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• A species is a group of similar organisms that are able to breed to produce fertile offspring
• Levels in the taxonomic hierarchy

  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Binomial naming system


  Gives an organism a genus and a species name

  
• The taxonomic hierarchy can be used to classify given organisms or recognize what taxonomic groups they belong to
• The initiation for evolving taxonomic systems was provided by Aristotle (384-322 BC)
• Aristotle's classification of animals

  • Divided animals into those with blood and those without blood
  • Classified animals based on gills, lungs, claws, teeth and other structures
  • Observed insects, fishes, birds and whales
  • Created insect orders like Coleoptera, Diptera
• Aristotle is considered the 'Father of Biological Classification'
• John Ray (1627 - 1705) stated that animals can be classified according to their way of living, actions, habits and body parts
• John Ray coined the term "species" as 'a reproducing unit'
• Carolus Linnaeus (1707 - 1778)


  • First introduced the hierarchic system, both in animal and plant kingdoms
  • Followed four categories namely class, order, genus, species for the animal world
  • Greatest contribution was the use of binomial nomenclature for all species of animals and plants

  
• Carolus Linnaeus has been called the 'Father of Taxonomy'

  
• Charles Darwin's 'Origin of species' in 1859 had an immediate acceptance among biologists
• Due to the influence of evolutionary ideas, taxonomy was studied as an important evidence in favour of evolution
• The development of modern taxonomy started during 1930s, with taxonomy being based on population studies and moving from the laboratory to the field
• Taxonomy was transformed into 'biological taxonomy' with the study of morphological characters along with behaviour, sound, ecology, genetics, zoogeography, physiology and biochemistry
• Taxonomy


  The theory and practice of classifying organisms
• Systematics


  The scientific study of the kinds and diversity of organisms and of any and all relationships among them
• Classification


  The ordering of animals into groups on the basis of their relationships
• Taxon


  A taxonomic group of any rank that is sufficiently distinct to be worthy of being assigned to a definite category
• Taxa in animal taxonomy

  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• The Hierarchic System of Classification arranges taxa from Phylum to Species based on specific characters of a group of organisms
• The kinds of organisms are fantastically diverse but are considered to be related, as they all evolved from a single ancestral animal more than half a billion years ago
• A Phylogenetic Tree is a diagram that represents evolutionary relationships among organisms
• Phylogenetic trees are hypotheses, not definitive facts
• Animal Phyla


  • Porifera
  • Cnidaria (Coelenterata)
  • Platyhelminthes
  • Nematoda
  • Annelida
  • Arthropoda
  • Mollusca
  • Echinodermata
  • Chordata
• Animals are classified into two distinct groups: invertebrates (animals without backbones) and vertebrates (animals with backbones)
• Phylogenetic trees


  Hypotheses about evolutionary relationships among organisms, not definitive facts
• The pattern of branching in a phylogenetic tree reflects how species or other groups evolved from a series of common ancestors
• Animal groups


  • Invertebrates (animals without backbones)
  • Vertebrates (animals with backbones)
• Invertebrate phyla


  • Porifera
  • Cnidaria (Coelenterata)
  • Platyhelminthes
  • Nematoda
  • Annelida
  • Arthropoda
  • Mollusca
  • Echinodermata

  
• Phylum Porifera (Sponges)


  • Simplest animals
  • Aquatic, mostly marine
  • Sessile (no locomotion)
  • Filter feeders
  • Reproduce sexually and asexually
• Phylum Cnidaria


  • Live in marine and freshwater habitats
  • Have tentacles with stinging cells
  • Radial symmetry
  • Have two body types
• Phylum Platyhelminthes


  • Worms with unsegmented, flattened bodies
  • Found in freshwater, saltwater, and on land
  • Have distinct head and tail regions
  • Free-living and parasitic forms
• Phylum Nematoda (Roundworms)


  • Slender, cylindrical bodies that taper at both ends
  • Can move through muscular contraction
  • Have complete digestive system
  • Free-living and parasitic forms
• Phylum Nematoda (Roundworms)


  • Epidermis covered in protective cuticle
  • Produce many eggs, have life cycles that ensure transmission to new hosts
• Phylum Annelida (Segmented Worms)


  • Cylindrical bodies divided into ring-like segments
  • Flexible bodies due to thick muscle layers
  • Predators, filter feeders, scavengers, and parasites
• Hermaphroditic


  Having both male and female reproductive parts
• Asexual reproduction (Annelids)


  Fission - worm makes copy of DNA and splits into two new individuals
• Phylum Mollusca (Mollusks)


  • Soft-bodied animals often covered in shells
  • Body covered in mantle tissue that secretes shell
  • Heterotrophs
  • Sexually reproducing
• Phylum Arthropoda


  • Most numerous and diverse animals
  • Body segmented into distinct specialized groups
  • Covered in chitinous exoskeleton