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M

TERMGROUPDEFINITION
MACROCYSTNPROTISTSPronunciation:

Etymology:

Macrocysts are large cysts formed during the sexual cycle of the cellular slime molds. These cysts have three walls. The sclerotium of Myxotists is sometimes called a macrocyst.
MACROEVOLUTIONNEVOLUTIONPronunciation: mak-ro-e-vo-LU-shun

Etymology: Macroevolution is derived from a Greek root makros (μάκρος, large or long), and a Latin root evolvere (to unroll or develop).

Macroevolution (n.) refers to evolution over long periods of time with a focus on the origin of higher taxa.
MACRONUCLEUSNPROTISTSPronunciation:

Etymology:

The macronucleus is a polyploid nucleus of ciliates. This nucleus participates in operation and maintenance of the cell.
MACROPHYLLNPLANTSPronunciation:

Etymology:

An macrophyll (=megaphyll) is a leaf that is derived from a lateral branch system which became webbed. The leaves of most extant vascular plants are macrophylls.
MAGNETOTACTICADJBACTERIAPronunciation:

Etymology:

Magnetotactic (adj.) organisms can detect and orient themselves in a magnetic field.
MALPIGHIAN TUBULENANIMALSPronunciation:

Etymology:

Malpighian tubules are excretory organs in arthropods. They are fine tubules attached at the hind gut and bathed in the haemolymph (blood) of the haemocoel from which they remove nitrogenous waste.
MANDIBLENANIMALSPronunciation:

Etymology:

Mandibles are the lower jaws of vertebrates. In arthropods mandibles are modified legs that serve as biting mouthparts.
MANTLENANIMALSPronunciation:

Etymology:

The mantle is the tissue that lies next to (and secretes) the shells of mollusks. Similar tissue underlies the shells of barnacles (arthropods) and brachiopods.
MASTAX (NO PLURAL)NANIMALSPronunciation:

Etymology:

Mastax is the pharynx of a rotifer, which contains the trophi.

μάσταξ (MASTAX) = MOUTH
MASTIGONEMENPLANTS, PROTISTSPronunciation:

Etymology:

Mastigonemes are flagellar hairs.
MAXILLA (MAXILLAE)NANIMALSPronunciation:

Etymology:

Maxillae (maxilla, sing.) are the paired lateral jaw-like appendages on the head or cephalothorax of arthropods; the upper jaw in vertebrates.
MEDULLARY LAYERNFUNGIPronunciation:

Etymology:

Loosely arranged layer of hyphae below the upper cortex and phycobiont zone.
MEDUSA (MEDUSAE)NANIMALSPronunciation:

Etymology:

The medusa to the swimming stage of a Cnidarian life cycle. Typically, it is mobile with a bell ringed by tentacles. In the Hydrozoa, the medusa is the sexual stage.
MEGAPHYLLNPLANTSPronunciation:

Etymology:

An megaphyll (=macrophyll) is a leaf that is derived from a lateral branch system which became webbed. Most extant vascular plants have macrophylls.
MEGASCLERENANIMALSPronunciation:

Etymology:

A megasclere is a sponge spicule (mineral either silicaceous or carbonaceous) that is large and structural. All classes have them. However, the calcareous sponges have only megascleres.
MEIOSIS (MEIOSES)NANIMALS, PLANTS, PROTISTS, FUNGIPronunciation: mi-O-sis

Etymology: Meiosis is derived from a Greek root that means less (meion, μείον). The reference is to the nature of the reduction division.

Meiosis (n.) is a special type of cell division that can only occur in cells with 2 sets or an even number of sets of chromosomes. As in mitosis, meiosis begins when the chromosomes have replicated. However, in meiosis the homologous chromosomes pair and separate during division I. That is followed by a second division in which the chromosome replicates separate (as in mitosis). Because meiosis requires a sequence of divisions, the meiotic products typically come in fours or in tetrads.
MEMBRANELLENPROTISTSPronunciation:

Etymology:

Membranelles are structures that resemble undulating membranes, however, they are formed by the lateral fusion of many flagella-cilia.
MERASPIDADJ OR NANIMALSPronunciation:

Etymology:

The meraspid (adj.) developmental stage of trilobites was the larval stage at which the number of body segments changes through successive molts.
MERISTEMNPLANTS, PROTISTSPronunciation:

Etymology:

A meristem is an embryonic layer of tissue in a multicellular organism. Mitosis by cells in the meristem gives rise to all tissues in the organism through differentiation. The merstem may be apical (at the tip) or intercalary (within the body of the organism).
MEROGONYNPROTISTSPronunciation:

Etymology:

