Terminology
The page contains terminology and select topics related to botany that are used on this website.
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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
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
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
Carpal
The female portion of a flowering plant. It is a modified megasporophyll that is enclosed to protect the seeds
After fertilization, the carpal 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
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
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)
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
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
Homologous (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
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 indicate the highly modified leaf that has become the carpal.
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)
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
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
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
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
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