Skip to main content
Biology LibreTexts

25.4: Glossary of Terms and Root Words

  • Page ID
  • Glossary of Terms and Root Words

    Use this document to look up the definitions for bolded terms in the lab manual, as well as the meanings of root words. See the image of the compound microscope for the bolded terms relating to this device.


    Abscission - the natural detachment of plant parts, such as with leaves in the winter

    Abiotic - nonliving

    Accessory fruit - a fruit where the fleshy material is not derived from the ovary. Ex. A strawberry or rose hip

    Achene - a dry fruit with a single seed surrounded by a pericarp that can be peeled away. Layers of the pericarp are not distinguishable with the naked eye. Ex. A sunflower seed.

    Actinomorphic - See “Radial symmetry”

    Adhesion - attraction between dissimilar molecules or substances (such as tape to paper)

    Adventitious root - a root that emerges from stem tissue

    Aerenchyma - parenchyma tissue with large air pockets for flotation

    Aggregate fruit - a fruit derived from a flower with multiple free carpels. Ex. A blackberry.

    Akinete - a form some cyanobacteria can take. Larger, thick-walled cells that tend to be more granular in appearance. Akinetes store large amounts of lipids and carbohydrates so that they have enough energy to begin a new colony if conditions become too cold or too dry for survival. Formation of akinetes can be triggered by dry or cold conditions.

    Alcohol fermentation - a form of fermentation performed by yeasts that converts pyruvate into ethanol and CO2 to replenish NAD+

    Alternate (leaf arrangement) - one leaf emerges at a node

    Alternation of generations - See “Haplodiplontic”

    amylo- starch (amylose)

    Amyloplast - a type of plastid that produces and stores starch. An amyloplast is a type of leucoplast, which are plastids that do not contain pigment.

    Anaphase - the stage of mitosis where spindle fibers pull sister chromatids to either side of the cell, splitting them into two separate chromosomes

    Anaphase I - the stage of meiosis I where spindle fibers pull homologous chromosomes to either side of the cell

    Anaphase II - the stage of meiosis II where spindle fibers pull sister chromatids to either side of the cell, splitting them into two separate chromosomes

    andro- male, man

    Androecium - the floral whorl composed of stamens

    Annual growth ring - a light and dark region of secondary xylem that forms in response to environmental conditions. The light portion of the ring is composed of larger cells, formed when water is abundant (also called early wood). The dark portion of the ring is composed of smaller diameter, densely packed cells, formed when water becomes more scarce (also called late wood).

    Annulus - a ring-like structure. In fungi, this refers to the partial veil remnants left around the stipe. In ferns, it refers to the ring of inflated cells around the sporangium that dries and pulls the sporangium open, releasing the spores.

    anth- flower

    Anther - pollen sacs in flowering plants

    Antheridiophore - a structure that bears antheridia

    Antheridium - a multicellular structure on the gametophyte that produce sperm by mitosis

    Antipodals - three haploid cells in the embryo sac located on the opposite end of the micropyle

    angio/angium- vessel

    Apical growth - growth extending from the tips (such as the tips of roots or shoots in plants)

    Apothecium - a (usually) cup-shaped fruiting body produced by some ascomycetes

    Arbuscule - a highly branched structure formed by endomycorrhizal fungi on the plasma membrane of plant root cells. The increased surface area increases the ability to exchange materials.

    Archegoniophore - a structure that bears archegonia

    Archegonium - a multicellular structure on the gametophyte that produce an egg by mitosis

    Ascocarp - a fruiting body (sexually reproducing structure) produced in the fungal phylum Ascomycota

    Ascospore - a haploid spore produced by meiosis, then mitosis, within the ascus of an ascomycete

    Ascus - a sac-like structure where meiosis occurs to produce spores in ascomycetes. Asci, plural.

    Asexual reproduction - a form of reproduction that produces identical copies of the parent cell (e.g. mitosis, binary fission, and budding)

    Astrosclereid - a sclereid cell that transverses the leaves of Nymphaea and forms star-like shapes

    ATP - (adenosine triphosphate) a high energy molecule with three negatively charged phosphate groups. ATP can “donate” a phosphate group to a reaction, breaking a high energy bond and releasing energy. This process is called phosphorylation. Most work done in cells is powered by ATP.

    ATP Synthase - an enzyme that uses the flow of H+ ions back down their concentration gradient (secondary active transport) to phosphorylate ADP into ATP.

    auto- self

    Autotroph - an organism that forms organic molecules from inorganic molecules. This can also be thought of as an organism that makes its own food (self-feeding).

    Auxospore - an enlarged spore produced by diatoms during sexual reproduction (and apparently sometimes through asexual reproduction)

    Axillary bud - a structure located in the axil of the leaf that produces a branch, flower, or inflorescence


    Bark - layers of periderm (phelloderm, cork cambium, and cork) form the outer bark, while the secondary phloem forms the inner bark.

    Basal meristem - meristematic tissue located at the base of a structure. Most plants grow from apical meristems, producing new tissue at and elongating from the tips. Basal meristems produce tissue where the tips are the oldest parts.

    Basidiocarp - a fruiting body (sexually reproducing structure) produced by some basidiomycetes

    Basidiospore - a haploid spore produced by meiosis within the basidium

    Basidium - a (usually) club-shaped structure that produces spores in the basidiomycetes

    Benthic - at the bottom of a body of water

    Berry - a fleshy fruit with a thin exocarp, fleshy mesocarp, and one to many seeds not enclosed within an endocarp derived from the ovary wall

    bi- two

    Bilateral symmetry - having one line of symmetry

    Binary fission - a form of asexual reproduction used by prokaryotic cells where the original cell expands as internal contents are replicated, then a new cell wall forms in the middle, dividing into two new, identical cells

    bio- life

    Bioavailable - a form that can be absorbed by and assimilated into an organism.

    Biotic - living

    Blade - the (usually) flat, photosynthetic portion of the leaf located at the end of the petiole. In brown algae, this is the leaf-like structure (or structures) on the thallus.

    Bud primordium - the early developmental stage of the axillary bud

    Bud scar - the scar left behind on a stem where the axillary bud has fallen off via abscission

    Budding - a form of asexual reproduction used by yeast where a smaller cell is made from the original cell, leaving a bud scar. The smaller cell grows to normal size after separation from the parent cell.

    Bulb - a rosette of fleshy leaves modified for storage, surrounding a short stem

    Bulliform cells - enlarged cells in the epidermis that respond to water loss by collapsing, causing the leaf to roll or fold and reducing sun exposure

    Bundle scars - scars left behind inside a leaf scar where the vascular bundles of the leaf travelled into the stem

    Bundle sheath - the ring of cells that surround a vascular bundle. This could be in the stems of monocots or in the leaves of either group.


    C3 - the “standard” and most energy efficient form of photosynthesis

    C4 - a form of photosynthesis performed by plants adapted to hot weather. RuBisCO is located in the bundle sheath cells, where CO2 is actively transported in the form of an acid to keep concentrations high. This occurs when stomata close to prevent water loss, limiting CO2 intake.

    Calvin cycle - the light independent phase of photosynthesis where RuBisCO fixes CO2 and the end product is glucose. This process occurs in the stroma of the chloroplast.

