3' UTR: 3' untranslated region; region just downstream of the protein-coding region in an RNA molecule that is not translated
5' cap: a methylated guanosine triphosphate (GTP) molecule that is attached to the 5' end of a messenger RNA to protect the end from degradation
5' UTR: 5' untranslated region; region just upstream of the protein-coding region in an RNA molecule that is not translated
7-methylguanosine cap: modification added to the 5' end of pre-mRNAs to protect mRNA from degradation and assist translation
A horizon: consists of a mixture of organic material with inorganic products of weathering
abduction: when a bone moves away from the midline of the body
abiotic: nonliving components of the environment
above-ground biomass: total mass of aboveground living plants per area
abscisic acid (ABA): plant hormone that induces dormancy in seeds and other organs
abscission: physiological process that leads to the fall of a plant organ (such as leaf or petal drop)
absorption spectrum: range of wavelengths of electromagnetic radiation absorbed by a given substance
abstract: opening section of a scientific paper that summarizes the research and conclusions
abyssal zone: deepest part of the ocean at depths of 4000 m or greater
Acanthostega: one of the earliest known tetrapods
accessory fruit: fruit derived from tissues other than the ovary
acclimatization: alteration in a body system in response to environmental change
acellular: lacking cells
acetyl CoA: combination of an acetyl group derived from pyruvic acid and coenzyme A, which is made from pantothenic acid (a B-group vitamin)
acetylcholine: neurotransmitter released by neurons in the central nervous system and peripheral nervous system
acetylcholinesterase: (AChE) enzyme that breaks down ACh into acetyl and choline
acid: molecule that donates hydrogen ions and increases the concentration of hydrogen ions in a solution
acid rain: corrosive rain caused by rainwater falling to the ground through sulfur dioxide gas, turning it into weak sulfuric acid; can damage structures and ecosystems
acidophile: organism with optimal growth pH of three or below
acoelomate: animal without a body cavity
acromegaly: condition caused by overproduction of GH in adults
acrosomal reaction: series of biochemical reactions that the sperm uses to break through the zona pellucida
actin: globular contractile protein that interacts with myosin for muscle contraction
Actinopterygii: ray-finned fishes
action potential: self-propagating momentary change in the electrical potential of a neuron (or muscle) membrane
activation energy: energy necessary for reactions to occur
activator: protein that binds to prokaryotic operators to increase transcription
active site: enzyme's specific region to which the substrate binds
active transport: method of transporting material that requires energy
acute disease: disease where the symptoms rise and fall within a short period of time
adaptation: heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment
adaptive evolution: increase in frequency of beneficial alleles and decrease in deleterious alleles due to selection
adaptive immunity: immunity that has memory and occurs after exposure to an antigen either from a pathogen or a vaccination
adaptive radiation: speciation when one species radiates to form several other species
adaptive radiation: rapid branching through speciation of a phylogenetic tree into many closely related species
Addison’s disease: disorder caused by the hyposecretion of corticosteroids
adduction: movement of the limbs inward after abduction
adenylate cyclase: an enzyme that catalyzes the conversion of ATP to cyclic AMP
adhesion: attraction between water molecules and other molecules
adrenal cortex: outer portion of adrenal glands that produces corticosteroids
adrenal gland: endocrine glands associated with the kidneys
adrenal medulla: inner portion of adrenal glands that produces epinephrine and norepinephrine
adrenocorticotropic hormone (ACTH): hormone released by the anterior pituitary, which stimulates the adrenal cortex to release corticosteroids during the long-term stress response
adventitious: describes an organ that grows in an unusual place, such as a roots growing from the side of a stem
adventitious root: aboveground root that arises from a plant part other than the radicle of the plant embryo
aerobic respiration: process in which organisms convert energy in the presence of oxygen
afferent arteriole: arteriole that branches from the cortical radiate artery and enters the glomerulus
affinity: attraction of molecular complementarity between antigen and antibody molecules
age structure: proportion of population members at specific age ranges
aggregate fruit: fruit that develops from multiple carpels in the same flower
aggressive display: visual display by a species member to discourage other members of the same species or different species
aldosterone: steroid hormone produced by the adrenal cortex that stimulates the reabsorption of Na+ from extracellular fluids and secretion of K+
aleurone: single layer of cells just inside the seed coat that secretes enzymes upon germination
algal bloom: rapid increase of algae in an aquatic system
alimentary canal: tubular digestive system with a mouth and anus
aliphatic hydrocarbon: hydrocarbon consisting of a linear chain of carbon atoms
alkaliphile: organism with optimal growth pH of nine or above
allantois: membrane of the egg that stores nitrogenous wastes produced by the embryo; also facilitates respiration
allele: gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes
allele frequency: (also, gene frequency) rate at which a specific allele appears within a population
allergy: immune reaction that results from immediate hypersensitivities in which an antibody-mediated immune response occurs within minutes of exposure to a harmless antigen
allopatric speciation: speciation that occurs via geographic separation
allopolyploid: polyploidy formed between two related, but separate species
allosteric inhibition: inhibition by a binding event at a site different from the active site, which induces a conformational change and reduces the enzyme's affinity for its substrate
alpha cell: endocrine cell of the pancreatic islets that produces the hormone glucagon
alpha-helix structure (α-helix): type of secondary protein structure formed by folding the polypeptide into a helix shape with hydrogen bonds stabilizing the structure
