Biology, P B-PLA
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
P blood group system, classification of human blood based on the presence of any of three substances known as the......
paedogenesis, reproduction by sexually mature larvae, usually without fertilization. The young may be eggs, such......
paedomorphosis, retention by an organism of juvenile or even larval traits into later life. There are two aspects......
pain, complex experience consisting of a physiological and a psychological response to a noxious stimulus. Pain......
Paleo diet, dietary regime based on foods humans presumably would have consumed during the Paleolithic Period (2.6......
paleoanthropology, interdisciplinary branch of anthropology concerned with the origins and development of early......
paleontology, scientific study of life of the geologic past that involves the analysis of plant and animal fossils,......
palynology, scientific discipline concerned with the study of plant pollen, spores, and certain microscopic planktonic......
Panama disease, a devastating disease of bananas caused by the soil-inhabiting fungus species Fusarium oxysporum......
pancreas, compound gland that discharges digestive enzymes into the gut and secretes the hormones insulin and glucagon,......
pandemic, outbreak of infectious disease that occurs over a wide geographical area and that is of high prevalence,......
Paneth’s cell, specialized type of epithelial cell found in the mucous-membrane lining of the small intestine and......
papillomavirus, any of a subgroup of viruses belonging to the family Papillomaviridae that infect birds and mammals,......
papovavirus, any virus in the families Papillomaviridae and Polyomaviridae. Papovaviruses are responsible for a......
paragonimiasis, infection caused by parasitic trematodes of the genus Paragonimus. Infection most commonly is with......
parallel evolution, the evolution of geographically separated groups in such a way that they show morphological......
paralysis, loss or impairment of voluntary muscular movement caused by structural abnormalities of nervous or muscular......
paramyxovirus, any virus belonging to the family Paramyxoviridae. Paramyxoviruses have enveloped virions (virus......
paranoia, the central theme of a group of psychotic disorders characterized by systematic delusions and of the......
parasitic disease, in humans, any illness that is caused by a parasite, an organism that lives in or on another......
parasitology, the study of animal and plant parasitism as a biological phenomenon. Parasites occur in virtually......
parathyroid gland, endocrine gland occurring in all vertebrate species from amphibia upward, usually located close......
parietal cell, in biology, one of the cells that are the source of the hydrochloric acid and most of the water......
parkinsonism, a group of chronic neurological disorders characterized by progressive loss of motor function resulting......
parthenocarpy, development of fruit without fertilization. The fruit resembles a normally produced fruit but is......
parturient paresis, in cattle, a disorder characterized by abnormally low levels of calcium in the blood (hypocalcemia).......
parvovirus, any virus belonging to the family Parvoviridae. Parvoviruses have small nonenveloped virions (virus......
pasteurellosis, any bacterial disease caused by Pasteurella species. The name is sometimes used interchangeably......
patch dynamics, in ecology, a theoretical approach positing that the structure, function, and dynamics of an ecological......
patent ductus arteriosus, congenital heart defect characterized by the persistence of the ductus arteriosus, a......
pathology, medical specialty concerned with the determining causes of disease and the structural and functional......
pectin, any of a group of water-soluble carbohydrate substances that are found in the cell walls and intercellular......
pectoralis muscle, any of the muscles that connect the front walls of the chest with the bones of the upper arm......
pectus excavatum, a chest deformity caused by depression of the breastbone, or sternum. Pectus excavatum is generally......
pedigree, a record of ancestry or purity of breed. Studbooks (listings of pedigrees for horses, dogs, etc.) and......
pelvic inflammatory disease (PID), general acute inflammation of the pelvic cavity in women, caused by bacterial......
pemphigus, a group of skin diseases characterized by large blisters that appear on the skin and mucous membranes.......
Penicillium, genus of blue or green mold fungi (kingdom Fungi) that exists as asexual forms (anamorphs, or deuteromycetes).......
penis, the copulatory organ of the male of higher vertebrates that in mammals usually also provides the channel......
peptic ulcer, lesion that occurs primarily in the mucous membrane of the stomach or duodenum (the upper segment......
perennial, any plant that persists for several years, usually with new herbaceous growth from a part that survives......
Peridinium, genus of cosmopolitan freshwater dinoflagellates in the family Peridiniaceae, consisting of at least......
periodic paralysis, any of the forms of a rare disorder that is characterized by relatively short-term, recurrent......
peristalsis, involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but......
peritoneum, large membrane in the abdominal cavity that connects and supports internal organs. It is composed of......
peritonitis, inflammation of the peritoneum, the membrane that lines the abdominal wall and then folds in to enclose......
Permian extinction, a series of extinction pulses that contributed to the greatest mass extinction in Earth’s history.......
peromelia, congenital absence or malformation of the extremities, of rare occurrence until the thalidomide tragedy......
perosis, a disorder of chicks, turkey poults, and young swans, characterized by enlargement of the hock, twisted......
peroxisome, membrane-bound organelle occurring in the cytoplasm of eukaryotic cells. Peroxisomes play a key role......
perseveration, the repetitive and uncontrollable continuation of a thought, behavior, or response, even when it......
personality disorder, mental disorder that is marked by deeply ingrained and lasting patterns of inflexible, maladaptive,......
pervasive developmental disorder (PDD), term historically used in reference to any of a group of conditions characterized......
pescatarianism, dietary practice based on the consumption of fish and shellfish to the exclusion of land-based......
