Characteristics and Classification of Living Organisms

• Characteristics of Living Organisms:

  • Movement: an action causing a change of position
  • Respiration: chemical reactions breaking down nutrients for energy
  • Sensitivity: ability to detect stimuli and respond
  • Growth: permanent increase in size and dry mass
  • Reproduction: processes making more of the same organism
  • Excretion: removal of toxic materials and waste products
  • Nutrition: taking in materials for energy, growth, and development
• Organisms are classified into species, defined as groups that can reproduce fertile offspring
• The Binomial System:

  • Organisms classified by Linnaeus into smaller groups
  • Scientific name in Latin: genus (capital letter) followed by species (lowercase)
  • Typed binomial names are always in italics, e.g., Homo sapiens
• Dichotomous Keys:

  • Used to identify organisms based on a series of questions
  • Leads the user through two descriptions at a time to the organism's name
  • Follow statements to successfully navigate the key
• Reflecting Evolutionary Relationships:

  • Classification systems aim to reflect evolutionary relationships
  • Based on shared features to determine relatedness
• Using DNA to Classify Organisms:

  • DNA sequences show evolutionary relationships
  • Similar base sequences indicate closely related species
  • Amino acid sequences can also determine relatedness
• The Five Kingdoms:

  • Animals, Plants, Fungi, Protoctists, Prokaryotes
  • Main features of animals and plants
• The Animal Kingdom:

  • Vertebrates have a backbone, invertebrates do not
  • Classes of vertebrates: Mammals, Reptiles, Fish, Amphibians, Birds
  • Invertebrates classified into Arthropods, including Crustaceans, Arachnids, Myriapods, Insects
• Viruses:

  • Not part of the classification system as they are not considered living
  • Take over host cell's metabolic pathways for replication