Classification

1. Classification - Chapter 17

2. Why do we need to classify? • Classifying things into groups helps us to see relationships and understand the world around us. • Classification is one way that humans simplify life in a complex world • The science of classification is called taxonomy or systematics.

3. History of Taxonomy • There are records of human attempts to classify organisms as far back as we can trace records. • Ancient Chinese organized into groups such as ‘fabulous ones’, or ‘ones that resemble flies from a distance’ • Aristotle was the first to classify according to structural similarities. He had two groups – Plants and Animals • Today we tend to use evolutionary relationships to classify organisms

4. History, cont • There is no one perfect system of classification. The system we use today was developed by Carolus Linnaeus (1707-1778) • Linnaeus was a Swedish botanist who was extraordinarily good at collecting, naming, and classifying organisms, especially plants. • Linnaeus published his classification system in a book called Systema Naturae

5. Development of Kingdoms • Kingdoms are the largest divisions in taxonomy • Aristotle -4th century B.C.- Two kingdoms- Plants and Animals • Ernest Haeckel (1894) 3 kingdoms – Plants, Animals, and Protista • Herbert Copeland (1956) 4 kingdoms- • Plants, Animals, Protista, and Bacteria

6. Robert Whittaker(1959) 5 kingdoms- Plants, Animals, Protista, Monera, and Fungi • Carl Woese (1977) 6 kingdoms- Plants, Animals, Eubacteria, Archebacteria, Protista, and Fungi. This was the first system that used evolution and molecular genetics • Woese also developed the Domain classification in 1990. This was a major overhaul of the classification system. The three domain system is based on molecular biology and groups all organisms into three domains • Bacteria, Archaea, and Eukarya

8. Linnaeus’ System • Linnaeus developed a two word naming system for organisms called binomial nomenclature. • The scientific name of an organism is usually based on Latin or Greek and consists of two names Ex: Homo sapien; Ursus arctos • The first name is the genus and is always capitalized and the second name is the species. The scientific name of an organism is typically italicized.

9. Linnaeus developed seven taxonomic categories. In order from the largest to the smallest they are: The more taxonomic categories a species has in common, the more closely related We currently use Eight categories with the addition of domains in the 1990’s. The Three domains are Bacteria, Archaea, and Eukarya

11. Evolutionary Classification • Darwin’s theory of evolution changed how scientists looked at classification. Traditional Linnean classification did not take into account evolutionary trends. • Today scientists use cladograms to show the evolutionary relationships among different organisms.

12. Cladograms

13. How do we classify? • Scientists often use dichotomous keys to classify organisms. • A dichotomous key is a forced choice system that gives you two choices as you move through a description of the characteristics of the organism

14. Six Kingdom System

15. KINGDOMS OF LIVING THINGSIN THE LINNAEAN CLASSIFICION SYSTEM

22. Modern Evolutionary Classification • Molecular clocks useDNA comparisonsto estimate the length oftimethat two species have beenevolving independently. • This relies on theratethat neutralmutationsaccumulate in the DNA of different species

24. Kingdoms and Domains • Using new tools available today, scientists have expanded upon Linnaeus’s system of classification. • The 6 kingdom system of classification includes the kingdoms Eubacteria,Archaebacteria,Protista,Fungi,Plantae, andAnimalia

25. Today, most scientists are now recognizing molecular evidence that requires the addition of a category even larger than kingdom: the domain • Domains: • Archaea • Bacteria • Eukarya