Taxonomy is the science of classifying groups of organisms based on their characteristics. Our taxonomic system was developed by Swedish botanist Carolus Linneaus in the 1700’s. He grouped organisms by their physical characteristics. Now, we also use genetic and biochemical information to classify organisms.

All organisms are slotted into eight nested levels of taxonomic categories known as ranks. The ranks go from biggest to smallest. This is a hierarchical system. Domain Kingdom Phylum Class Order Family Genus species

There are 8 different groups called taxa (singular - taxon) that are used to classify organisms. Domain is the largest and most general taxon but is often skipped. Kingdom is the second largest taxon. Species is the smallest taxon as it includes only a single type of organism. A species is defined as individuals that can interbreed and produce fertile offspring.

Evidence Used for Taxonomy Organisms have evolved to survive in their environment. Taxonomy helps us classify organisms to see how closely related they are. The taxonomic relationship between two organisms is based on three types of evidence: 1. Anatomical evidence – do the structures of the organisms look the same? 2. Physiological evidence – do the proteins and enzymes in the cells work the same? 3. DNA evidence - how genetically closely related are the genes and the proteins they make?

How to classify Red Pandas? Scientists have long argued if the red panda should be classified with the bear or raccoon families. What do you think? Recent DNA analysis suggests that red pandas are in a separate family of their own, but more closely related to weasels and raccoons than bears.

SPECIES What questions could you ask about anatomy, physiology or DNA evidence to categorize the animals shown into different groups? Are the tails used for balance? Are they carnivores or omnivores? Do they hibernate? What sounds do they make?

A domain is the highest level of taxonomic classification The three domains are Bacteria, Archaea, and Eukarya Bacteria and Archaea are also names of kingdoms The domain Eukarya contains the other 4 kingdoms of Protista, Fungi, Plantae and Animalia

The domains are based on two types of cells - prokaryotes and eukaryotes. Bacteria and Archaea are prokaryote cells that lack a nucleus and membrane bound organelles and are much smaller. All the organisms in the domain Eukarya have cells that evolved a nuclear membrane to protect DNA and they have organelles like Golgi apparatus and endoplasmic reticulum.

Taxonomic classification often skips the domain and starts with the kingdoms shown below: Bacteria - also called Monera or Eubacteria Archaea – separated from bacteria in the 1990’s Protista Fungi Plantae Animalia The 6 Kingdoms

This chart describes the main characteristics that differentiate the organisms in the six kingdoms. As we study each kingdom you should focus on the cell types, number of cells, the cell wall material, nutrition and reproduction. Characteristics of the Six Kingdoms

Viruses – Living or Not? Viruses do have nucleic acids but reproduce only inside a host organism Do not have cells Cannot make proteins themselves Cannot use energy Without a host a virus is simply a group of chemicals. So viruses are not considered living organisms and do not get a taxonomic classification.