Family (biology)

Family (biology)

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In biological classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....

, family is
  • a taxonomic rank
    Taxonomic rank
    In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

    . Other well-known ranks are life
    Life
    Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

    , domain
    Domain (biology)
    In biological taxonomy, a domain is the highest taxonomic rank of organisms, higher than a kingdom. According to the three-domain system of Carl Woese, introduced in 1990, the Tree of Life consists of three domains: Archaea, Bacteria and Eukarya...

    , kingdom
    Kingdom (biology)
    In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...

    , phylum
    Phylum
    In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

    , class
    Class (biology)
    In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

    , order
    Order (biology)
    In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

    , genus
    Genus
    In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

    , and species
    Species
    In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

    , with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the prefix sub-: subfamily (Latin: ).
  • a taxonomic unit, a taxon
    Taxon
    |thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

    , in that rank. In that case the plural is families (Latin )
Example: Walnut
Walnut
Juglans is a plant genus of the family Juglandaceae, the seeds of which are known as walnuts. They are deciduous trees, 10–40 meters tall , with pinnate leaves 200–900 millimetres long , with 5–25 leaflets; the shoots have chambered pith, a character shared with the wingnuts , but not the hickories...

s and hickories
Hickory
Trees in the genus Carya are commonly known as hickory, derived from the Powhatan language of Virginia. The genus includes 17–19 species of deciduous trees with pinnately compound leaves and big nuts...

 belong to Juglandaceae
Juglandaceae
The Juglandaceae, also known as the Walnut Family, is a family of trees, or sometimes shrubs, in the order Fagales. Various members of this family are native to the Americas, Eurasia, and Southeast Asia....

, the walnut family.


What does and does not belong to each family is determined by a taxonomist. Similarly for the question if a particular family should be recognized at all. Often there is no exact agreement, with different taxonomists each taking a different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing a family. Some taxa are accepted almost universally, while others are recognised only rarely.

History


The taxonomic term was first used by French botanist Pierre Magnol
Pierre Magnol
Pierre Magnol was a French botanist. He was born in the city of Montpellier, where he lived and worked for the biggest part of his life. He eventually became Professor of Botany and Director of the Royal Botanic Garden of Montpellier and even held a seat in the Académie Royale des Sciences de...

 in his (1689) where he called the seventy-six groups of plants he recognised in his tables families (). The concept of rank at that time was not yet settled, and in the preface to the Magnol spoke of uniting his families into larger , which is far from how the term is used today.

Carolus Linnaeus used the word in his (1751) to denote major groups of plants: tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s, herb
Herb
Except in botanical usage, an herb is "any plant with leaves, seeds, or flowers used for flavoring, food, medicine, or perfume" or "a part of such a plant as used in cooking"...

s, fern
Fern
A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s, palms, and so on. He used this term only in the morphological section of the book, discussing the vegetative and generative organs of plants. Subsequently, in French botanical publications, from Michel Adanson
Michel Adanson
Michel Adanson was a French naturalist of Scottish descent.Adanson was born at Aix-en-Provence. His family moved to Paris on 1730. After leaving the College Sainte Barbe he was employed in the cabinets of R. A. F. Reaumur and Bernard de Jussieu, as well as in the Jardin des Plantes. At the end of...

's (1763) and until the end of the 19th century, the word was used as a French equivalent of the Latin (or ). In nineteenth century works such as the of Augustin Pyramus de Candolle and the of George Bentham
George Bentham
George Bentham CMG FRS was an English botanist, characterized by Duane Isely as "the premier systematic botanist of the nineteenth century".- Formative years :...

 and Joseph Dalton Hooker
Joseph Dalton Hooker
Sir Joseph Dalton Hooker OM, GCSI, CB, MD, FRS was one of the greatest British botanists and explorers of the 19th century. Hooker was a founder of geographical botany, and Charles Darwin's closest friend...

 this word was used for what now is given the rank of family.

In zoology, the family as a rank intermediate between order and genus was introduced by Pierre André Latreille
Pierre André Latreille
Pierre André Latreille was a French zoologist, specialising in arthropods. Having trained as a Roman Catholic priest before the French Revolution, Latreille was imprisoned, and only regained his freedom after recognising a rare species he found in the prison, Necrobia ruficollis...

 in his (1796). He used families (some of them not named) in some but not in all his orders of "insects" (which then included all arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s).

Uses


Families can be used for evolutionary, palaeontological and generic studies because they are more stable than lower taxonomic levels such as genera and species.

See also

  • Systematics
    Systematics
    Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...

    , the study of the diversity of life
  • Cladistics
    Cladistics
    Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

    , the classification of organisms by their order of branching in an evolutionary tree
  • Phylogenetics
    Phylogenetics
    In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...

    , the study of evolutionary relatedness among various groups of organisms
  • Taxonomy
    Taxonomy
    Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

  • Virus classification
    Virus classification
    Virus classification is the process of naming viruses and placing them into a taxonomic system. Similar to the classification systems used for cellular organisms, virus classification is the subject of ongoing debate and proposals. This is mainly due to the pseudo-living nature of viruses, which...

  • List of Anuran families
  • List of Testudines families
  • List of fish families
  • List of families of spiders

Compare:
  • family
    Family
    In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...

  • protein family
    Protein family
    A protein family is a group of evolutionarily-related proteins, and is often nearly synonymous with gene family. The term protein family should not be confused with family as it is used in taxonomy....

  • gene family
    Gene family
    A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions...