1. Characteristics & Classification of Living Organisms

• Characteristics of Living Organisms

  • Movement: an action by an organism or part of an organism causing a change of position or place
  • Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy for metabolism
  • Sensitivity: the ability to detect or sense stimuli in the internal or external environment and to make appropriate responses
  • Growth: a permanent increase in size and dry mass by an increase in cell number or cell size or both
  • Reproduction: the processes that make more of the same kind of organism
  • Excretion: the removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements
  • Nutrition: the taking in of materials for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds, ions and usually need water
• MRS. H. GREN


  Mnemonic to remember the characteristics of living organisms
• Species


  A group of organisms that can reproduce to produce fertile offspring
• How organisms are classified


  • Species can be classified into groups by the features that they share
  • All mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas)
• Binomial system


  • Organisms are named in Latin using two parts: the genus (always given a capital letter) and the species (starting with a lower case letter)
  • When typed, binomial names are always in italics
• Sequence of classification


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• KING PHILIP CAME OVER FOR GRAN'S SPAGHETTI


  Mnemonic to remember the sequence of classification
• How do you use a dichotomous key?


  1. Pick a single organism to start with

  2. Follow the statements from the beginning

  3. Answer each statement or question using the information provided

  4. Eventually there will be no more statements or questions left and you will have the name of the organism

  5. Pick another organism and start at the beginning of the key again, repeating until all organisms are named
• Reflecting evolutionary relationships


  • Traditional biological classification systems grouped organisms based on the features that they shared
  • If organisms shared more similar features then they were said to be more closely related
  • Using the physical features of species has many limitations and can often lead to the wrong classification of species
• Using DNA to classify organisms


  • Organisms share features because they originally descend from a common ancestor
  • Studies of DNA sequences of different species show that the more similar the base sequences in the DNA of two species, the more closely related those two species are (and the more recent in time their common ancestor is)
  • DNA sequences can show how closely related different species are
• The Five Kingdoms


  • Animals
  • Plants
  • Fungi
  • Protoctists
  • Prokaryotes
• Main features of all animal cells

  • They are multicellular
  • Their cells contain a nucleus
• DNA sequences can show how closely related different species are
• Brachinus armiger and Brachinus hirsutusare two species

  More closely related than any other species in the list as their DNA sequences are identical except for the last but one base
• The Five Kingdoms


  • Animals
  • Plants
  • Fungi
  • Protoctists
  • Prokaryotes
• Animals


  • Multicellular
  • Cells contain a nucleus but no cell walls or chloroplasts
  • Feed on organic substances made by other living things
• Plants


  • Multicellular
  • Cells contain a nucleus, chloroplasts and cellulose cell walls
  • Feed by photosynthesis
• Vertebrate classes


  • Fish
  • Amphibians
  • Reptiles
  • Birds
  • Mammals
• Invertebrates

  • Do not possess a backbone
  • Classified based on whether they have legs or not
• Arthropod classes


  • Insects
  • Arachnids
  • Crustaceans
  • Myriapods
• Defining features set a group apart from other groups, while main features are shared between groups
• Fungi


  • Usually multicellular
  • Cells have nuclei and cell walls not made from cellulose
  • Do not photosynthesize but feed by saprophytic or parasitic nutrition
• Protoctists


  • Most are unicellular but some are multicellular
  • All have a nucleus, some may have cell walls and chloroplasts
  • Some photosynthesise and some feed on organic substances
• Prokaryotes


  • Often unicellular
  • Cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria
• Plants


  • At least some parts are green due to chlorophyll
  • Include ferns and flowering plants
• Ferns


  • Have leaves called fronds
  • Reproduce by spores produced on the underside of fronds
• Flowering plants


  • Reproduce sexually by means of flowers and seeds
  • Seeds produced inside the ovary at the base of the flower
• Monocotyledons


  One cotyledon (seed leaf) in the seed
• Dicotyledons


  Two cotyledons (seed leaves) in the seed
• Monocotyledons vs Dicotyledons


  • Flowers: Petals in multiples of 3 vs Petals in multiples of 4 or 5
  • Leaves: Parallel veins vs Reticulated veins
• Viruses


  • Not considered living things
  • Take over a host cell's metabolic pathways to make copies of themselves
  • Consist of genetic material (RNA or DNA) inside a protein coat