Peyer patch, any of the nodules of lymphatic cells that aggregate to form bundles or patches and occur usually......
phagocyte, type of cell that has the ability to ingest, and sometimes digest, foreign particles, such as bacteria,......
phagocytosis, process by which certain living cells called phagocytes ingest or engulf other cells or particles.......
pharyngitis, inflammatory illness of the mucous membranes and underlying structures of the throat (pharynx). Inflammation......
pharynx, cone-shaped passageway leading from the oral and nasal cavities in the head to the esophagus and larynx.......
phenology, the study of phenomena or happenings. It is applied to the recording and study of the dates of recurrent......
phenotype, all the observable characteristics of an organism that result from the interaction of its genotype (total......
phenylketonuria (PKU), hereditary inability of the body to metabolize the amino acid phenylalanine. Phenylalanine......
pheochromocytoma, tumour, most often nonmalignant, that causes abnormally high blood pressure (hypertension) because......
pheromone, any endogenous chemical secreted in minute amounts by an organism in order to elicit a particular reaction......
photodynamism, conversion of certain substances in the skin of animals into other substances by the action of light.......
photolysis, chemical process by which molecules are broken down into smaller units through the absorption of light.......
photoperiodism, the functional or behavioral response of an organism to changes of duration in daily, seasonal,......
photophore, light-emitting organ present in fireflies and certain other bioluminescent animals. Photophores are......
photoreception, any of the biological responses of animals to stimulation by light. In animals, photoreception......
photorecovery, restoration to the normal state, by the action of visible light, of the deoxyribonucleic acid composing......
photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical......
phycology, the study of algae, a large heterogeneous group of chiefly aquatic plants ranging in size from microscopic......
Phycomycetes, an obsolete name formerly used to describe lower fungi in the classes Chytridiomycetes, Hyphochytridiomycetes,......
phylogenetic tree, a diagram showing the evolutionary interrelations of a group of organisms derived from a common......
phylogenetics, in biology, the study of the ancestral relatedness of groups of organisms, whether alive or extinct.......
phylogeny, the history of the evolution of a species or group, especially in reference to lines of descent and......
Physarum, large genus of true slime molds, accounting for about 20 percent of the species of the phylum Mycetozoa......
physiology, study of the functioning of living organisms, animal or plant, and of the functioning of their constituent......
phytoflagellate, any member of a group of flagellate protozoans that have many characteristics in common with typical......
phytoplankton, a flora of freely floating, often minute organisms that drift with water currents. Like land vegetation,......
pica, mental health condition, a type of eating disorder, characterized by the compulsive eating of substances......
Pick disease, form of premature dementia caused by atrophy of the frontal and temporal lobes of the brain. It resembles......
picornavirus, any of a group of viruses constituting the family Picornaviridae, a large group of the smallest known......
Pilobolus, a cosmopolitan genus of at least five species of fungi in the family Pilobolaceae (order Mucorales)......
pineal gland, endocrine gland found in vertebrates that is the source of melatonin, a hormone derived from tryptophan......
pineal tumour, mass of abnormal tissue arising in the pineal gland and occurring most often in children and young......
pinguecula, very common yellow-white nodule in the conjunctiva at the front of the eye, usually on the side of......
pinocytosis, a process by which liquid droplets are ingested by living cells. Pinocytosis is one type of endocytosis,......
pinta, chronic tropical skin disease characterized initially by the appearance of dry, scaly papular lesions followed......
pioneer species, species that are the first to colonize newly created environments or recently disturbed environments......
pituitary gland, ductless gland of the endocrine system that secretes hormones directly into the bloodstream. The......
plague, infectious disease caused by Yersinia pestis, a bacterium transmitted from rodents to humans by the bite......
plankton, marine and freshwater organisms that, because they are nonmotile or too small or weak to swim against......
plant cell, the basic unit of all plants. Plant cells, like animal cells, are eukaryotic, meaning they have a membrane-bound......
plant development, a multiphasic process in which two distinct plant forms succeed each other in alternating generations.......
- Introduction
- Germination, Embryogenesis, Maturation
- Zygote, Embryo, Seedling
- Embryogenesis, Meristems, Apical
- Nutrient Dependence, Embryo Nutrition, Seed Germination
- Breaking Dormancy
- Meristems, Growth, Cells
- Shoot System, Derivatives
- Leaf Production, Photosynthesis, Morphogenesis
- Branching, Shoot, Axillary Buds
- Root System, Derivatives
- Correlations, Morphogenesis, Genetics
- Environmental Control, Hormones, Genes
- Senescence, Aging, Growth
plant disease, an impairment of the normal state of a plant that interrupts or modifies its vital functions. All......
- Introduction
- Causes, Symptoms, Prevention
- Epiphytotics, Symptoms, Control
- Soil pH, Fungi, Bacteria
- Symptoms, Causes, Control
- Chemical Control, Prevention, Treatment
- Resistance, Breeding, Genetics
- Toxic Chemicals
- Transmission, Pathogens, Symptoms
- Symptoms, Causes, Treatments
- Causes, Symptoms, Prevention
- Nematodes, Parasitic, Control
plant virus, any of a number of agents that can cause plant disease. Plant viruses are of considerable economic......
plantar fasciitis, swelling or degeneration of the plantar fascia, the thick band of connective tissue that runs......
plasma, the liquid portion of blood. Plasma serves as a transport medium for delivering nutrients to the cells......
plasmid, in microbiology, an extrachromosomal genetic element that occurs in many bacterial strains. Plasmids are......
