Biology, GRO-ILE

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.
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Biology Encyclopedia Articles By Title

ground substance
ground substance, an amorphous gel-like substance present in the composition of the various connective tissues.......
group selection
group selection, in biology, a type of natural selection that acts collectively on all members of a given group.......
growth curve
growth curve, in biology, a curve in graph form that shows the change in the number of cells (or single-celled......
growth medium
growth medium, solution freed of all microorganisms by sterilization (usually in an autoclave, where it undergoes......
guinea worm disease
guinea worm disease, infection in humans caused by a parasite known as the guinea worm (Dracunculus medinensis).......
Gulf War syndrome
Gulf War syndrome, cluster of illnesses in veterans of the Persian Gulf War (1990–91). Gulf War syndrome is characterized......
Gymnodinium
Gymnodinium, genus of marine or freshwater dinoflagellate algae (family Gymnodiniaceae). Like all dinoflagellates,......
gymnostome
gymnostome, any ciliated protozoan of the large holotrichous order Gymnostomatida; included are oval to elongated......
Haemophilus
Haemophilus, genus of bacteria that, though often coccobacillus, vary widely in shape in the family Pasteurellaceae.......
hair
hair, in mammals, the characteristic threadlike outgrowths of the outer layer of the skin (epidermis) that form......
hairball
hairball, gastrointestinal obstruction occurring in cats and resulting from accumulation of swallowed hair; the......
hallucination
hallucination, the experience of perceiving objects or events that do not have an external source, such as hearing......
hamartoma
hamartoma, benign tumourlike growth made up of normal mature cells in abnormal number or distribution. While malignant......
hammertoe
hammertoe, deformity of the second, third, or fourth toe in which the toe is bent downward at the middle joint......
hamstring
hamstring, any of the three muscles at the back of the thigh that begin at the pelvis (specifically originating......
hantavirus
hantavirus, (genus Hantavirus), any member of a genus of viruses (Hantavirus) of the family Bunyaviridae that cause......
haplosporidian
haplosporidian, any protozoan of the sporozoan subclass Haplosporea. They are internal parasites of invertebrates......
Hardy-Weinberg law
Hardy-Weinberg law, an algebraic equation that describes the genetic equilibrium within a population. It was discovered......
Harpellales
Harpellales, order of fungi (phylum Glomeromycota, kingdom Fungi) with a vegetative body (thallus) consisting of......
Hartnup disease
Hartnup disease, inborn metabolic disorder involving the amino acid tryptophan. Normally, one of the metabolic......
haustorium
haustorium, highly modified stem or root of a parasitic plant or a specialized branch or tube originating from......
headache
headache, pain in various parts of the head. Headaches affect nearly everyone at some time in their life, recurrent......
hearing
hearing, in biology, physiological process of perceiving sound. See ear; mechanoreception; perception; sound...
heart
heart, organ that serves as a pump to circulate the blood. It may be a straight tube, as in spiders and annelid......
heart disease
heart disease, any disorder of the heart. Examples include coronary heart disease, congenital heart disease, and......
heart rate
heart rate, the number of times the ventricles of the heart contract and relax (that is, beat) per minute or other......
heart rot
heart rot, any of several diseases of trees, root crops, and celery. Most trees are susceptible to heart-rotting......
heart sound
heart sound, audible rhythmic vibrations in the heart, typically heard through a stethoscope pressed to the chest......
heartworm disease
heartworm disease, parasitic disease, predominantly of dogs but also occurring in cats, that is caused by the nematode......
heaves
heaves, chronic disorder of the lungs of horses and cows, characterized by difficult breathing and wheezy cough.......
HeLa cell
HeLa cell, a cancerous cell belonging to a strain continuously cultured since its isolation in 1951 from a patient......
Helicosporidium
Helicosporidium, protozoan parasite genus found in insects. It is the only genus of the cnidosporidian phylum Myxozoa......
hematology
hematology, branch of medical science concerned with the nature, function, and diseases of the blood. In the 17th......
hemoglobinopathy
hemoglobinopathy, any of a group of disorders caused by the presence of variant hemoglobin in the red blood cells.......
hemolysis
hemolysis, breakdown or destruction of red blood cells so that the contained oxygen-carrying pigment hemoglobin......
hemophilia
hemophilia, hereditary bleeding disorder caused by a deficiency of a substance necessary for blood clotting (coagulation).......
hepadnavirus
hepadnavirus, any virus belonging to the family Hepadnaviridae. Hepadnaviruses have small, enveloped, spherical......
herbarium
herbarium, collection of dried plant specimens mounted on sheets of paper. The plants are usually collected in......
herd immunity
herd immunity, state in which a large proportion of a population is able to repel an infectious disease, thereby......
hereditary spherocytosis
hereditary spherocytosis, congenital blood disorder characterized by an enlarged spleen, spherical (rather than......
heritability
heritability, amount of phenotypic (observable) variation in a population that is attributable to individual genetic......
hernia
hernia, protrusion of an organ or tissue from its normal cavity. The protrusion may extend outside the body or......
herpangina
herpangina, mild viral infection with sudden onset that is caused by several types of enteroviruses and seen most......
herpesvirus
herpesvirus, any virus belonging to the family Herpesviridae. These viruses are pathogenic (disease-causing) in......
herpetology
herpetology, scientific study of amphibians and reptiles. Like most other fields of vertebrate biology (e.g., ichthyology,......
hibernation
hibernation, a state of greatly reduced metabolic activity and lowered body temperature adopted by certain mammals......
high-risk pregnancy
high-risk pregnancy, pregnancy in which the mother, the fetus, or the newborn has an elevated risk of experiencing......
hindbrain
