Classification Organizing Life’s Diversity

Organizing Life’s Diversity At least 1.7 million species of living organisms have been discovered The list grows longer every year What should we do with them? How are they to be classified?

18.1 Classification A. How classification begins 1. Biologists want to better understand organisms so they organize them. 2. One tool that they use to do this is classification a. the grouping of objects or information based on similarities.

18.1 Classification 3. Taxonomy is the branch of biology that groups and names organisms based their different characteristics.

B. Aristotle’s System 1. The Greek philosopher Aristotle (384-322 B.C.) developed the first widely accepted system of biological classification. 2. He classified all the organisms he knew into two groups: plants and animals. 3. According to his system, birds, bats, and flying insects are classified together even though they have little in common besides the ability to fly.

C. Linnaeus’s System 1. In the late eighteenth century, a Swedish botanist, Carolus Linnaeus (1707-1778), developed a method of grouping organisms that is still used by scientists today. 2. Based on physical and structural similarities of organisms. 3. As a result, the groupings revealed the relationships of the organisms.

C. Linnaeus’s System 4. Linnaeus developed a two-word naming system called binomial nomenclature to identify species. 5. Each species is assigned a two part scientific name. 6. Scientific names are always written in italics 7. The first word is capitalized and the second word is lowercase. Homo sapiens

C. Linnaeus’s System 8. The first part of the scientific name is the genus 9. The second part of the scientific name is the species Do Ursus arctos and Ursus maritimus belong to the same species? To the same genus?

C. Linnaeus’s System 10. Linnaeus’s hierarchical system of classification includes eight levels. 11. Each of these levels is called a taxon. From smallest to largest Species Genus Family Order Class Phylum Kingdom Domain

C. Linnaeus’s System 12. Species – organisms that look alike and successfully interbreed ; the smallest and most specific of the taxonomic categories 13. Domain – the largest and most inclusive of the taxonomic categories

D. Scientific and common names 1. Taxonomists are required to use Latin The language is no longer used in conversation and it does not change. Why do scientists use Latin names for classification? Because it is no longer used in conversation so it never changes

Taxonomic Categories Kingdom (most broad) King Phylum Philip Class Came Order Over Family For Genus Green Species (most specific) Soup

Which taxon contains the others? Order Class Genus Family

F. Taxonomy: A useful tool 1. Remember taxonomy is the study of classifying organisms 2. Some biologists use a dichotomous key 3. A Dichotomous Key is made up of a set of paired numbered statements. Each set deals with a single characteristic of an organism, such as leaf shape or arrangement. 3. By following the key, a specific organism can be identified based on characteristics. Example: 1. a) Is the leaf simple? Go to 2 b) Is the leaf compound? Go to 3 2. a) Are margins of the leaf jagged? Go to 4 b) Are margins of the leaf smooth? Go to 5

AGENDA – 3/19/15 Take out packet please Bell-Ringer: Dichotomous Key Finish Part A of packet Benchmarks: If you have not finished, you need to finish the test before or after school or during lunch.

Bell-Ringer: 3/19/15 What is a dichotomous key? A dichotomous key is a set of paired statements that can be used to identify organisms.

Evidence to Classify Organisms 1. Physical characteristics 2. Behavioral – breeding behavior 3. Chromosomes 4. DNA/Biochemistry

Evidence to Classify Organisms 1. Physical characteristics a. Structural similarities among species reveal relationships b. The presence of many shared physical structures implies that species are closely related and may have evolved from a common ancestor.

Evidence to Classify Organisms 2. Behavioral – breeding behavior a. Two species of frogs, Hyla versicolor and Hyla chrysoscelis live in the same area and look similar b. During the breeding season there is an obvious difference in their mating behavior – different pitch rate between the calls

Evidence to Classify Organisms 3. Chromosomes a. Both the number and structure of chromosomes, as seen during mitosis and meiosis, provide evidence about relationships among species. For example, cauliflower, cabbage, kale, and broccoli look different but have chromosomes that are almost identical in structure.

Evidence to Classify Organisms 4. DNA/Biochemistry a. Closely related species have similar DNA sequences and therefore proteins b. In general, the more inherited nucleotide sequences that two species share, the more closely related they are.

A. DNA B. Chromosomes C. Taxon D. Behavioral Which of the following is NOT a way to determine evolutionary relationships? A. DNA B. Chromosomes C. Taxon D. Behavioral

Evolutionary Classification Biologists group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities The evolutionary history of a species is called its phylogeny.

B. Phylogenetic Classification: Models 1. Cladistics – system of classification based on phylogeny a. Characteristics and organisms can be organized on a tree-like model b. Starts with a common ancestor c. Groups of organisms diverge from the ancestor d. Nodes are where the organisms branch off – these are anatomical relationships like backbones, tails, etc e. All of the organisms have the trait after the node f. Shown on a cladogram

Cladogram Allosaurus Velociraptor Robin Archaeopteryx Sinornis Theropods Feathers with shaft, veins, and barbs Flight feathers; arms as long as legs 3-toed foot; wishbone Down feathers Light bones