Lewis/Life - Glossary

A

aboral end AB-or-al end The end of an animal's body opposite its mouth. 511

abscisic acid ab-SIS-ik AS-id A plant hormone that inhibits growth. 578

abscission zone ab-SCISZ-on ZONE A region at the base of the petiole from which leaves shed. 546

abyssal zone a-BIS-al ZONE Part of the ocean that light does not reach. 883

accessory pigment Plant pigment other than chlorophyll that extends the range of light wavelengths useful in photosynthesis. 150

acetyl CoA formation AS-eh-til FOR-MAY-shun The first step in aerobic respiration. In the mitochondrion, pyruvic acid loses a carbon dioxide and bonds to coenzyme A to form acetyl CoA. 127

acid A molecule that releases hydrogen ions into water. 40

acid precipitation Low pH precipitation caused by sulfur and nitrogen oxides that form when pollution reacts with water in the upper atmosphere, forming hydrochloric and sulfuric acids. 894

acoelomate a-SEE-lo-mayt Animals that lack a coelom (body cavity) 511.

acrocentric ak-ro-SEN-trik A chromosome whose centromere divides the chromosome into a long arm and a short arm. 296

acrosome AK-ro-som A protrusion on the anterior end of a sperm cell containing digestive enzymes that enable the sperm to penetrate layers around the oocyte. 204

actin AK-tin A type of protein in the thin myofilaments of skeletal muscle cells. Also part of cytoskeletons. 100, 597

action potential An electrochemical change that occurs across the cell membrane of a neuron. 611

active immunity Immunity generated by an organism's production of antibodies and cytokines. 798

active site The part of an enzyme that provides catalysis. 50

active transport Movement of a molecule through a membrane against its concentration gradient, using a carrier protein and energy from ATP. 92

adaptation An inherited trait that enables an organism to survive a particular environmental challenge. 10

adaptive radiation ah-DAP-tiv RAID-ee-AY-shun The divergence of several new types of organisms from a single ancestral type. 381

adenine AD-eh-neen One of two purine nitrogenous bases in DNA and RNA. 51

adenosine triphosphate ah-DEN-o-seen tri-FOS-fate (ATP) A molecule whose three high-energy phosphate bonds power many biological processes. 92, 117

adhesion ad-HE-jhun The tendency of water to hydrogen bond to other compounds. 40

adipocyte a-DIP-o-site Fat cell. 594

adipose tissue AD-eh-pose TISH-ew Tissue consisting of cells laden with lipid. 44, 594

adrenal glands ad-REE-nal GLANZ Paired two-part glands that sit atop the kidneys and produce catecholamines, mineralocorticoids, glucocorticoids, and sex hormones. 667

adrenocorticotropic hormone ah-DREEN-o-KOR-tah-ko-TROP-ik HOR-moan (ACTH) A hormone of the anterior pituitary that stimulates the adrenal cortex to secrete hormones. 667

adventitious root ad-ven-TISH-shus ROOT Root that forms on stems or leaves. 546

aerial root AIR-ee-al ROOT Adventitious root that forms and grows up in the air. 550

afferent arteriole AF-fer-ent are-TEAR-ee-olz Branches of the renal artery that approach the proximal portion of a nephron. 781

age structure The distribution of ages of individuals of a population. 838

alcoholic fermentation AL-ko-HALL-ik FER-men-TAY-shun An anaerobic step that yeast use after glycolysis that breaks down pyruvic acid to ethanol and carbon dioxide. 137

algae AL-gee Unicellular or multicellular photosynthetic eukaryotes that generally lack roots, stems, leaves, conducting vessels, and complex sex organs. 458

allele ah-LEEL An alternate form of a gene. 200, 265

allergy mediator AL-er-gee MEED-ee-a-ter Biochemical, such as histamine and heparin, that mast cells release when contacting an allergen, causing allergy symptoms. 800

allopolyploid AL-lo-POL-ee-ploid An organism with multiple chromosome sets resulting from mating of individuals of different species. 414