Merogony is a type of schizogony that produces merozoites, stages that also can undergo multiple cell divisions.
MESARCHADJPLANTSPronunciation:

Etymology:

A mesarch (adj) stele is one in which the protoxylem forms between the center and outer part of the xylem.
MESENTARYNANIMALSPronunciation:

Etymology:

A membrane which attaches an organ to the abdominal wall.
MESOGLOEANANIMALSPronunciation:

Etymology:

Mesoglea is an acellular connective tissue region between the epidermis and gastrodermis of Radiata.
MESOHYLNANIMALSPronunciation:

Etymology:

Mesohyl is the internal layer of sponges. It is the layer in which living cells, particularly amoebocytes, occur.
MESOMITOTICADJPROTISTSPronunciation:

Etymology:

Mesomitotic (adj.) mitosis occurs in open mitotic systems with delayed breakdown of the nuclear envelope and no persistent nucleolus. No centrioles.
MESOSOMENANIMALSPronunciation:

Etymology:

The mesosome is a body region in phoronids that bears the lophophores.
METACENTRIC CENTRIOLENPPLANTSPronunciation:

Etymology:

Metacentric centrioles are unusual in that they form near the metaphase plate of certain green algae.
METACERCARIA (METACERCARIAE)NANIMALSPronunciation:

Etymology:

Metacercariae (metacercaria, sing.) are the final larval stages in digenean flukes. They usually are formed when the cercaria encysts. Metacercariae are the stages that infect the primary (vertebrate) hosts.
METAMERIC SEGMENTNPANIMALSPronunciation:

Etymology:

Metameric segments are body segments that are repeated and identical.
METAMITOTICADJANIMALS, PLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

Metamitotic (adj.) mitosis occurs in open mitotic systems with breakdown of the nuclear envelope and nucleolus. No centrioles.
MICROAEROPHILICADJECOLOGYPronunciation:

Etymology:

Microaerophilic (adj.) organisms require (or tolerate) small concentrations of elemental oxygen for metabolism.
MICROGAMETENANIMALS, PLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

Microgametes (sperm) develop from a microgamont in apicomplexans.
MICRONEMENPROTISTSPronunciation:

Etymology:

Micronemes are dense bodies associated with the apical complex in the apicomplexa. They seem to be secretion bodies from the golgi.
MICRONUCLEUS (MICRONUCLEI)NPROTISTSPronunciation:

Etymology:

The micronucleus is a diploid nucleus of ciliates. This nucleus participates in meiosis and mitosis.
MICROPHYLLNPLANTSPronunciation:

Etymology:

An microphyll is a type of leaf that has a simple vascular trace going into it. The vascular trace does not produce a gap in the stele. Microphylls are characteristic of of the club mosses (Lycopodophyta).
MICROPYLENPLANTSPronunciation:

Etymology:

An opening in the integuments of an ovule that exposes part of the megasporangial wall (a chamber called a pollen chamber in gymnosperms). Thus, in gymnosperms, pollen enters the micropyle and germinates in the pollen chamber. However, because the micropyle is not exposed in flowering plants, their pollen germinates on the stigma. The pollen tube grows through the style, and enters the ovule through the micropyle.
MICROSCLERENANIMALSPronunciation:

Etymology:

A microsclere is a sponge spicule (mineral either silicaceous or carbonaceous) that is small and used for reinforcing. Not found in calcareous sponges.
MICROSPORENPLANTS, PROTISTSPronunciation:

Etymology:

Microspores is a small spore, and the term is applied to many different types of spores in the microbial eukaryotes and plants. Usually, they are the products of meiosis.
MICROTUBULAR FLAGELLAR ROOTNPANIMALS, PLANTS, PROTISTS, FUNGIPronunciation:

Etymology:

Many flagellar basal bodies are associated with a microtubular array of varied structure, but invariant within a species or higher taxon.
MICROVILLUS (MICROVILLI)NANIMALSPronunciation:

Etymology:

These are also called costae (ribs). They are small finger-like extensions of the cell surface. They function in choanoflagellates as filter baskets that surround the flagellum.
MIDGUTNANIMALSPronunciation:

Etymology:

Midgut (also called mesenteron) is the mid portion of the digestive tract, lined with endodermis and derived from the archenteron.
MIRACIDIUM (MIRACIDIA)NANIMALSPronunciation:

Etymology:

Miracidia (miracidium, sing.) are the first larval stages in digenean flukes. They emerge from the egg as free-swimming ciliated larvae and infect snails in which cercariae are formed.
MITOSIS (MITOSES)NPANIMALS, PLANTS, PROTISTS, FUNGI, BACTERIAPronunciation: mi-TO-sis

Etymology: The term mitosis was created by Walther Fleming (1882) from a Greek root that means thread (mitos, μίτος). The reference is to the thread-like nature of the chromosomes.