    Calyptra - tissue from the female gametophyte that is carried on top of the developing sporophyte in the bryophytes

    Calyx - the floral whorl composed of sepals

    CAM - Crassulacean acid metabolism. This is a form of photosynthesis performed by plants adapted to dry weather. Stomata close during the day to prevent transpiration and open at night to let in CO2. The CO2 is actively transported into the central vacuole and converted into an acid. During the day, it is converted back into CO2 so photosynthesis can occur.

    Cap (pileus) - the top of a mushroom. The spore producing surface is on the underside of the cap (usually).

    Capillary action - the tendency of a liquid to rise or fall as a result of surface tension

    Capsule - a dry fruit with multiple fused carpels that open at maturity. Ex. Cotton. Note: this term is also often used to describe the structure that encases the sporangia in mosses.

    Carotenoids - red, orange, and yellow pigments found in plants, green algae, and photosynthetic heterokonts. These are often used to protect from sun damage or to signal ripening in fruits, as well as absorb some of the green parts of the spectrum of light.

    carp- of the fruit or fruiting body

    Carpogonium - a structure produced on the red algae female gametophyte. It consists of the egg and the trichogyne and may also be called the carpogonial branch.

    Carposporangium - a structure that produces carpospores

    Carpospore - a diploid spore that is identical to the zygote in the red algae life cycle. Carpospores grow by mitosis into a tetrasporophyte.

    Carposporophyte - a multicellular diploid phase in the red algal life cycle that produces clones of the zygote called carpospores

    Caryopsis - a dry fruit similar to an achene, but the pericarp is fused to the seed. This fruit type is produced by members of the Poaceae (grass family). Ex. A corn kernel.

    Casparian strip - a layer of suberin that coats the endodermis in roots. This layer forms in patches, leaving passage cells at the xylem poles.

    Cell wall - a rigid structure that encloses the plasma membrane. The presence and composition of the cell wall are useful features in classifying and identifying organisms.

    Cellulose - a polysaccharide found in plant cell walls. Cellulose is also found in the cell walls of oomycetes and red, green, and brown algae.

    Central cell - a cell in the embryo sac containing two polar nuclei

    Central vacuole - a (generally) large, fluid-filled organelle enclosed by a membrane (the tonoplast). The central vacuole often takes up the majority of a plant cell and is responsible for storage of compounds (ex. toxins, anthocyanins, and salts) and turgidity of the plant cell, which contributes to rigidity of the entire plant.

    Centric - (a diatom) with radial symmetry

    Centromere - the central region of a chromosome where sister chromatids are attached (in replicated chromosomes)

    Chemical energy - energy stored in the bonds between atoms within molecules

    Chemiosmosis - the movement of ions from areas of high concentration to low concentration across a semipermeable membrane. This happens with H+ flow through ATP synthase in both cellular respiration and photosynthesis.

    Chemosynthesis - a cellular process that uses chemical energy derived from oxidizing (stealing electrons from) inorganic compounds to build organic molecules. In this process, the inorganic compound is the electron donor. The waste product will depend on what the initial inorganic compound is (for example, if hydrogen sulfide is used, sulfur and water could be produced as waste products).

    Chitin - polysaccharide (carbohydrate) found in fungal cell walls and arthropod exoskeletons

    Chlorenchyma - parenchyma cells with chloroplasts for photosynthesis

    Chlorophyll - a photosynthetic pigment that reflects light in the green portion of the spectrum. These molecules can harvest energy from the blue and, to a lesser extent, red part of the spectrum of light by emitting an electron after absorbing a photon. All photosynthetic organisms covered in this class contain chlorophyll a, which is the primary molecule involved in the light-harvesting portion of photosynthesis.

    Chloroplast - a double-membrane bound organelle derived from bacterial endosymbiosis that contains chlorophyll and is responsible for photosynthesis. Chloroplasts can be converted into chromoplasts or leucoplasts, when needed.

    Chromatin - DNA wound around histone proteins

    chromo/chroma- color

    Chromoplast - a double-membrane bound organelle derived from bacterial endosymbiosis that contains pigments other than chlorophyll, such as carotenoids. Often found in ripening fruits to attract animals with the red hues.

    Chromosome - chromatin that has been tightly packaged in preparation for cell division

    Chytrid - an aquatic fungus with swimming spores (zoospores)

    Circinate vernation - the process by which fern fiddleheads unfurl in the spring

    Citric acid cycle - a process that takes place in the matrix of a mitochondrion during cellular respiration. ATP, NADH, and FADH2 (as well as some CO2) are produced.

    Cladode - a stem that has been modified for photosynthesis, often green with increased surface area

    Clamp connection - a rounded structure that forms on the side of a basidiomycete hypha as nuclei divide

    Classification - a system of categorizing organisms into like groups

    Cleistothecium - an enclosed, microscopic fruiting body produced by some ascomycetes

    Coenocytic - this can refer to fungal hyphae with no septations (cross walls) or, more generally, to any cell with many nuclei

    Coevolution - the linked evolution of two interacting species

    Cohesion - attraction between like molecules (for example the attraction of a partial positive charge on the hydrogen atom of one water molecule to the partial negative charge on the oxygen atom of another water molecule)

    Collenchyma - cells with unevenly thickened primary walls, often involved in flexible support in young growing tissues

    Community - multiple interacting populations living in the same area at the same time

    Companion cell - a cell with a nucleus paired with a sieve tube element. The companion cell acts as the command center for that sieve tube element.

    Complete (flower) - a flower containing all four floral whorls

    Complex septation - also called a dolipore septum. The walls around the pore in the septum are swollen and two structures that look like parentheses (aptly called parenthesomes) flank the pore.

    Conceptacle - a chamber inside the Fucus receptacle that houses the gametangia

    Cone - see “strobilus”

    Conidiophore - a structure that bears conidia

    Conidium - a spore produced by mitosis (asexual reproduction) in molds

    Conjugation tube - a structure produced in Spirogyra that allows mating to occur between compatible colonies. Cell contents are transferred through the conjugation tube.

    Consumer - an organism that eats other organisms as an energy source. A primary consumer eats producers, a secondary consumer eats primary consumers (though it may also eat producers), and a tertiary consumer eats secondary consumers (though it may also eat both primary consumers and producers, as well).

    Cork - suberized cells that are dead at functional maturity produced in the periderm during secondary growth. Cork cells form the outermost layer of stems and roots in secondary growth.

    Cork cambium - the secondary meristem that produces cork to the outside and phelloderm to the inside

    Corm - a stem that has been modified for storage. Nodes on the corm produce papery leaves.

    Corolla - the floral whorl composed of petals

    Cortex - tissue produced by the ground meristem, located between the vascular tissue and the epidermis

    Costa - the central “vein” in a moss leaf. Note: mosses do not have true vascular tissue, particularly not in the gametophyte.

    Cotyledon - the first leaf or leaves to appear as a seed germinates

    Crossing over - during prophase I of meiosis, homologous chromosomes align and can swap regions of DNA, resulting in increased genetic variety within an organism’s gametes.

    Crustose - a lichen that is completely appressed (stuck up against) what it is growing on. Cannot be (easily) removed from this substrate.

