dead space: area in the lung that lacks proper ventilation or perfusion
dead zone: area within an ecosystem in lakes and near the mouths of rivers where large areas of ecosystems are depleted of their normal flora and fauna; these zones can be caused by eutrophication, oil spills, dumping of toxic chemicals, and other human activities
death rate (D): number of deaths within a population at a specific point in time
decomposer: organism that carries out the decomposition of dead organisms
deductive reasoning: form of logical thinking that uses a general inclusive statement to predict specific results
degeneracy: (of the genetic code) describes that a given amino acid can be encoded by more than one nucleotide triplet; the code is degenerate, but not ambiguous
dehydration synthesis: (also, condensation) reaction that links monomer molecules, releasing a water molecule for each bond formed
demographic-based population model: modern model of population dynamics incorporating many features of the r- and K-selection theory
demography: statistical study of changes in populations over time
denaturation: loss of shape in a protein as a result of changes in temperature, pH, or chemical exposure
denature: process that changes a substance's natural properties
dendrite: structure that extends away from the cell body to receive messages from other neurons
dendritic cell: immune cell that processes antigen material and presents it on the surface of other cells to induce an immune response
denitrification: transformation of nitrate from soil to gaseous nitrogen compounds such as N2O, NO, and N2
density-dependent regulation: regulation of population that is influenced by population density, such as crowding effects; usually involves biotic factors
density-independent regulation: regulation of populations by factors that operate independent of population density, such as forest fires and volcanic eruptions; usually involves abiotic factors
dentary: single bone that comprises the lower jaw of mammals
deoxynucleotide: individual DNA monomer (single unit)
deoxyribonucleic acid (DNA): double-helical molecule that carries the cell's hereditary information
dephosphorylation: removal of a phosphate group from a molecule
depolarization: change in the membrane potential to a less negative value
depression: movement downward of a bone, such as after the shoulders are shrugged and the scapulae return to their normal position from an elevated position; opposite of elevation
dermal tissue: protective plant tissue covering the outermost part of the plant; controls gas exchange
descending limb: part of the loop of Henle that descends from the renal cortex into the renal medulla
descriptive science: (also, discovery science) form of science that aims to observe, explore, and investigate
desmosome: linkages between adjacent epithelial cells that form when cadherins in the plasma membrane attach to intermediate filaments
determinate cleavage: cleavage pattern in which developmental fate of each blastomere is tightly defined
detrital food web: type of food web in which the primary consumers consist of decomposers; these are often associated with grazing food webs within the same ecosystem
Deuteromycota: former form phylum of fungi that do not have a known sexual reproductive cycle (presently members of two phyla: Ascomycota and Basidiomycota)
deuterostome: blastopore develops into the anus, with the second opening developing into the mouth
diabetes insipidus: disorder caused by underproduction of ADH
diabetes mellitus: disorder caused by low levels of insulin activity
diabetogenic effect: effect of GH that causes blood glucose levels to rise similar to diabetes mellitus
diacylglycerol (DAG): cleavage product of PIP2 that is used for signaling within the plasma membrane
diaphragm: domed-shaped skeletal muscle located under lungs that separates the thoracic cavity from the abdominal cavity
diaphysis: central shaft of bone, contains bone marrow in a marrow cavity
diapsid: animal having two temporal fenestrae in the cranium
diarthrosis: joint that allows for free movement of the joint; found in synovial joints
diastole: relaxation phase of the cardiac cycle when the heart is relaxed and the ventricles are filling with blood
Dicer: enzyme that chops the pre-miRNA into the mature form of the miRNA
dicot: (also, eudicot) related group of angiosperms whose embryos possess two cotyledons
dideoxynucleotide: individual DNA monomer that is missing a hydroxyl group (–OH)
diffusion: passive transport process of low-molecular weight material according to its concentration gradient
digestion: mechanical and chemical breakdown of food into small organic fragments
dihybrid: result of a cross between two true-breeding parents that express different traits for two characteristics
dimer: chemical compound formed when two molecules join together
dimerization: (of receptor proteins) interaction of two receptor proteins to form a functional complex called a dimer
dioecious: describes a species in which the male and female reproductive organs are carried on separate specimens
dipeptidase: protease that breaks down peptides to single amino acids; secreted by the brush border of small intestine
diphyodont: refers to the possession of two sets of teeth in a lifetime
diploblast: animal that develops from two germ layers
diploid: cell, nucleus, or organism containing two sets of chromosomes (2n)
diplontic: diploid stage is the dominant stage
directional selection: selection that favors phenotypes at one end of the spectrum of existing variation
disaccharide: two sugar monomers that a glycosidic bond links
discontinuous variation: inheritance pattern in which traits are distinct and are transmitted independently of one another
discussion: section of a scientific paper in which the author interprets experimental results, describes how variables may be related, and attempts to explain the phenomenon in question
dispersal: allopatric speciation that occurs when a few members of a species move to a new geographical area
dissociation: release of an ion from a molecule such that the original molecule now consists of an ion and the charged remains of the original, such as when water dissociates into H+ and OH-
distal convoluted tubule (DCT): part of the renal tubule that is the most distant from the glomerulus
