Chapter 17, Problem 20STP

Summary Introduction

To write:

The kind of evidence which could help scientists to find out whether eubacteria or archaebacteria evolved earlier on Earth.

Justification of the specific kinds of data needed to collect to draw the conclusion.

Introduction:

The phylogenetic tree of life consists of two major categories:

• Prokarya.
• Eukarya.

Explanation of Solution

To determine whether eubacteria or archaebacteria evolved earlier on Earth, some evidences may be used.

Gene sequencing is a major technique which may be used as an evidence to determine the bacterial phylogeny. The chemical fossils of unique lipids may be used as a source of information.

Through gene sequencing, it has been determined that archaebacetria evolved earlier 0

The same lipids as found in archaebacteria have been found in shales dating back to 2.7 billion years ago and in Precambrian formations as well.

The oldest traces range from the Itua district in Greenland where the oldest sediments foemd 3.8 billion years ago are found.

Thus, the archeal lineage may be considered as the oldest and most ancient existence on Earth.

The eubacteria are characterized by a rigid cell wall, in contrast to the peptidoglycan molecules (except methanobacteria, which has pseudopeptidoglycan in their cell wall) found in archaebacteria.

To use gene sequencing as a technique, the genetic material of both must be present. The lipids needed to determine the sequence of the two forms of Kingdom Monera must be available.

Conclusion

Thus, out of the two, archaebacteria is believed to have evolved earlier due to the techniques of gene sequencing and lipid study.