    Cuticle - a waxy layer made of the lipid cutin that coats the epidermis in plants

    cyan- blue

    cyst- a sac or bladder containing fluid

    Cystocarp - a structure produced on the female gametophyte of red algae. The carpogonium enlarges and the zygote develops inside, growing by mitosis into the carposporophyte. Female gametophyte tissue (the pericarp) surrounds the carposporophyte. These two components together comprise the cystocarp.

    cyto- cell, cellular

    Cytokinesis - division of the cytoplasm through the formation of a new cell wall during mitosis and meiosis, which happens concurrently with telophase.

    Cytoplasm - everything inside the plasma membrane, excluding the nucleus. This term is often confused with the term cytosol, which refers to the jelly-like matrix that fills the cell and surrounds the organelles, if present.

    Cytoplasmic streaming - movement of the cytoplasm around the cell to transport nutrients, organelles, or other materials


    Decomposer - an organism that breaks down dead organic matter, transforming the molecules trapped within those organisms into forms that are released into the environment and their respective nutrient cycles. This term is synonymous with the terms saprobe and saprophyte.

    Dehiscent - a dry fruit that opens on its own at maturity, usually to disperse the seeds

    Dendrochronology - a process used to determine the order and timing (chronology) of events using information in tree rings

    Dependent variable - the variable(s) in a scientific experiment that you record data on during and/or after your experiment

    di- two; double

    Diffusion - the tendency of particles to move from areas of high concentration to areas of lower concentration due to random movements and entropy

    Dikaryon - a dikaryotic fungal thallus

    Dikaryotic - having two unfused, haploid nuclei per cell (n+n)

    Dioecious - male and female reproductive structures are produced on different plants

    Diploid - having two sets of chromosomes (2n)

    Diplontic - a life cycle where the multicellular stage is diploid

    Dispersal agent - in angiosperms, the organism or phenomenon that aids in dispersal of the seeds

    Double fertilization - the fertilization of both the egg (producing a zygote) and the polar nuclei (producing the endosperm) in the angiosperm life cycle. A form of double fertilization also occurs in gnetophytes, but the result is two fertilized eggs.

    Drupe - a (typically) fleshy fruit with a thin exocarp, fleshy mesocarp, stony endocarp, and (typically) a single seed. Ex. A peach.


    Ecosystem - the biotic and abiotic components of an environment and the interactions between these components

    Ectomycorrhizal - a mycorrhizal association formed by some Ascomycota and Basidiomycota (and at least one zygomycete) around the cells of plant roots, forming a fungal sheath around the roots and a hartig net within the roots. See “mycorrhizal” for more information.

    Egg - the haploid cell produced by the megagametophyte that must fuse with a sperm to produce a zygote

    Elaters - elongate structures that promote spore dispersal by interacting with moisture in the air (hygroscopic movement). Found on the spores of Equisetum and in the sporangia of bryophtyes.

    Electromagnetic energy - energy that travels as a wave and does not require a medium. For example, light is a form of electromagnetic energy because it can travel as a wave through the vacuum of space. Sound, even though it travels as a wave, is not a form of electromagnetic energy because it requires a medium, such as air or water, to transmit it. Sound does not travel in space! So, laser gun battle in space = totally silent.

    Electron transport chain - a series of protein complexes that transfer electrons between each other. The energy from the electrons allows some of these protein complexes to pump H+ across the membrane.

    Embryo - a zygote that is retained and nourished by the female gametophyte.

    Embryo sac - the mature megagametophyte of an angiosperm, containing 7 cells and 8 nuclei

    endo- inside, internal, inner

    Endocarp - the innermost layer of the pericarp in a fruit. In a peach, the endocarp is the stony pit enclosing the seed.

    Endodermis - the innermost layer of the cortex in the root (also present surrounding the transfusion tissue in a pine needle)

    Endogenous - formed from within

    Endomycorrhizal - fungi that penetrate between the cell wall and plasma membrane of plant roots, establishing a mutualistic exchange of materials. This is a trait shared by all of Glomeromycota.

    Endosperm - the result of a sperm fertilizing the polar nuclei (central cell) in the embryo sac. This triploid tissue is consumed by the growing zygote in an angiosperm seed.

    epi- on top of

    Epidermis - the outermost layer of the plant, composed of a single cell layer. These cells are parenchyma and often include specialized cells, such as trichomes or guard cells.

    Epiphyte - growing on a plant

    eryth- red

    eu- true

    Eudicot - (alternatively called dicot) flowering plants that produce two cotyledons

    Eukaryote - an organism that can be unicellular or multicellular, but each cell with contain a nucleus (though this may be lost in some plant cells). Eukaryotes have linear DNA that is stored inside the nucleus and their cells contain membrane-bound organelles like mitochondria and the endoplasmic reticula.

    exo- outer

    Exocarp - the outer layer of the pericarp in a fruit. In a peach, the exocarp is the fuzzy skin.

    Exogenous - formed on the exterior


    Fascicular cambium - residual procambium within vascular bundles that joins with the interfascicular cambium to form the vascular cambium in eudicots

    Fermentation - a process that occurs after glycolysis to restore NAD+, such as the production of lactate or ethanol

    Fiber - an elongated sclerenchyma cell with tapered ends whose function is structural support

    Fiddlehead - a frond that has yet to unfurl via circinate vernation

    Filament - (in flowers) the stem-like structure that holds the anthers aloft

    Flagellum - a long projection that can be present on both prokaryotic and eukaryotic cells that is used for movement

    Floret - a flower in an inflorescence

    Floridean starch - the form of starch used by red algae as a storage carbohydrate

    Flower - a set of modified leaves that promote fertilization (pollination)

    Foliose - leaf-like. In lichens, a flattened thallus with two distinct sides (can be removed from substrate).

    Follicle - a dry fruit composed of a single carpel that splits open along a single seam at maturity

    Food - compounds your body can break down to get energy, usually carbohydrates

    Food web - an interconnected network of organisms participating in the flow of energy through an ecosystem. A food web involves primary producers, consumers, and decomposers. At each transition in a food web from one organism to another, about 90% of the available energy is lost as heat.

    Foot - the base of the sporophyte seta, where it attaches to the gametophyte

    Frond - the megaphyll of plants in subclass polypodiidae in the Ferns

    Fruit - the swollen ovary and enclosed seeds produced by angiosperms

    Frustule - the silica cell wall of diatoms, composed of two valves

    Fruticose - a lichen that is three dimensional, but without two distinct sides. Often called “busy” or “shrubby”

    Fucoxanthin - a carotenoid found in photosynthetic heterokonts

    Funiculus - transitional tissue between the angiosperm ovary and the developing ovule, much like an umbilical cord


    G0 - the stage of the cell cycle when a cell ceases to divide and specializes

    G1 - the stage of the cell cycle when cytoplasmic contents are duplicated

    G2 - the final stage of the cell cycle, where a cell is verified to be ready for division

    Galactans - sulfated polysaccharides present in the cell walls of red algae

    Gametangium - a structure that produces gametes

    Gamete - a haploid cell that must fuse with another haploid cell to form a zygote

    Gametophyte - a haploid, multicellular generation that produces gametes by mitosis

    gamy- union, marriage

    Gametophyte dominant - a life cycle where the gametophyte is larger, longer-lived, and nutritionally responsible for the sporophyte

    Gas bladder - a pocket in the thallus of brown algae that traps gases to act as a float

    Gemma - an asexual clone of plant tissues, such as in thalloid liverwort gametophytes (gemmae, plural)

    Gemmae cup - a cup-like structure where gemmae are produced

    Generative cell - the haploid cell in pollen grains that divides to produce sperm

    Gills (lamellae) - structures in some mushrooms where the spore producing basidia are located

    glyco- relating to sugar (often glucose)

    Glycogen - a polysaccharide (carbohydrate) used to store sugars in fungi, animals, and other heterotrophs

    Glycolysis - the first stage in cellular respiration or fermentation, where glucose is broken down into two molecules of pyruvate. This occurs in the cytoplasm.