alteration: change of the set point in a homeostatic system
alternation of generations: life-cycle type in which the diploid and haploid stages alternate
alveolar duct: duct that extends from the terminal bronchiole to the alveolar sac
alveolar PO2: partial pressure of oxygen in the alveoli (usually around 100 mmHg)
alveolar sac: structure consisting of two or more alveoli that share a common opening
alveolar ventilation: how much air is in the alveoli
alveolus: (plural: alveoli) (also, air sac) terminal region of the lung where gas exchange occurs
Alzheimer’s disease: neurodegenerative disorder characterized by problems with memory and thinking
amino acid: a protein's monomer; has a central carbon or alpha carbon to which an amino group, a carboxyl group, a hydrogen, and an R group or side chain is attached; the R group is different for all 20 common amino acids
amino acid-derived hormone: hormone derived from amino acids
aminoacyl tRNA synthetase: enzyme that “charges” tRNA molecules by catalyzing a bond between the tRNA and a corresponding amino acid
aminopeptidase: protease that breaks down peptides to single amino acids; secreted by the brush border of small intestine
ammonia: compound made of one nitrogen atom and three hydrogen atoms
ammonification: process by which ammonia is released during the decomposition of nitrogen-containing organic compounds
ammonotelic: describes an animal that excretes ammonia as the primary waste material
amnion: membrane of the egg that protects the embryo from mechanical shock and prevents dehydration
amniote: animal that produces a terrestrially adapted egg protected by amniotic membranes
amoebocyte: sponge cell with multiple functions, including nutrient delivery, egg formation, sperm delivery, and cell differentiation
amphiarthrosis: joint that allows slight movement; includes syndesmoses and symphyses
Amphibia: frogs, salamanders, and caecilians
amphiphilic: molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments
ampulla of Lorenzini: sensory organ that allows sharks to detect electromagnetic fields produced by living things
amygdala: structure within the limbic system that processes fear
anabolic: (also, anabolism) pathways that require an energy input to synthesize complex molecules from simpler ones
anaerobic: process that does not use oxygen
anaerobic: refers to organisms that grow without oxygen
anaerobic cellular respiration: process in which organisms convert energy for their use in the absence of oxygen
analogy: (also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path
analytical model: ecosystem model that is created with mathematical formulas to predict the effects of environmental disturbances on ecosystem structure and dynamics
anaphase: stage of mitosis during which sister chromatids are separated from each other
anapsid: animal having no temporal fenestrae in the cranium
anatomical dead space: (also, anatomical shunt) region of the lung that lacks proper ventilation/perfusion due to an anatomical block
androecium: sum of all the stamens in a flower
androgen: male sex hormone such as testosterone
aneuploid: individual with an error in chromosome number; includes chromosome segment deletions and duplications
aneuploidy: condition of a cell having an extra chromosome or missing a chromosome for its species
angina: pain caused by partial blockage of the coronary arteries by the buildup of plaque and lack of oxygen to the heart muscle
angiotensin converting enzyme (ACE): enzyme that converts angiotensin I to angiotensin II
angiotensin I: product in the renin-angiotensin-aldosterone pathway
angiotensin II: molecule that affects different organs to increase blood pressure
angular movement: produced when the angle between the bones of a joint changes
anion: negative ion that is formed by an atom gaining one or more electrons
Annelida: phylum of vermiform animals with metamerism
anoxic: without oxygen
antenna protein: pigment molecule that directly absorbs light and transfers the energy absorbed to other pigment molecules
anterior pituitary: portion of the pituitary gland that produces six hormones; also called adenohypophysis
anther: sac-like structure at the tip of the stamen in which pollen grains are produced
antheridium: male gametangium
Anthophyta: phylum to which angiosperms belong
anthropoid: monkeys, apes, and humans
anti-diuretic hormone (ADH): hormone that prevents the loss of water
antibiotic: biological substance that, in low concentration, is antagonistic to the growth of prokaryotes
antibiotic resistance: ability of an organism to be unaffected by an antibiotic's actions
antibody: protein that is produced by plasma cells after stimulation by an antigen; also known as an immunoglobulin
anticodon: three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon
antidiuretic hormone (ADH): hormone produced by the hypothalamus and released by the posterior pituitary that increases water reabsorption by the kidneys
antigen: foreign or “non-self” protein that triggers the immune response
antigen-presenting cell (APC): immune cell that detects, engulfs, and informs the adaptive immune response about an infection by presenting the processed antigen on the cell surface
antioxidant: agent that prevents cell destruction by reactive oxygen species
antipodals: the three cells away from the micropyle
antiporter: transporter that carries two ions or small molecules in different directions
Anura: frogs
anus: exit point for waste material
aorta: major artery of the body that takes blood away from the heart
apex consumer: organism at the top of the food chain
aphotic zone: part of the ocean where no light penetrates
apical bud: bud formed at the tip of the shoot
apical meristem: meristematic tissue located at the tips of stems and roots; enables a plant to extend in length
apocrine gland: scent gland that secretes substances that are used for chemical communication
Apoda: caecilians
apodeme: ingrowth of an animal’s exoskeleton that functions as an attachment site for muscles
apomixis: process by which seeds are produced without fertilization of sperm and egg
apoptosis: programmed cell death
aposematic coloration: warning coloration used as a defensive mechanism against predation
appendicular skeleton: composed of the bones of the upper limbs, which function to grasp and manipulate objects, and the lower limbs, which permit locomotion
applied science: form of science that aims to solve real-world problems
