Evolution of Classification Systems

Question 1

Three Domain System

Answer 1

• This is the current classification system used by scientists.
• Prokaryotae kingdom becomes divided into 2: Archaebacteria & Eubacteria
• Three domains: Archaea. Bacteria, and Eukarya.
• The organisms in the different domains contain unique form of rRNA and different ribosomes:
• Eukarya have 80s ribosomes; RNA polymerase has 12 proteins.
• Archaea have 70s ribosomes; RNA polymerase of different organisms contains between 8-10 proteins
• Bacteria have 70s ribosomes; RNA polymerase contains 5 proteins

Question 2

Archaebacteria and Eubacteria

Answer 2

• Archaebacteria are ancient bacteria that can live in extreme environments like hot thermal vents.
• Eubacteria, also known as true bacteria, are found in all environments; most bacteria are from Eubacteria kingdom.

Question 3

Changes to classification systems

Answer 3

• Early classification systems only used observable features to place organisms into groups.
• Through the study of genetics and other biological molecules, scientists can now study the evolutionary relationships between organisms. These links can be used to classify.
• When organisms evolve, their internal and external features change, as does their DNA as DNA codes for these characteristics.
• More closely related organisms will have more similar molecules and DNA.
• Example of a protein that has changed is haemoglobin which has 4 polypeptide chains but this haemoglobin differs from chimpanzees’ by only one amino acid and by gorillas in 3. This indicates a common ancestry between the various primate groups.