Mitosis is a type of nuclear division in which the daughter nuclei have the same complement of chromosomes as each other and the parent nucleus. The particular stages in mitosis vary from group to group.
MITOSIS CLOSED (MITOSES CLOSED)NPPLANTS, PROTISTSPronunciation:

Etymology:

Mitosis is closed when the segregation of daughter chromosomes occurs within the bounds of the nuclear membrane (the nuclear membrane does not break down).
MIXOTROPHICADJECOLOGYPronunciation:

Etymology:

A mixotrophic organism obtains food either by autotrophic or saprobic means. Also called mesotrophic.
MOLECULAR CLOCKNPEVOLUTIONPronunciation & Etymology: The phrase is formed from two common English words. The meaning is that molecular changes occur at statistically regular rates from which evolutionary events can be timed.

The molecular clock is a theory that molecules evolve at an approximately constant rate which allows us to infer the time since species diverged based on similarities in particular molecules.
MONOCOTNPLANTSPronunciation:

Etymology:

Flowering plants with one cotyledon.
MONOPHYLETICADJSYSTEMATICSPronunciation: mo-no-fi-LE-tik

Etymology: Monophyletic is derived from two Greek roots that mean only or one (mono, μόνο) and tribe (fyli, φυλή).

Monophyletic is an adjective that means all taxa, populations, or individuals are descended from a common ancestor.
MONOPODIALADJPLANTSPronunciation:

Etymology:

Monopodial (adj.) pseudopodia describes the condition where an amoeboid makes a single major pseudopodium at a time.
MONOSPORENPLANTSPronunciation:

Etymology:

Monospores are exospores formed as asexual spores in certain brown and red algae.
MONOSULCATEADJPLANTSPronunciation:

Etymology:

A pollen grain with one groove or furrow.
MOTILEADJANIMALS, PLANTS, PROTISTS, FUNGI, BACTERIAPronunciation: MO-t’l

Etymology: Motile comes from the Latin, motus, a participle of the verb movere, which means to move.

Although the Latin word means general movement, the Biological term means a cell or colony of cells that move by means of flagella.
MUCILAGE CANALNPPLANTSPronunciation:

Etymology:

Ducts or channels in the axes of cycads and ginkgophytes that contain mucilage, a water-soluble substance which solidifies upon exposure to the air and likely serves to protect against invasion of the tissue by fungi and bacteria.
MUCOCYSTNPROTISTSPronunciation:

Etymology:

A mucocyst (also called mucus body, muciferous body, mucus trichocyst) is an organelle or inclusion that extrudes mucus.
MULTIAXIALADJPLANTS, PROTISTS, FUNGI, BACTERIAPronunciation:

Etymology:

A multiaxial structure (also called a fountain structure) produces a thallus in which the axis is made of many parallel filaments.
MULTI-LAYERED STRUCTURE (ALSO CALLED MLS)NPPLANTSPronunciation:

Etymology:

A multilayered structure (MLS) is a microtubular array that is at the base of the basal bodies in the motile cells of certain green algae and embryophytes. The MLS seems to be part of the microtubular organizing center for the cytoskeleton of the cell.
MULTIPLE FRUITNPPLANTSPronunciation:

Etymology:

A fruit formed from an inflorescence and often including bracts.
MULTISERIATEADJPLANTS, PROTISTSPronunciation:

Etymology:

Multiseriate (adj.) describes a filament formed by cells that can divide in planes perpendicular and parallel to its axis. The outcome is a filament axis of more than one cell in its linear arrangement.
MUREINNBACTERIAPronunciation:

Etymology:

Murein is a class of peptidoglycans found in the walls of Eubacteria.
MUTATIONNEVOLUTIONPronunciation:

Etymology:

Random change in genetic material; can be beneficial, harmful, or neutral.
MYCELIUM (MYCELIA)NPROTISTS, FUNGI, BACTERIAPronunciation:

Etymology:

A mycelium (mycelia, pl.) is a mass of hyphae or fungus-like filaments.
MYCOBIONTNFUNGIPronunciation:

Etymology:

The fungal component of a lichen.
MYONEMENPROTISTSPronunciation:

Etymology:

A myoneme is a structure that operates as a muscle fiber. It can be found in the stalk of certain sessile ciliates like Vorticella.
MYXOSPORENBACTERIAPronunciation:

Etymology:

Myxospores are exospores that are produced usually in complex sporangia (spore-bearing structures) by members of the Myxobacteria.
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