1. Classification Chapter 17, Sections 1 and 4

2. Why classify? Provides a way to organize living things Ensures scientists are using a common language when talking about living things Provides a way to organize living things Ensures scientists are using a common language when talking about living things

3. How are Things Classified? Old way – by physical similarities New way – by molecular (DNA, RNA, amino acid) similarities Increased understanding about DNA has caused some revisions Old way – by physical similarities New way – by molecular (DNA, RNA, amino acid) similarities Increased understanding about DNA has caused some revisions

4. Who & When: Development of Today’s Classification System Carolus Linnaeus - a Swedish botanist During mid-1700s Only 2 kingdoms – plants and animals Carolus Linnaeus - a Swedish botanist During mid-1700s Only 2 kingdoms – plants and animals

5. Levels of Classification From broadest (biggest) group to most specific (smallest): Kingdom Phylum Class Order Family Genus Species From broadest (biggest) group to most specific (smallest): Kingdom Phylum Class Order Family Genus Species There are many mnemonic devices to help you remember these levels; write down your favorite or make up a new one: ______________________ ______________________ ______________________ There are many mnemonic devices to help you remember these levels; write down your favorite or make up a new one: ______________________ ______________________ ______________________

7. Rules for Scientific Naming Each species’ name is unique and usually descriptive Scientific names: Latin or Latinized words Genus and species name This is called binomial nomenclature (two-name naming) Genus name is capitalized Species name is all lowercase Both words are italicized or underlined Each species’ name is unique and usually descriptive Scientific names: Latin or Latinized words Genus and species name This is called binomial nomenclature (two-name naming) Genus name is capitalized Species name is all lowercase Both words are italicized or underlined

8. Two Kingdoms Up until the 1950s – 1960s, most textbooks still only referred to two kingdoms: Plants, which included all bacteria and fungi Animals, which included all protozoa (single-celled, eukaryotic organisms) Up until the 1950s – 1960s, most textbooks still only referred to two kingdoms: Plants, which included all bacteria and fungi Animals, which included all protozoa (single-celled, eukaryotic organisms)

9. Five Kingdoms In 1959, Whittaker developed the 5- Kingdom system Monera included all of the prokaryotes (cells without nuclei); all others were eukaryotic.

10. Six Kingdoms More recently, scientists split the kingdom Monera into two distinct groups (Eubacteria & Archaebacteria), creating 6 Kingdoms

11. Kingdoms of Life, cont’d These six kingdoms have now been grouped under a higher category: domain There are 3 domains: Bacteria Archaea Eukarya These six kingdoms have now been grouped under a higher category: domain There are 3 domains: Bacteria Archaea Eukarya

13. Characteristic Archae- bacteria BacteriaProtistaFungiPlantaeAnimalia Cell Type (prokaryotic or eukaryotic) Prokaryotic Eukaryotic # of cells (uni or multicellular) Unicellular Unicellular & Multicellular Multicellular Presence or absence of nucleus in cell Absent Present Presence or absence of cell wall Present Present in some Present Absent Cell wall composition No peptidoglycan PeptidoglycanVariesChitincellulosen/a Mode of nutrition (hetero / autotrophic) Autotrophic & heterotrophic HeterotrophicAutotrophicHeterotrophic Presence or absence of locomotion Present in some Absent Present Characteristics of Each Kingdom

14. Dichotomous Keys Dichotomous keys are used to distinguish between organisms that are closely related. At each step on the key, the user is given two choices. Each alternative leads to another question, until the organism is identified. Dichotomous keys are used to distinguish between organisms that are closely related. At each step on the key, the user is given two choices. Each alternative leads to another question, until the organism is identified.

15. Sample Dichotomous Key This simple example of a dichotomous key shows how each “question” must be a yes / no question that divides the organisms into two groups.