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Learn Biology Online - Biology Articles, TutorialsDictionary OnlineMain Navigation Search Dictionary Articles Tutorials Biology Forum Learn Biology Online Biology Online is the world’s most comprehensive database of Biology terms and topics. Since 2001 it has been the resource of choice for professors, students, and professionals needing answers to Biology questions. Search over 75,000+ terms, news, insights, discoveries, and trends in Biology below: Featured Terms All Terms Search A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A Abiotic Active transport Adaptation Aerobic bacteria Alimentary canal Allele Allopatric speciation Amphipathic Anabolism Anaerobic Anaerobic respiration Analogous Analogous structures Anatomy Angiosperm Animal Animal cell Antagonistic Muscle Antigen Apoenzyme Asexual reproduction Assimilation Autocrine signaling Autotroph Axon hillock Axon terminal B Bacteria Balanced diet Base-pairing rule Benign Biennial Binary fission Binomial nomenclature Biodiversity Biological system Biology Biome Biosphere Biotic Biotic factor Biotic potential Biuret test Bivalent Body fluid Bolus injection Bone matrix Book lungs Botany Buck’s traction Budding C Carbon fixation Carrier protein Carrying capacity Cell Cell morphology Cell wall Cellular respiration Chemiosmosis Chloroplast Chordata Chromatin Chromosomal mutation Chromosome Class Codominance Codon Coenzyme Cohesion Commensalism Complete dominance Concentration gradient Condyloid joint Convergent evolution Convoluted coronavirus COVID-19 Cross-linking Cytokinesis Cytoplasm D Darwinian fitness Deciduous forest Decomposer Definitive host Dehydration reaction Demographic transition Dense irregular connective tissue Dense regular connective tissue Density dependent factor Density dependent limiting factor Deoxyribonucleic acid Desiccation Diaphoresis Diarthrodial joint Dichotomous Differentiation Diffusion Diploid Disruptive Selection Divergent evolution Dominant Dominant species E Ecological niche Ecosystem Ecosystem diversity Element Endemic Endocytosis Endomembrane system Endosymbiosis Endosymbiotic theory Energy coupling Environment Environmental resistance Epidermis Epistasis Equilibrium Eukaryote Eukaryotic cells Evolution Exon Exotic species Exudate F Facilitated diffusion Facultative anaerobe Family Family traits Fastidious Fecundity Feedback mechanism Female Fermentation Fibrinous exudate Fibrocartilage Filtration First-order kinetics Fitness Flaccid Flora Fluid mosaic model Focus Follicle-stimulating hormone Fragmentation Frameshift mutation Fundamental niche Fungi G Gamete Ganglia Gene Genetic diversity Genetic drift Genetic material Genetics Genome Genotype Genotypic ratio Genus Glucose Glycerol Glycogenolysis Glycolipid Glycolysis Golgi apparatus Graded potential Gram-positive bacilli Gram-positive cocci Group translocation Growth Guanine H Haploid Heredity Hermaphrodite Heterotroph Heterozygous Homeostasis Homo sapiens sapiens Homogenous Homologous Homologous chromosome Homologous structures Homozygous Host cell Hyaline cartilage Hydrophilic Hydrophobic Hyperosmotic Hypersensitivity Hypertonic Hypomelanism Hypothesis Hypotonic Hypotonic solution Hypotonicity I Immunoglobulin Imprinting In situ Incomplete dominance Incubation period Independent variable Individual Induced fit model Inoculation Inoculum Inorganic compound Intercalary meristem Intermediate host Interphase Interspecific competition Interstitial fluid Intracellular digestion Involuntary muscle Iodine test Ionic bond Isotonic J Jaundice Jaw Jaw jerk reflex Jellyfish Joint Joint capsule Joints of pelvic girdle Jugulo-omohyoid node Juice Juncturae cinguli membri superioris K Kcat Kd Kelp Kempner diet Keq Keratin Keratinocyte Kernel Ketose Ki Kidney Kidney calices Kilocalorie Kind Kinesis Kinetochore Kingdom Kingdom Animalia Kleptoparasitism Krebs cycle L Labia Lacuna Lanugo