Terminology

Abaxial

• The bottom side of a leaf

Adaxial

• The topside of a leaf

Adaptation

• A feature or characteristic of an organism that allows it to survive in its environment 

Algae

• Aquatic, usually photosynthetic organisms that come from a wide range of evolutionary groups. Large algae is sometimes called seaweed or kelps (e.g., rhodophytes, chlorophytes, phaeophytes, dinoflagellates, diatoms, etc.)

Allele

• One form or variant of a particular gene. Species tend to have many alleles for each gene.

Allopatric Speciation

• A geographic barrier separates populations that evolve “away” from each other 

Allopolyploidy

• Inter-breeding of different species which results in having more than the usual number of chromosomes

Ancestral

• Appearing earlier in evolutionary time or longer ago compared to today 

Angiosperm

• A flowering and fruiting plant. 

• A plant that has seeds contained inside a ripened ovary, which is called the fruit.

Anisogamy

• Gametes are different sizes and/or shapes 

Antheridium

• A structure that contains the plant sperm; located on the gametophyte

Apomorphy

• A derived trait, which defines a monophyletic clade of taxa

Archegonium

• A structure that contains a plant egg; located on the gametophyte

Artificial Selection

• A similar process that is controlled by humans to breed favorable plants and animals 

Ascoma 

• The larger ascus-producing structure in the Ascomycota (e.g. morel, truffle), 

• Comprised of dikaryotic filaments (n+n)

Autoecious

• Having "one home", such as a parasite that requires only one host 

• Contrast with heteroecious

Ascus 

• Finger-like, spore-producing structure in the Ascomycota

• It is the only diploid (2n) structure in the ascomycete lifecycle 

Autopolyploidy

• Doubling of chromosomes within an individual 

Autotroph

• An organism that can make its own food

Basidium

• Club-shaped, spore-producing structure in the Basidiomycota

• It is the only diploid (2n) structure in the basidiomycete lifecycle 

Basidioma

• The larger basidium-producing structure in the Basidiomycota (e.g. mushroom, toadstool), comprised of dikaryotic (n+n) filaments

Branching Patterns

• The pattern and mechanism by which the apical cell, or meristem, of a plant stem produces branches

• e.g. dichotomous (isotomous, anisotomous, pseudomonopodial), monopodial, etc.

Bryophyte

• A non-vascular plant, which does not branch in the spore-bearing stage

• i.e. mosses, liverworts, and hornworts

Carpel

• The female portion of a flowering plant. It is a modified megasporophyll that is enclosed to protect the seeds

• After fertilization, the carpel becomes the fruit

Carposporophyte

• Multicellular, diploid stage (sporophyte) that forms from a fertilization event. e.g. red algae

Carpospores

• Asexual spores that produce tetrasporophytes. e.g. red algae

Cell

• The smallest structural and functional unit of an organism, typically microscopic and consisting of cytoplasm and a nucleus enclosed in a membrane

Centromere

• The region of a chromosome to which the spindles attach during cell division

Chlorophyll

• A green pigment contained in the chloroplasts that captures sunlight to make sugars. The are different forms of chlorophylls found in photosynthetic groups

Chromatid

• Each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA

Chromosome

• A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Cladistics

• Method to determine natural relationships of organisms based on the history or evolution of groups, generating a visual tree-like representation (cladogram) of the evolutionary relationships between groups.

Cladogram

• A visual representation of the evolutionary relationship between organisms; a phylogenetic tree 

Clamp connections

• Structure found in basidiomycetes, which connects two cells during division 

Coenocytic

• Having cells with many nuclei and lacking cross walls. e.g. slime molds

Cone

• A reproductive structure with aggregated seeds or spores on modified stems and/or leaves

• Compound cone: A cone constructed with seeds attached to lateral branch systems (e.g. female pine cones)

• Simple cone: A cone constructed with seeds attached to lateral leaves (e.g. cycad cones, male pine cones)

Conidia

• A chain of asexual spores attached to a conidiophore. e.g. Penicillium

• These spores are not contained inside of a spore sac, such as a sporangium

Conidiophore

• Stalk holding the conidia (-"phore" means stalk) 

Convergent Evolution

• The evolution of similar forms or functions in evolutionary unrelated groups, which do not share the most common ancestor 

Derived

• Appearing later in evolution, or more recently to modern times

Dichotomous

• To split into two, such as forked branching

Dikaryotic

• A condition in which each cell has 2 nuclei. e.g. basidiomycetes, ascomycetes 

Dioecious

• Separate female and male individuals

Diploid (2n)

• Having two sets of chromosomes in each cell; therefore two copies (alleles) of each gene

Diplontic life cycle

• A life cycle in which there is a multicellular sporophyte, but a unicellular gametophyte (e.g. some algae and vertebrate animals)

• The sporophyte (or diploid stage) is dominant and multicellular, producing unicellular gametes through meiosis.