distraction display: visual display used to distract predators away from a nesting site
divergent evolution: process by which groups of organisms evolve in diverse directions from a common point
diversifying selection: selection that favors two or more distinct phenotypes
DNA barcoding: molecular genetic method for identifying a unique genetic sequence to associate with a species
DNA methylation: epigenetic modification that leads to gene silencing; a process involving adding a methyl group to the DNA molecule
DNA microarray: method to detect gene expression by analyzing many DNA fragments that are fixed to a glass slide or a silicon chip to identify active genes and identify sequences
dominant: trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait
dominant lethal: inheritance pattern in which an allele is lethal both in the homozygote and the heterozygote; this allele can only be transmitted if the lethality phenotype occurs after reproductive age
dormancy: period of no growth and very slow metabolic processes
dorsal cavity: body cavity on the posterior or back portion of an animal; includes the cranial and vertebral cavities
dorsal hollow nerve cord: hollow, tubular structure derived from ectoderm, which is located dorsal to the notochord in chordates
dorsiflexion: bending at the ankle such that the toes are lifted toward the knee
double circulation: flow of blood in two circuits: the pulmonary circuit through the lungs and the systemic circuit through the organs and body
double fertilization: two fertilization events in angiosperms; one sperm fuses with the egg, forming the zygote, whereas the other sperm fuses with the polar nuclei, forming endosperm
down feather: feather specialized for insulation
down-regulation: a decrease in the number of hormone receptors in response to increased hormone levels
downstream: nucleotides following the initiation site in the direction of mRNA transcription; in general, sequences that are toward the 3' end relative to a site on the mRNA
duodenum: first part of the small intestine where a large part of digestion of carbohydrates and fats occurs
dura mater: tough outermost layer that covers the central nervous system
eccrine gland: sweat gland
Ecdysozoa: clade of protostomes that exhibit exoskeletal molting (ecdysis)
Echinodermata: phylum of deuterostomes with spiny skin; exclusively marine organisms
ecological pyramid: (also, Eltonian pyramid) graphical representation of different trophic levels in an ecosystem based of organism numbers, biomass, or energy content
ecology: study of interaction between living things and their environment
ecosystem: all the living things in a particular area together with the abiotic, nonliving parts of that environment
ecosystem: community of living organisms and their interactions with their abiotic environment
ecosystem diversity: variety of ecosystems
ecosystem dynamics: study of the changes in ecosystem structure caused by changes in the environment or internal forces
ecosystem services: human benefits and services provided by natural ecosystems
ectomycorrhiza: mycorrhizal fungi that surround the roots with a mantle and have a Hartig net that extends into the roots between cells
Ectomycorrhizae: mycorrhizae in which the fungal hyphae do not penetrate the root cells of the plant
ectotherm: animal incapable of maintaining a relatively constant internal body temperature
Ediacaran period: geological period (630–542 million years ago) when the oldest definite multicellular organisms with tissues evolved
effector cell: lymphocyte that has differentiated, such as a B cell, plasma cell, or cytotoxic T lymphocyte
efferent arteriole: arteriole that exits from the glomerulus
elastase: pancreatic protease
elastic recoil: property of the lung that drives the lung tissue inward
elastic work: work conducted by the intercostal muscles, chest wall, and diaphragm
electrocardiogram (ECG): recording of the electrical impulses of the cardiac muscle
electrochemical gradient: a combined electrical and chemical force that produces a gradient
electrogenic pump: pump that creates a charge imbalance
electrolyte: ion necessary for nerve impulse conduction, muscle contractions, and water balance
electrolyte: solute that breaks down into ions when dissolved in water
electromagnetic spectrum: range of all possible frequencies of radiation
electron: negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of –1 unit
electron configuration: arrangement of electrons in an atom’s electron shell (for example, 1s22s22p6)
electron microscope: an instrument that magnifies an object using an electron beam that passes and bends through a lens system to visualize a specimen
electron orbital: how electrons are spatially distributed surrounding the nucleus; the area where we are most likely to find an electron
electron transfer: movement of electrons from one element to another; important in creating ionic bonds
electron transport chain: group of proteins between PSII and PSI that pass energized electrons and use the energy released by the electrons to move hydrogen ions against their concentration gradient into the thylakoid lumen
electronegativity: ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms
electrophoresis: technique used to separate DNA fragments according to size
element: one of 118 unique substances that cannot break down into smaller substances; each element has unique properties and a specified number of protons
elevation: movement of a bone upward, such as when the shoulders are shrugged, lifting the scapulae
embryophyte: other name for land plant; embryo is protected and nourished by the sporophyte
emergent vegetation: wetland plants that are rooted in the soil but have portions of leaves, stems, and flowers extending above the water’s surface
emerging disease: disease making an initial appearance in a population or that is increasing in incidence or geographic range
Emsleyan/Mertensian mimicry: type of mimicry where a harmful species resembles a less harmful one
enantiomers: molecules that share overall structure and bonding patterns, but differ in how the atoms are three dimensionally placed such that they are mirror images of each other
Enantiornithes: dominant bird group during the Cretaceous period
endemic: species found only in a specific geographic area that is usually restricted in size