Law of Dominance Law of Independent Assortment Law of Segregation Lethal mutation Leukocytosis Life Ligase Light energy Limiting factor Lipid Lipolysis Longitudinal section Loose associations Loose connective tissue Lysis Lysosome M Matrix Median Medium Meiosis Memory cell Metabolism Metamerism Microbe Micromolecule Missense mutation Mitochondrion Mitosis Monosaccharide Morphology Multiple alleles Muscular system Mutagen Mutation Mutualism Mutualistic symbiosis Myocardium N Naked virus Natural selection Negative feedback Nematocyst Nephron Nerve impulse Net photosynthesis Net primary productivity Neutral mutation Non Random Mating Non-living thing Nondisjunction Nuclear envelope Nucleolus Nucleosome Nucleotide Nucleus Null hypothesis Nulliparity O Obligate aerobe Obligate anaerobe Obligate parasite Observation Okazaki fragment Oligosaccharide Omnivore Open circulatory system Opportunistic pathogen Opsonization Orbits Order Organelle Organic compound Organic matter Organic molecule Organism Organization Osmosis Osmotic Potential Osseous tissue Oxidation P Parenchyma Parthenogenesis Passive transport Peritoneum Phagocytosis Phenotype Phenotypic ratio Phosphodiester bond Phylum Physiological adaptation Pinocytosis Pioneer species Pleiotropy Polygenic inheritance Polypeptide Population Positive feedback Postulate Primary succession Process Progeny Prokaryote Protein synthesis Protist Punnett Square Pyruvate Q Quadrangular cartilage Quadrantanopia Quadrat Quantitative analysis Quantitative trait Quaternary structure Quellung phenomenon Quenching Quill Quinacrine banding Quinone R Race Radial symmetry Realized niche Recessive Redox reaction Reducing sugar Reduction Regulation Relative fitness Replication Reproduction Reservoir host Residue Respiration rate Resting potential Reticular connective tissue Revolution Rhizome Ribonucleic acid Ribosome S Saccharide Sarcolemma Secondary consumer Selectively-permeable membrane Semilunar valve Sex-linked trait Sexual reproduction Simple diffusion Simple squamous epithelium Single stranded DNA virus Skeletal system Smooth endoplasmic reticulum Smooth muscle Solute Solvent Species Starch Stimulus Structure Substrate Symbiosis Sympatric speciation Synergistic effect System T Tap water enema Taxis Taxon Taxonomy Telophase Telophase II Thalassophobia Theory Thermophile Thin filament Thymine Tissue Totipotent Traits Transcription (biology) Translation Tree Triploblastic Trophic level True breeding Turgidity Turgor pressure U Ultradian rhythm Unconditioned stimulus Undergrowth Undulating membrane Unicellular Uniform Unipennate muscle Uniport Unipotent cell Universal solvent Unmyelinated neuron Unsaturated fatty acid Unsustainability Uracil Urethra Urinary system Urine Uterine cycle Uterine involution V Vapor Variable Variation Vascular plants Vector Vegetable Vegetative reproduction Ventilation Vertical gene transfer Vesicle Vestibule Vestigial Viability Viable Virulence Viscera Viscous Vmax Voice quality Voluntary muscle W Wagners syndrome Walnut Waste management Wasted ventilation Water Water mold Water potential Water table Wavelength Waxes Weather Weed White adipose tissue White blood cell White line of toldt Wild type Wood Wood units Wuchereria bancrofti X X chromosome X linkage X-linked X-linked inheritance X-ray Xanthophyceae Xanthophyll Xanthophyte Xerophile Xerophthalmia Xerophyte Xxy syndrome Xylem Xylem fiber Xylem parenchyma Xylem vessel Y Y chromatin Y chromosome Y linkage Y-linked gene Y-linked inheritance Yac Yeast Yellow fever virus Yield Ym-shift Young-helmholtz theory of colour vision Youpon Z Z disc Zebra Zeitgeber Zinc Zonation Zone of inhibition Zooflagellate Zoogeography Zoology Zoomastigophora Zooplankton Zoospermia Zoospore Zwitterion Zygote Zygotene Zymogen Zymogen granules Featured Forum Topics See all Topics Explore our Forums and discover the living world. 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