Skip to content

A

TERMGROUPDEFINITION
ABAXIALADJPLANTSPronounciation: ab-AX i-al.

Etymology: Abaxial is derived from two Latin terms ab (away from) and axis (originally, the axil of a wagon).

Abaxial (adj.) is a botanical term that means the underside of a leaf, or the side facing away from the stem (the axis).
ABDOMENNANIMALSClick here
ACANTHELLA (ACANTHELLAE)NANIMALSClick here
ACANTHOR (ACANTHI)NANIMALSClick here
ACENTRIC MITOSISNPPLANTS, ANIMALS, PROTISTS, FUNGIPronunciation: a-SEN-trik mi-TO-sis.

Etymology: Acentric mitosis is derived from a phrase of two terms mitosis (defined elsewhere) and centriole (defined elsewhere). The prefix a- is Greek for without, so a centric means without centrioles.

Acentric mitosis means mitosis without centrioles. Although this does occur in many groups of eukaryotes, it is diagnostic for certain groups of green algae. (see also Centric Mitosis)
ACHENENPLANTSPronunciation: a-KEEN.

Etymology: This botanical term is derived from two Greek roots a- (without) and khaino (χαίνω; to yawn). Literally, it means that the fruit does not “yawn” or open up.

An achene (n) is a small, dry, 1-seeded, indehiscent fruit with a thin wall, and always derived from one carpel. It is distinguished from a nut by being thin, almost papery rather than stony. Perhaps, the most familiar achene is the fruit of the sunflower, erroneously called a sunflower seed.
ACOELOMNANIMALSPronounciation: A-SEE-LOME.

Acoelom is the type of body cavity in triploblastic animals such as flatworms in which the persistent blastocoel has become filled with parenchyma.
ACROCARPOUSADJPLANTSPronunciation: ak-ro-KAR-pus.

Etymology: This term is derived from two Greek roots that mean summit or limb (akron, άκρον) and fruit (karpos, καρπός).

The reference is to a fruiting body that occurs at the summit or tip of the stem. It is an adjective most often used with mosses and liverworts to describe the terminal location of the archegonium and the subsequent sporophyte in some taxa. The alternative is pleurocarpous (fruiting on the sides of the axes).
ACRONNANIMALSPronunciation: a-KRON.

Etymology: It is derived from the Greek akron, which means summit.

Acron (n.) is the preoral part of the insect head, the “summit” of the body.
ACTINOMORPHICADJPLANTSPronunciation: ak-tin-o-MOR-fik.

Etymology: It is derived from two Greek roots that mean ray of light (aktina-ακτίνα) and form (morphos- μορφή).

This is an adjective that defines the structure of a flower according to its symmetry. An actinomorphic flower is radially symmetrical. That is, such a flower is divisible through the center of the flower in several or many longitudinal planes such that the halves form mirror images in each case.
ACTINOSTELENPLANTSClick here
ADAPTATIONNEVOLUTIONPronunciation: a-dap-TA-shun

Etymology: Adaptation is derived from the Latin adaptere, which means to fit. The -tion suffix, which means the act of, converts the verb to a noun.

In evolutionary theory, an adaptation (n.) is a heritable trait that improves an organisms’ ability to survive and reproduce in its environment. In behavior, adaptation means that the organism has become habituated to a particular level of stimulation so that an even larger stimulus is required to elicit a response.
ADAXIALADJPLANTSThe adaxial (adj) surface of a leaf is the top or that surface that faces the apical meristem.
ADDUCTOR MUSCLENPANIMALSPronunciation: a-DUK-tur. Mu-s’lz

Etymology: Adductor is derived from a Latin verb that means to draw toward (adducere).

Adductor muscles (n) are pillar-like muscles that serve to close the shells of bivalve mollusks.
ADVENTITIOUS ROOTNPPLANTSPronunciation: ad-ven-TI-shus roots

Etymology: Adventitious is derived from the past participle of a Latin verb that means to arrive (adventum). The meaning in this context is something that is extra or foreign.

Adventitious roots develop secondarily from stem axes.
AECIOSPORE -SEE AECIUMNFUNGIPronunciation: E-se-a-spor

Etymology: Aecium is a Latin form of a Greek term that means not seemly or an injury (ἀεικίη)

An Aeciospore(n.) is a spore produced in the aecidium.
AECIUM (AECIA)NFUNGIClick here
AERENCHYMANPLANTSPronunciation: a-REN-ka-ma

Etymology:

Aerenchyma (n.) is an airy tissue found in roots of plants, which allows exchange of gases between the shoot and roots.
AEROBENBACTERIA. PROTISTSPronunciation: Er-obes

Etymology: Aerobes is derived from Greek terms aero (air) and bios (life).