endemic disease: disease that is constantly present, usually at low incidence, in a population
endemic species: species native to one place
endergonic: describes chemical reactions that require energy input
endocardium: innermost layer of tissue in the heart
endocarp: innermost part of fruit
endochondral ossification: process of bone development from hyaline cartilage
endocrine cell: cell that releases ligands involved in endocrine signaling (hormones)
endocrine gland: gland that secretes hormones into the surrounding interstitial fluid, which then diffuse into blood and are carried to various organs and tissues within the body
endocrine signal: long-distance signal that is delivered by ligands (hormones) traveling through an organism's circulatory system from the signaling cell to the target cell
endocrine system: system that controls the response of the various glands in the body and the release of hormones at the appropriate times
endocytosis: type of active transport that moves substances, including fluids and particles, into a cell
endodermis: layer of cells in the root that forms a selective barrier between the ground tissue and the vascular tissue, allowing water and minerals to enter the root while excluding toxins and pathogens
endomembrane system: group of organelles and membranes in eukaryotic cells that work together modifying, packaging, and transporting lipids and proteins
endoplasmic reticulum (ER): series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids
endoskeleton: skeleton of living cells that produces a hard, mineralized tissue located within the soft tissue of organisms
endosperm: triploid structure resulting from fusion of a sperm with polar nuclei, which serves as a nutritive tissue for embryo
endospermic dicot: dicot that stores food reserves in the endosperm
endosymbiosis: engulfment of one cell within another such that the engulfed cell survives, and both cells benefit; the process responsible for the evolution of mitochondria and chloroplasts in eukaryotes
endosymbiotic theory: theory that states that eukaryotes may have been a product of one cell engulfing another, one living within another, and evolving over time until the separate cells were no longer recognizable as such
endotherm: animal capable of maintaining a relatively constant internal body temperature
energy budget: allocation of energy resources for body maintenance, reproduction, and parental care
energy coupling: process during which energy released by one reaction is used to drive another reaction
enhancer: segment of DNA that is upstream, downstream, perhaps thousands of nucleotides away, or on another chromosome that influence the transcription of a specific gene
enterocoelom: coelom formed by fusion of coelomic pouches budded from the endodermal lining of the archenteron
enterocoely: mesoderm of deuterostomes develops as pouches that are pinched off from endodermal tissue, cavity contained within the pouches becomes coelom
enthalpy: a system's total energy
entropy (S): measure of randomness or disorder within a system
envelope: lipid bilayer that encircles some viruses
environmental disturbance: change in the environment caused by natural disasters or human activities
enzyme: catalyst in a biochemical reaction that is usually a complex or conjugated protein
enzyme-linked receptor: cell-surface receptor with intracellular domains that are associated with membrane-bound enzymes
eosinophil: leukocyte that responds to parasites and is involved in the allergic response
ependymal: cell that lines fluid-filled ventricles of the brain and the central canal of the spinal cord; involved in production of cerebrospinal fluid
epicardium: outermost tissue layer of the heart
epicotyl: embryonic shoot above the cotyledons
epidemic: disease that occurs in an unusually high number of individuals in a population at the same time
epidermis: outer layer (from ectoderm) that lines the outside of the animal
epidermis: single layer of cells found in plant dermal tissue; covers and protects underlying tissue
epigenetic: heritable changes that do not involve changes in the DNA sequence
epilepsy: neurological disorder characterized by recurrent seizures
epinephrine: hormone released by the adrenal medulla in response to a short term stress
epiphyseal plate: region between the diaphysis and epiphysis that is responsible for the lengthwise growth of long bones
epiphysis: rounded end of bone, covered with articular cartilage and filled with red bone marrow, which produces blood cells
epiphyte: plant that grows on other plants but is not dependent upon other plants for nutrition
epistasis: antagonistic interaction between genes such that one gene masks or interferes with the expression of another
epithelial tissue: tissue that either lines or covers organs or other tissues
epitope: small component of an antigen that is specifically recognized by antibodies, B cells, and T cells; the antigenic determinant
equilibrium: steady state of relative reactant and product concentration in reversible chemical reactions in a closed system
equilibrium: steady state of an ecosystem where all organisms are in balance with their environment and each other
erythropoietin (EPO): hormone produced by the kidneys to stimulate red blood cell production in the bone marrow
esophagus: tubular organ that connects the mouth to the stomach
essential nutrient: nutrient that cannot be synthesized by the body; it must be obtained from food
estivation: torpor in response to extremely high temperatures and low water availability
estrogen: reproductive hormone in females that assists in endometrial regrowth, ovulation, and calcium absorption
estrogens: a group of steroid hormones, including estradiol and several others, that are produced by the ovaries and elicit a suite of characteristics (including increased development of breast tissue, redistribution of fat towards hips, legs, and breast, and the maturation of the uterus and vagina) as well as control the maturation of the ova
estuary: biomes where a source of fresh water, such as a river, meets the ocean
ethology: biological study of animal behavior
ethylene: volatile plant hormone that is associated with fruit ripening, flower wilting, and leaf fall
eucoelomate: animal with a body cavity completely lined with mesodermal tissue