appositional growth: increase in the diameter of bones by the addition of bone tissue at the surface of bones
aquaporin: channel protein that allows water through the membrane at a very high rate
arachnoid mater: spiderweb-like middle layer of the meninges that cover the central nervous system
arbuscular mycorrhiza: mycorrhizal association in which the fungal hyphae enter the root cells and form extensive networks
Arbuscular mycorrhizae: mycorrhizae commonly involving Glomeromycetes in which the fungal hyphae penetrate the cell walls of the plant root cells (but not the cell membranes)
Archaeopteryx: transition species from dinosaur to bird from the Jurassic period
archegonium: female gametangium
archenteron: primitive gut cavity within the gastrula that opens outward via the blastopore
archosaur: modern crocodilian or bird, or an extinct pterosaur or dinosaur
arcuate artery: artery that branches from the interlobar artery and arches over the base of the renal pyramids
aromatic hydrocarbon: hydrocarbon consisting of closed rings of carbon atoms
arteriole: small vessel that connects an artery to a capillary bed
artery: blood vessel that takes blood away from the heart
Arthropoda: phylum of animals with jointed appendages
articulation: any place where two bones are joined
ascending limb: part of the loop of Henle that ascends from the renal medulla to the renal cortex
ascocarp: fruiting body of ascomycetes
Ascomycota: (also, sac fungi) phylum of fungi that store spores in a sac called ascus
asexual reproduction: form of reproduction that produces offspring that are genetically identical to the parent
assimilation: biomass consumed and assimilated from the previous trophic level after accounting for the energy lost due to incomplete ingestion of food, energy used for respiration, and energy lost as waste
assortative mating: when individuals tend to mate with those who are phenotypically similar to themselves
astrocyte: glial cell in the central nervous system that provide nutrients, extracellular buffering, and structural support for neurons; also makes up the blood-brain barrier
asymmetrical: describes animals with no axis of symmetry in their body pattern
asymptomatic disease: disease where there are no symptoms and the individual is unaware of being infected unless lab tests are performed
atherosclerosis: buildup of fatty plaques in the coronary arteries in the heart
atom: smallest and most fundamental unit of matter that retains the properties of an element
atom: the smallest unit of matter that retains all of the chemical properties of an element
atomic mass: calculated mean of the mass number for an element’s isotopes
atomic number: total number of protons in an atom
ATP: adenosine triphosphate, the cell’s energy currency
ATP synthase: (also F1F0 ATP synthase) membrane-embedded protein complex that adds a phosphate to ADP with energy from protons diffusing through it
atrial natriuretic peptide (ANP): hormone produced by the heart to reduce blood volume, pressure, and Na+ concentration
atrioventricular valve: one-way membranous flap of connective tissue between the atrium and the ventricle in the right side of the heart; also known as tricuspid valve
atrium: (plural: atria) chamber of the heart that receives blood from the veins and sends blood to the ventricles
attention deficit hyperactivity disorder (ADHD): neurodevelopmental disorder characterized by difficulty maintaining attention and controlling impulses
attenuation: weakening of a virus during vaccine development
audition: sense of hearing
auditory ossicle: (also, middle ear) transduces sounds from the air into vibrations in the fluid-filled cochlea
auricle: cartilaginous outer ear
Australopithecus: genus of hominins that evolved in eastern Africa approximately four million years ago
autism spectrum disorder (ASD): neurodevelopmental disorder characterized by impaired social interaction and communication abilities
autoantibody: antibody that incorrectly marks “self” components as foreign and stimulates the immune response
autocrine signal: signal that is sent and received by the same or similar nearby cells
autoimmune response: inappropriate immune response to host cells or self-antigens
autoimmunity: type of hypersensitivity to self antigens
autoinducer: signaling molecule secreted by bacteria to communicate with other bacteria of its kind
autonomic nervous system: part of the peripheral nervous system that controls bodily functions
autopolyploid: polyploidy formed within a single species
autosome: any of the non-sex chromosomes
autosomes: any of the non-sex chromosomes
auxin: plant hormone that influences cell elongation (in phototropism), gravitropism, apical dominance, and root growth
avidity: total binding strength of a multivalent antibody with antigen
axial skeleton: forms the central axis of the body and includes the bones of the skull, the ossicles of the middle ear, the hyoid bone of the throat, the vertebral column, and the thoracic cage (ribcage)
axillary bud: bud located in the axil: the stem area where the petiole connects to the stem
axon: tube-like structure that propagates a signal from a neuron’s cell body to axon terminals
axon hillock: electrically sensitive structure on the cell body of a neuron that integrates signals from multiple neuronal connections
axon terminal: structure on the end of an axon that can form a synapse with another neuron
AZT: anti-HIV drug that inhibits the viral enzyme reverse transcriptase
B cell: lymphocyte that matures in the bone marrow and differentiates into antibody-secreting plasma cells
B horizon: soil layer that is an accumulation of mostly fine material that has moved downward
back mutation: when a live virus vaccine reverts back to it disease-causing phenotype
bacteriophage: virus that infects bacteria
balanced chemical equation: statement of a chemical reaction with the number of each type of atom equalized for both the products and reactants
ball-and-socket joint: joint with a rounded, ball-like end of one bone fitting into a cuplike socket of another bone
barcoding: molecular biology technique in which one or more short gene sequences taken from a well-characterized portion of the genome is used to identify a species
bark: tough, waterproof, outer epidermal layer of cork cells
basal angiosperms: a group of plants that probably branched off before the separation of monocots and eudicots
basal ganglia: interconnected collections of cells in the brain that are involved in movement and motivation; also known as basal nuclei
