Biology, SEM-SUN
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
semispinalis muscle, any of the deep muscles just to either side of the spine that arise from the transverse processes......
senses, means by which animals detect and respond to stimuli in their internal and external environments. The senses......
sensory neuron, nerve cell that carries information about changes in external and internal environments to the......
human sensory reception, means by which humans react to changes in external and internal environments. Ancient......
sepsis, systemic inflammatory condition that occurs as a complication of infection and in severe cases may be associated......
septicemia, infection resulting from the presence of bacteria in the blood (bacteremia). The onset of septicemia......
serum, the portion of plasma remaining after coagulation of blood, during which process the plasma protein fibrinogen......
serum albumin, protein found in blood plasma that helps maintain the osmotic pressure between the blood vessels......
sex chromosome, either of a pair of chromosomes that determine whether an individual is male or female. The sex......
sex determination, the establishment of the sex of an organism, usually by the inheritance at the time of fertilization......
sex hormone, a chemical substance produced by a sex gland or other organ that has an effect on the sexual features......
sex-controlled character, a genetically controlled feature that may appear in organisms of both sexes but is expressed......
sex-limited character, an observable feature appearing only in members of one sex of a given population of organisms,......
sex-linked character, an observable feature of an organism controlled by the genes on the chromosomes that determine......
human sexual activity, any activity—solitary, between two persons, or in a group—that induces sexual arousal. There......
sexual differentiation, in human embryology, the process by which the male and female sexual organs develop from......
sexual dysfunction, the inability of a person to experience sexual arousal or to achieve sexual satisfaction under......
sexual intercourse, reproductive act in which the male reproductive organ (in humans and other higher animals)......
sexual reproduction, the production of new organisms by the combination of genetic information of two individuals......
sexual selection, theory in postulating that the evolution of certain conspicuous physical traits—such as pronounced......
sexually transmitted disease (STD), any disease (such as syphilis, gonorrhea, AIDS, or a genital form of herpes......
sheathed bacteria, group of microorganisms found widely in nature in slow-running water, many species of which......
shellfish poisoning, illness in humans resulting from the eating of certain mussels and clams. The source of the......
shigella, (genus Shigella), genus of rod-shaped bacteria in the family Enterobacteriaceae, species of which are......
shigellosis, infection of the gastrointestinal tract by bacteria of the genus Shigella. The illness produces cramplike......
shiitake mushroom, (Lentinula edodes), edible and medicinal wood-dwelling fungus, native to East Asia. The shiitake......
shock, in physiology, failure of the circulatory system to supply sufficient blood to peripheral tissues to meet......
shoulder, in anatomy, the joint between the arm, or forelimb, and the trunk, together with the adjacent tissue,......
sick building syndrome (SBS), term applied to a situation in which some or all the people occupying a building......
SIV, infectious agent of the genus Lentivirus in the family Retroviridae. The virus infects primates of the infraorder......
Sjögren syndrome, chronic inflammatory disorder characterized by severe dryness of the eyes and mouth that results......
skeletal muscle, in vertebrates, most common of the three types of muscle in the body. Skeletal muscles are attached......
skeleton, the supportive framework of an animal body. The skeleton of invertebrates, which may be either external......
human skeleton, the internal skeleton that serves as a framework for the body. This framework consists of many......
skin cancer, disease characterized by the uncontrolled growth of cells in the skin. Skin cancers are of two distinct......
skin disease, any of the diseases or disorders that affect the human skin. They have a wide range of causes. Although......
skin squeeze, effect on the skin of exposure to a pressure less than that of the surrounding environmental pressure.......
human skin, in human anatomy, the covering, or integument, of the body’s surface that both provides protection......
skull, skeletal framework of the head of vertebrates, composed of bones or cartilage, which form a unit that protects......
sleep, a normal, reversible, recurrent state of reduced responsiveness to external stimulation that is accompanied......
slime mold, any of about 500 species of primitive organisms containing true nuclei and resembling both protozoan......
small intestine, a long, narrow, folded or coiled tube extending from the stomach to the large intestine; it is......
smell, the detection and identification by sensory organs of airborne chemicals. The concept of smell, as it applies......
smooth endoplasmic reticulum (SER), meshwork of fine disklike tubular membrane vesicles, part of a continuous membrane......
smooth muscle, muscle that shows no cross stripes under microscopic magnification. It consists of narrow spindle-shaped......
smut, plant disease primarily affecting grasses, including corn (maize), wheat, sugarcane, and sorghum, caused......
snow mold, plant disease that attacks cereals, forage grasses, and turf grasses in northern areas of North America,......
social Darwinism, the theory that human groups and races are subject to the same laws of natural selection as Charles......
sociobiology, the systematic study of the biological basis of social behaviour. The term sociobiology was popularized......
sodium deficiency, condition in which sodium is insufficient or is not utilized properly. Sodium is an element......
soil seed bank, natural storage of seeds in the leaf litter, on the soil surface, or in the soil of many ecosystems,......
soleus muscle, a flat, broad muscle of the calf of the leg lying just beneath the gastrocnemius muscle. It arises......
soma, in biology, all the living matter of an animal or a plant except the reproductive, or germ, cells. The distinction......
sooty mold, plant disease characterized by splotchy black stains or coatings on leaves, stems, and fruit. The black......
