · UNIT 48

Neurons, Synapses, and Signaling

This original learning layer turns Level 4 unit into a advanced map of neuronal structure, membrane voltage, action potentials, axonal conduction, synapses, integration, transmitters, and evidence. It is written for Level 3 Biology through advanced study while keeping the first assessment tier genuinely accessible.

10 lessons70 min
LEVEL 4 · UNIT 49

Nervous Systems

This original learning layer turns Level 4 unit into a advanced map of nervous-system organization, vertebrate brain specialization, cortical processing, plasticity, memory, and disorder evidence. It is written for Level 3 Biology through advanced study while keeping the first assessment tier genuinely accessible.

10 lessons70 min
LEVEL 4 · UNIT 50

Sensory and Motor Mechanisms

This original learning layer turns Level 4 unit into a advanced map of sensory reception, hearing, equilibrium, vision, taste, smell, muscle contraction, skeletal mechanics, and locomotion. It is written for Level 3 Biology through advanced study while keeping the first assessment tier genuinely accessible.

10 lessons70 min
LEVEL 4 · UNIT 51

Animal Behavior

This original learning layer turns Level 4 unit into a advanced map of behavioral mechanism, development, learning, ecology, evolution, and social interaction. It is designed for Level 3 Biology through advanced study while keeping the first assessment tier genuinely accessible.

10 lessons70 min
LEVEL 4 · UNIT 52

An Introduction to Ecology and the Biosphere

This original learning layer turns Level 4 unit into a advanced map of ecological scale, climate, terrestrial and aquatic biomes, distribution limits, and eco-evolutionary feedback. It supports Level 3 Biology through advanced study while keeping the first assessment tier genuinely accessible.

10 lessons70 min
LEVEL 4 · UNIT 53

Population Ecology

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers only. Explanations, models, datasets, questions, calculations, and answers were independently written. Unless a primary study is explicitly cited, numerical datasets are fictional teaching data.

10 lessons70 min
LEVEL 4 · UNIT 54

Community Ecology

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers only. Explanations, models, datasets, questions, calculations, and answers were independently written. Unless a primary study is explicitly cited, numerical datasets are fictional teaching data.

10 lessons70 min
LEVEL 4 · UNIT 55

Ecosystems and Restoration Ecology

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers only. Explanations, models, datasets, questions, calculations, and answers were independently written. Unless a primary study is explicitly cited, numerical datasets are fictional teaching data.

10 lessons70 min
LEVEL 4 · UNIT 56

Conservation Biology and Global Change

This is an original study artifact with no course prose, figures, answer keys, or PDF content. Its assessment prompts are not course questions or an answer-key reconstruction. Page numbers are navigation markers only. Explanations, models, datasets, questions, calculations, and answers were independently written. Unless a primary study is explicitly cited, numerical datasets are fictional teaching data.

10 lessons70 min