Taxonomy

• Taxonomy

  The hierarchical biological classification system
• Domain


  The highest taxonomic rank in the hierarchical biological classification system, above the kingdom level
• Domains

  • Archaea
  • Bacteria
  • Eukarya
• Archaea


  • Single-celled microorganisms with structure similar to bacteria
• Bacteria

  • Includes the prokaryotes people encounter on an everyday basis
  • Most bacterial species are heterotrophic, they acquire their food from organic matter
  • The largest number of bacteria are saprobic, meaning that they feed on dead or decaying organic matter
• Bacteria

  • Ubiquitous, mostly free-living organisms often consisting of one biological cell
  • Typically a few micrometers in length
  • Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats
  • Bacteria play a vital role in many stages of the nutrient cycle by recycling nutrients and the fixation of nitrogen from the atmosphere
  • Bacteria are responsible for the putrefaction stage in the decomposition of dead bodies
• Eukarya

  • Constitute the domain of Eukarya or Eukaryota, organisms whose cells have a membrane-bound nucleus
  • All animals, plants, fungi, and many unicellular organisms are eukaryotes
  • Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes
• Kingdom


  The second highest classification into which living organisms are grouped in Linnean taxonomy, ranking above a phylum
• Archaebacteria

  • A group of microorganisms considered to be an ancient form of life that evolved separately from the bacteria and blue-green algae, and they are sometimes classified as a kingdom
• Protista

  • Contains the protists, or all the organisms that do not fit into the other kingdoms of life
  • Protists can be heterotrophic or autotrophic, mobile or immobile, single-celled or multi-celled, solo or a member of a colony
  • They are categorized into three main categories based on how they obtain nutrients
• Fungi


  • Eukaryotic organisms that include microorganisms such as yeasts, moulds and mushrooms
  • These organisms are classified under kingdom fungi
  • The organisms found in Kingdom fungi contain a cell wall and are omnipresent
  • They are classified as heterotrophs among the living organisms
• Plantae

  • Includes all the plants
  • They are eukaryotic, multicellular and autotrophic organisms
  • The plant cell contains a rigid cell wall
  • Plants have chloroplast and chlorophyll pigment, which is required for photosynthesis
• Animalia

  • Includes all animal species
  • All members of this kingdom are multicellular and have eukaryotic cells
  • They are also heterotrophic, meaning they consume other organisms
• Porifera

  • Sponges constitute the phylum Porifera, and have been defined as sessile metazoans (multicelled immobile animals) that have water intake and outlet openings connected by chambers lined with choanocytes, cells with whip-like flagella
• Cnidaria

  • Cnidaria are diploblastic animals; in other words, they have two main cell layers, while more complex animals are triploblasts having three main layers
  • The two main cell layers of cnidarians form epithelia that are mostly one cell thick, and are attached to a fibrous basement membrane, which they secrete
  • They also secrete the jelly-like mesoglea that separates the layers
  • Epitheliomuscular cells whose bodies form part of the epithelium but whose bases extend to form muscle fibers in parallel rows
  • The fibers of the outward-facing cell layer generally run at right angles to the fibers of the inward-facing one
  • In Anthozoa (anemones, corals, etc.) and Scyphozoa (jellyfish), the mesoglea also contains some muscle cells
  • Cnidocytes, the harpoon-like "nettle cells" that give the phylum Cnidaria its name, appear between or sometimes on top of the muscle cells
  • Nerve cells. Sensory cells appear between or sometimes on top of the muscle cells, and communicate via synapses (gaps across which chemical signals flow) with motor nerve cells, which lie mostly between the bases of the muscle cells
  • Interstitial cells, which are unspecialized and can replace lost or damaged cells by transforming into the appropriate types, are found between the bases of muscle cells
• Platyhelminthes

  • The lack of circulatory and respiratory organs limits platyhelminths to sizes and shapes that enable oxygen to reach and carbon dioxide to leave all parts of their bodies by simple diffusion
  • Hence, many are microscopic, and the large species have flat ribbon-like or leaf-like shapes
• Nematoda

  • Roundworms or eelworms constitute the phylum Nematoda
  • They are a diverse animal phylum inhabiting a broad range of environments
  • Most species are free-living, feeding on microorganisms, but there are many that are parasitic
  • The parasitic worms (helminths) are the cause of soil-transmitted helminthiases
• Annelida

  • The Annelids are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms
  • They also have parapodia for locomotion
  • Most textbooks still use the traditional division into polychaetes (almost all marine), oligochaetes (which include earthworms) and leech-like species
• Mollusca

  • The four most universal features defining modern molluscs are a body largely consisting of solid muscle, a mantle with a significant cavity used for breathing and excretion, the presence of a radula (except for bivalves), and the structure of the nervous system
  • Other than these common elements, molluscs express great morphological diversity, so many textbooks base their descriptions on a "hypothetical ancestral mollusc" which has a single, "limpet-like" shell on top, made of proteins and chitin reinforced with calcium carbonate, and secreted by a mantle covering the whole upper surface
  • The underside of the animal consists of a single muscular "foot"
• Arthropoda

  • Arthropods are invertebrates in the phylum Arthropoda
  • They possess an exoskeleton with a cuticle made of chitin, often mineralised with calcium carbonate
  • They have a body with differentiated (metameric) segments, and paired jointed appendages
  • In order to keep growing, they must go through stages of moulting, a process by which they shed their exoskeleton to reveal a new one
  • They are an extremely diverse group, with up to 10 million species
• Echinodermata

  • Echinodermata includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies"
  • While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry (pentamerous symmetry), and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone
  • The phylum contains about 7,000 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum
  • The first definitive echinoderms appeared near the start of the Cambrian
• Chordata


  • All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics (synapomorphies) that distinguish them from other taxa: a notochord, a hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post-anal tail
  • Chordates are also bilaterally symmetric, have a coelom, possess a closed circulatory system, and exhibit metameric segmentation
  • Analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and inner mitochondrial membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cephalochordates
• Agnatha

  • An infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms) species
  • Among recent animals, cyclostomes are sister to all vertebrates with jaws, known as gnathostomes
• Chondrichthyes

  • A class of jawed fish that contains the cartilaginous fish or chondrichthyians, which all have skeletons primarily composed of cartilage
• Osteichthyes

  • Also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue
  • They can be contrasted with the Chondrichthyes (cartilaginous fish) and the extinct placoderms and acanthodians, which have endoskeletons primarily composed of cartilage
  • The vast majority of extant fish are members of Osteichthyes, being an extremely diverse and abundant group consisting of 45 orders, over 435 families and 28,000 species
• Amphibia

  • Amphibians have a skeletal system that is structurally homologous to other tetrapods, though with a number of variations
  • They all have four limbs except for the legless caecilians and a few species of salamander with reduced or no limbs
  • The bones are hollow and lightweight
• Reptilia

  • Reptiles, as commonly defined, are a group of tetrapods with an ectothermic ('cold-blooded') metabolism and amniotic development
  • Living reptiles comprise four orders: Testudines (turtles), Crocodilia (crocodilians), Squamata (lizards and snakes), and Rhynchocephalia (the tuatara)
• Aves

  • Birds (class Aves) – winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals
  • There are around 10,000 living species, making them the most varied of tetrapod vertebrates
  • They inhabit ecosystems across the globe, from the Arctic, to the Antarctic
• Mammalia

  • A mammal is a vertebrate animal of the class Mammalia
  • Mammals are characterized by the presence of milk-producing mammary glands for feeding their young, a neocortex region of the brain, fur or hair, and three middle ear bones
• Taxonomy of human
• Low biodiversity
• High biodiversity