Characteristics of Living Organisms

  1. Movement: action by an organism or part of an organism causing a change of position or place
  2. Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy
  3. Sensitivity: ability to detect or sense changes in the environment (stimuli) and to make responses
  4. Growth: permanent increase in size and dry mass by an increase in cell number or cell size or both
  5. Reproduction: processes that make more of the same kind of organism
  6. Excretion: removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements
  7. Nutrition: taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them


Concept & Use of a Classification System

  • Organisms can be classified into groups by the features that they share
  • Classification systems aim to reflect evolutionary relationships (change of adaptive features of a population over time, as a result of natural selection)
  • Species: organisms which can reproduce successfully
  • Morphology: the overall form and shape of their bodies e.g. wings or legs
  • Anatomy: the detailed body structure determined by dissection


Binomial system

A system of naming species in which the scientific name of an organism is made up of two parts showing the genus (starting with a capital letter) and species (starting with a lower-case letter), written in italics when printed (therefore underlined when written)
e.g. Homo sapiens

Kingdom, Phylum, Class, Order, Family, Genus, Species


  1. Animal: Multi-cellular ingestive heterotrophs (eat living organisms)
  2. Plant: Multi-cellular photosynthetic autotrophic (make their own food) organism with a cellulose cell wall.
  3. Fungi: Single celled or multi cellular heterotrophic organism with cell wall not made of cellulose, spread by spreading of spores in moist/dark/warm environment, saprotrophs (feed off dead organisms) or parasites
  4. Prokaryotes: Single celled organism with no true nucleus
  5. Protoctista: Single celled organism with a nucleus


Classifying Plants

  • Flowering plants:
  • They are plants with roots, stems and leaves
  • Reproduce sexually by means of flowers and seeds
  • Seeds are produced inside the ovary in the flower


Monocotyledons Dicotyledons
One cotyledon Two cotyledons
Parallel veins Veins netlike
Fibrous root Taproot present
Floral parts in 3s Floral parts in 4s or 5s


Viruses and Bacteria


Virus Bacteria
Covered by: Protein coat Cell wall
Cell membrane: No Yes
Cytoplasm: No Yes
Genetic material: DNA or RNA – only a few genes DNA – enough for several 100 genes
Living or not? Non-living unless in host Living


Dichotomous Keys

Dichotomous key: uses visible features to classify organisms. It is which gives you a choice of two features and you follow the one that applies: each choice leads to another choice until the organism is narrowed down to its genus and finally species.

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