    Granum - a stack of thylakoids in a chloroplast (grana, plural)

    Gravitropism - movement or growth with respect to the pull of gravity (toward or away from)

    Ground meristem - the primary meristem that produces ground tissue, cortex, and pith. In the root, it also produces the endodermis (the innermost layer of the cortex).

    Ground tissue - tissue produced by the ground meristem with no particular organizational structure, such as in the stems of monocots.

    Guard cell - a parentheses-shaped parenchyma cell in the epidermis of a plant that regulates the opening and closing of a stoma, depending on water availability

    gyn- female, woman

    Gynoecium - the floral whorl composed of carpels


    H+ - a hydrogen atom that is missing an electron. A hydrogen ion. A proton.

    Haploid - having one set of chromosomes (n)

    Haplodiplontic - a life cycle where there is a multicellular haploid phase and a multicellular diploid phase (also called alternation of generations or, occasionally, sporic meiosis)

    Haplontic - a life cycle where the multicellular phase is haploid

    Head (flower) - an inflorescence where florets are directly attached to the receptacle. There can be ray florets and/or disc florets present. Also called a capitulum.

    Heartwood - secondary xylem that is no longer conducting water. Often darker in color and is located in the center of the stem.

    Heliotropism - movement or growth with respect to the sun

    Hesperidium - a modified berry with a leathery rind. Locules are filled with juicy trichomes. Ex. An orange.

    hetero- other

    Heterocyst - a form some cyanobacteria can take. Heterocysts are larger, round, thick-walled cells that can appear yellow and have two polar bodies, one on each end where they attach to other cells in the colony. These individuals are involved in nitrogen fixation and so cannot perform photosynthesis.

    Heterosporous - producing two different spore types: microspores and megaspores

    Heterotroph - an organism that consumes other organisms, living or dead, as a carbon source.

    Holdfast - a structure at the base of brown algal thalli that attaches the thallus to a surface

    homo- same

    Homologous chromosomes - chromosomes from different parental origin that contain the same genes in the same order. For example, you have homologous copies of chromosome 1, one from each parent.

    Homosporous - producing a single spore type that grows into a bisexual gametophyte

    hydro- water

    Hydrophyte - a plant adapted to aquatic environments (or high water levels)

    hyper- over, above

    Hypertonic - a solution with a higher ratio of dissolved solutes to water than the solution on the other side of a semipermeable membrane

    Hypha - a walled, thread-like cellular structure that fungal body plans are composed of

    hypo- under, below

    Hypodermis - a layer or multiple layers of cells just under the epidermis

    Hypothesis - a proposed explanation for a phenomenon that is both testable and falsifiable

    Hypotonic - a solution with a lower ratio of dissolved solutes to water than the solution on the other side of a semipermeable membrane


    Imperfect (flower) - a flower containing either an androecium or gynoecium, but not both

    Incomplete (flower) - a flower missing at least one floral whorl

    Indehiscent - a dry fruit that does not open on its own at maturity

    Independent assortment - an event in meiosis that results in increased genetic diversity. During metaphase I, homologous chromosomes line up randomly on either side of the metaphase plate, resulting in different combinations of chromosomes in each meiotic event.

    Independent variable - the variable in a scientific experiment that you change between treatment groups

    Indusium - an umbrella-like structure in a fern sorus that protects the developing sporangia

    Inflorescence - a compound flower composed of multiple florets

    Inner bark - secondary phloem

    Integument - the protective layer surrounding a developing ovule in seed plants. After fertilization, it becomes the seed coat.

    Interfascicular cambium - cells in the pith rays that join with the fascicular cambium to form the vascular cambium in eudicots

    Intermembrane space - the area between two membranes, such as between the inner and outer membranes in a mitochondrion

    Internode - the region of the plant stem between nodes

    Interphase - cells spend most of their time in this part of the cell cycle. It is broken into three distinct phases that prepare a cell for division.

    iso - same

    Isomorphic - sharing the same overall form

    Isotonic - two solutions on either side of a semipermeable membrane that have the same ratio of dissolved solutes to water


    No current entries under “J”.


    karyo- seed (in biology, this term refers to the nucleus)

    Karyogamy - fusion of two nuclei

    Kinetochore - a region on the centromere of a chromosome where spindle fibers attach during cell division

    Krebs cycle - see “citric acid cycle”


    Lactic acid fermentation - a form of fermentation performed by animal cells and bacteria that converts pyruvate into lactate to replenish NAD+. H+ are produced as a byproduct, hence the name lactic acid.

    Latex - a compound produced by some groups of plants that often serves a protective function. It can contain toxic compounds and/or gum up the mouthparts of insects

    Leaf - a plant organ with lignified vascular tissue that emerges from a node in the position of the leaf, below the axillary bud (away from the growing tip of the branch)

    Leaf axil - the area formed in the angle between the petiole of the leaf and the stem

    Leaf scar - the scar left behind on a stem where the leaf has fallen off or was removed

    Leaf primordium - the early developmental stage of a leaf

    Legume - a dry fruit composed of a single carpel that splits open along two seams at maturity. This is the fruit of plants in the Fabaceae (bean family). Ex. A lupine pod or a peanut.

    Lenticel - a tear in the periderm of woody plants that allows for the exchange of gases with the exterior environment

    leuco- white or colorless

    Leucoplast - a double-membraned organelle derived from bacterial endosymbiosis that does not contain pigment. Leucoplasts synthesize and store lipids or starch, such as in amyloplasts.

    Lichen - a symbiotic relationship between a fungus and an alga and/or a cyanobacterium

    Life cycle - a summary of the major events in a species’ development, including fertilization, growth, and reproduction

    Lignin - a tough, complex polymer in the secondary walls of sclerenchyma cells. A primary component of wood, along with cellulose.

    Link reaction - the transportation of pyruvate from the cytoplasm of the cell into the matrix of the mitochondrion. In the process, pyruvate is converted to acetyl-CoA.

    Locule - a compartment of an angiosperm ovary representing one carpel

    lyse- to break apart


    Mannitol - a type of carbohydrate produced by fungi involved in lichen symbiosis

    Matrix (mitochondrion) - the fluid-filled area enclosed by the inner membrane in a mitochondrion

    Megagametophyte - a haploid, multicellular stage in heterosporous alternation of generations that produces eggs by mitosis

    Megaphyll - a leaf with branching vascular tissue

    Megaspore - a haploid cell produced via meiosis of the megasporocyte. This cell grows by mitosis into a megagametophyte.