• Gametes fuse during fertilization to produce a multicellular sporophyte

• Also called a gametic meiosis

Domain

• The highest (most general) taxonomic designation

• The taxonomic unit above Kingdom (e.g. Bacteria, Archaea, Eukarya) 

Embryo

• In botany, the first stage of the sporophyte, formed from fertilization, but also protected and nourished by the female gametophyte

• Compare to zygote which is not protected and nourished

Endosporic

• Within a spore; usually refers to a gametophyte that does not emerge from the spore and matures inside.

Endosymbiosis

• A process in which an organism is consumed but survives inside another organism

• e.g. the plant chloroplast or eukaryote mitochondria derived from a prokaryotic organism being co-opted by a larger organism early in Earth's history

Eukaryote

• Organisms that possess organelles such as a nucleus (e.g. plants, fungi, animals, algae)

• Organisms that are capable of sexual reproduction

Evolution

• The change in allele frequency within a population's gene pool over time 

Fertilization

• Fusion of sperm and egg to produce a zygote 

Filamentous

• Threadlike connection of cells 

Gametangium

• A haploid structure that holds gametes (e.g. antheridium, archegonium, oogonium) 

• Plurilocular gametangium: A multiple-chambered, reproductive structure found in the brown algae that produces gametes 

Gamete

• A haploid reproductive structure, such as an egg and sperm. If fused together will form a diploid zygote 

Gametic Meiosis

• See diplontic life cycle

Gametophyte

• The multicellular, haploid phase of an organism, which creates gametes through mitosis 

Gene Flow

• The movement of reproducing individuals of a species into a new population; introducing new alleles 

Gene Pool

• Sum total of all alleles, of all the genes, of all individuals, in a population. 

Genetic Drift

• Changes due to random chance that affects the frequency of alleles in a population 

Genotype

• All genes possessed by an organism 

Gymnosperm

• A vascular plant that possesses seeds and pollen

• These plants usually have cones that house their seeds and pollen organs (e.g. conifers, Ginkgo, cycads)

Haplo-diplontic life cycle

• A life cycle in which there is a multicellular gametophyte and multicellular sporophyte (e.g. land plants/embryophytes) 

• Special cells on the sporophyte (sporocytes) go through meiosis to create spores which germinate into multicellular gametophytes. 

• Gametophytes produce sperm and egg which fuse to produce multicellular sporophytes. 

• Also called Alternation of Generations or Sporic Meiosis or a Diplo-haplontic lifecycle

Haploid (1n)

• Having a single set of chromosomes in each cell; therefore only one copy of each gene

Haplontic life cycle

• A life cycle in which there is a multicellular gametophyte, but a unicellular sporophyte (e.g. fungi and some algae)

• The gametophyte (or haploid stage) is dominant and multicellular, producing gametes through mitosis.

• Fusion (or fertilization) of gametes produces a unicellular zygote, which then undergoes meiosis to produce haploid spores.

• Also called a zygotic meiosis

Hardy-Weinberg Equilibrium

• A principle that states that the frequency of alleles in a population’s gene pool remains constant, unless certain conditions apply, such as mutations, gene flow, natural selection, and/or selective mating 

Heteroecious

• Having "different homes", such as a parasite that requires two different hosts to complete lifecycle 

• Contrast with autoecious

Heterosporous

• Having two types of spores: microspores and megaspores 

• Contrast with homosporous

Heterotroph

• An organism that derives energy from other organisms

Homology (of organs)

• Being similar in position, structure, and evolutionary origin but not necessarily in function

Homosporous

• Having one type of spore

• Contrast with heterosporous

Hyphae

• Fungal filaments (hair-like cells); the body of a fungus 

Incertae sedis

• Having an undefined category or grouping 

Isogamous

• Gametes are all same size / shape 

Karyogamy

• The fusion of two nuclei. e.g. formation of a zygote in the basidiomycetes

Kelp

• A large plant-like algae "rooted" to the seafloor and growing vast lengths to the surface (e.g., Macrocystis) 

Macroevolution

• Large scale evolutionary change; above the species level. 

• Origin of major groups 

Megaphylls

• Leaves with a complex, branching veins in the blade

• Feature of the Euphyllophyte clade; 

• Also called euphylls

Megasporangium

• A spore sac that contains megaspores

Megaspore

• A large spore that creates a female gametophyte (see spore) 

Megasporophyll

• A specialized leaf that protects the megasporangia of spore-bearing plants. This term is also used in seed plants to refer to the highly modified leaf that has evolved into the carpel.

Meiosis

• Cell division, which creates four haploid cells from a single diploid cell

Microevolution

• Small scale evolutionary change; at the species-level; Origin of new species 

Microphylls

• Leaves with a single, unbranched vein in the blade

• Feature of the lycophyte clade; also called lycophylls

Microsporangium

• A spore sac that contains microspores

Microspore

• A smaller spore that creates a male gametophyte (see spore) 

Mitosis

• Cell division which creates two identical cells from a single cell; growth

Monokaryotic

• Condition in which each cell has only 1 nucleus

• Contrast with dikaryotic

Monophyletic

• A group that includes an ancestor and all derived taxa; natural evolutionary group 

Multicellular

• An organism that is composed of many cells

Mutations

• Changes to an allele form of a gene; most of the changes are harmful to the organism. Mutations are the raw material for evolution. 

