Biology, REG-SEM
How do plants feed themselves? How did dogs evolve from wolves? What good is the appendix in humans, anyway? Such questions fall within the domain of biology, which seeks to understand living organisms and their vital processes (although the jury’s still out on what our appendixes are for). Biology’s diverse fields include botany, ecology, evolution, genetics, medicine, physiology, and zoology.
Biology Encyclopedia Articles By Title
regeneration, in biology, the process by which some organisms replace or restore lost or amputated body parts.......
relapsing fever, infectious disease characterized by recurring episodes of fever separated by periods of relative......
relaxin, in common usage, the two-chain peptide hormone H2 relaxin, which belongs to the relaxin peptide family......
REM sleep, one of two phases in the sleep cycle, in which a person experiences dreams, atonia (reduced muscle tone),......
renal artery, one of the pair of large blood vessels that branch off from the abdominal aorta (the abdominal portion......
renal capsule, thin membranous sheath that covers the outer surface of each kidney. The capsule is composed of......
renal corpuscle, filtration unit of vertebrate nephrons, functional units of the kidney. It consists of a knot......
renal lobe, region of the kidney consisting of the renal pyramid and the renal cortex. See renal...
renal pelvis, enlarged upper end of the ureter, the tube through which urine flows from the kidney to the urinary......
renal pyramid, any of the triangular sections of tissue that constitute the medulla, or inner substance, of the......
renal system, in humans, organ system that includes the kidneys, where urine is produced, and the ureters, bladder,......
- Introduction
- Vessels, Nerves, Function
- Ureters, Urinary Bladder, Kidneys
- Urine, Excretion, Bladder
- Urine, Kidneys, Excretion
- Blood Flow, Glomerulus, Nephron
- Tubule Function, Urine Formation, Excretion
- Urine Concentration, Kidneys, Excretion
- Acid-Base Balance, pH Regulation, Homeostasis
- Urine Collection, Emission
- Tests, Function, Kidney
- Hormones, Regulation, Function
renal system disease, any of the diseases or disorders that affect the human urinary system. They include benign......
renin-angiotensin system, physiological system that regulates blood pressure. Renin is an enzyme secreted into......
reovirus, any of a group of ribonucleic acid (RNA) viruses constituting the family Reoviridae, a small group of......
reproduction, process by which organisms replicate themselves. In a general sense reproduction is one of the most......
reproductive behaviour, any activity directed toward perpetuation of a species. The enormous range of animal reproductive......
- Introduction
- Hormones, Courtship, Mating
- Courtship, Mating, Parenting
- Protective Adaptations
- Group Care, Parental Investment, Social Structure
- Invertebrates, Mating, Courtship
- Mollusks, Courtship, Spawning
- Insects, Courtship, Mating
- Courtship, Mating, Parenting
- Courtship, Nesting, Mating
- Evolution, Animals, Mating
reproductive system disease, any of the diseases and disorders that affect the human reproductive system. They......
- Introduction
- Infertility, Endometriosis, PCOS
- Intersexuality, Hormones, Disorders
- Precocious Puberty, Hormone Imbalance, Endocrine Disorders
- Menorrhagia, Endometriosis, Uterine Fibroids
- Impotence, Infertility, Endocrine Disorders
- Syphilis, STD, Bacteria
- Genital Herpes, Symptoms, Treatment
- Genital Warts, HPV, Symptoms
- Trichomoniasis, Symptoms, Treatment
- Infections, Symptoms, Treatments
- Tumours, Diagnosis, Treatment
- Testicular Cancer
- Uterine Fibroids, Symptoms, Treatment
animal reproductive system, any of the organ systems by which animals reproduce. The role of reproduction is to......
- Introduction
- Sponges, Coelenterates, Flatworms
- Annelids, Mollusks, Reproduction
- Arthropods, Fertilization, Reproduction
- Fertilization, Gametes, Union
- Parthenogenesis, Reproduction, Fertilization
- Embryo Development, Fertilization, Nutrition
- Vertebrates, Fertilization, Reproduction
- Male Systems, Hormones, Reproductive Organs
- Accessory Glands, Fertilization, Reproduction
- Female Anatomy, Fertilization, Reproduction
- Tracts, Hormones, Fertilization
- Internal Fertilization, Adaptations, Reproduction
- Gonads, Hormone Cycles, Reproduction
human reproductive system, organ system by which humans reproduce and bear live offspring. Provided all organs......
respiratory disease, any of the diseases and disorders of the airways and the lungs that affect human respiration.......