eukaryote: organism with cells that have nuclei and membrane-bound organelles
eukaryote-first hypothesis: proposal that prokaryotes evolved from eukaryotes
eukaryotic cell: cell that has a membrane-bound nucleus and several other membrane-bound compartments or sacs
eukaryotic initiation factor-2 (eIF-2): protein that binds first to an mRNA to initiate translation
Eumetazoa: group of animals with true differentiated tissues
euploid: individual with the appropriate number of chromosomes for their species
eutherian mammal: mammal that possesses a complex placenta, which connects a fetus to the mother; sometimes called placental mammals
eutrophication: process whereby nutrient runoff causes the excess growth of microorganisms, depleting dissolved oxygen levels and killing ecosystem fauna
evaporation: change from liquid to gaseous state at a body of water's surface, plant leaves, or an organism's skin
eversion: movement of the sole of the foot outward, away from the midline of the body; opposite of inversion
evolution: the process of gradual change in a population or species over time
evolutionary fitness: (also, Darwinian fitness) individual’s ability to survive and reproduce
excitatory postsynaptic potential (EPSP): depolarization of a postsynaptic membrane caused by neurotransmitter molecules released from a presynaptic cell
exergonic: describes chemical reactions that release free energy
exine: outermost covering of pollen
exocarp: outermost covering of a fruit
exocytosis: process of passing bulk material out of a cell
exon: sequence present in protein-coding mRNA after completion of pre-mRNA splicing
exoskeleton: a secreted cellular product external skeleton that consists of a hard encasement on the surface of an organism
exotic species: (also, invasive species) species that has been introduced to an ecosystem in which it did not evolve
expiratory reserve volume (ERV): amount of additional air that can be exhaled after a normal exhalation
exponential growth: accelerating growth pattern seen in species under conditions where resources are not limiting
expressed sequence tag (EST): short STS that is identified with cDNA
extant: still-living species
extension: movement in which the angle between the bones of a joint increases; opposite of flexion
external fertilization: fertilization of egg by sperm outside animal body, often during spawning
extinct: no-longer-existing species
extinction: disappearance of a species from Earth; local extinction is the disappearance of a species from a region
extinction rate: number of species becoming extinct over time, sometimes defined as extinctions per million species–years to make numbers manageable (E/MSY)
extracellular digestion: food is taken into the gastrovascular cavity, enzymes are secreted into the cavity, and the cells lining the cavity absorb nutrients
extracellular domain: region of a cell-surface receptor that is located on the cell surface
extracellular matrix: material secreted from animal or fungal cells that provides mechanical protection and anchoring for the cells in the tissue
extremophile: organism that grows under extreme or harsh conditions
F1: first filial generation in a cross; the offspring of the parental generation
F2: second filial generation produced when F1 individuals are self-crossed or fertilized with each other
facial bone: one of the 14 bones that form the face; provides cavities for the sense organs (eyes, mouth, and nose) and attachment points for facial muscles
facilitated transport: process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins
FACT: complex that “facilitates chromatin transcription” by disassembling nucleosomes ahead of a transcribing RNA polymerase II and reassembling them after the polymerase passes by
facultative anaerobes: organisms that can perform both aerobic and anaerobic respiration and can survive in oxygen-rich and oxygen-poor environment
fall and spring turnover: seasonal process that recycles nutrients and oxygen from the bottom of a freshwater ecosystem to the top
fallout: direct deposit of solid minerals on land or in the ocean from the atmosphere
false negative: incorrect test result that should have been positive
falsifiable: able to be disproven by experimental results
family: division of order in the taxonomic classification system
fecundity: potential reproductive capacity of an individual
feedback inhibition: a product's effect of a reaction sequence to decrease its further production by inhibiting the first enzyme's activity in the pathway that produces it
femur: (also, thighbone) longest, heaviest, and strongest bone in the body
fermentation: process of regenerating NAD+ with either an inorganic or organic compound serving as the final electron acceptor; occurs in the absence of oxygen
fern: seedless vascular plant that produces large fronds; the most advanced group of seedless vascular plants
fertilization: union of two haploid cells from two individual organisms
FEV1/FVC ratio: ratio of how much air can be forced out of the lung in one second to the total amount that is forced out of the lung; a measurement of lung function that can be used to detect disease states
fibrous connective tissue: type of connective tissue with a high concentration of fibers
fibrous joint: joint held together by fibrous connective tissue
fibrous root system: type of root system in which the roots arise from the base of the stem in a cluster, forming a dense network of roots; found in monocots
fibula: (also, calf bone) parallels and articulates with the tibia
filament: thin stalk that links the anther to the base of the flower
first messenger: the hormone that binds to a plasma membrane hormone receptor to trigger a signal transduction pathway
fission: (also, binary fission) method by which multicellular organisms increase in size or asexual reproduction in which a unicellular organism splits into two separate organisms by mitosis
fixed action pattern: series of instinctual behaviors that, once initiated, always goes to completion regardless of changes in the environment
flagellum: (plural = flagella) long, hair-like structure that extends from the plasma membrane and moves the cell
flame cell: (also, protonephridia) excretory cell found in flatworms
flat bone: thin and relatively broad bone found where extensive protection of organs is required or where broad surfaces of muscle attachment are required