Mycelium

• Mass of hyphae; the “body” of a fungus 

Natural Selection

• The process by which favorable traits that are heritable become more common in successive generations of a population of reproducing organisms 

Non-random or Selective Mating

• Choosing a mate, or mating, based upon specific traits

• Mating, and ultimately fertilization, is not random. 

Nucellus

• The megasporangium of a seed plant that contains one megaspore

• This tissue layer that is beneath the integuments of the seed, but outside of the megaspore.

Oogamous (Oogamy)

• ♀ gametes non-motile, ♂ gamete motile 

Oogonium

• A structure that contains eggs in algae or fungi

Opisthokonts

• A group of eukaryotes that cells that exhibit with a single, posterior flagellum, such as a human sperm cell. 

Paraphyletic

• A group that is a grade of taxa that include an ancestor, but not all derived taxa 

Parenchymatous

• Three-dimensional connection of cells

Phenotype

• The physical appearance of an organism 

Phyletic Gradualism

• Evolutionary change occurs at a slow but constant rate 

Phylogenetic Tree

• A visual representation of the evolutionary relationship between organisms; a cladogram 

Plasmodium

• Blob-like protoplasm, which has a coencytic structure. e.g. myxomycetes

Plasmogamy

• The fusion of the protoplasm of two cells, but not their nuclei 

Plesiomorphy

• An ancestral trait

Polyphyletic

• A group that is a selection of non-contingent taxa 

Population

• Localized group of individuals belonging to the same species 

Prokaryote

• Organisms without an organized nucleus or organelles 

Pseudoparenchymatous

• Composed of many interwoven filamentous strands, given the appearance of parenchymatous

Pteridophyte

• A vascular, spore-bearing plant

• This is not considered to be a true evolutionary grouping, but is useful for teaching about the lifecycles of ancestral vascular plants (e.g. ferns, lycophytes)

Punctuated Equilibrium

• Evolution that occurs in quick rates followed by long period of relatively little change 

Pyrenoid

• Sub-cellular structures found inside algal chloroplasts which concentrate carbon dioxide for photosynthesis

Seaweed

• A macroscopic, sometimes plant-like, algae (e.g., Fucus)

Sensu lato

• "In the loose sense"; a general definition of a group 

Sensu stricto

• "In the strict sense"; a specific definition of a group 

Septate

• cells having cross walls 

Siphonous

• Threadlike, coenocytic cells; multiple nuclei per cell. 

Speciation

• The origin of a new species 

Species

• A group of populations that could interbreed 

Spermatia

• Non-motile sperm (lack flagella). e.g. red algae

Sporangium

• A structure that contains spores 

• Unilocular sporangia: A single-chambered reproductive structure found in the brown algae that produces spores through meiosis

Sporangiophore

• A stalk that holds a sporangium (-"phore" means stalk) 

Spore

• A microscopic propagule, which is roughly spherical

• Usually the haploid products of meiosis of a diploid cell (sporocyte); called a meiospore

• 4 haploid spores are produced for each sporocyte 

Sporic Meiosis

• See haplo-diplontic life cycle

Sporocyte

• A diploid cell that goes through meiosis to produce 4 haploid spores

• Sometimes called a spore mother cell

Sporophyll

• A specialized leaf that protects the sporangia of spore-bearing plants

• This term is also used in seed plants to indicate the leaf that protects the seeds.

Sporophyte

• The multicellular, diploid phase of an organism, which creates spores through meiosis 

Stele

• The pattern in which xylem and phloem are arranged inside of a plant

• Usually displayed as the pattern observed in cross-section of the stem. 

Sympatric Speciation

• Genetic changes create a reproductive barrier which allow a new species to arise even though it is within a breeding distance 

Synapomorphy

• A shared derived feature 

Taxonomy

• A classification system used to sort organisms based upon similarities 

Tetrasporophyte

• Multicellular, diploid stage (sporophyte) that produces haploid spores within the body of the plant. e.g. red algae 

Tetraspores

• Haploid products produced through meiosis by a tetrasporophyte. e.g. red algae 

Thallus

• Flattened “body” of an organism. e.g. liverwort or brown algae

Trichogyne

• A hair-like female structure that "catches" male gametes. e.g. red algae

Triploid

• Having three sets of chromosomes in each cell; therefore three copies (alleles) of each gene

Unicellular

• An organism that is one, single cell

Vascular (of cells)

• Specialized cells that move water, minerals, and/or sugars (e.g. xylem, phloem)

Zygosporangium

• A diploid (embryo) product that results from the fusion of gametangia. e.g. mucoromycetes

Zoospore

• Spore, produced by meiosis, with a flagellum for motility. e.g. chytridiomycetes

Zygote

• In botany, the first stage of the diploid sporophyte, formed from fertilization

• The zygote is not nourished or protected by the mother organism

• Compare to embryo

Zygotic Meiosis

• see Haplontic life cycle