hindbrain, region of the developing vertebrate brain that is composed of the medulla oblongata, the pons, and the......
hip
hip, in anatomy, the joint between the thighbone (femur) and the pelvis; also the area adjacent to this joint.......
hip dysplasia
hip dysplasia, in dogs, abnormal development of the hip joint on one or both sides of the body, occurring primarily......
hippocampus
hippocampus, region of the brain that is associated primarily with memory. The name hippocampus is derived from......
histogenesis
histogenesis, series of organized, integrated processes by which cells of the primary germ layers of an embryo......
histology
histology, branch of biology concerned with the composition and structure of plant and animal tissues in relation......
histoplasmosis
histoplasmosis, infection with the fungus Histoplasma capsulatum, occurring in humans and other animals. The disease......
HIV
HIV, retrovirus that attacks and gradually destroys the immune system, leaving the host unprotected against infection.......
hives
hives, a hypersensitive skin reaction characterized by the sudden appearance of very itchy, slightly raised, smooth,......
hog cholera
hog cholera, serious and often fatal viral disease of swine. Characterized by high fever and exhaustion, the disease......
Holliday junction
Holliday junction, cross-shaped structure that forms during the process of genetic recombination, when two double-stranded......
homeostasis
homeostasis, any self-regulating process by which biological systems tend to maintain stability while adjusting......
homology
homology, in biology, similarity of the structure, physiology, or development of different species of organisms......
homunculus
homunculus, diminutive fully formed human body, historically believed to inhabit a germ cell (an egg or a sperm)......
hookworm disease
hookworm disease, parasitic infestation of humans, dogs, or cats caused by bloodsucking worms living in the small......
human aging
human aging, physiological changes that take place in the human body leading to senescence, the decline of biological......
human development
human development, the process of growth and change that takes place between birth and maturity. Human growth is......
human ecology
human ecology, man’s collective interaction with his environment. Influenced by the work of biologists on the interaction......
human genome
human genome, all of the approximately three billion base pairs of deoxyribonucleic acid (DNA) that make up the......
Human Genome Project
Human Genome Project (HGP), an international collaboration that successfully determined, stored, and rendered publicly......
human papillomavirus
human papillomavirus (HPV), any of a subgroup of viruses belonging to the family Papovaviridae that infect humans,......
humour
humour, (from Latin “liquid,” or “fluid”), in early Western physiological theory, one of the four fluids of the......
Huntington disease
Huntington disease , a relatively rare, and invariably fatal, hereditary neurological disease that is characterized......
hydatidiform mole
hydatidiform mole, in human pregnancy, abnormal growth of the chorion, the outermost vascular membrane that in......
hydramnios
hydramnios, excess of amniotic fluid, the liquid that surrounds the fetus in the uterus. Chronic hydramnios, in......
hydrocephalus
hydrocephalus, accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain, causing......
hydrogenosome
hydrogenosome, membrane-bound organelle found in the cytoplasm of eukaryotic cells (cells with clearly defined......
hymenium
hymenium, a spore-bearing layer of tissue in fungi (kingdom Fungi) found in the phyla Ascomycota and Basidiomycota.......
hymenomycetes
hymenomycetes, name often given to an informal grouping of fungi that are members of the phylum Basidiomycota (kingdom......
hypercalcitoninemia
hypercalcitoninemia, abnormally high blood concentrations of calcitonin, a protein hormone secreted by parafollicular......
hyperglycemia
hyperglycemia, elevation of blood glucose concentrations above the normal range; it is the laboratory finding that......
hyperkeratosis
hyperkeratosis, in cattle, a disease characterized by inflammation and thickening of the horny covering of the......
hypermastigote
hypermastigote, any member of the zooflagellate protozoan order Hypermastigida. Hypermastigotes are complex, uninucleate,......
hyperopia
hyperopia, refractive error or abnormality in which the cornea and lens of the eye focus the image of the visual......
hypertension
hypertension, condition that arises when the blood pressure is abnormally high. Hypertension occurs when the body’s......
hyperthyroidism
hyperthyroidism, excess production of thyroid hormone by the thyroid gland. Most patients with hyperthyroidism......
hypoglycemia
hypoglycemia, reduction of the concentration of glucose in the blood below normal levels, commonly occurring as......
hypogonadism
hypogonadism, in men, decreased testicular function that results in testosterone deficiency and infertility. Hypogonadism......
hypophosphatemia
hypophosphatemia, reduction in the concentration of phosphate in the blood serum, thus disrupting the body’s energy......
hypoprothrombinemia
hypoprothrombinemia, disease characterized by a deficiency of the blood-clotting substance prothrombin, resulting......
hypothalamus
hypothalamus, region of the brain lying below the thalamus and making up the floor of the third cerebral ventricle.......
hypothyroidism
hypothyroidism, a deficiency in hormone production by the thyroid gland. Hypothyroidism usually results from a......
hypoxia
hypoxia, in biology and medicine, condition of the body in which the tissues are starved of oxygen. In its extreme......
ich
ich, parasitic disease that affects a variety of freshwater fish species and that is caused by the ciliated protozoan......
ichthyology
ichthyology, scientific study of fishes, including, as is usual with a science that is concerned with a large group......
ichthyosis
ichthyosis, a hereditary condition involving dryness and scaliness of the skin brought about by excessive growth......
Ii blood group system
Ii blood group system, classification of human blood based on the presence of antigens I and i on the surface of......
ileum
ileum, the final and longest segment of the small intestine. It is specifically responsible for the absorption......

Biology Encyclopedia Articles By Title