Aerobes (n) are those bacteria that require free oxygen for metabolism.
AGAMONTNPROTISTSPronunciation:

Etymology:

An agamont (n.) is a term specific to groups like Foraminiferotista in which it is the diploid phase (the phase that can undergo meiosis).
AGGREGATE FRUITNPPLANTSPronunciation:

Etymology:

An aggregate fruit (n.) formed by the joining of several carpels that were separate in the flower.
AKINETENBACTERIAPronunciation:

Etymology:

Akinetes (n.) are special cells in certain filamentous Cyanobacteria that likely serve as asexual reproductive structures.
ALGA (ALGAE)NECOLOGYPronunciation:(alga, sing.)

Etymology:

Algae (n.) is an ecological term for photosynthetic organisms that are unicellular, filamentous, or colonial.
ALGINIC ACIDNPPROTISTSPronunciation:

Etymology:

Alginic acid (n.) is a polysaccharide characteristic of the phaeophytes. It can be up to 40% of the dry weight of the organism.
ALGIVEROUSADJANIMALS, PROTISTSPronunciation:

Etymology:

Algiverous (adj.) means algae-eating.
ALLOPATRIC SPECIATIONNPEVOLUTIONClick here
ALTERNATION OF GENERATIONNPANIMALS, PLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

A life cycle exhibits alternation of generation when it involved the alternation of haploid (gamete-producing) and diploid (spore-producing) phases.
ALVEOLUS (ALVEOLI)NANIMALS, PROTISTSPronunciation:

Etymology:

Alveoli (n.) are membrane-bound sacs that lie beneath the plasmalemma in the Kingdom Alveolata (Dinoflagellates, Ciliates, and Apicomplexans). The presence of alveoli appears to be one of the defining synapomorphies of the group.
AMNIONNANIMALSClick here
ANCESTORNEVOLUTIONPronunciation: AN-ses-t’r

Etymology: Ancestor is derived from two Latin roots that mean before (ante) and to go (cedere). It literally means to go before.

An ancestor is any organism, population, or species from which some other organism, population, or species is descended.
ANISOGAMOUSADJANIMALS, PLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

Anisogamous (adj.) describes sexual reproduction in which the gametes are structurally similar, but not identical.
AMOEBOCYTENANIMALSClick here
AMPHIGASTRIUM (AMPHIGASTREA)NPLANTSPronunciation:

Etymology:

An amphigastrea is a small leaf on the under side of the stem in the leafy liverworts (Also called an underleaf)
AMPHIDNANIMALSClick here
AMPHIPHLOIC SIPHONOSTELENPPLANTSPronunciation:

Etymology:

An amphiphloic siphonostele (=solenostele) is a type of siphonostele with phloem in rings on the inside and outside of the xylem.
AMPULLA (AMPULLAE)NANIMALSPronunciation:(ampulla, sing.)

Etymology:

Ampullae (n.) are interior parts of the echinoderm tube feet. They extend into the water vascular cavity. It also refers to the posterior, expanded part of the phoronid body.
ANISOKONTN & ADJPLANTS, PROTISTSPronunciation:

Etymology:

Anisokont flagella (n.) are those flagella that are unequal in length, form, or direction.
ANTERIORLY-DIRECTED FLAGELLUMNPPLANTS, PROTISTSPronunciation:

Etymology:

An anteriorly-directed flagellum extends in the direction of the motion of the motile cell. The interpretation is that the flagellum functions by pulling the cell.
ANTHERNPLANTSPronunciation:

Etymology:

An anther (n.) is a part of the stamen that produces pollen.
ANTHERIDIANPLANTSPronunciation:

Etymology:

Male reproductive structure that produces and protects sperm in embryophytes.
ANTHERIDIAL BRANCHNPLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

An antheridial branch (n.) filament that bears gametangia that produce sperm or spermatia.
ANTHERIDIAL INITIALNPLANTSPronunciation:

Etymology:

The initial cell that gives rise to the nuclei of the sperm cells in the pollen grain.
APLANOSPORENBACTERIA, PROTISTS, PLANTS, FUNGIPronunciation:

