Biology, HIN-IND
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
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, abnormal development of the hip joint, in which the socket of the pelvis, known as the acetabulum,......
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 (family Retroviridae) that attacks and progressively weakens the immune system by targeting cells......
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......
Hormone
Hormone, organic substance secreted by plants and animals that functions in the regulation of physiological activities......
- Introduction
- Vertebrates, Endocrine, Neuroendocrine
- LH, ICSH, Endocrine
- Thyroid Gland, Metabolism, Hormone Production
- Parathyroid, Calcium, Parathormone
- Glucagon, Pancreas, Regulation
- Reproductive, Endocrine, Glands
- Endocrine Glands, Secretions, Hormone Functions
- Molting, Insects, Juveniles
- Plant Growth, Photosynthesis, Reproduction
- Growth Inhibitors
How Botanical Gardens Save Plants with Science
Many people think of botanical gardens as little more than highly landscaped parks. Full of beauty and peace, botanical......
How do birds know when to fly south?
In the Northern Hemisphere, migratory birds tend to fly south to spend the winter in warmer locales. (Though in......
How do fireflies light up?
Fireflies light up summer nights using a chemical process known as bioluminescence, the key chemical players of......
How do fish breathe?
Fish primarily breathe through gills, which are specialized organs that extract dissolved oxygen from water. The......
How do fish reproduce?
Fish reproduction is a fascinating process that varies significantly across different species. Most bony fishes......
How do fish sleep?
Fish enter a restful state marked by minimal movement and decreased responsiveness. During this time, they maintain......
How do frogs breathe?
Frogs have an adaptable respiratory system that allows them to breathe in multiple ways throughout their life cycle......
How Do Glowworms Glow?
There are actually a number of different insects known as "glowworms," and they have a variety of mechanisms for......
How do horses sleep?
Horses sleep both standing up and lying down. Most of their sleeping time is spent standing, which is crucial for......
How do penguins stay warm?
Penguins have a unique feather arrangement and body structure that provides excellent insulation. Their short,......
How do plants grow?
Unlike most animals, plants continue to grow throughout their entire life span. Plant growth and plant development......
How do snakes swallow large prey?
Snakes have a unique and fascinating way of swallowing prey that is much larger than their own heads and even bodies.......
How Easy Is It to Clone Your Pet?
American gridiron great Tom Brady announced the successful cloning of his beloved pet dog, a pit bull mix named......
How Is Inflammation Involved in Swelling?
Immediately following an injury, the traumatized area becomes red, warm, and painful, and it begins to swell. The......
How long can ticks live without food?
Ticks are parasitic, blood-feeding arachnids with more than 800 species worldwide. They are remarkably resilient......
How long can whales hold their breath?
Whales can hold their breath for varying durations depending on the species, with some capable of staying submerged......
How long does it take food to digest?
The process of food digestion typically takes between 24 and 72 hours. The precise length of time is determined......
How long does it take for rigor mortis to set in?
Rigor mortis sets in about two to six hours after death, starting in the smaller muscles of the body, such as those......
How many eyes does a spider have?
Spiders typically have eight eyes, although some species may have fewer. The number and arrangement of eyes can......
How many hearts does an octopus have?
An octopus has three hearts, facilitating efficient nutrient and oxygen delivery throughout its eight-armed body.......
How many pints of blood does a human have?
A typical adult human has approximately 8 to 12 pints (about 4.5 to 6.8 liters) of blood circulating through their......
How many stomachs does a cow have?
Cows do not have four stomachs, as is sometimes thought. They have one stomach divided into four compartments—the......
How much does a human brain weigh?
The adult male human brain typically weighs between 1,300 grams and 1,400 grams (2.87 to 3.08 pounds), making up......
How Much Sleep Do You Need?
Sleep is a biological necessity, and sleep needs change throughout life. Newborns may need as many as 17 hours......
How Much Water Should a Person Drink in a Day?
The popular recommendation to drink 8 cups of water every day isn’t as definitive as it may seem. The amount of......
How the First Surviving Quintuplets Became a Tourist Attraction
On May 28, 1934, a miracle happened. In a modest farmhouse in Corbeil, Ontario, Canada, parents Oliva and Elzire......
How Were Viruses Discovered?
Scientific understanding of viruses emerged in the 1890s, with the work of Russian microbiologist Dmitry I. Ivanovsky......
Hughes Medical Institute
Hughes Medical Institute, American philanthropic foundation, established in 1953 by the aviator and industrialist......
human aging
human aging, physiological changes that take place in the human body leading to senescence, the decline of biological......
Human Ancestors
Modern human beings—that is, the species Homo sapiens—emerged relatively recently, only about 315,000 to 150,000......
human cardiovascular system
human cardiovascular system, organ system that conveys blood through vessels to and from all parts of the body,......