flexion: movement in which the angle between the bones decreases; opposite of extension
flight feather: feather specialized for flight
flow-resistive: work of breathing performed by the alveoli and tissues in the lung
flower: branches specialized for reproduction found in some seed-bearing plants, containing either specialized male or female organs or both male and female organs
fluid mosaic model: describes the plasma membrane's structure as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains attached to proteins or lipids, respectively), resulting in a fluid character (fluidity)
follicle stimulating hormone (FSH): reproductive hormone that causes sperm production in males and follicle development in females
follicle-stimulating hormone (FSH): hormone produced by the anterior pituitary that stimulates gamete production
food chain: linear representation of a chain of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics
food web: graphic representation of a holistic, nonlinear web of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics
foodborne disease: any illness resulting from the consumption of contaminated food, or of the pathogenic bacteria, viruses, or other parasites that contaminate food
foraging: behaviors species use to find food
forced expiratory volume (FEV): (also, forced vital capacity) measure of how much air can be forced out of the lung from maximal inspiration over a specific amount of time
forearm: extends from the elbow to the wrist and consists of two bones: the ulna and the radius
foreign DNA: DNA that belongs to a different species or DNA that is artificially synthesized
foundation species: species which often forms the major structural portion of the habitat
founder effect: event that initiates an allele frequency change in part of the population, which is not typical of the original population
fovea: region in the center of the retina with a high density of photoreceptors and which is responsible for acute vision
fragmentation: cutting or fragmenting of the original animal into parts and the growth of a separate animal from each part
free energy: Gibbs free energy is the usable energy, or energy that is available to do work
free nerve ending: ending of an afferent neuron that lacks a specialized structure for detection of sensory stimuli; some respond to touch, pain, or temperature
frequency-dependent selection: selection that favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection)
frog: tail-less amphibian that belongs to the clade Anura
frontal (coronal) plane: plane cutting through an animal separating the individual into front and back portions
frontal lobe: part of the cerebral cortex that contains the motor cortex and areas involved in planning, attention, and language
fruit: thickened tissue derived from ovary wall that protects the embryo after fertilization and facilitates seed dispersal
FtsZ: tubulin-like protein component of the prokaryotic cytoskeleton that is important in prokaryotic cytokinesis (name origin: Filamenting temperature-sensitive mutant Z)
functional group: group of atoms that provides or imparts a specific function to a carbon skeleton
functional residual capacity (FRC): expiratory reserve volume plus residual volume
functional vital capacity (FVC): amount of air that can be forcibly exhaled after taking the deepest breath possible
furcula: wishbone formed by the fusing of the clavicles
fusiform: animal body shape that is tubular and tapered at both ends
fusion: method of entry by some enveloped viruses, where the viral envelope fuses with the plasma membrane of the host cell
G-protein: a membrane protein activated by the hormone first messenger to activate formation of cyclic AMP
G-protein-linked receptor: cell-surface receptor that activates membrane-bound G-proteins to transmit a signal from the receptor to nearby membrane components
G0 phase: distinct from the G1 phase of interphase; a cell in G0 is not preparing to divide
G1 phase: (also, first gap) first phase of interphase centered on cell growth during mitosis
G2 phase: (also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis
gall: appearance of a plant tumor
gallbladder: organ that stores and concentrates bile
gametangium: structure on the gametophyte in which gametes are produced
gamete: haploid reproductive cell or sex cell (sperm, pollen grain, or egg)
gametic barrier: prezygotic barrier occurring when closely related individuals of different species mate, but differences in their gamete cells (eggs and sperm) prevent fertilization from taking place
gametophyte: a multicellular haploid life-cycle stage that produces gametes
gametophyte: multicellular stage of the plant that gives rise to haploid gametes or spores
gap junction: channel between two adjacent animal cells that allows ions, nutrients, and low molecular weight substances to pass between cells, enabling the cells to communicate
gastric inhibitory peptide: hormone secreted by the small intestine in the presence of fatty acids and sugars; it also inhibits acid production and peristalsis in order to slow down the rate at which food enters the small intestine
gastric phase: digestive phase beginning once food enters the stomach; gastric acids and enzymes process the ingested materials
gastrin: hormone which stimulates hydrochloric acid secretion in the stomach
gastrodermis: inner layer (from endoderm) that lines the digestive cavity
gastrovascular cavity: opening that serves as both a mouth and an anus, which is termed an incomplete digestive system
gastrovascular cavity: digestive system consisting of a single opening
gastrula: stage of animal development characterized by the formation of the digestive cavity
gastrulation: process in which the blastula folds over itself to form the three germ layers
GC-rich box: (GGCG) nonessential eukaryotic promoter sequence that binds cellular factors to increase the efficiency of transcription; may be present several times in a promoter
gel electrophoresis: technique used to separate molecules on the basis of size using electric charge
gemma: (plural, gemmae) leaf fragment that spreads for asexual reproduction
gemmule: structure produced by asexual reproduction in freshwater sponges where the morphology is inverted
gene: physical and functional unit of heredity, a sequence of DNA that codes for a protein.