    Megasporocyte - a diploid cell produced by the sporophyte that will divide by meiosis to produce the megaspore(s) that grow into megagametophyte(s)

    Megastrobilus - a structure on the sporophyte that produces the megagametophytes

    Meiosis - a type of cell division that halves the number of chromosomes and results in 4 genetically distinct daughter cells. For example, one diploid cell could go through meiosis to produce 4 haploid cells. This type of division is used for sexual reproduction.

    Meristem - a region of cells that divides by mitosis to produce new tissues

    Mesocarp - the middle layer of the pericarp in a fruit. In a peach, the mesocarp is fleshy.

    Mesophyll - the tissue in a leaf between the upper and lower epidermis that is not the vascular tissue

    Mesophyte - a plant adapted to moderate environmental conditions

    meso- middle

    Metaphase - the stage in mitosis where chromosomes align in the center of the cell

    Metaphase I - the stage in meiosis I where homologous chromosomes align across from each other in the center of the cell. The alignment is random, so each time meiosis occurs, there can be a different arrangement of chromosomes on either side. See “independent assortment”.

    Metaphase II - the stage in meiosis II where chromosomes align in the center of the cell

    Metaphase plate - a region in the center of a dividing cell, equidistant from the poles, where chromosomes line up

    Middle lamella - a pectin-rich layer between plant cell walls

    Microgametophyte - a haploid, multicellular stage in heterosporous alternation of generations that produces sperm by mitosis

    Microphyll - a leaf with a single, unbranched vein of vascular tissue

    Micropyle - a gap in the integument where the pollen drop is secreted and pollen grains (or tubes) can access the ovule

    Microspore - a haploid cell produced via meiosis of the microsporocyte. This cell grows by mitosis into a microgametophyte.

    Microsporocyte - a diploid cell produced by the sporophyte that will divide by meiosis to produce the microspore(s) that grow into microgametophyte(s)

    Microstrobilus - a structure on the sporophyte that produces the microgametophytes

    Middle lamella - a pectin-rich region between adjacent cells

    Mitosis - a type of cell division that results in two identical daughter cells, both identical to each other and to the parent cell. This type of division is used for growth, repair, and asexual reproduction. Mitosis refers strictly to the division of the nucleus, while cytokinesis is the division of the rest of the cell contents.

    Mitosporangium - a structure that produces spores by mitosis, such as in asexually reproducing Rhizopus

    Mold - asexually reproducing mycelial fungus

    mono- one, singular

    Monocot - flowering plants that produce a single cotyledon

    Monoecious - male and female reproductive structures are produced on the same plant

    Monomer - a molecule that can bind to other molecules of the same type and form a polymer. A repeating subunit of a larger molecule.

    Monoplastidic (cell) - a cell having only a single plastid, such as the single large chloroplast in the cells of Anthocerophyta

    morph- form

    Multicellular - an organism composed of multiple interacting cells

    Multiple fruit - a single fruit that is composed of many florets from the same inflorescence. Ex. A pineapple.

    Mutualism - a type of symbiosis in which both partners get a net benefit from the interaction.

    Mycelium - the fungal body, composed of hyphal filaments

    myco- fungus

    Mycobiont - the fungal partner in a lichen

    Mycorrhizal - a type of mutualistic relationship between plants and fungi. The fungus enters the plant through the roots and takes sugars from the plant. In exchange, the plant takes water and dissolved nutrients (particularly nitrogen and phosphorus) from the fungus.


    NADH - a molecule that carries two high energy electrons from glycolysis or the citric acid cycle to the electron transport chain in cellular respiration

    NADP+ reductase - reduces (adds electrons to) a molecule of NADP+ to create high-energy NADPH. The H+ is added to balance the negative charge from one of the added electrons.

    NADPH - a molecule that carries two high energy electrons from the electron transport chain to the Calvin cycle in photosynthesis

    Negative control - a group in your experiment that should show no change from initial conditions. If change occurs in the negative control, your experiment could have false positives.

    Netted root system - a root system where there is no central, larger root. Most roots are relatively the same diameter.

    Nitrogen fixation - the process of converting atmospheric nitrogen (N2) into bioavailable forms, such as ammonia (NH3). This process is carried out by certain bacteria using the enzyme nitrogenase and by the action of lighting ripping through the atmosphere, splitting molecules apart.

    Node - the region on a stem where a leaf and axillary bud emerge. The axillary bud emerges on the side of the node closest to the growing tip of the stem.

    Nonpolar - a type of covalent bond that is equally shared, resulting in no residual charges on the atoms. Nonpolar compounds “like” to interact with other nonpolar compounds.

    Nucellus - the nutritive tissue provided by the megasporangium to the growing embryo in seed plants

    Nuclear envelope - a double-membraned structure composed of phospholipids that encloses the genetic material of the cell

    Nucleoid - a region in prokaryotes that contains all or most of the genetic material. A nucleoid is not surrounded by a membrane.

    Nucleolus - a dense region within the nucleus that often appears as a dark dot. A single nucleus can contain several nucleoli. This region is where ribosomes are synthesized and contains a large amount of RNA.

    Nucleus - a double-membrane bound organelle in eukaryotes that contains the organism’s genetic material. The nucleus is often referred to as the command center of the cell, both DNA replication and transcription occur within this organelle. In multicellular organisms, some eukaryotic cells may lack a nucleus at maturity, such as sclerenchyma.

    Null hypothesis - an “anti-hypothesis” that predicts no relationship between the dependent and independent variables

    Nut - a dry fruit with a stony pericarp encasing a single, large seed. Ex. An acorn.


    Oogonium - a structure in heterokonts where the eggs are produced

    Oospore - a thick-walled zygote produced in the oogonium of oomycetes

    Operculum - a cap-like structure that covers the opening of the moss capsule until the spores are ready to be dispersed

    Opposite (leaf arrangement) - two leaves emerge at a node

    Organ - a collection of tissues working toward the same function, such as a leaf, stem or root

    Osmosis - the diffusion of water across a semipermeable membrane

    Ostiole - a small opening, such as at the top of a Fucus conceptacle

    Outer bark - periderm or layers of periderm

    ova- egg

    Ovary - a structure that encloses the ovules in angiosperms and will develop into the pericarp when fertilized

    Ovule - a structure in seed plants that contains the megagametophyte and will develop into a seed when fertilized

    Ovuliferous scale - a cone scale in the megastrobilus of conifers where seeds develop


    Palisade mesophyll - tissue in eudicot leaves that is composed of elongated cells that look like columns, full of chloroplasts photosynthesizing

    Panicle - a branched raceme inflorescence

    Parasitism - a type of symbiosis in which one partner gets a net benefit, while the other gets a net negative impact.

    Parenchyma - cells with an even, thin primary wall and no secondary wall that are alive at functional maturity.

    Passage cells - cells where the xylem is closest to the endodermis in the root where the Casparian strip forms last. This allows water to be transported into the xylem from root hairs.

    Pedicel - the stem that attaches to a floret

    Peduncle - the stem that attaches to a flower at the receptacle

    Pennate - (a diatom) with bilateral symmetry

    Peptidoglycan - a substance found in bacterial cell walls that consists of interlinked carbohydrates and polypeptides. Antibacterials like penicillin work by inhibiting the formation of peptidoglycan.

    Pepo - a modified berry with a tough, rind-like exocarp. Ex. A pumpkin.