basal metabolic rate (BMR): metabolic rate at rest in endothermic animals
basal nuclei: see basal ganglia
basal taxon: branch on a phylogenetic tree that has not diverged significantly from the root ancestor
base: molecule that donates hydroxide ions or otherwise binds excess hydrogen ions and decreases the hydrogen ions' concentration in a solution
basic science: science that seeks to expand knowledge and understanding regardless of the short-term application of that knowledge
basidiocarp: fruiting body that protrudes from the ground and bears the basidia
Basidiomycota: (also, club fungi) phylum of fungi that produce club-shaped structures (basidia) that contain spores
basidium: club-shaped fruiting body of basidiomycetes
basilar membrane: stiff structure in the cochlea that indirectly anchors auditory receptors
basophil: leukocyte that releases chemicals usually involved in the inflammatory response
Batesian mimicry: type of mimicry where a non-harmful species takes on the warning colorations of a harmful one
bedrock: solid rock that lies beneath the soil
behavior: change in an organism’s activities in response to a stimulus
behavioral biology: study of the biology and evolution of behavior
behavioral isolation: type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place
benthic realm: (also, benthic zone) part of the ocean that extends along the ocean bottom from the shoreline to the deepest parts of the ocean floor
beta cell: endocrine cell of the pancreatic islets that produces the hormone insulin
beta-pleated sheet (β-pleated): secondary structure in proteins in which hydrogen bonding forms “pleats” between atoms on the polypeptide chain's backbone
bicarbonate (HCO−3) ion: ion created when carbonic acid dissociates into H+ and (HCO−3)
bicarbonate buffer system: system in the blood that absorbs carbon dioxide and regulates pH levels
bicuspid valve: (also, mitral valve; left atrioventricular valve) one-way membranous flap between the atrium and the ventricle in the left side of the heart
bilateral symmetry: type of symmetry in which there is only one plane of symmetry, so the left and right halves of an animal are mirror images
bile: digestive juice produced by the liver; important for digestion of lipids
binary fission: prokaryotic cell division process
binomial nomenclature: system of two-part scientific names for an organism, which includes genus and species names
biochemistry: study of the chemistry of biological organisms
biodiversity: variety of a biological system, typically conceived as the number of species, but also applying to genes, biochemistry, and ecosystems
biodiversity hotspot: concept originated by Norman Myers to describe a geographical region with a large number of endemic species and a large percentage of degraded habitat
bioenergetics: study of energy flowing through living systems
biofilm: microbial community that is held together by a gummy-textured matrix
biogeochemical cycle: cycling of mineral nutrients through ecosystems and through the nonliving world
biogeography: study of the geographic distribution of living things and the abiotic factors that affect their distribution
biological carbon pump: process by which inorganic carbon is fixed by photosynthetic species that then die and fall to the sea floor where they cannot be reached by saprobes and their carbon dioxide consumption cannot be returned to the atmosphere
biological macromolecule: large molecule necessary for life that is built from smaller organic molecules
biological nitrogen fixation: conversion of atmospheric nitrogen into ammonia exclusively carried out by prokaryotes
biology: the study of life
bioluminescence: generation and emission of light by an organism, as in dinoflagellates
biomagnification: increasing concentrations of persistent, toxic substances in organisms at each trophic level, from the primary producers to the apex consumers
biomarker: individual protein that is uniquely produced in a diseased state
biomass: total weight, at the time of measurement, of living or previously living organisms in a unit area within a trophic level
biome: ecological community of plants, animals, and other organisms that is adapted to a characteristic set of environmental conditions
bioremediation: use of microbial metabolism to remove pollutants
biosphere: collection of all the ecosystems on Earth
biotechnology: use of biological agents for technological advancement
biotechnology: any technological application that uses living organisms, biological systems, or their derivatives to produce or modify other products
biotic: living components of the environment
biotic potential (rmax): maximal potential growth rate of a species
bipolar neuron: neuron with two processes from the cell body, typically in opposite directions
biramous: referring to two branches per appendage
birth rate (B): number of births within a population at a specific point in time
Black Death: devastating pandemic that is believed to have been an outbreak of bubonic plague caused by the bacterium Yersinia pestis
blastocyst: structure formed when cells in the mammalian blastula separate into an inner and outer layer
blastopore: opening into the archenteron that forms during gastrulation
blastula: 16–32 cell stage of development of an animal embryo
blending theory of inheritance: hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance
blood pressure (BP): pressure of blood in the arteries that helps to push blood through the body
blood urea nitrogen (BUN): estimate of urea in the blood and an indicator of kidney function
body plan: morphology or defining shape of an organism
bolus: mass of food resulting from chewing action and wetting by saliva
bone: (also, osseous tissue) connective tissue that constitutes the endoskeleton
bone remodeling: replacement of old bone tissue by new bone tissue
botany: study of plants
bottleneck effect: magnification of genetic drift as a result of natural events or catastrophes
botulism: disease produced by the toxin of the anaerobic bacterium Clostridium botulinum
Bowman's capsule: structure that encloses the glomerulus
brachiation: movement through trees branches via suspension from the arms
brainstem: portion of the brain that connects with the spinal cord; controls basic nervous system functions like breathing, heart rate, and swallowing
branch point: node on a phylogenetic tree where a single lineage splits into distinct new ones
bronchiole: airway that extends from the main tertiary bronchi to the alveolar sac