gene expression: processes that control the turning on or turning off of a gene
gene flow: flow of alleles in and out of a population due to the individual or gamete migration
gene pool: all the alleles that the individuals in the population carry
gene targeting: method for altering the sequence of a specific gene by introducing the modified version on a vector
gene therapy: technique used to cure inheritable diseases by replacing mutant genes with good genes
gene therapy: treatment of genetic disease by adding genes, using viruses to carry the new genes inside the cell
gene transfer agent (GTA): bacteriophage-like particle that transfers random genomic segments from one species of prokaryote to another
genetic diagnosis: diagnosis of the potential for disease development by analyzing disease-causing genes
genetic diversity: variety of genes in a species or other taxonomic group or ecosystem, the term can refer to allelic diversity or genome-wide diversity
genetic drift: effect of chance on a population’s gene pool
genetic engineering: alteration of the genetic makeup of an organism
genetic map: outline of genes and their location on a chromosome
genetic marker: gene or sequence on a chromosome with a known location that is associated with a specific trait
genetic recombination: DNA exchange between homologous chromosome pairs
genetic structure: distribution of the different possible genotypes in a population
genetic testing: process of testing for the presence of disease-causing genes
genetic variance: diversity of alleles and genotypes in a population
genetically modified organism (GMO): organism whose genome has been artificially changed
genome: total genetic information of a cell or organism
genome annotation: process of attaching biological information to gene sequences
genome fusion: fusion of two prokaryotic genomes, presumably by endosymbiosis
genome mapping: process of finding the location of genes on each chromosome
genomic library: collection of cloned DNA which represents all of the sequences and fragments from a genome
genomics: study of entire genomes including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species
genotype: underlying genetic makeup, consisting of both physically visible and non-expressed alleles, of an organism
genus: division of family in the taxonomic classification system; the first part of the binomial scientific name
geographical variation: differences in the phenotypic variation between populations that are separated geographically
geometric isomer: isomer with similar bonding patterns differing in the placement of atoms alongside a double covalent bond
germ cells: specialized cell line that produces gametes, such as eggs or sperm
germ layer: collection of cells formed during embryogenesis that will give rise to future body tissues, more pronounced in vertebrate embryogenesis
gestation: length of time for fetal development to birth
gibberellin (GA): plant hormone that stimulates shoot elongation, seed germination, and the maturation and dropping of fruit and flowers
gigantism: condition caused by overproduction of GH in children
gill circulation: circulatory system that is specific to animals with gills for gas exchange; the blood flows through the gills for oxygenation
ginkgophyte: gymnosperm with one extant species, the Ginkgo biloba: a tree with fan-shaped leaves
gizzard: muscular organ that grinds food
glabrous: describes the non-hairy skin found on palms and fingers, soles of feet, and lips of humans and other primates
glia: (also, glial cells) cells that provide support functions for neurons
gliding movement: when relatively flat bone surfaces move past each other
global climate change: altered global weather patterns, including a worldwide increase in temperature, due largely to rising levels of atmospheric carbon dioxide
Glomeromycota: phylum of fungi that form symbiotic relationships with the roots of trees
glomerular filtration: filtration of blood in the glomerular capillary network into the glomerulus
glomerular filtration rate (GFR): amount of filtrate formed by the glomerulus per minute
glomerulus: in the olfactory bulb, one of the two neural clusters that receives signals from one type of olfactory receptor
glomerulus (renal): part of the renal corpuscle that contains the capillary network
glucagon: hormone produced by the alpha cells of the pancreas in response to low blood sugar; functions to raise blood sugar levels
glucocorticoid: corticosteroid that affects glucose metabolism
gluconeogenesis: synthesis of glucose from amino acids
glucose-sparing effect: effect of GH that causes tissues to use fatty acids instead of glucose as an energy source
GLUT protein: integral membrane protein that transports glucose
glycogen: storage carbohydrate in animals
glycogenolysis: breakdown of glycogen into glucose
glycolipid: combination of carbohydrates and lipids
glycolysis: process of breaking glucose into two three-carbon molecules with the production of ATP and NADH
glycoprotein: combination of carbohydrates and proteins
glycosidic bond: bond formed by a dehydration reaction between two monosaccharides with eliminating a water molecule
gnathostome: jawed fish
gnetophyte: gymnosperm shrub with varied morphological features that produces vessel elements in its woody tissues; the phylum includes the genera Ephedra, Gnetum, and Welwitschia
goiter: enlargement of the thyroid gland caused by insufficient dietary iodine levels
Golgi apparatus: eukaryotic organelle comprised of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution
Golgi tendon organ: muscular proprioceptive tension receptor that provides the sensory component of the Golgi tendon reflex
gomphosis: the joint in which the tooth fits into the socket like a peg
gonadotropin: hormone that regulates the gonads, including FSH and LH
gonadotropin-releasing hormone (GnRH): hormone from the hypothalamus that causes the release of FSH and LH from the anterior pituitary
good genes hypothesis: theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease
Gorilla: genus of gorillas
gradual speciation model: model that shows how species diverge gradually over time in small steps
grafting: method of asexual reproduction where the stem from one plant species is spliced to a different plant
Gram negative: bacterium whose cell wall contains little peptidoglycan but has an outer membrane
