Classification of Life

I. Grouping Organisms taxonomy - the field of biology that identifies and classifies organisms   taxonomists analyze shared characteristics to determine evolutionary relationships

I. Grouping Organisms biological classification systems group the most closely related organisms together

Carl Linnaeus Classification used today - developed by Carl Linnaeus (mid 1700’s)   Linneaus’ system originally included five levels of classification; modern scientists have added two more

Classification System 1. Kingdom - (most general) 2. Phyla (sing: phylum) 3. Class 4. Order 5. Family 6. Genus 7. Species (most specific)

Species Members of the same species can interbreed and produce fertile offspring

II. The Kingdoms A. Archebacteria - extremists (prokaryotic) B. Eubacteria - generalists (prokaryotic) bacteria are difficult to classify, evolutionary relationships unclear, don’t fossilize well

C. Protista unicellular/multicellular eukaryotic cells not specialized autotrophs/ heterotrophs ex. amoeba, algae, kelp

D. Fungi eukaryotic multicellular have cell walls Yeast Mildew eukaryotic multicellular have cell walls heterotrophs - release digestive enzymes onto a food source and absorb nutrients - ex. molds, mildews, yeast Club Fungi

E. Plantae eukaryotic multicellular have cell walls autotrophs (most)

F. Animalia eukaryotic no cell walls heterotrophs ex. sponges, insects, tigers

III. Naming Organisms crawdad, crayfish, rock lobster all different names for the same species   clear communication among scientists around the world requires an international system for naming organisms

III. Naming Organisms Binomial nomenclature: two names   organisms scientific name consists of the genus name and the species name.

III. Naming Organisms crayfish: Cambarus bartoni genus name is capitalized, species name lower case name should be italicized or underlined

IV. Evolutionary Relationships Phylogenetic tree shows the evolutionary relationships among organisms more distant ancestors appear at the base more recent relatives make up the branches

V. Ways to Classify 1) Structure 2) Fossil Record 3) Biochemical Analysis (DNA sequencing, comparison of proteins) Despite the methods of classification, it is still often difficult to classify organisms

V. Ways to Classify Taxonomy constantly changes as new information is discovered and theories are refined.

VI. Identifying Organisms Dichotomous key is a tool used for identifying organisms (aka biological key) A dichotomous key lists specific observable traits.

VI. Identifying Organisms For each trait, the key consists of two contrasting options. By picking the option that matches the organisms features, you can identify organisms Dichotomous keys are often found in field guides

Dichotomous Key 1a …Has feathers go to 2 1b … no feathers go to 3 2a swims… duck 2b does not swim…hen 3a has legs … lizard 3b no legs … snake OR

VII. Uses of Classification Taxonomists estimate that there are 2- 100 million different species on Earth today and only 1.5 million species have been named and identified.   The variety in living things is called biodiversity

VII. Uses of Classification Thousands of researchers study many different species Their work can reveal unknown facts about a species. Ex. 1994: new species of tree kangaroo discovered in New Guinea

VII. Uses of Classification Also an unknown fungus was discovered. This fungus produces the drug cyclosporin which is used to prevent the rejection of transplanted organs

Reflection Questions 1. What are the seven levels of classification in order? 2. What is taxonomy? 3. List the six kingdoms and give at least two characteristics of each kingdom. 4. What are the different ways scientists classify organisms? 5. What is the purpose of a phylogenetic tree?