Characteristics, classification and features of organisms

• Characteristics of Living Organisms

  • Movement
  • Respiration
  • Sensitivity
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• There are millions of species of organisms on Earth
• Species


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

  • Features that they share
  • Can be classified into smaller and more specialized groups
• Binomial system


  Organisms are named in Latin using two parts: genus (capital letter) and species (lowercase letter)
• Sequence of classification


  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Dichotomous keys


  • Used to identify organisms based on a series of questions about their features
  • Branching into two descriptions at a time
• Using DNA to classify organisms

  • Organisms share features because they descend from a common ancestor
  • DNA sequence similarities show how closely related species are
• The Five Kingdoms


  • Animals
  • Plants
  • Fungi
  • Protoctists
  • Prokaryotes
• Main features of all animals

  • Multicellular
  • Cells contain a nucleus
• DNA sequences can show how closely related different species are
• As DNA base sequences are used to code for amino acid sequences in proteins, the similarities in amino acid sequences can also be used to determine how closely related organisms are
• 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 groups apart, 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


  • Flowers have petals in multiples of 3
  • Leaves have parallel veins
• Dicotyledons


  • Flowers have petals in multiples of 4 or 5
  • Leaves have reticulated veins
• Viruses are not part of any classification system as they are not considered living things
• Viruses


  • Do not carry out the seven life processes for themselves
  • Take over a host cell's metabolic pathways to make copies of themselves
  • Structure is genetic material (RNA or DNA) inside a protein coat