Taxonomy Introduction

Taxonomy Taxonomy is the science of CLASSIFICATION. It is a method of grouping organisms according to their presumed natural relationships.

Taxonomy is important because… It is a way: Of organizing information. Of learning more about organisms. Of communicating with other scientists using a common language. Of avoiding common names that are misleading. Example: a crawfish is not a fish.

Aristotle Aristotle was a Greek philosopher who first classified living things over 2000 years ago. He grouped organisms into two major categories: plants and animals. Animals were then subdivided based on habitat: land, water, or air dwellers. Plants were subdivided based on size and pattern of growth.

Problems with Aristotle’s System During the 15th and 16th centuries, there was a period of scientific exploration and newly discovered organisms did not fit into Aristotle’s categories. In addition, the use of common names was problematic.

Carolus Linnaeus Linnaeus was a Swedish naturalist who devised a system of grouping organisms into hierarchical categories. He used form and structure (morphology) to categorize organisms.

Linnaeus’ Changes Linnaeus made three important changes to Aristotle’s system: He classified plants and animals into more groups. He based his system on specific traits. He gave organisms names that described their traits. 7 levels vs 8 levels – Video (1st 2 minutes)

8 Levels of Classification - Video Domain Kingdom Phylum Class Order Family Genus Species King Phillip Came Over From Greece Singing

Example #1: Leopard

Example #2: Human Kingdom Animalia Phylum Chordata Class Mammalia Order Primates Family Hominidae Genus Homo Species sapien

Binomial Nomenclature Species have two names which compose their scientific (species) name. The first word is the genus; the second word is the species. Example: Homo sapien.

Genus species Rules The 1st letter of the genus (1st word) must always be capitalized. The 1st letter of the species (2nd word) is lowercase. When typed, the genus and species are written in italics. When handwritten, the genus and species are underlined. Example: Canis familiaris

Modern Taxonomy Classification based on physical structure alone may not be sufficient. Taxonomists also compare embryology, chromosomes, and/or biochemistry.

Embryological Evidence Embryology is the study of the development of an organism. Includes studying the embryo – an immature organism contained within the coverings of an egg or within the body of the mother Similarities in embryos of very dissimilar organisms may indicate that two species are related. During very early development, similarities and differences often appear soon after an egg is fertilized.

Embryological Evidence

Chromosomal Comparison Counting and comparing chromosome shapes MAY be used to determine if two species are closely related. Chromosomes of humans and chimpanzees are surprisingly similar. Humans have 46; chimps have 48. Think about this, a deer mouse also has 48 chromosomes.

Chimp vs. Human Chromosomes Notice that many genes (colored sections) on both human and chimp chromosomes line up. At some point during evolution, chromosome 2 split in chimpanzees resulting in an extra chromosome pair.

Biochemical Comparison Biochemistry is the study of the chemical processes and transformations in living organisms. This includes comparing DNA, RNA, and proteins to determine relatedness. For example, the hemoglobin amino acid sequences in humans and chimps are very similar

Cladograms and Phylogenic trees Diagrams that show the relationship of a group of species based on common characteristics

What’s the difference? Many scientist use these terms interchangeably but there are some difference: Phylogenic trees are more precise in showing how much time there was between changes (evolution) or branches in the tree

Example