classification of living organisms

• The domain is the highest level of classification, which includes groups such as Bacteria, Archaea, and Eukarya.
• 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
• A species is defined as a group of organisms that can reproduce to produce fertile offspring
• • The species in these groups have more and more features in common the more subdivided they get
  • He named organisms in Latin using the binomial system where the scientific name of an organism is made up of two parts starting with the genus (always given a capital letter) and followed by the species (starting with a lower case letter)
  • When typed binomial names are always in italics (which indicates they are Latin) e.g. Homo sapiens
  • The sequence of classification is: Kingdom, Phylum, Class, Order, Family, Genus, Species
• Dichotomous keys are used to identify organisms based on a series of questions about their features
• • Classification systems aim to reflect evolutionary relationships between species
  • 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
  • In the past, scientists have encountered many difficulties when trying to determine the evolutionary relationships of species based on this method
  • Using the physical features of species (such as colour/shape/size) has many limitations and can often lead to the wrong classification of species
• Organisms share features because they originally descend from a common ancestor
• Example: all mammals have bodies covered in hair, feed young from mammary glands and have external ears (pinnas)
• Originally, organisms were classified using morphology (the overall form and shape of the organism, e.g. whether it had wings or legs) and anatomy (the detailed body structure as determined by dissection)
• DNA sequencing allowed for a more scientific approach to classifying organisms
• 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)
• • The first division of living things in the classification system is to put them into one of five kingdoms. They are:
  • Animals
  • Plants
  • Fungi
  • Protoctists
  • Prokaryotes
  • Main features of all animals:
  • they are multicellular
  • their cells contain a nucleus but no cell walls or chloroplasts
  • they feed on organic substances made by other living things
  • Main features of all plants:
  • they are multicellular
  • their cells contain a nucleus, chloroplasts and cellulose cell walls
  • they all feed by photosynthesis
• MYRIAPODS:

  • Legs: 10 or more pairs
  • Body: Many segments
  • Antennae: 1 pair
• • Insects
  • Legs: 10 or more pairs
  • Body: 3 parts (head, thorax, abdomen)
  • Wings: 2 pairs (most insects)
  • Antennae: 1 pair
• Crustaceans

  • Legs: 5 or more pairs
  • Body: 2 parts (cephalothorax, abdomen)
  • Antennae: 2 pairs
• Arachnids:

  • Legs: 8
  • Body: 2 parts (cephalothorax, abdomen)
  • Antennae: No