bronchus: (plural: bronchi) smaller branch of cartilaginous tissue that stems off of the trachea; air is funneled through the bronchi to the region where gas exchange occurs in alveoli
brumation: period of much reduced metabolism and torpor that occurs in any ectotherm in cold weather
budding: method of exit from the cell used in certain animal viruses, where virions leave the cell individually by capturing a piece of the host plasma membrane
budding: form of asexual reproduction that results from the outgrowth of a part of a cell leading to a separation from the original animal into two individuals
buffer: substance that resists a change in pH by absorbing or releasing hydrogen or hydroxide ions
bulb: modified underground stem that consists of a large bud surrounded by numerous leaf scales
bulbourethral gland: secretion that cleanses the urethra prior to ejaculation
bush meat: wild-caught animal used as food (typically mammals, birds, and reptiles); usually referring to hunting in the tropics of sub-Saharan Africa, Asia, and the Americas
C horizon: layer of soil that contains the parent material, and the organic and inorganic material that is broken down to form soil; also known as the soil base
CA-MRSA: MRSA acquired in the community rather than in a hospital
CAAT box: (GGCCAATCT) essential eukaryotic promoter sequence involved in binding transcription factors
caecilian: legless amphibian that belongs to the clade Apoda
calcification: process of deposition of mineral salts in the collagen fiber matrix that crystallizes and hardens the tissue
calcitonin: hormone produced by the parafollicular cells of the thyroid gland that functions to lower blood Ca2+ levels and promote bone growth
calorie: amount of heat required to change the temperature of one gram of water by one degree Celsius
Calvin cycle: light-independent reactions of photosynthesis that convert carbon dioxide from the atmosphere into carbohydrates using the energy and reducing power of ATP and NADPH
calyx: whorl of sepals
calyx: structure that connects the renal pelvis to the renal medulla
Cambrian explosion: time during the Cambrian period (542–488 million years ago) when most of the animal phyla in existence today evolved
camouflage: avoid detection by blending in with the background
canaliculus: microchannel that connects the lacunae and aids diffusion between cells
candela: (cd) unit of measurement of luminous intensity (brightness)
canopy: branches and foliage of trees that form a layer of overhead coverage in a forest
capillary: smallest blood vessel that allows the passage of individual blood cells and the site of diffusion of oxygen and nutrient exchange
capillary action: occurs because water molecules are attracted to charges on the inner surfaces of narrow tubular structures such as glass tubes, drawing the water molecules to the tubes' sides
capillary bed: large number of capillaries that converge to take blood to a particular organ or tissue
capsid: protein coating of the viral core
capsomere: protein subunit that makes up the capsid
capsule: external structure that enables a prokaryote to attach to surfaces and protects it from dehydration
capsule: case of the sporangium in mosses
captacula: tentacle-like projection that is present in tusks shells to catch prey
carbaminohemoglobin: molecule that forms when carbon dioxide binds to hemoglobin
carbohydrate: biological macromolecule in which the ratio of carbon to hydrogen and to oxygen is 1:2:1; carbohydrates serve as energy sources and structural support in cells and form arthropods' cellular exoskeleton
carbon fixation: process of converting inorganic CO2 gas into organic compounds
carbonic anhydrase (CA): enzyme that catalyzes carbon dioxide and water into carbonic acid
carboxypeptidase: protease that breaks down peptides to single amino acids; secreted by the brush border of the small intestine
cardiac cycle: filling and emptying the heart of blood by electrical signals that cause the heart muscles to contract and relax
cardiac muscle tissue: muscle tissue found only in the heart; cardiac contractions pump blood throughout the body and maintain blood pressure
cardiac output: the volume of blood pumped by the heart in one minute as a product of heart rate multiplied by stroke volume
cardiomyocyte: specialized heart muscle cell that is striated but contracts involuntarily like smooth muscle
carnivore: animal that consumes animal flesh
carotenoid: photosynthetic pigment (yellow-orange-red) that functions to dispose of excess energy
carpel: single unit of the pistil
carpus: eight bones that comprise the wrist
carrier protein: membrane protein that moves a substance across the plasma membrane by changing its own shape
carrying capacity (K): number of individuals of a species that can be supported by the limited resources of a habitat
cartilage: type of connective tissue with a large amount of ground substance matrix, cells called chondrocytes, and some amount of fibers
cartilaginous joint: joint in which the bones are connected by cartilage
Casineria: one of the oldest known amniotes; had both amphibian and reptilian characteristics
Casparian strip: waxy coating that forces water to cross endodermal plasma membranes before entering the vascular cylinder, instead of moving between endodermal cells
catabolic: (also, catabolism) pathways in which complex molecules break down into simpler ones
catabolite activator protein (CAP): protein that complexes with cAMP to bind to the promoter sequences of operons which control sugar processing when glucose is not available
Catarrhini: clade of Old World monkeys
cation: positive ion that is formed by an atom losing one or more electrons
caveolin: protein that coats the plasma membrane's cytoplasmic side and participates in the liquid uptake process by potocytosis
cDNA library: collection of cloned cDNA sequences
cell: smallest fundamental unit of structure and function in living things
cell cycle: ordered series of events involving cell growth and cell division that produces two new daughter cells
cell necrosis: cell death
cell plate: structure formed during plant cell cytokinesis by Golgi vesicles, forming a temporary structure (phragmoplast) and fusing at the metaphase plate; ultimately leads to the formation of cell walls that separate the two daughter cells
cell theory: see unified cell theory
cell wall: rigid cell covering comprised of various molecules that protects the cell, provides structural support, and gives shape to the cell