- Introduction
- Origin, Development & Function
- Heart Wall, Blood Flow, Circulation
- Coronary Arteries, Heart Valves, Blood Flow
- Electrocardiogram, Heartbeat, Circulation
- Arteries, Veins, Capillaries
- Arteries, Circulation, Blood Flow
- Pulse, Circulation, Blood Vessels
- Superior Vena Cava, Tributaries, Circulation
- Inferior Vena Cava, Tributaries, Circulation
- Capillaries, Circulation, Oxygenation
human development
human development, the process of growth and change that takes place between birth and maturity. Human growth is......
human disease
human disease, an impairment of the healthy state of the human body that interrupts or modifies its vital functions.......
- Introduction
- Prevention, Diagnosis, Treatment
- Metabolism, Control, Regulation
- Immune Response, Pathogens, Prevention
- Signs, Symptoms, Diagnosis
- Causes, Pathogens, Symptoms
- Genetic, Inherited, Congenital
- Chemical Injury, Poisoning, Symptoms
- Injury, Trauma, Prevention
- Autoimmune, Allergies, Infections
- Bacteria, Viruses, Fungi
- Fungi, Parasites, Infections
- Cancer, Causes, Treatment
- Carcinogens, Causes, Prevention
- Malnutrition, Deficiencies, Imbalances
- Psychiatric, Mental, Disorders
- Classifications, Causes, Symptoms
human ecology
human ecology, man’s collective interaction with his environment. Influenced by the work of biologists on the interaction......
human evolution
human evolution, the process by which human beings developed on Earth from now-extinct primates. Viewed zoologically,......
- Introduction
- Miocene, Bipedalism, Adaptations
- Fossils, Species, Adaptations
- Bipedalism, Adaptations, Fossils
- Hominin, Habitats, Adaptations
- Brain Size, Adaptations, Fossils
- Tool Design, Refinements, Technology
- Tooth Reduction, Bipedalism, Brain Size
- Emergence, Homo Sapiens, Bipedalism
- Language, Culture, Lifeways
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......
iliocostalis muscle
iliocostalis muscle, any of the deep muscles of the back that, as part of the erector spinae (sacrospinalis) muscle......
iliotibial band syndrome
iliotibial band syndrome (ITBS), inflammation of the band of fibrous tissue known as the iliotibial band (or tract),......
iminoglycinuria
iminoglycinuria, inborn impairment of the transport system of the kidney tubules, which normally reabsorb the amino......
immune system
immune system, the complex group of defense responses found in humans and other advanced vertebrates that helps......
- Introduction
- Interferons, Antibodies, Cells
- Macrophages, Antigens, Defense
- Lymphocytes, Antigens, Immunity
- Antigens, Cells, Receptors
- Lymphocytes, Diversity, Adaptive
- IgA, IgG, IgM
- T Cells, Antigens, Receptors
- T Cells, B Cells, Activation
- Antibodies, Mediated, Mechanisms
- Killer Cells, Antigens, Defense
- Cancer Immunity, T-cells, Antigens
- Evolution, Defense, Adaptation
immune system disorder
immune system disorder, any of various failures in the body’s defense mechanisms against infectious organisms.......
immunity
immunity, in biology, the ability of the body to prevent or defeat infection from invading microorganisms or parasites.......
immunization
immunization, process by which resistance to disease is acquired or induced in plants and animals. This discussion......
immunodeficiency
immunodeficiency, defect in immunity that impairs the body’s ability to resist infection. The immune system may......
immunology
immunology, the scientific study of the body’s resistance to invasion by other organisms (i.e., immunity). In a......
impetigo
impetigo, inflammatory skin infection that begins as a superficial blister or pustule that then ruptures and gives......
implantation
implantation, in reproduction physiology, the adherence of a fertilized egg to a surface in the reproductive tract,......
imposter syndrome
imposter syndrome, a persistent unjustified feeling that one’s success is fraudulent. Imposter syndrome is characterized......
in vitro fertilization
in vitro fertilization (IVF), medical procedure in which mature egg cells are removed from a woman, fertilized......
inborn error of metabolism
inborn error of metabolism, any of multiple rare disorders that are caused by an inherited genetic defect and that......
Inbreeding
Inbreeding, the mating of individuals or organisms that are closely related through common ancestry, as opposed......
incidence
incidence, in epidemiology, occurrence of new cases of disease, injury, or other medical conditions over a specified......
inclusive fitness
inclusive fitness, theory in evolutionary biology in which an organism’s genetic success is believed to be derived......
induced pluripotent stem cell
induced pluripotent stem cell (iPS cell), immature cell that is generated from an adult (mature) cell and that......
induction
induction, in embryology, process by which the presence of one tissue influences the development of others. Certain......