Etymology:

Non-motile resting spore.
APOMORPHIC CHARACTERNPEVOLUTIONClick here
APOTHECIUM (APOTHECIA)NFUNGIPronunciation:

Etymology:

Open-aired perithecia.
ARCHAEGONIAL CHAMBERNPPLANTPronunciation:

Etymology:

The archaegonial chamber is a small cavity between the nucellus and megagametophyte into which the archegonium (or its reduced derivative) exposes the egg to the pollen tube.
ARCHAEGONIUM (ARCHEGONIA)NPLANTPronunciation:

Etymology:

The female reproductive organ containing the egg.
ARILNPLANTPronunciation:

Etymology:

Outgrowths of the funiculus (stalk that attaches the ovule to the placenta), forming a cup-shaped appendage or outer covering of a seed.
ARTHROSPORENFUNGIPronunciation:

Etymology:

Cell formed by fragmentation of fungal hyphae.
ARTIFICIAL TAXON (ARTIFICIAL TAXA)NPSYSTEMATICSPronunciation:

Etymology:

An incomplete evolutionary lineage (paraphyletic or polyphyletic grouping).
ASCOCARPNFUNGIPronunciation:

Etymology:

Mature fruiting body of ascomycetes; contain asci.
ASCOGENOUS HYPHANPFUNGIPronunciation:

Etymology:

Specialized cells that contain pairs of nuclei of opposite mating types.
ASCOMA (ASCOMATA)NFUNGIPronunciation:

Etymology:

Disc-shaped ascocarp.
ASCOSPORENFUNGIPronunciation:

Etymology:

Sexually produced fungal spores formed within an ascus.
ASCUS (ASCI)NFUNGIPronunciation:

Etymology:

Sac-like structure in which sexually produced ascospores are produced.
ASEPTATEADJPLANTS, PROTISTS, FUNGI, BACTERIAPronunciation:

Etymology:

Lacking septa (partitions within the hyphae).
ASEXUAL REPRODUCTIONNPANIMALS, PLANTS, PROTISTS, FUNGI, BACTERIAPronunciation:

Etymology:

As the name implies, asexual reproduction is the formation of offspring without the union of gametes. Usually, asexual reproduction involves the production of specialized cells or multicellular structures that can give rise to new individuals.
ATACTOSTELENPLANTSPronunciation:

Etymology:

Characteristic of monocots, vascular bundles distributed throughout the ground tissue.
ATRACTOPHORENPROTISTSPronunciation:

Etymology:

An atractophore is a rod-like structure that elaborates from the basal body and behaves as a centriole.
ATRIAL SIPHONNPANIMALSPronunciation:

Etymology:

The atrial siphon is the excurrent siphon.
AURICLENANIMALSPronunciation:

Etymology:

An auricle is the lateral lobe on the head of a turbellarian.
AUTOGAMYNANIMALS, PLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

Autogamy is a special kind of sexual reproduction in which the fusing nuclei are derived from the same parental nucleus.
AWNNPLANTPronunciation:

Etymology:

A bristle at the tip of a leaf.
AXOBLASTNANIMALPronunciation:

Etymology:

Axoblasts are rhombozoan reproductive cells that occur within the Rhombozoan axial cell. They each develop into vermiform larvae within the axial cell.
AXONEMENPROTISTSPronunciation:

Etymology:

An axoneme is the microtubular array in the eukaryotic flagellum. That is, an axoneme is the flagellum devoid of its outer membrane.
AXOPLASTNPROTISTSronunciation:

Etymology:

An axoplast is a central granule (sometimes called centroplast) that has no internal differentiation. The axopods arise from the central granule of certain “radiolarians”.
AXOPOD (AXOPODS OR AXOPODIA)NPROTISTSPronunciation:

Etymology:

An axopod is a thin pseudopodium that is permanent and stiff due to the presence of an internal microtubular structure. This is characteristic of the Actinopodotista.
AXOSTYLENPROTISTSPronunciation:

Etymology:

An axostyle is rod-like microtubular structure that occurs in certain Metamonadotista and Parabasalotista. The axostyle runs through the axis of the cell from the anterior (usually anchored around the nucleus) to the posterior end, often forming an extended point at the posterior end.
Print Friendly, PDF & Email

Document Footer

Skip to toolbar