cell-cycle checkpoint: mechanism that monitors the preparedness of a eukaryotic cell to advance through the various cell-cycle stages
cell-mediated immune response: adaptive immune response that is carried out by T cells
cell-surface receptor: cell-surface protein that transmits a signal from the exterior of the cell to the interior, even though the ligand does not enter the cell
cellular cloning: production of identical cell populations by binary fission
cellulose: polysaccharide that comprises the plants' cell wall; provides structural support to the cell
centimorgan (cM): (also, map unit) relative distance that corresponds to a 0,01 recombination frequency
central dogma: states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins
central vacuole: large plant cell organelle that regulates the cell’s storage compartment, holds water, and plays a significant role in cell growth as the site of macromolecule degradation
centriole: rod-like structure constructed of microtubules at the center of each animal cell centrosome
centromere: region at which sister chromatids are bound together; a constricted area in condensed chromosomes
centrosome: region in animal cells made of two centrioles that serves as an organizing center for microtubules
cephalic phase: first phase of digestion, controlled by the neural response to the stimulus provided by food
Cephalochordata: chordate clade whose members possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage
cephalothorax: fused head and thorax in some species
cerebellum: brain structure involved in posture, motor coordination, and learning new motor actions
cerebral cortex: outermost sheet of brain tissue; involved in many higher-order functions
cerebrospinal fluid (CSF): clear liquid that surrounds the brain and spinal cord and fills the ventricles and central canal; acts as a shock absorber and circulates material throughout the brain and spinal cord
chain termination method: method of DNA sequencing using labeled dideoxynucleotides to terminate DNA replication; it is also called the dideoxy method or the Sanger method
channel: width of a river or stream from one bank to the other bank
channel protein: membrane protein that allows a substance to pass through its hollow core across the plasma membrane
chaperone: (also, chaperonin) protein that helps nascent protein in the folding process
charophyte: other term for green algae; considered the closest relative of land plants
chelicera: modified first pair of appendages in subphylum Chelicerata
chemical bond: interaction between two or more of the same or different atoms that results in forming molecules
chemical diversity: variety of metabolic compounds in an ecosystem
chemical energy: potential energy in chemical bonds that releases when those bonds are broken
chemical reaction: process leading to rearranging atoms in molecules
chemical reactivity: the ability to combine and to chemically bond with each other
chemical synapse: small space between axon terminals and dendrites of nerve cells where neurotransmitters function
chemiosmosis: process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane
chemoautotroph: organism that can build organic molecules using energy derived from inorganic chemicals instead of sunlight
chemoautotroph: organism capable of synthesizing its own food using energy from inorganic molecules
chemotroph: organism that obtains energy from chemical compounds
chiasmata: (singular, chiasma) the structure that forms at the crossover points after genetic material is exchanged
chitin: type of carbohydrate that forms the outer skeleton of all arthropods that include crustaceans and insects; it also forms fungi cell walls
chloride shift: exchange of chloride for bicarbonate into or out of the red blood cell
chlorophyll: green pigment that captures the light energy that drives the light reactions of photosynthesis
chlorophyll a: form of chlorophyll that absorbs violet-blue and red light and consequently has a bluish-green color; the only pigment molecule that performs the photochemistry by getting excited and losing an electron to the electron transport chain
chlorophyll b: accessory pigment that absorbs blue and red-orange light and consequently has a yellowish-green tint
chloroplast: plant cell organelle that carries out photosynthesis
chloroplast: organelle in which photosynthesis takes place
choanocyte: (also, collar cell) sponge cell that functions to generate a water current and to trap and ingest food particles via phagocytosis
cholecystokinin: hormone that stimulates the contraction of the gallbladder to release bile
Chondrichthyes: jawed fish with paired fins and a skeleton made of cartilage
chondrocyte: cell found in cartilage
Chordata: phylum of animals distinguished by their possession of a notochord, a dorsal, hollow nerve cord, an endostyle, pharyngeal slits, and a post-anal tail at some point in their development
Chordata: phylum of animals distinguished by their possession of a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some point during their development
chorion: membrane of the egg that surrounds the embryo and yolk sac
choroid plexus: spongy tissue within ventricles that produces cerebrospinal fluid
chromatid: single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere
chromatin: protein-DNA complex that serves as the chromosomes' building material
chromophore: molecule that absorbs light
Chromosomal Theory of Inheritance: theory proposing that chromosomes are the genes' vehicles and that their behavior during meiosis is the physical basis of the inheritance patterns that Mendel observed
chromosome: structure within the nucleus that comprises chromatin that contains DNA, the hereditary material
chromosome inversion: detachment, 180° rotation, and chromosome arm reinsertion
chronic infection: describes when the virus persists in the body for a long period of time
chylomicron: small lipid globule
chyme: mixture of partially digested food and stomach juices
chymotrypsin: pancreatic protease
chytridiomycosis: disease of amphibians caused by the fungus Batrachochytrium dendrobatidis; thought to be a major cause of the global amphibian decline
Chytridiomycota: (also, chytrids) primitive phylum of fungi that live in water and produce gametes with flagella
cilium: (plural = cilia) short, hair-like structure that extends from the plasma membrane in large numbers and functions to move an entire cell or move substances along the cell's outer surface
