Molecular taxonomy, also known as molecular systematics, is a branch of biology that uses molecular data, such as DNA sequences, to classify organisms and study their evolutionary relationships. It has revolutionized our understanding of the diversity and relatedness of different species.
Prokaryotes
Prokaryotes are single-celled organisms that lack a nucleus and membrane-bound organelles. They are classified into two main groups based on molecular taxonomy:
a) Bacteria: Bacteria are the most abundant and diverse group of prokaryotes. Molecular studies have revealed several phyla within the bacterial domain, including Proteobacteria, Firmicutes, Actinobacteria, and Cyanobacteria, among others. These classifications are based on the analysis of conserved genes, such as the 16S rRNA gene.
b) Archaea: Archaea are another group of prokaryotes that have distinct molecular characteristics. They often inhabit extreme environments such as hot springs, deep-sea hydrothermal vents, and salt lakes. Archaea are divided into several phyla, including Euryarchaeota, Crenarchaeota, and Thaumarchaeota, based on molecular analysis.
Eukaryotes
Eukaryotes are organisms with cells that contain a nucleus and membrane-bound organelles. Molecular taxonomy has significantly contributed to our understanding of eukaryotic diversity and has led to the identification of several major groups:
a) Protists: Protists are a diverse group of eukaryotes that do not fit into the categories of plants, animals, or fungi. They include unicellular organisms such as amoebas, ciliates, and flagellates, as well as some multicellular algae. Molecular studies have provided insights into the evolutionary relationships among different protist lineages and have led to the reclassification of some groups.
b) Fungi: Fungi are a kingdom of eukaryotic organisms that include mushrooms, yeasts, and molds. Molecular taxonomy has helped clarify the relationships among fungal groups and has led to the identification of several phyla, including Ascomycota, Basidiomycota, Zygomycota, and Chytridiomycota.
c) Plants: Molecular taxonomy has played a crucial role in understanding the evolutionary relationships among plants. It has revealed the major divisions within the plant kingdom, such as angiosperms (flowering plants), gymnosperms (cone-bearing plants), ferns, and mosses. Molecular data has also helped resolve the relationships among these groups and provided insights into the diversification of land plants.
d) Animals: Molecular taxonomy has had a significant impact on our understanding of animal diversity and evolution. It has helped in classifying animals into major phyla, such as Chordata (which includes vertebrates), Arthropoda (including insects and crustaceans), Mollusca (snails, clams, and octopuses), and Porifera (sponges), among others. Molecular data has provided insights into the evolutionary relationships among animal groups and has contributed to the field of phylogenetics.