parent_taxon phegopteris
A fern is a member of a group of about 10 , 560 known extant species of vascular plants that reproduce via spores and have neither seeds nor flowers . They differ from mosses by being vascular , i . e ., having certain tissue that conducts water and nutrients . They have branched stems and leaves like other vascular plants . These are " megaphylls ", which are more complex than the simple " microphylls " of clubmosses . Most ___MASK94___ are Leptosporangiate ___MASK94___ , sometimes denominated the " true ___MASK94___ ": they produce what are called " fiddleheads " that uncoil and expand into fronds . Deoxyribonucleic acid ( DNA ) is a molecule that carries the genetic instructions used in the growth , development , functioning and reproduction of all known living organisms and many viruses . DNA and RNA are nucleic acids ; alongside proteins , lipids and complex carbohydrates ( polysaccharides ), they are one of the four major types of macromolecules that are essential for all known forms of life . Most DNA molecules consist of two biopolymer strands coiled around each other to form a double ___MASK78___ . A genus ( genera ) is a taxonomic rank used in the biological classification of living and fossil organisms in biology . In the hierarchy of biological classification , genus comes above species and below family . In binomial nomenclature , the genus name forms the first part of the binomial species name for each species within the genus . ___MASK1___ is a family of about 900 species of ferns in the eupolypods II clade of the order Polypodiales , in the class Polypodiopsida . Sexual reproduction is a form of reproduction where two morphologically distinct types of specialized reproductive cells called gametes fuse together , involving a female ' s large ovum ( or egg ) and a male ' s smaller sperm . Each gamete contains half the number of chromosomes of normal cells . They are created by a specialized type of cell division , which only occurs in eukaryotic cells , known as meiosis . The two gametes fuse during fertilization to produce DNA replication and the creation of a single - celled zygote which includes genetic material from both gametes . In a process called genetic recombination , genetic material ( DNA ) joins up so that homologous chromosome sequences are aligned with each other , and this is followed by exchange of genetic information . Two rounds of cell division then produce four daughter cells with half the number of chromosomes from each original parent cell , and the same number of chromosomes as both parents , though self - fertilization can occur . For instance , in ___MASK72___ reproduction each ___MASK72___ cell contains 46 chromosomes , 23 pairs , except gamete cells , which only contain 23 chromosomes , so the child will have 23 chromosomes from each parent genetically recombined into 23 pairs . Cell division initiates the development of a new individual organism in multicellular organisms , including animals and plants , for the vast majority of whom this is the primary method of reproduction . In biology , a species ( abbreviated sp ., with the plural form species abbreviated spp .) is the basic unit of biological classification and a taxonomic rank . A species is often defined as the largest group of organisms in which two individuals can produce fertile offspring , typically by sexual reproduction . While this definition is often adequate , looked at more closely it is often problematic . For example , in a species complex , the boundaries between closely related species become unclear or disappear altogether . Other ways of defining species include similarity of DNA , morphology , or ecological niche . The presence of locally adaptive traits may further subdivide species into infraspecific taxa such as subspecies . In biology , an organism is any contiguous living system , such as an ___MASK19___ , plant , fungus , archaeon , or bacterium . All known types of organisms are capable of some degree of response to stimuli , reproduction , growth and development and homeostasis . An organism consists of one or more cells ; when it has one cell it is known as a unicellular organism ; and when it has more than one it is known as a multicellular organism . Most unicellular organisms are of microscopic scale and are thus loosely described as microorganisms . Humans are multicellular organisms composed of many trillions of cells grouped into specialized tissues and organs . The order ___MASK76___ encompasses the major lineages of polypod ___MASK94___ , which comprise more than 80 % of today ' s fern species . They are found in many parts of the world including tropical , semitropical and temperate areas . The characteristics of this group include : sporangia with a vertical annulus interrupted by the stalk and stomium ; indusia laterally or centrally attached ( or lost ); gametophytes green , chordate , and surficial . ___MASK56___ ( maiden ferns ) is a genus of ferns in the family ___MASK1___ , order Polypodiales . If the genus is defined fairly broadly , it contains 875 species , many of which are extremely similar to one another , and is found nearly worldwide . The ferns are terrestrial , with the exception of a few which are lithophytes ( grow on rocks ). The bulk of the species are tropical , although there are a number of temperate species . Binomial nomenclature ( also called binominal nomenclature or binary nomenclature ) is a formal system of naming species of living things by giving each a name composed of two parts , both of which use Latin grammatical forms , although they can be based on words from other languages . Such a name is called a binomial name ( which may be shortened to just " binomial "), a binomen or a scientific name ; more informally it is also called a Latin name . The first part of the name identifies the genus to which the species belongs ; the second part identifies the species within the genus . For example , humans belong to the genus " ___MASK42___ " and within this genus to the species " ___MASK42___ sapiens ". The " formal " introduction of this system of naming species is credited to Carl Linnaeus , effectively beginning with his work " Species Plantarum " in 1753 . But Gaspard Bauhin , in as early as 1623 , had introduced in his book " Pinax theatri botanici " ( English , " Illustrated exposition of plants ") many names of genera that were later adopted by Linnaeus . Phegopteris is a genus of ___MASK94___ known collectively as the beech ___MASK94___ . Traditionally this genus included only the first three species listed . However , recent genetic evidence clearly shows that the genera Macrothelypteris and Pseudophegopteris , as well as other segregates from the genus ___MASK56___ , are closely related to Phegopteris in a single clade , and so are now included as Phegopteris species .