Gram positive: bacterium that contains mainly peptidoglycan in its cell walls
granum: stack of thylakoids located inside a chloroplast
granzyme: protease that enters target cells through perforin and induces apoptosis in the target cells; used by NK cells and killer T cells
gravitropism: response of a plant growth in the same direction as gravity
grazing food web: type of food web in which the primary producers are either plants on land or phytoplankton in the water; often associated with a detrital food web within the same ecosystem
greenhouse effect: warming of Earth due to carbon dioxide and other greenhouse gases in the atmosphere
greenhouse gases: atmospheric gases such as carbon dioxide and methane that absorb and emit radiation, thus trapping heat in Earth’s atmosphere
gross primary productivity: rate at which photosynthetic primary producers incorporate energy from the sun
ground tissue: plant tissue involved in photosynthesis; provides support, and stores water and sugars
group I virus: virus with a dsDNA genome
group II virus: virus with an ssDNA genome
group III virus: virus with a dsRNA genome
group IV virus: virus with an ssRNA genome with positive polarity
group V virus: virus with an ssRNA genome with negative polarity
group VI virus: virus with an ssRNA genome converted into dsDNA by reverse transcriptase
group VII virus: virus with a single-stranded mRNA converted into dsDNA for genome replication
growth factor: ligand that binds to cell-surface receptors and stimulates cell growth
growth hormone (GH): hormone produced by the anterior pituitary that promotes protein synthesis and body growth
growth hormone-inhibiting hormone (GHIH): hormone produced by the hypothalamus that inhibits growth hormone production, also called somatostatin
growth hormone-releasing hormone (GHRH): hormone released by the hypothalamus that triggers the release of GH
guanine diphosphate (GDP): molecule that is left after the energy is used to start translation
guanine triphosphate (GTP): energy-providing molecule that binds to eIF-2 and is needed for translation
guard cells: paired cells on either side of a stoma that control stomatal opening and thereby regulate the movement of gases and water vapor
gustation: sense of taste
gymnosperm: seed plant with naked seeds (seeds exposed on modified leaves or in cones)
gynoecium: (also, carpel) structure that constitutes the female reproductive organ
gynoecium: the sum of all the carpels in a flower
gyrus: (plural: gyri) ridged protrusions in the cortex
habitat isolation: reproductive isolation resulting when species' populations move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the same species' other populations
habituation: ability of a species to ignore repeated stimuli that have no consequence
hagfish: eel-like jawless fish that live on the ocean floor and are scavengers
hairpin: structure of RNA when it folds back on itself and forms intramolecular hydrogen bonds between complementary nucleotides
halophile: organism that require a salt concentration of at least 0.2 M
handicap principle: theory of sexual selection that argues only the fittest individuals can afford costly traits
haplodiplodontic: haploid and diploid stages alternate
haploid: cell, nucleus, or organism containing one set of chromosomes (n)
haplontic: haploid stage is the dominant stage
haustoria: modified hyphae on many parasitic fungi that penetrate the tissues of their hosts, release digestive enzymes, and/or absorb nutrients from the host
Haversian canal: contains the bone’s blood vessels and nerve fibers
haze-effect cooling: effect of the gases and solids from a volcanic eruption on global climate
heat: energy transferred from one system to another that is not work (energy of the molecules' motion or particles)
heat energy: total bond energy of reactants or products in a chemical reaction
heat of vaporization of water: high amount of energy required for liquid water to turn into water vapor
heirloom seed: seed from a plant that was grown historically, but has not been used in modern agriculture on a large scale
helicase: during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds
helper T lymphocyte (TH): cell of the adaptive immune system that binds APCs via MHC II molecules and stimulates B cells or secretes cytokines to initiate the immune response
heme group: centralized iron-containing group that is surrounded by the alpha and beta subunits of hemoglobin
hemizygous: presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant
hemocoel: internal body cavity seen in arthropods
hemocoel: cavity into which blood is pumped in an open circulatory system
hemoglobin: molecule in red blood cells that can bind oxygen, carbon dioxide, and carbon monoxide
hemolymph: mixture of blood and interstitial fluid that is found in insects and other arthropods as well as most mollusks
herbaceous: grass-like plant noticeable by the absence of woody tissue
herbivore: animal that consumes a strictly plant diet
herbivory: consumption of plants by insects and other animals
heritability: fraction of population variation that can be attributed to its genetic variance
hermaphrodite: referring to an animal where both male and female gonads are present in the same individual
hermaphroditism: state of having both male and female reproductive parts within the same individual organism; refers only to nonhuman animals
heterodont tooth: different types of teeth that are modified for different purposes
heterogeneity: number of ecological niches
heterospecifics: individuals that are members of different species
heterosporous: produces two types of spores
heterothallic: describes when only one mating type is present in an individual mycelium
heterotroph: organism that consumes organic substances or other organisms for food
heterozygous: having two different alleles for a given gene on the homologous chromosome
hibernation: torpor over a long period of time, such as a winter
hilum: region in the renal pelvis where blood vessels, nerves, and ureters bunch before entering or exiting the kidney
hinge joint: slightly rounded end of one bone fits into the slightly hollow end of the other bone
hippocampus: brain structure in the temporal lobe involved in processing memories
histone: one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes
