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This set contains the content understandings, applications, skills and nature of science syllabus statements for IB Biology topic 5.3: Classification and Biodiversity.
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The binomial system has been a successful system because it is functional, has been the only system that is recognized worldwide, and has been used over the last 250+ years of naming species. Having an internationally recognized system of naming species facilitates communication between people with a different language. 

Archaea
DNA with histone proteins.
Usually have intron DNA sequences.
Cell walls not made of peptidoglycan.
Membrane phospholipids can be branched.
Different ribosomes than eubacteria.
Not sensitive to antibiotics that affect eubacteria.
Can live in extreme environments (hot springs, salt lakes, marshlands, oceans, gut of ruminants and humans).
Eubacteria
DNA without histone proteins.
Usually do no have intron DNA sequences.
Cell walls made of peptidoglycan.
Membrane phospholipids not branched.
Different ribosomes than archaea.
Sensitive to antibiotics that do not affect archaea.
Most do not live in extreme environments.
DNA with histone proteins.
Usually have intron DNA sequences.
Cell walls not made of peptidoglycan.
Membrane phospholipids can be branched.
Different ribosomes than eubacteria.
Not sensitive to antibiotics that affect eubacteria.
Can live in extreme environments (hot springs, salt lakes, marshlands, oceans, gut of ruminants and humans).
Eubacteria
DNA without histone proteins.
Usually do no have intron DNA sequences.
Cell walls made of peptidoglycan.
Membrane phospholipids not branched.
Different ribosomes than archaea.
Sensitive to antibiotics that do not affect archaea.
Most do not live in extreme environments.
Genetic sequencing provided researchers a new way of analyzing relationships between organisms. The three domain system groups organisms primarily based on differences in ribosomal RNA (rRNA) structure. Ribosomal RNA is a molecular building block for ribosomes. Each of these three domains contains unique rRNA. 

There is ongoing debate about the early evolution of life on Earth and the placement of the three domains on a tree diagram. The current consensus places the last universal common ancestor (LUCA) at the root of the tree with two branches, one leading to the eubacteria (B) and the other two the archaea (A) and eukaryota (E).

Artificial classification is the grouping of organisms into groups on the basis of observable structural features (e.g. the grouping together of plants according to the number and situation of their stamens, styles, and stigmas rather than their evolutionary relationships). As knowledge of homologous structures, genetics and evolutionary relationships has grown, artificial systems have been superseded by systems of natural classification, which considers evolutionary relationships for groupings. 