alternation of generations The plant life cycle, which alternates between a diploid sporophyte stage and a haploid gametophyte stage. 192

alveolar duct al-vee-o-ler DUCT In lungs, the narrowed ending of bronchioles that opens into a cluster of alveoli. 739

alveoli al-VEE-o-li Microscopic air sacs in the lungs. 739

amino acid ah-MEEN-o AS-id An organic molecule consisting of a central carbon atom bonded to a hydrogen atom, an amino group, a carboxylic acid, and an R group. 46

amino group a-MEEN-o GROOP A nitrogen atom single-bonded to two hydrogen atoms. 47

ammonia ah-MOAN-ee-ah A nitrogenous waste generated by deamination of amino acids (NH3). 776

amoebocyte a-MEE-bo-site Mobile cell in a sponge. 515

ampullae am-PULL-ee The enlarged bases of the semicircular canals in the inner ear, lined with hair cells that detect fluid movement and convert it into action potentials. 655

anabolism an-AB-o-liz-um Metabolic reactions that use energy to synthesize compounds. 114

anaerobe AN-air-robe Organism that can live in an environment lacking oxygen. 127

anaerobic respiration an-air-RO-bic res-per-A-shun Cellular respiration in the absence of oxygen. 140

analogous structure ah-NAL-eh-ges struc-chore Body part in different species that is similar in function but not in structure that evolved in response to a similar environmental challenge. 394

anaphase AN-ah-faze The stage of mitosis when centromeres split and two sets of chromosomes part. 171

anaphase I AN-ah-faze I Anaphase of meiosis I; homologs separate. 201

anaphase II AN-ah-faze II Anaphase of meiosis II, when chromatids separate. 201

androecium an-dro-EE-shee-um The innermost whorl of a flower's corolla, consisting of male reproductive structures. 563

aneuploid AN-you-ploid A cell with one or more extra or missing chromosomes. 298

angiosperm AN-gee-o-sperm Flowering plant. 492

Animalia an-i-MAIL-ya The kingdom that includes the animals. 14, 429

annelid AN-eh-lid A segmented worm. 513

annuli AN-yew-li Demarcations between the segments of leeches. 521

antagonistic muscles antag-o-nis-tik MUS-uls Two muscles or muscle groups that flank a bone and move it in opposite directions. 700

anther AN-ther Pollen-producing oval body at the tip of a stamen. 563

antheridia an-ther-ID-ee-a In algae, structures that contain sperm. In plants, multicellular male structures where gametes form. 464, 493

anthocyanin an-tho-SI-ah-nin Pigment produced in senescent plant cells. 587

antibody an-tee-BOD-ee Protein that B cells secrete that recognizes and binds to foreign antigens, disabling them or signaling other cells to do so. 790

anticodon AN-ti-ko-don A three-base sequence on one loop of a transfer RNA molecule that is complementary to an mRNA codon and joins an amino acid and its mRNA instructions. 329

antidiuretic hormone an-ti-di-yur-ET-ik HOR-moan (ADH) A hypothalamic hormone released from the posterior pituitary that acts on kidneys and smooth muscle cells of blood vessels to maintain the composition of body fluids. 665

antigen AN-tee-gen The specific parts of molecules that elicit an immune response. 85

antigen binding site AN-tee-gen BIND-ing SITE Specialized ends of antibodies that bind specific antigens. 796

antiparallelism AN-ti-PAR-a-lel-izm The head-to-tail relationship of the two rails of the DNA double helix. 313

anus A-nus The opening to the anal canal. 764

aorta a-OR-tah The largest artery; it leaves the heart. 720

apical meristems A-pik-el MER-ee-stemz Unspecialized plant cells that divide, near the tips of roots and shoots. 534

apolipoprotein APER-o-LIP-o-PRO-teen The protein parts of cholesterol-carrying molecules. 94

apoptosis ape-o-toe-sis Programmed cell death. 177

appendicular skeleton AP-en-DIK-u-lar SKEL-eh-ten In vertebrates, the limb bones and the bones that support them. 685

appendix ap-PEN-diks A thin tube extending from the cecum in the human digestive system. 763

aqueous humor AY-kwee-us HU-mer In the eye, a nutritive, watery fluid between the cornea and the lens that focuses incoming light rays and maintains the shape of the eyeball. 649

aqueous solution AWK-kwee-us so-LEW-shun A solution in which water is the solvent. 40, 87