histone acetylation: epigenetic modification that leads to gene expression; a process involving adding or removing an acetyl functional group
holistic ecosystem model: study that attempts to quantify the composition, interactions, and dynamics of entire ecosystems; often limited by economic and logistical difficulties, depending on the ecosystem
holoblastic: complete cleavage; takes place in cells with a small amount of yolk
holoenzyme: prokaryotic RNA polymerase consisting of α, α, β, β', and σ; this complex is responsible for transcription initiation
homeostasis: ability of an organism to maintain constant internal conditions
homeostasis: dynamic equilibrium maintaining appropriate body functions
hominin: species that are more closely related to humans than chimpanzees
hominoid: pertaining to great apes and humans
Homo: genus of humans
Homo sapiens sapiens: anatomically modern humans
homologous chromosomes: chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent
homologous recombination: process by which homologous chromosomes undergo reciprocal physical exchanges at their arms, also crossing over
homologous structures: parallel structures in diverse organisms that have a common ancestor
homology: similarity in characteristics resulting from a shared ancestry
homosporous: produces one type of spore
homothallic: describes when both mating types are present in mycelium
homozygous: having two identical alleles for a given gene on the homologous chromosome
honest signal: trait that gives a truthful impression of an individual’s fitness
horizon: soil layer with distinct physical and chemical properties, which differs from other layers depending on how and when it was formed
horizontal gene transfer (HGT): (also, lateral gene transfer) transfer of genes between unrelated species
horizontal transmission: transmission of a disease between unrelated individuals
hormonal stimuli: release of a hormone in response to another hormone
hormone: chemical signaling molecule, usually protein or steroid, secreted by endocrine cells that act to control or regulate specific physiological processes
hormone receptor: the cellular protein that binds to a hormone
hornworts: group of non-vascular plants in which stomata appear
horsetail: seedless vascular plant characterized by joints
host: an organism that is invaded by a pathogen or parasite
host: organism a parasite lives on
host DNA: DNA that is present in the genome of the organism of interest
Hox gene: (also, homeobox gene) master control gene that can turn on or off large numbers of other genes during embryogenesis
human beta chorionic gonadotropin (β-HCG): hormone produced by the chorion of the zygote that helps to maintain the corpus luteum and elevated levels of progesterone
humerus: only bone of the arm
humoral immune response: adaptive immune response that is controlled by activated B cells and antibodies
humoral stimuli: control of hormone release in response to changes in extracellular fluids such as blood or the ion concentration in the blood
humus: organic material of soil; made up of microorganisms, dead animals, and plants in varying stages of decay
hybrid: offspring of two closely related individuals, not of the same species
hybrid zone: area where two closely related species continue to interact and reproduce, forming hybrids
hybridization: process of mating two individuals that differ with the goal of achieving a certain characteristic in their offspring
hydrocarbon: molecule that consists only of carbon and hydrogen
hydrogen bond: weak bond between slightly positively charged hydrogen atoms and slightly negatively charged atoms in other molecules
hydrogenosome: organelle carried by parabasalids (Excavata) that functions anaerobically and outputs hydrogen gas as a byproduct; likely evolved from mitochondria
hydrolysis: reaction that causes breakdown of larger molecules into smaller molecules by utilizing water
hydrophilic: describes ions or polar molecules that interact well with other polar molecules such as water
hydrophilic: molecule with the ability to bond with water; “water-loving”
hydrophobic: describes uncharged nonpolar molecules that do not interact well with polar molecules such as water
hydrophobic: molecule that does not have the ability to bond with water; “water-hating”
hydrosphere: area of the Earth where water movement and storage occurs
hydrostatic skeleton: skeleton that consists of aqueous fluid held under pressure in a closed body compartment
hydrothermal vent: fissure in Earth’s surface that releases geothermally heated water
Hylobatidae: family of gibbons
Hylonomus: one of the earliest reptiles
hyoid bone: lies below the mandible in the front of the neck
hyperextension: extension past the regular anatomical position
hyperglycemia: high blood sugar level
hyperopia: (also, farsightedness) visual defect in which the image focus falls behind the retina, thereby making images in the distance clear, but close-up images blurry
hyperplasia: abnormally high cell growth and division
hyperpolarization: change in the membrane potential to a more negative value
hypersensitivities: spectrum of maladaptive immune responses toward harmless foreign particles or self antigens; occurs after tissue sensitization and includes immediate-type (allergy), delayed-type, and autoimmunity
hyperthermophile: organism that grows at temperatures between 80–122 °C
hyperthyroidism: overactivity of the thyroid gland
hypertonic: situation in which extracellular fluid has a higher osmolarity than the fluid inside the cell, resulting in water moving out of the cell
hypha: fungal filament composed of one or more cells
hypocotyl: embryonic axis above the cotyledons
hypoglycemia: low blood sugar level
hypophyseal portal system: system of blood vessels that carries hormones from the hypothalamus to the anterior pituitary
hypoplasia: abnormally low cell growth and division
hypothalamus: brain structure that controls hormone release and body homeostasis
hypothesis: suggested explanation for an observation, which one can test
hypothesis-based science: form of science that begins with a specific question and potential testable answers
hypothyroidism: underactivity of the thyroid gland
hypotonic: situation in which extracellular fluid has a lower osmolarity than the fluid inside the cell, resulting in water moving into the cell
Biology 2e, March 28, 2018, OpenStax, https://openstax.org/books/biology-2e/pages/1-introduction