    Perfect (flower) - a flower containing both an androecium and a gynoecium

    peri- around

    Perianth - the outer whorls of a flower, composed of the calyx and corolla

    Pericarp (fruits) - tissue that develops from the ovary wall in angiosperms and encloses the developing seeds. The pericarp is composed of the exocarp, mesocarp, and endocarp.

    Pericarp (Rhodophyta) - the female gametophyte tissue that surrounds the carposporophyte in the cystocarp

    Pericycle - a layer of meristematic tissue in the root, just inside the endodermis, that produces lateral roots and secondary meristems

    Periderm - an exterior layer produced during secondary growth composed of phelloderm, cork cambium, and cork. Also called outer bark.

    Peristome teeth - sheets of cells that look like papery teeth that interact with moisture in the air (hygroscopic movement) to help spores disperse from the capsule in some mosses

    Perithecium - a microscopic, flask-shaped fruiting body produced by some ascomycetes

    Perforation plate - an opening at the end of a vessel element that allows for the passage of water and dissolved nutrients from cell to cell.

    Petiole - the structure that attaches the leaf blade to the stem. Some plants lack petioles and these leaves are called sessile.

    phaeo- dusky (often refers to organisms with golden brown hues)

    Phagocytosis - to consume by engulfing. The process of engulfing creates a compartment called a phagosome, where acids or other digestive fluids can be secreted for breakdown of the engulfed material.

    Phelloderm - large storage cells produced to the inside of the cork cambium in secondary growth

    Phloem - the conducting tissue in plants that transports sugars produced during photosynthesis.

    Phloem fibers - clusters of fibers located in the phloem that provide structural support (other phloem cells lack a secondary wall).

    Phloem rays - parenchyma cells that connect the secondary phloem to the secondary xylem

    phore- bearer of

    photo- light

    Photobiont - the photosynthetic partner in a lichen, such as green algae or cyanobacteria

    Photon - a particle of light

    Photorespiration - a process that occurs when RuBisCO binds to oxygen instead of CO2; no glucose is made and energy is wasted in the process. This occurs when concentrations of CO2 are low.

    Photosynthesis - a cellular process that uses electromagnetic energy (sunlight) to assemble molecules of glucose from carbon dioxide. Water is used as an electron donor and oxygen is produced as a waste product (in oxygenic photosynthesis). Chemical formula: 6CO2 + 6H2O --(in the presence of sunlight)--> C6H12O6 + 6O2

    Photosystems I & II - complexes containing chlorophyll, located in the thylakoid membrane, that absorb photons during photosynthesis.

    Phototropism - movement or growth with respect to a light source

    Phycobilins - polar pigments found in red algae and cyanobacteria

    Phycocyanin - a blue phycobilin, more prominent in cyanobacteria

    Phycoerythrin - a red phycobilin, more prominent in red algae

    Phyllode - a modified petiole that is flattened to function like a leaf

    phyll- leaf

    Phylogeny - a hypothesis on the evolutionary relationships between organisms depicted as a branching tree diagram

    phyte/phyto- plant

    Phytoplankton - microscopic, photosynthesizing organisms in aquatic environments

    Pilus - a projection from a prokaryotic cell that is used to interact with other cells. Pili, plural.

    Pinnae - leaflets on a pinnately compound leaf (pinna, singular), such as a fern frond

    Pit connection - a connection of the cytoplasm between adjacent cells formed due to incomplete cytokinesis. Found in Rhodophyta.

    Pith - tissue produced by the ground meristem that is enclosed by vascular tissue

    Placenta - a region of tissue in the ovary wall that supplies nutrition to the developing ovule and then seed through the funiculus

    Planktonic - free-floating; wandering

    plasm- living substance, tissue

    Plasma membrane - a semi-permeable membrane composed of a phospholipid bilayer and a fluid mosaic of proteins, lipids, and associated carbohydrates that encloses the cytoplasm. In general, plasma membrane controls what enters and exits the cell. Nonpolar molecules like oxygen and carbon dioxide, and small molecules like water, can freely diffuse across. Molecules that are too large or too polar (charged) must be transported across.

    Plasmid - a small loop of DNA that can be transmitted between organisms. Antibiotic resistance genes are often carried on plasmids.

    Plasmodesma - a tube of plasma membrane that traverses the cell wall and middle lamella, connecting the cytoplasm of adjacent cells (plasmodesmata, plural).

    Plasmogamy - fusion of the cytoplasm of two cellular structures

    Ploidy - the number of sets of chromosomes an organism has

    Pneumatophore - a root that has been modified to grow above ground and access oxygen for plants that live in flooded environments, e.g. mangroves

    Polar - a type of covalent bond that is unequally shared, resulting in partial charges on the atoms. Polar compounds are partially charged and “like” to interact with other polar or ionic (charged) compounds.

    Pollen - the microgametophyte of gymnosperms and angiosperms. Pollen grains deliver the sperm to the egg.

    Pollen cone - see “microstrobilus”

    Pollination - the successful transfer of pollen from one plant to another. This process is often mediated by insects, wind, or other vectors.

    Pollination syndrome - a set of floral characteristics that have evolved in response to a particular pollinator

    Pome - a fleshy fruit encased in a swollen hypanthium, the papery endocarp forms a “core”. Ex. An apple.

    Population - individuals of the same species living in the same environment at the same time

    Positive control - a group in your experiment that should show normal/expected results. If no change occurs in the positive control, your experiment could have false negatives.

    Prickle - a modified region of the epidermis that functions as a sharp armament for protection

    Primary consumer - an organism that eats primary producers, often called herbivores.

    Primary endosymbiosis - an evolutionary process by which, in this case, a photosynthetic cyanobacterium was engulfed by a heterotrophic ancestor of the red algae. The cyanobacterium was not digested and evolved into a double membrane chloroplast. This process also occurred with mitochondria.

    Primary meristem - a region of cells produced by the apical meristem that divides to produce primary tissues

    Primary phloem - phloem tissue produced by the procambium

    Primary producer - an organism that uses some external, abiotic energy source, such as electromagnetic or chemical energy, to build organic molecules. Example: plants use energy derived from sunlight to molecules of glucose.

    Primary tissue - a region of cells produced by a primary meristem that collaborate toward a shared function

    Primary wall - a semi-rigid structure that surrounds the plasma membrane. All plant cells have a primary wall composed of cellulose.

    Primary xylem - xylem tissue produced by the procambium

    pro- before

    Procambium - the primary meristem that produces the primary xylem and primary phloem. In the root, it also produces the pericycle.

    Prokaryote - a unicellular organism that lacks a nucleus or membrane-bound organelles. The DNA in a prokaryote occurs as a single, circular chromosome. Prokaryotic cells are surrounded by a cell wall, though the composition can vary depending on whether it is a bacterium or an archaean.

    Prop root - an adventitious root used to provide stability or to attach onto other organisms

    Prophase - the first stage of mitosis, where the nuclear envelope and nucleoli break down, spindle fibers form, and chromatin condenses into chromosomes

    Prophase I - the first stage of meiosis I, where the nuclear envelope and nucleoli break down, spindle fibers form, and chromatin condenses into chromosomes. Homologous chromosomes pair and crossing over occurs.

    Prophase II - the first stage of meiosis II, similar to prophase of mitosis. In meiosis of a diploid cell, cells are haploid when prophase II begins.