cingulate gyrus: helps regulate emotions and pain; thought to directly drive the body’s conscious response to unpleasant experiences
circadian: describes a time cycle about one day in length
circumduction: movement of a limb in a circular motion
cis-acting element: transcription factor binding sites within the promoter that regulate the transcription of a gene adjacent to it
citric acid cycle: (also Krebs cycle) series of enzyme-catalyzed chemical reactions of central importance in all living cells for extraction of energy from carbohydrates
cladistics: system to organize homologous traits to describe phylogenies
class: division of phylum in the taxonomic classification system
classical conditioning: association of a specific stimulus and response through conditioning
clathrates: frozen chunks of ice and methane found at the bottom of the ocean
clathrin: protein that coats the plasma membrane's inward-facing surface and assists in forming specialized structures, like coated pits, for phagocytosis
clavicle: S-shaped bone that positions the arms laterally
clay: soil particles that are less than 0.002 mm in diameter
cleavage: cell divisions subdividing a fertilized egg (zygote) to form a multicellular embryo
cleavage furrow: constriction formed by an actin ring during cytokinesis in animal cells that leads to cytoplasmic division
climate: long-term, predictable atmospheric conditions present in a specific area
climax community: final stage of succession, where a stable community is formed by a characteristic assortment of plant and animal species
cline: gradual geographic variation across an ecological gradient
clitellum: specialized band of fused segments, which aids in reproduction
clitoris: sensory structure in females; stimulated during sexual arousal
cloaca: common body opening for the digestive, excretory, and reproductive systems found in non-mammals, such as birds
clonal selection: activation of B cells corresponding to one specific BCR variant and the dramatic proliferation of that variant
clone: exact replica
closed circulatory system: system in which the blood is separated from the bodily interstitial fluid and contained in blood vessels
club mosses: earliest group of seedless vascular plants
Cnidaria: phylum of animals that are diploblastic and have radial symmetry
cnidocyte: specialized stinging cell found in Cnidaria
cochlea: whorled structure that contains receptors for transduction of the mechanical wave into an electrical signal
codominance: in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic
codon: three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation
coelom: lined body cavity
coenocytic hypha: single hypha that lacks septa and contains many nuclei
coenzyme: small organic molecule, such as a vitamin or its derivative, which is required to enhance an enzyme's activity
cofactor: inorganic ion, such as iron and magnesium ions, required for optimal enzyme activity regulation
cognitive learning: knowledge and skills acquired by the manipulation of information in the mind
cohesin: proteins that form a complex that seals sister chromatids together at their centromeres until anaphase II of meiosis
cohesion: intermolecular forces between water molecules caused by the polar nature of water; responsible for surface tension
coleoptile: covering of the shoot tip, found in germinating monocot seeds
coleorhiza: covering of the root tip, found in germinating monocot seeds
colinear: in terms of RNA and protein, three “units” of RNA (nucleotides) specify one “unit” of protein (amino acid) in a consecutive fashion
collenchyma cell: elongated plant cell with unevenly thickened walls; provides structural support to the stem and leaves
colloid: fluid inside the thyroid gland that contains the glycoprotein thyroglobulin
columnar epithelia: epithelia made of cells taller than they are wide, specialized in absorption
commensalism: symbiotic relationship in which one member benefits while the other member is not affected
commensalism: relationship between species wherein one species benefits from the close, prolonged interaction, while the other species neither benefits nor is harmed
community: set of populations inhabiting a particular area
compact bone: forms the hard external layer of all bones
companion cell: phloem cell that is connected to sieve-tube cells; has large amounts of ribosomes and mitochondria
competitive exclusion principle: no two species within a habitat can coexist when they compete for the same resources at the same place and time
competitive inhibition: type of inhibition in which the inhibitor competes with the substrate molecule by binding to the enzyme's active site
complement system: array of approximately 20 soluble proteins of the innate immune system that enhance phagocytosis, bore holes in pathogens, and recruit lymphocytes; enhances the adaptive response when antibodies are produced
compliance: measurement of the elasticity of the lung
compound: substance composed of molecules consisting of atoms of at least two different elements
compound leaf: leaf in which the leaf blade is subdivided to form leaflets, all attached to the midrib
concentration gradient: area of high concentration adjacent to an area of low concentration
conceptual model: (also, compartment model) ecosystem model that consists of flow charts that show the interactions of different compartments of the living and nonliving components of the ecosystem
conclusion: section of a scientific paper that summarizes the importance of the experimental findings
condensin: proteins that help sister chromatids coil during prophase
conditioned behavior: behavior that becomes associated with a specific stimulus through conditioning
condyloid joint: oval-shaped end of one bone fitting into a similarly oval-shaped hollow of another bone
cone: weakly photosensitive, chromatic, cone-shaped neuron in the fovea of the retina that detects bright light and is used in daytime color vision
conifer: dominant phylum of gymnosperms with the greatest variety of trees
conispiral: shell shape coiled around a horizontal axis
conjugation: process by which prokaryotes move DNA from one individual to another using a pilus
connective tissue: type of tissue made of cells, ground substance matrix, and fibers
consensus: DNA sequence that is used by many species to perform the same or similar functions
conspecifics: individuals that are members of the same species
