AQA Biology Unit 2: 14 Classification

• Classification is the organisation of living organisms into group
• A species is the basic unit of classification and is a group of similar organisms that can breed together to produce fertile offspring

Naming Species: Binomial System

• The Binomial System features:
  • A universal system based on Latin or Greek names
  • The generic name (first name) is the genus the organism belongs to
  • The specific name (second name) is the species
  • The first letter of the generic name is in upper case and the specific name in lower case

Grouping Species

• Taxonomy: The theory and practice of biological classification
• There are two main forms of classification:
  • Artificial Classification: divides organisms according to useful differences at the time such as colour or size. The characteristics are analogous as they have the same function but not the same evolutionary origins
  • Natural Classification: Based on evolutionary relationships between organisms and ancestors, classifies species into groups using shared features from their ancestors and arranges the groups into a hierarchy
• Relationships in the natural classification are based on homologous characteristics

Organising Groups of Species (Taxonomy)

• Taxon: each group within a natural biological classification
• The hierarchical order (taxonomic ranks) is based on evolutionary line of descents
• The ranks are:
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

Phylogeny

• Is the evolutionary relationship between organisms
• The phylogeny of an organism reflects the evolutionary branch that it led up to
• The relationship with different species is shown in a phylogenetic tree where the oldest species are at the bottom of the tree