Variety of Life Revision

Summary of topic



  • A species (basic unit of classification) is a group of individuals of common ancestry that closely resemble each other, and are normally capable of interbreeding to produce fertile offspring.
  • Species are classified into groups within a hierarchy. In descending order this hierarchy is: 

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

  • Species are named according to a binomial system. The genus name is given first, followed by a species name. For example, Homo sapiens 
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The five kingdoms

  • Organisms are grouped into five kingdoms

Prokaryotae (bacteria) , Protoctista , Fungi , Plantae , Animalia.

  • Prokaryotae - prokaryotic cells, reproduction by division, DNA naked/circular, smaller ribosomes, walls made of peptidoglycan. E.g. rod-shaped bacterium
  • Protoctista - eukaryotic, unicellular OR multicellular showing limited differentiation, herterotrophs (Phylum Protozoa) or autotrophs (Phylum Chlorophyta)
  • Fungi - eukaryotic, multicellular and some unicellular, consist of hyphae with chitin cell wall, lysotrophs, extracellular digestion. E.g. mould, toadstools, yeast
  • Plantae - eukaryotic, multicellular, cellulose cell wall, autotrophs, photosynthetic possessing chlorophyll in chloroplasts. E.g. ferns, mosses, flowering plants
  • Animalia - eukaryotes, multicellular, lack cell wall, heterotrophic, digestive system, locomotion. E.g. chordates, arthropods
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  • A phylogenetic classification is a system that reflects the ancestral or evolutionary relationship between groups
  • Modern methods of establishing relationships include comparison of amino acid sequences in proteins and of nucleotide sequences in DNA and RNA. Closely-related organisms possess a high degree of agreement in the molecular structure of their proteins, DNA and RNA
  • Unfamiliar organisms can be identified using an appropriate dichrotomous key
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  • Species diversity can be measured by using the Simpson's index (D). Simpson's index (D) values lie between 0 and 1, with values closer to zero indicating greater diversity
  • The 'richness' of a region (such as Northern Ireland) can be described in terms of the diversity of its ecosystems (or habitats)
  • Genetic diversity reflects the genetic variability of a species and is important in allowing for the continued adaptability of a species
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