Archaea ar-KEE-a One of the three domains of life. Archaea are unicellular and have a combination of characteristics unlike those of the other two domains. 430

archegonia arch-eh-GO-nee-a Multicellular structures in plants where female gametes form. 493, 560

arteriole are-TEER-ee-ol Small, elastic blood vessel that arises from arteries and leads into capillaries. 708

artery AR-teh-ree Large, elastic blood vessel that leaves the heart and branches into arterioles. 708

arthropod AR-throw-pod Animals with three segmented body regions, a jointed exoskeleton, blood in body cavities, and a complex nervous system. Includes spiders and insects. 513

artificial selection Selective breeding. 381

ascending limb ay-sen-ding LIM The distal portion of the loop of the nephron, which ascends from the kidney's medulla. 783

asci ASS-key Sexual cells of fungi. 481

ascomycete ass-ko-mi-SEET Fungus that has saclike asci that house ascospores. 478

asexual reproduction Reproduction in which a cell doubles its contents and then divides into two identical cells. 10, 192

atom AT-um A chemical unit, composed of protons, neutrons, and electrons, that cannot further break down by chemical means. 32

atomic number a-TOM-ic NUM-ber The number in an element's box in the periodic table that indicates number of protons or electrons. 33

ATP synthase ATP SIN-thaze An enzyme that allows protons to move through the mitochondrial membrane and trigger phosphorylation of ADP to ATP. 129

atriopore AYT-ree-o-pore The hole in a lancelet through which water exits the body. 526

atrioventricular node A-tree-o-ven-TRIK-yu-lar NODE (AV node) Specialized muscle cells that branch into a network of Purkinje fibers, which conduct electrical stimulation six times faster than other parts of the heart. 722

atrioventricular valve A-tree-o-ven-TRIK-yu-lar VALV (AV valve) Flap of tissue between each atrium and ventricle that moves in response to the pressure changes of ventricular contraction. 720

atrium ATE-tree-um An upper heart chamber. 710

atrophy AT-tre-fee Muscle degeneration resulting from lack of use or immobilization. 702

auditory nerve AWD-eh-tore-ee NERV Nerve fibers from the cochlea in the inner ear to the cerebral cortex. 654

autoantibody AW-toe-AN-tee-bod-ee Antibody that attacks the body's tissues, causing autoimmune disease. 800

autoimmunity AW-toe-imm-YUN-i-tee An organism's immune system attacking its own body. 800

autonomic nervous system aw-toe-nom-ik NER-ves sis-tum Motor pathways that lead to smooth muscle, cardiac muscle, and glands. 622

autopolyploid aw-toe-POL-ee-ploid An organism with multiple chromosome sets. 414

autosomal dominant AW-toe-soe-mal DOM-i-nent An allele that masks the expression of another allele. 267

autosomal recessive AW-toe-soe-mal re-SESS-ive An allele whose expression is masked by another allele. 267

autosome AW-toe-soam A nonsex chromosome. 198

autotroph(ic) AW-toe-trof An organism that manufactures nutrients using energy from the environment. 14, 112, 146

auxin AWK-zin A type of plant hormone that elongates cells in seedlings, shoot tips, embryos, and leaves. 569

axial skeleton AX-ee-al SKEL-eh-ten In a vertebrate skeleton, the skull, vertebral column, ribs, and sternum. 685

axil AX-el The regions between a leaf stalk and stem. 541

axon AKS-on A thick branch of a neuron that sends messages. 596, 611

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