Principles of Taxonomy and Classifying Organisms

Biochemical Relationships – All forms of like share organic molecules that are almost identical from species to species. Taxonomists use these molecular similarities and differences to classify organisms in much the same way as anatomists use comparisons among visible body structures.

Homologous Structures – These are parts of different organisms, often quite different, that developed from the same ancestral body parts. Taxonomists study and identify use homologous structures by studying and identify homologous structures in adult organisms in developing embryos, and in well-preserved fossils.

Evolutionary Relationships – Taxonomists attempt to group organisms in ways that show their evolutionary relationships. Taxonomists do this by identifying and studying homologous structures in adult organisms, developing embryos, and in well-preserved fossils. Species shown to be closely related are classified together.

When working with the diversity of life, a system is needed to classify certain organisms. This system consists of assigning a name and placing the organism into a group with a real biological mania.

• Monera – All prokaryotes are placed in the kingdom Monera. All prokaryote is a single-celled organism that lacks a nucleus. Monerans are placed at the base of our evolutionary tree.

• Protista – Protista is made up of all the single-celled eukaryote organisms. Eukaryotes differ from prokaryotes in that they have a nucleus and membrane bound organelles. Protista is further divided into animal-like protists, plant like protists, and fungus-like protists.

• Fungi – Fungi are heterotrophic, meaning they must obtain their food. They do not carry out photosynthesis. They have many nuclei and do not always have separate cells separated by cell walls.

• Plantae – Members of kingdom Plantae are multicellular autotrophs (meaning the make their own food). They carry out photosynthesis in order to obtain energy. Examples are flowering plants, mosses, and ferns.

• Animalia – Members of Animalia are multicellular heterotrophs. They have cell membranes without cell walls. They are incredibly diverse.