    Protoderm - the primary meristem that produces the epidermis

    Pyrenoid - a dense region where carbon fixation happens within chloroplasts of many groups of algae and hornworts

    Pyruvate - a three carbon compound formed from the breakdown of glucose during glycolysis


    No current entries under “Q”.


    Raceme - an inflorescence where florets are attached to a central axis by pedicels

    Rachis - the central stem in a pinnately compound leaf, where the leaflets attach

    Radial symmetry - multiple lines of symmetry can be drawn

    Random fertilization - reproductive propagules (such as eggs and sperm) are not individually selected by the parents for the production of offspring, but are paired on chance

    Raphide - a needle-like crystal of calcium oxalate that forms in the tissues of certain plants

    Receptacle - in flowers, the point where all of the whorls attach to the peduncle. In Fucus, the swollen ends of the thallus.

    Residual procambium - procambial tissue (the primary meristem that forms the vascular tissue) remaining between the xylem and phloem of eudicot vascular bundles in primary growth

    Resin - a sticky substance produced in some gymnosperms and angiosperms that works to seal wound damage and prevent infection and herbivory

    Resin canal - a channel that runs through the tissues of some gymnosperms and angiosperms to secrete and transport resin

    rhiz- root

    Rhizoid - a root-like structure that lacks vascular tissue and has the function of anchorage

    Rhizome - a modified stem that travels horizontally below ground, producing new shoots and adventitious roots at nodes, resulting in asexual reproduction of the shoot

    Ribosomes - complexes of proteins and RNA that function as an enzyme. This enzyme reads RNA to build proteins during a process called translation. The ribosome forms a peptide bond between amino acids, releasing a water molecule in the process. This is why proteins are called polypeptides.

    Root - a plant organ whose function is anchorage and water absorption. Roots have a specific sequence of development and organization of tissues that is different from stems and leaves.

    Root apical meristem (RAM) - the meristem responsible for producing the primary meristems in the root. All cells in the root ultimately derive from this meristem.

    Root cap - cells that are produced by the RAM to the outside of the root and sloughed off continually. These cells protect the growing tip, lubricate its journey through the soil, and interact with microbes in the vacinity of the root.

    Root hair - a single epidermal cell that elongates to maximize surface area. Root hairs are only produced at the growing tips of the root system.

    RuBisCO - Ribulose-1,5-bisphosphate carboxylase/oxygenase. This enzyme fixes CO2 during the Calvin cycle of photosynthesis. If CO2 concentrations are low, it may bind to oxygen instead, causing photorespiration.


    S-phase - the stage of interphase where DNA is replicated

    Samara - a winged achene. Ex. A maple helicopter is both a samara and a schizocarp.

    Sapwood - secondary xylem that is still actively conducting water. Often lighter in color than the heartwood

    sapro- death, decay

    Saprobe - see “Decomposer”

    Saprophyte - see “Decomposer”

    Schizocarp - a fruit that breaks into multiple pieces (separate carpels) when mature

    scler- hard, tough

    Sclereid - a sclerenchyma cells that (generally) serves a protective function. In pears, these cells dominate unripened fruits, making them difficult to eat.

    Sclerenchyma - a cell with a secondary wall that is dead at functional maturity

    Secondary consumer - see “Consumer”

    Secondary endosymbiosis - an evolutionary process by which, in this case, a red alga was engulfed by a heterotrophic oomycete. The red alga was not digested and evolved into a four membrane chloroplast. This type of endosymbiosis has occurred multiple times.

    Secondary growth - the production of secondary tissues, resulting in lateral growth. Occurs in gymnosperms and some angiosperms

    Secondary phloem - phloem tissue produced by the vascular cambium. Also called inner bark.

    Secondary wall - a wall in plant cells that is formed within the primary wall. The secondary wall contains lignin, providing structural support, but its formation kills the cell eventually. This cell wall is present in sclerenchyma cells.

    Secondary xylem - xylem tissue produced by the vascular cambium. Also called wood.

    Seed - a structure produced by gymnosperms and angiosperms that houses the growing embryo and supplies nutrition via the nucellus and the megagametophyte.

    Seed coat - the integument forms the seed coat after fertilization of the egg. This structure surrounds and protects the seed.

    Seed cone - see “megastrobilus”

    Septum - division; divider. For example, the cross walls between cells in hyphae.

    Serpentine - a mineral that, when present in soils, results in low Ca:Mg ratios and often contains heavy metals

    Seta - a stem-like structure that holds up the sporangium in the sporophytes of some bryophytes (setae, plural)

    Sexual reproduction - production of offspring through the fusion of cells that were produced during meiosis

    Shoot apical meristem (RAM) - the meristem responsible for producing the primary meristems in the shoot. All cells in the shoot ultimately derive from this meristem.

    Sieve cell - a conducting cell in the xylem

    Sieve tube element - a conducting cell in the xylem of angiosperms that lacks a nucleus

    Simple pore - a hole in the epidermis that is not regulated by guard cells

    Simple septation - in ascomycetes, the cross walls between cells have a hole in the center

    Sister chromatid - one of two replicated, attached, identical chromosomes

    som(e)- body

    Sorus - a cluster of sporangia, such as on a fern frond (sori, plural)

    Sperm - a gamete that fuses with an egg. Generally smaller than the egg and often with flagella.

    Spermatangium - a structure that produces spermatia

    Spermatium - the nonmotile male gametes of red algae. This term is also used to describe a stage in the life cycle of rust fungi.

    Spike - an inflorescence where florets are sessile, attached directly to a central axis

    Spindle - a network of microtubules that organizes and separates chromosomes during cell division

    Spine - a leaf that has been modified into a sharp armament for protection

    Splash cup - the head of a male gametophyte in mosses, where antheridia await raindrops to splash sperm out

    Spongy mesophyll - tissue in eudicot leaves that is full of air pockets for gas exchange during photosynthesis, located below the palisade mesophyll

    Sporangiophore - a structure that holds up sporangia (such as the T-shaped projections on Equisetum strobili)

    Sporangium - a structure that produces spores

    Spore - a propagule that grows by mitosis (it does not fuse with another propagule)

    Sporophyll - a leaf where spores are produced

    Sporophyte - the multicellular, diploid phase of the plant life cycle that produces spores by meiosis

    Sporophyte dominant - a life cycle where the sporophyte is larger, longer-lived, and nutritionally independent from the gametophyte

    Stamen - a floral structure composed of anthers and a filament

    Standardized variables - variables in your experiment that are kept the same across all treatment groups and control groups

    Stem - a plant organ with lignified vascular tissue that emerges from a node in the position of the axillary bud (toward the growing tip of the branch)

    Sterigma - a projection from a basidium that the basidiospore sits atop in phylum Basidiomycota. Sterigmata, plural.

    Stigma - the pollen receiving part of the carpel, located at the end of the style

    Stipe - the stem-like structure in brown algae and fungi

    Stipular spines - stipules modified as sharp armaments for a protective function

    Stipules - paired appendages at the base of a leaf

    Stolon - a stem that grows horizontally above ground, producing new shoots and adventitious roots at nodes, resulting in asexual reproduction of the shoot

    Stoma - an opening in the epidermis of a plant that is flanked by two guard cells, allowing for regulated gas exchange with the exterior environment.