- Introduction
- Immunity, Pathogens, Defense
- Morphology, Pathology, Diagnosis
- Asthma, COPD, Pneumonia
- Legionnaires, Bacteria, Symptoms
- Asthma, Symptoms, Treatment
- Bronchi, Acute, Symptoms
- Chronic Bronchitis, Symptoms, Treatment
- Lung Cancer, Symptoms, Treatment
- Occupational Lung, Prevention, Treatment
- Industrial Chemicals, Toxicity, Symptoms
- Circulation, Symptoms, Treatment
respiratory distress syndrome of newborns, a common complication in infants, especially in premature newborns,......
respiratory system, the system in living organisms that takes up oxygen and discharges carbon dioxide in order......
human respiratory system, the system in humans that takes up oxygen and expels carbon dioxide. The human gas-exchanging......
- Introduction
- Pharynx, Airways, Lungs
- Trachea, Stem Bronchi
- Lungs, Airways, Oxygen
- Blood Vessels, Lymphatic Vessels, Nerves
- Control, Lungs, Airway
- Chemoreceptors, Lungs, Airways
- Lung Receptors, Muscle Receptors, Ventilation
- Mechanics, Lungs, Airways
- Lungs, Airways, Oxygen
- Oxygen Transport, Lungs, Airways
- Gas Exchange, Lungs, Airways
- Abnormal Gas Exchange
- Circulation, Metabolism, Oxygen
- Adaptations, Lungs, Airways
- Swimming, Diving, Lungs
resting potential, the imbalance of electrical charge that exists between the interior of electrically excitable......
reticular fibre, in anatomy, fine fibrous connective tissue occurring in networks to make up the supporting tissue......
reticulocyte, non-nucleated stage in the development of the red blood cell, just before full maturity is reached.......
retina, layer of nervous tissue that covers the inside of the back two-thirds of the eyeball, in which stimulation......
retinitis pigmentosa, group of hereditary eye diseases in which progressive degeneration of the retina leads to......
retinopathy of prematurity, disease in which retinal blood vessels develop abnormally in the eyes of premature......
retrovirus, any of a group of viruses that belong to the family Retroviridae and that characteristically carry......
Rett syndrome, rare progressive neurological disorder characterized by severe intellectual disability, autism-like......
Reye syndrome, acute neurologic disease that develops primarily in children following influenza, chicken pox, or......
Rh blood group system, system for classifying blood groups according to the presence or absence of the Rh antigen,......
rhabdovirus, any of a group of viruses constituting the family Rhabdoviridae, responsible for rabies and vesicular......
rheumatic fever, inflammatory disease of the heart, joints, central nervous system, and subcutaneous tissues that......
rheumatism, any of several disorders that have in common inflammation of the connective tissues, especially the......
rheumatoid arthritis, chronic, frequently progressive disease in which inflammatory changes occur throughout the......
rhinitis, generic term for inflammation of the mucous tissue of the nose. Rhinitis may be allergic in origin and......
rhinophyma, extensive overgrowth of the lower part of the nose. The sebaceous (oil-producing) glands seem to be......
rhinovirus, a group of viruses capable of causing common colds in human adults and children. They belong to the......
rhizopod, any member of the protozoan superclass Rhizopoda. Three types of pseudopodia (cytoplasmic extensions)......
Rhizopus, cosmopolitan genus of some 10 species of filamentous fungi in the family Rhizopodaceae (formerly Mucoraceae),......
rib, any of several pairs of narrow, curved strips of bone (sometimes cartilage) attached dorsally to the vertebrae......
ribose, five-carbon sugar found in RNA (ribonucleic acid), where it alternates with phosphate groups to form the......
ribosomal RNA (rRNA), molecule in cells that forms part of the protein-synthesizing organelle known as a ribosome......
ribosome, particle that is present in large numbers in all living cells and serves as the site of protein synthesis.......
rice bacterial blight, deadly bacterial disease that is among the most destructive afflictions of cultivated rice......
rickets, disease of infancy and childhood characterized by softening of the bones, leading to abnormal bone growth......
rickettsia, (family Rickettsiaceae), family of bacteria, made up of two genera, Rickettsia and Orientia. The term......
rigor mortis, physiological process that occurs within hours after death, wherein muscle tissue stiffens. Rigor......
Riley-Day syndrome, an inherited disorder occurring almost exclusively in Ashkenazic Jews that is caused by abnormal......
rinderpest, an acute, highly contagious viral disease of ruminant animals, primarily cattle, that was once common......
Ringer’s solution, one of the first laboratory solutions of salts in water shown to prolong greatly the survival......
ringworm, superficial skin lesions caused by a highly specialized group of fungi called dermatophytes that live......
RNA, complex compound of high molecular weight that functions in cellular protein synthesis and replaces DNA (deoxyribonucleic......
rockweed, common name for various species of brown algae growing attached to intertidal rocks. See Fucus;...