contig: larger sequence of DNA assembled from overlapping shorter sequences
continuous variation: inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them
contour feather: feather that creates an aerodynamic surface for efficient flight
contraception: (also, birth control) various means used to prevent pregnancy
contractile vacuole: vesicle that fills with water (as it enters the cell by osmosis) and then contracts to squeeze water from the cell; an osmoregulatory vesicle
control: part of an experiment that does not change during the experiment
convergent evolution: process by which groups of organisms independently evolve to similar forms
coral reef: ocean ridges formed by marine invertebrates living in warm, shallow waters within the photic zone
core enzyme: prokaryotic RNA polymerase consisting of α, α, β, and β' but missing σ; this complex performs elongation
corm: rounded, fleshy underground stem that contains stored food
cornea: transparent layer over the front of the eye that helps focus light waves
corolla: collection of petals
corona: wheel-like structure on the anterior portion of the rotifer that contains cilia and moves food and water toward the mouth
coronary artery: vessel that supplies the heart tissue with blood
coronary vein: vessel that takes blood away from the heart tissue back to the chambers in the heart
corpus callosum: thick fiber bundle that connects the cerebral hemispheres
cortex: ground tissue found between the vascular tissue and the epidermis in a stem or root
cortex (animal): outer layer of an organ like the kidney or adrenal gland
cortical nephron: nephron that lies in the renal cortex
cortical radiate artery: artery that radiates from the arcuate arteries into the renal cortex
corticosteroid: hormone released by the adrenal cortex in response to long-term stress
cortisol: glucocorticoid produced in response to stress
cotyledon: primitive leaf that develops in the zygote; monocots have one cotyledon, and dicots have two cotyledons
cotyledon: fleshy part of seed that provides nutrition to the seed
countercurrent exchanger: peritubular capillary network that allows exchange of solutes and water from the renal tubules
countercurrent multiplier: osmotic gradient in the renal medulla that is responsible for concentration of urine
courtship display: visual display used to attract a mate
covalent bond: type of strong bond formed between two atoms of the same or different elements; forms when electrons are shared between atoms
coxal bone: hip bone
cranial bone: one of eight bones that form the cranial cavity that encloses the brain and serves as an attachment site for the muscles of the head and neck
cranial nerve: sensory and/or motor nerve that emanates from the brain
Craniata: clade composed of chordates that possess a cranium; includes Vertebrata together with hagfishes
cranium: bony, cartilaginous, or fibrous structure surrounding the brain, jaw, and facial bones
Crocodilia: crocodiles and alligators
crop: cultivated plant
cross reactivity: binding of an antibody to an epitope corresponding to an antigen that is different from the one the antibody was raised against
cross-pollination: transfer of pollen from the anther of one flower to the stigma of a different flower
crossover: exchange of genetic material between nonsister chromatids resulting in chromosomes that incorporate genes from both parents of the organism
Cryogenian period: geologic period (850–630 million years ago) characterized by a very cold global climate
cryptochrome: protein that absorbs light in the blue and ultraviolet regions of the light spectrum
cryptofauna: invertebrates found within the calcium carbonate substrate of coral reefs
ctenidium: specialized gill structure in mollusks
cuboidal epithelia: epithelia made of cube-shaped cells, specialized in glandular functions
Cushing’s disease: disorder caused by the hypersecretion of glucocorticoids
cutaneous respiration: gas exchange through the skin
cuticle: waxy covering on the outside of the leaf and stem that prevents the loss of water
cuticle: waxy protective layer on the leaf surface
cuticle (animal): the tough, external layer possessed by members of the invertebrate class Ecdysozoa that is periodically molted and replaced
cutting: method of asexual reproduction where a portion of the stem contains nodes and internodes is placed in moist soil and allowed to root
cyanobacteria: bacteria that evolved from early phototrophs and oxygenated the atmosphere; also known as blue-green algae
cycad: gymnosperm that grows in tropical climates and resembles a palm tree; member of the phylum Cycadophyta
cyclic AMP (cAMP): second messenger that is derived from ATP
cyclic AMP-dependent kinase: (also, protein kinase A, or PKA) kinase that is activated by binding to cAMP
cyclin: one of a group of proteins that act in conjunction with cyclin-dependent kinases to help regulate the cell cycle by phosphorylating key proteins; the concentrations of cyclins fluctuate throughout the cell cycle
cyclin-dependent kinase (Cdk): one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or inactivated by phosphorylation
cypris: larval stage in the early development of crustaceans
cytochrome complex: group of reversibly oxidizable and reducible proteins that forms part of the electron transport chain between photosystem II and photosystem I
cytogenetic mapping: technique that uses a microscope to create a map from stained chromosomes
cytokine: chemical messenger that regulates cell differentiation, proliferation, gene expression, and cell trafficking to effect immune responses
cytokinesis: division of the cytoplasm following mitosis that forms two daughter cells.
cytokinin: plant hormone that promotes cell division
cytopathic: causing cell damage
cytoplasm: entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals
cytoplasmic streaming: movement of cytoplasm into an extended pseudopod such that the entire cell is transported to the site of the pseudopod
cytoskeleton: protein fiber network that collectively maintains the cell's shape, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move independently
cytosol: the cytoplasm's gel-like material in which cell structures are suspended
cytotoxic T lymphocyte (CTL): adaptive immune cell that directly kills infected cells via perforin and granzymes, and releases cytokines to enhance the immune response
Biology 2e, March 28, 2018, OpenStax, https://openstax.org/books/biology-2e/pages/1-introduction