CHAPTER 2 (Classification)

• Binomial system before the 18th century


  Each organism has a lengthy descriptive name. E.g. if they were streamlined and swam ("Beasts of the Water"), or had wings and flew ("Creatures of the Air") - they were classified in the same groups. As more people studied nature, it became obvious that a butterfly's wings were very different structures than a bird's wings.
• Binomial System in the 18th century


  CAROLUS LINNEAUS, a Swedish botanist and natural historian simplified the classic scientific classification. Its called Binomial system of nomenclature.
• Each species in Binomial system


  Is assigned with a two-part name (scientific name) that is generally derived from Greek or Latin words. Usually it composed of Latinized version of the names of persons, places or characteristics. For example; Escherichia coli

  • Theodor Escherich (Scientist who discover it)
  • Coli (Inhabit the colon)
• The importance of binomial system

   Allows biology to become an

  international language.

   Although at different locations and

  languages, an organism can be

  universally identified by its scientific

  name.

   This also eliminates repeated study

  done on the same organism
• Rules of writing a scientific name

  – Genus name must be capitalized – Specific epithet is not capitalized – Both names must be either Underlined or Italicized – Genus name can be used alone to designate all species in the genus – Specific epithet can never be used alone
• In a scientific name;

  – First part designates the genus (pl:genera) – Second part designates the specific epithet (name) – Example: Felis catus or Felis catus
• Same specific epithet name

  Homarus americanus

  ( Atlantic Lobster) Ursus americanus ( Black Bear) Bufo americanus ( American Toad)
• Taxonomy is that branch of biology dealing with the


  • Identification, naming and identifying of organisms.

  • Because there are millions of organisms, classification systems are developed to facilitate the identification of species from the vast array of biological organisms.
• Linnaeus assigned species to a hierarchy of group called taxon


  Carolus Linnaeus also designed this practice of classification, which besides dealing with binomial system of nomenclature, also includes a process of ordering organisms into groups in the basis of affinity or relationship between them.
• In Linnaean classification; 


  • The narrowest category -species, the broadest - the kingdom.

  • Organisms arranged into taxonomic categories, or taxa (singular:taxon) that show degrees of similarities among them
• In Linnaean classification;

  • The narrowest category -species, the broadest - the kingdom. • Organisms arranged into taxonomic categories, or taxa (singular:taxon) that show degrees of similarities among them

  
• Taxonomy Species 


  - a group of similar organisms that can interbreed in their own natural environment - reproductively isolated from other organisms

  
• Example Taxonomy —classification of corn

  
• The importance of taxonomy

  i. Easier to retrieve information from about 30 million sp ii. Easier to predict the characteristics of a new-found species based on the existing species. iii. Easier to explain evolutionary relationship
• History of Classification (1)

  • From the time of Aristotle to the mid 19th century, all living things were divided into two kingdoms plant and animal.
  • After the development of microscope, scientists faced difficulties in classifying microorganisms eg Euglena characteristics of both plant and animals.
  • In 1866, Ernst H. Haeckel created a third kingdom, the Protista. He included among the protists all the simple forms of life such as bacteria + algae + protozoa + multicellular fungi + sponges.
• History of Classification (2)

  • Studies of different structure and function of cells led to the recognition of two general patterns of cellular organization, prokaryotic and eukaryotic.
  • In 1937, a French marine Biologist Eduord Chatton suggested the term ‘procariotique’ and ‘eucariotique’.
  • In 1956, Lynn Margulis and H.F. Copeland proposed a scheme of classifying prokaryotes and eukaryotes by the following four kingdom system Monera, Protoctista, Plantae and Animalia.
• History of Classification (3)

  • In 1969, R.H. Whittaker proposed a taxonomic system that separate the Protoctista into two kingdoms - Protista and Fungi but retained the Monera, Plantae and Animalia.
  • After refinements of the Whittaker’s system by several taxonomists, the five kingdom system of classification was created.

  
• History of Classification (4)

  • In 1970s, Carl R. Woese studied the evolutionary relationship between organisms by realizing their RNA. He proposed that there are two fundamentally different groups of bacteria, Archaebacteria and Eubacteria.
  • Given this molecular evidence, biologists separate the kingdom Monera into kingdom Archaebacteria and Eubacteria.
  • Carl R. Woese also proposed of elevating the three cell types to a level above kingdom, which are called domain.
• History of Classification

  
• Five-kingdom classification system (Kingdom Monera)

   Consists of all prokaryotic organisms, including eubacteria (true bacteria), cyanobacteria and archaebacteria.  All monerans are unicellular, lack true nuclei and lack membrane-enclosed organelles.  Reproduction in the Kingdom Monera occurs mainly by binary fission

  
• Five-kingdom classification system (Kingdom Protista)


   All protists are simple eukaryotes with a true membrane-enclosed nucleus and organelles within their cytoplasm.  Most are unicellular, but some are organized into colonies.  Many protists live in fresh water, some live in seawater, and a few live in soil.  There are protists that resemble fungi, plants and animals.

  
• Five-kingdom classification system (Kingdom Fungi)

   Include mostly multicellular and unicellular organisms.  Fungi are heterotroph, obtaining nutrients solely by absorption of organic matter from other organisms.  Fungi form spores but do not form seeds.  Although some fungi do cause diseases to plants, animals or even human, others are important economically and ecologically

  
• Five-kingdom classification system (Kingdom Plantae)

   Most plants live on land unlike their algal ancestors which are adapted to aquatic habitats.  Plants contain chlorophyll in organelles called chloroplast.  Plants can be divided into seedless vascular plants and seed bearing vascular plants.  Seed bearing vascular plants can be divided into gymnosperms and angiosperms

  
• Five-kingdom classification system (Kingdom Animalia)

   All animals are multicelled, aerobic heterotrophs that ingest or parasitize other organisms.  Nearly all kinds have tissues, organs, and organ systems and are motile during at least a part of their life cycle.  Include all animals derived from zygotes (a cell formed by the union of two gametes, such as egg and sperm.  Animals reproduce sexually and asexually

  
• Six-kingdom classification system


   Separates the Kingdom Monera into archaebacteria and eubacteria.  Archaebacteria differ in the small subunit of 16S ribosomal RNA (sequence analysis)  There is also absence of peptidoglycan in their cell walls  Unique cell membrane structure that contribute to their ability to survive in harsh environment.

  
• Three-domain classification system

   Domain Bacteria - All bacteria are unicellular prokaryotes. Their common name is eubacteria (true bacteria)  Domain Archaea - All archaea are unicellular prokaryotes, besides characteristics mentioned before, they differed from eubacteria by thriving in extreme habitats.  Domain Eukarya - All are eukaryotic cells, they possess a true nucleus and have abundance of organelles.

  
• Classification System

  
• Systematics (1)

  • Systematics is the modern classification. It is a study of evolutionary or phylogenetic relationship. • The goal of systematics is to reconstruct phylogeny, the evolutionary history of a group of organism from a common ancestor.

  
• Systematic (2)


  • Patterns of shared characteristics can be depicted in a diagram called the cladogram • A clade is a group of species that includes an ancestral species and its descendants

  
• Monophyletic

  Single tribe / Grouping of the ancestral species and ALL the descendants

  
• Paraphyletic

  Grouping that consists of the ancestor and SOME (not all) of the ancestor’s descendants

  
• Polyphyletic

  Grouping of several species that LACK a common ancestor