Sordariomycetes, class of several thousand species of sac fungi in the phylum Ascomycota (kingdom Fungi). The fungi......
sore mouth, viral disease of sheep and goats. The disease is characterized by the emergence of blisters, pustules,......
sound reception, response of an organism’s aural mechanism, the ear, to a specific form of energy change, or sound......
- Introduction
- Invertebrate Organs
- Tympanal Organs, Hearing, Ears
- Electrophysiology, Hearing, Perception
- Fishes, Amphibians, Mechanisms
- Hearing, Ears, Sensory Cells
- Amphibians, Hearing, Sensitivity
- Lizard Hearing, Acoustic Signals, Vibrations
- Turtle Hearing, Low Frequency, Adaptations
- Auditory Perception, Bird Hearing, Acoustic Signals
- Mammal Hearing, Frequency, Acoustics
- Echolocation, Bats, Sonar
- Echolocation, Mammals, Bats
spatial disorientation, the inability of a person to determine his true body position, motion, and altitude relative......
speciation, the formation of new and distinct species in the course of evolution. Speciation involves the splitting......
species, in biology, classification comprising related organisms that share common characteristics and are capable......
speech disorder, any of the disorders that impair human speech. Human communication relies largely on the faculty......
sperm, male reproductive cell, produced by most animals. With the exception of nematode worms, decapods (e.g.,......
sperm competition, a special form of mating competition that occurs in sexual species when females accept multiple......
spermatogenesis, the origin and development of the sperm cells within the male reproductive organs, the testes.......
sphincter muscle, any of the ringlike muscles surrounding and able to contract or close a bodily passage or opening.......
spinal cord, major nerve tract of vertebrates, extending from the base of the brain through the canal of the spinal......
spinalis muscle, any of the deep muscles of the back near the vertebral column that, as part of the erector spinae......
spiracle, in arthropods, the small external opening of a trachea (respiratory tube) or a book lung (breathing organ......
Spirillum, genus of spiral-shaped bacteria of the family Spirillaceae, aquatic except for one species (S. minus)......
spirochete, (order Spirochaetales), any of a group of spiral-shaped bacteria, some of which are serious pathogens......
split-brain syndrome, condition characterized by a cluster of neurological abnormalities arising from the partial......
spontaneous generation, the hypothetical process by which living organisms develop from nonliving matter; also,......
spore, a reproductive cell capable of developing into a new individual without fusion with another reproductive......
sporophyte, in plants and certain algae, the nonsexual phase (or an individual representing the phase) in the alternation......
staphylococcus, (genus Staphylococcus), group of spherical bacteria, the best-known species of which are universally......
stem cell, an undifferentiated cell that can divide to produce some offspring cells that continue as stem cells......
Stemonitis, large genus of true slime molds (class Myxomycetes; q.v.) typical of the order Stemoniales. The species......
stereotyped response, unlearned behavioral reaction of an organism to some environmental stimulus. It is an adaptive......
Still’s disease, rheumatoid arthritis in children. The major difference between this illness and rheumatoid arthritis......
stinkhorn, any fungus of the order Phallales (phylum Basidiomycota, kingdom Fungi), typified by a phalluslike,......
stolon, in biology, a special slender horizontal branch serving to propagate the organism. In botany a stolon—also......
stomach, saclike expansion of the digestive system, between the esophagus and the small intestine; it is located......
stomach cancer, a disease characterized by abnormal growth of cells in the stomach. The incidence of stomach cancer......
stonewort, (order Charales), order of green algae (class Charophyceae) comprising six genera. Most stoneworts occur......
strabismus, misalignment of the eyes. The deviant eye may be directed inward toward the other eye (cross-eye, or......
strangles, horse disease caused by Streptococcus equi, a bacterium that invades nasal and throat passages and forms......
streptococcus, (genus Streptococcus), group of spheroidal bacteria belonging to the family Streptococcaceae. The......
stress, in psychology and biology, any environmental or physical pressure that elicits a response from an organism.......
stroke, sudden impairment of brain function resulting either from a substantial reduction in blood flow to some......
stunt, in agriculture, common symptom of plant disease, resulting in reduced size and loss of vigour. Stunting......
stuttering, speech defect characterized by involuntary repetition of sounds or syllables and the intermittent blocking......
sty, acute painful modular infection of one or more glands of the eyelid. Two types are distinguished: the external......
substance use disorder, recurrent use of drugs or alcohol that impairs psychological and physical function and......
sucking, drawing of fluids into the mouth by creating a vacuum pressure in the oral cavity. Mammalian infants rely......
sudden infant death syndrome, unexpected death of an apparently healthy infant from unexplained causes. SIDS is......
suffocation, the stoppage or impeding of respiration, as by strangulation, choking on food, or other exclusion......
sulfhemoglobinemia, presence in the blood of sulfhemoglobin, the product of abnormal, irreversible binding of sulfur......
sulfur bacterium, any of a diverse group of microorganisms capable of metabolizing sulfur and its compounds and......
sunburn, acute cutaneous inflammation caused by overexposure to ultraviolet (UV) radiation of the so-called UVB......
sunscald, common disorder of exposed, thin-barked trees, shrubs, and other plants. Dead patches form on the sun-exposed......