    Stomatal crypt - a cavity in the lower epidermis of a leaf where stomata are located

    Strobilus - a structure where gametophytes are produced in most SVPs and gymnosperms. The strobilus is composed of sporophylls (or similar structures) and sporangia.

    Stroma - the fluid inside a chloroplast, much like the cytosol of a cell

    Stromatolite - a formation created by the layering of photosynthetic bacteria, mucilage, and calcium carbonate. The first widely agreed upon evidence of life can be found in fossilized stromatolites.

    Storage root - a root modified to store water or carbohydrates

    Style - the structure that the pollen tube grows down to reach the ovary, located between the ovary and stigma

    Suberin - a waxy lipid that forms the Casparian strip and is present in cork cells

    Succulent - a plant or swollen tissue that stores water and can use this water for metabolic purposes during periods of drought

    Sunken stoma - a stoma located in a depression in the epidermis to prevent water loss

    Surface tension - a property caused by the attraction of partial charges between molecules in a liquid. This property minimizes surface area.

    sym- shared

    Symbiosis - when two or more organisms of different species live in close proximity to one another, sharing some aspect of their life cycle.

    Synergids - two haploid cells that flank the egg in the embryo sac

    synthesis- to form or put together


    Taproot - a root system that has a larger central root with smaller lateral roots, such as a carrot or a turnip.

    Telomere - the region at the end of a chromosomal arm

    Telophase - the stage of mitosis where the chromosomes decondense into chromatin, the spindle breaks down, and the nuclear envelope and nucleoli reform. Cytokinesis happens during this stage of mitosis.

    Telophase I - the stage of meiosis I where the chromosomes decondense into chromatin, the spindle breaks down, and the nuclear envelope and nucleoli reform. Cytokinesis happens during this stage of meiosis, resulting in two haploid cells.

    Telophase II - the stage of meiosis II where the chromosomes decondense into chromatin, the spindle breaks down, and the nuclear envelope and nucleoli reform. Cytokinesis happens during this stage of meiosis, resulting in four haploid cells.

    Tendril - a modified leaf or branch used for attachment and/or climbing

    Terminal bud - the bud at the end of a stem where the next year’s growth is formed

    Terminal bud scales - modified leaves (bracts) that cover and protect the developing terminal bud

    Terminal bud scale scars - scars left behind on a stem where the terminal bud scales have fallen off after the new tissue emerges. The distance between terminal bud scale scars indicates one year of growth (in a temperate climate).

    Tertiary consumer - see “Consumer”

    Tetrasporangium - a structure that produces tetraspores

    Tetraspore - a haploid spore produced by meiosis in the red algae life cycle. Tetraspores develop into either male or female gametophytes.

    Tetrasporophyte - the multicellular diploid that undergoes meiosis in the red algae life cycle

    Thallus - a body composed of undifferentiated tissues

    Thalloid - having a thallus for a body plan

    Thigmotropism - movement or growth in response to touch

    Thin layer chromatography - a process used to separate substances by polarity

    Thorn - a stem modified as a sharp armament for protection

    Thylakoid - a high surface area structure in chloroplasts with chlorophyll molecules in the membrane. This is where the electron transport chain of photosynthesis occurs.

    Thylakoid space - the internal area of a thylakoid

    Tissue - a collection of cells working toward the same function

    Tonicity - the amount of dissolved solutes in the solution relative to another solution on the other side of a membrane. This can also be thought of as osmotic potential.

    Tonoplast - the membrane that encloses the central vacuole in plant cells.

    troph- feeding

    Tracheid - a long, narrow sclerenchyma cell in the xylem with tapered ends and bordered pits. These cells conduct water in the xylem tissue.

    Tracheophytes - plants that have lignified vascular tissue. This group includes seedless vascular plants, gymnosperms, and angiosperms.

    Transfusion tissue - tissue that surrounds the vascular bundles in some xerophytic leaves, located within the endodermis

    Transpiration - the evaporation of water from plant tissues

    Trap - a leaf that has been modified to capture organisms, most often insects, to digest for nutrients missing from the plant’s environment

    Treatment group - a group in your experiment where you have made some modification to the independent variable

    trich- hair

    Trichogyne - a slender tube that the spermatium travels through to get to the egg in the red algal life cycle

    Trichome - a parenchyma cell that projects outward as a hair from the epidermis

    Trumpet hyphae - sugar-conducting cells present in some brown algae

    Tube cell - the cell in pollen grains that grows the pollen tube to the ovule for the sperm to travel down

    Tuber - an underground stem modified for storage that can produce new shoots from nodes called “eyes”

    Turgid - the state of being filled to swollen, such as with plant cells


    Umbel - an inflorescence where pedicels converge on a single point where they attach to the peduncle

    uni- singular, one

    Unicellular - an organism composed of a single cell. Unicellular organisms can be prokaryotic or eukaryotic.

    Universal veil - some mushrooms start out covered by a material called a universal veil. As they grow, they break through this veil, often leaving remnants in areas of the mushroom.

    Universal veil scales (warts) - remnants of the universal veil on the cap of a mushroom


    Vascular cambium - the secondary meristem that makes the secondary xylem to the inside and secondary phloem to the outside

    Vascular cylinder - when the vascular tissue forms a ring that divides the ground tissue into two distinct regions. This is present in monocot roots and eudicot stems.

    Vascular tissue - composed of xylem tissue that conducts water and dissolved nutrients, and phloem tissue that conducts photosynthates

    Vegetative - a cell, organ, or life stage of an organism that is not actively involved in reproduction. When referring to cyanobacteria, the vegetative cells are the individuals that are performing photosynthesis for the colony. For Spirogyra, the vegetative cells are those that are not undergoing sexual reproduction to form a zygote. In plants, vegetative parts (you might call them vegetables) are anything that is not a fruit or flower.

    Vessel element - a wide sclerenchyma cell in the xylem with perforation plates at each end. These cells conduct water in the xylem tissue of angiosperms and gnetophytes.

    Volva - remnants of the universal veil at the base of a mushroom


    Whorled (leaf arrangement) - three or more leaves emerge at a node


    xanth- yellow

    xero/xeric- dry

    Xerophyte - a plant adapted to dry environmental conditions

    Xerophytic leaf - a leaf that has specifically adapted to dry conditions

    Xylem - the lignified, water conducting tissue in a plant

    Xylem rays - sheets of parenchyma cells that traverse the secondary xylem


    Yeast - a unicellular fungus


    Zone of division - a region in the growing root tip where the RAM and primary meristems are located. Generally, this zone ends around where the root cap stops.

    Zone of elongation - a region in the growing root tip where cells exit the cell cycle and begin to get larger

    Zone of maturation - a region in the growing root tip where cells differentiate into specialized cells or tissues

    zoo- animal

    Zoosporangium - a structure that produces zoospores

    Zoospore - swimming spore (has at least one flagellum)

    zygo- can mean yoke-shaped, paired, or joined

    Zygomorphic - see “bilateral symmetry”

    Zygosporangium - a large, ornamented structure where both fertilization and meiosis occur in some lineages of early fungi (formerly classified as the Zygomycota)

    Zygote - the first diploid cell in an organism’s life cycle

    Contributors and Attributions