Rocky Mountain spotted fever, form of tick-borne typhus first described in the Rocky Mountain section of the United......
roseola infantum, infectious disease of early childhood marked by rapidly developing high fever (to 106° F) lasting......
rot, any of several plant diseases, caused by any of hundreds of species of soil-borne bacteria, fungi, and funguslike......
rotational stress, physiological changes that occur in the body when it is subjected to intense gyrational or centrifugal......
rotavirus, any of a group of viruses in the family Reoviridae that are known as the leading cause of severe diarrhea......
rough endoplasmic reticulum (RER), series of connected flattened sacs, part of a continuous membrane organelle......
royal jelly, thick, white, nutritious substance fed to bee larvae. Secreted from glands in the heads of worker......
rubella, contagious viral disease that runs a mild and benign course in most people. Although rubella is not usually......
runaway selection hypothesis, in biology, an explanation first proposed by English statistician R.A. Fisher in......
rust, plant disease caused by more than 7,000 species of fungi of the phylum Basidiomycota. Rust affects many economically......
saccade, fast, intermittent eye movement that redirects gaze. Saccades may involve the eyes alone or, more commonly,......
Saccharomyces, genus of yeasts belonging to the family Saccharomycetaceae (phylum Ascomycota, kingdom Fungi). An......
Salmonella, (genus Salmonella), group of rod-shaped, gram-negative, facultatively anaerobic bacteria in the family......
salmonellosis, any of several bacterial infections caused by certain species of Salmonella, important as the cause......
sarcodine, any protozoan of the superclass (sometimes class or subphylum) Sarcodina. These organisms have streaming......
sarcoidosis, systemic disease that is characterized by the formation of granulomas (small grainy lumps) in affected......
sarcoma, tumour of connective tissue (tissue that is formed from mesodermal, or mesenchymal, cells). Sarcomas are......
SARS, highly contagious respiratory illness characterized by a persistent fever, headache, and bodily discomfort,......
sartorius muscle, (from the Latin sartor, “mender”), long, narrow, ribbonlike thigh muscle beginning at the front......
scab, in botany, any of several bacterial or fungal plant diseases characterized by crustaceous lesions on fruits,......
scabies, skin inflammation accompanied by severe itching, particularly at night, caused by the itch mite (Sarcoptes......
scale, in zoology, small plate or shield forming part of the outer skin layers of certain animals. Scales provide......
Scenedesmus, genus of about 70 species of colonial green algae (family Scenedesmaceae), a common component of freshwater......
schistosomiasis, group of chronic disorders caused by small parasitic flatworms (family Schistosomatidae) commonly......
schizophrenia, any of a group of severe mental disorders that have in common symptoms such as hallucinations, delusions,......
scleritis, inflammation of the sclera, the white part of the eye. The inflammation is immune-mediated and is commonly......
scleroderma, a chronic disease of the skin that also can affect the blood vessels and various internal organs.......
sclerotium, a persistent, vegetative, resting spore of certain fungi (e.g., Botrytis, Sclerotium). It consists......
scorch, symptom of plant disease in which tissue is “burned” because of unfavourable conditions or infection by......
scrapie, fatal neurodegenerative disease of sheep and goats. Scrapie has been endemic in British sheep, particularly......
scrotum, in the male reproductive system, a thin external sac of skin that is divided into two compartments; each......
sea lettuce, (genus Ulva), genus of green algae (family Ulvaceae) usually found growing on rocky shores of seas......
seaweed, any of the red, green, or brown marine algae that grow along seashores. Seaweeds are generally anchored......
secretion, in biology, production and release of a useful substance by a gland or cell; also, the substance produced.......
secretor system, phenotype based on the presence of soluble antigens on the surfaces of red blood cells and in......
seed, the characteristic reproductive body of both angiosperms (flowering plants) and gymnosperms (e.g., conifers,......
- Introduction
- Gymnosperm, Embryo, Structure
- Size, Predation, Protection
- Animal Dispersal, Germination, Fruits
- Wind Dispersal, Pollination, Germination
- Water Dispersal, Germination, Viability
- Germination, Embryo, Plant Growth
- Afterripening, Stratification, Temperature
- Photosynthesis, Germination, Dispersal
seed dispersal, in botany, the movement or spread of seeds away from the parent plant. Given that seeds are essentially......
segmentation, in zoology, the condition of being constructed of a linear series of repeating parts, each being......
selection, in biology, the preferential survival and reproduction or preferential elimination of individuals with......
selection coefficient, in genetics, a measure of the relative reduction in the contribution that a particular genotype......
self-fertilization, fusion of male and female gametes (sex cells) produced by the same individual. Self-fertilization......
semen, fluid that is emitted from the male reproductive tract and that contains sperm cells, which are capable......
semilunar valve, either of two pocketlike half-moon-shaped structures located between the left ventricle and the......
seminal vesicle, either of two elongated saclike glands that secrete their fluid contents into the ejaculatory......
