Ch 17 Classification Taxonomy Classification Organizing Grouping Separating

Ch. 17 Classification & Taxonomy

Classification: • • • Organizing Grouping Separating Categorizing Sorting

Why Classify? • • • Increases understanding Eases identification More efficient Less clutter Saves time Makes “life” easier

Biodiversity • There are ______ different types (species) of organisms on Earth!

Taxonomy: Science of naming and classifying organisms. Early Taxonomy • Cave Folks • Aristotle: 2 K years ago. Greek philosopher and naturalist that classified organisms according to structural similarities and locomotion.

• Romans/Greeks classified organisms into broad groups • Until the mid-1700’s, organisms were given long descriptive names in Latin – “polynomials” • Carolus (Carl) Linnaeus: Swedish botanist. 1750’s. System based on organism’s form or structure. Binomial Nomenclature.

Binomial Nomenclature: Each organism given two Latin names…. . • • Genus: (general name) “Washington” Contains similar species Species: (specific name) “George”

Scientific Name: Genus + species name. • Always either underlined or italicized! • Give biologists a common way of communicating regardless of their native language. Homo sapiens or Homo sapiens

Linnaeus also devised a system of inclusive groups for the complete classification of an organism.

8 Classification Groups Domain Kingdom Phylum Class Order Family Genus Species

Domains: Contain Kingdoms. Only 3. Archaea, Bacteria (both prokaryotes), and Eukarya

How Biologists Classify Organisms • Biological Species: Group of natural populations that are capable of interbreeding and producing fertile offspring. • - Only useful for sexually reproducing organisms. Useless for asexually reproducing species.

Mule: offspring of male donkey and female horse

Coydog

Liger

Tiger Musky

• Reproductive Isolation: Occurs when a barriers separates two or more groups of organisms and prevents them from interbreeding. • When reproductive barriers between two species are not complete, the two species are usually closely related.

• In Kingdom Animalia, strong barriers to hybridization usually exist. • In practice, the best way to recognize species is by studying the organism’s features/structures

1. 5 million species named and described to date. Phylogeny: Evolutionary history of a species Similar characteristics may indicate that two species share a common ancestor. Or, may also be evidence of convergent evolution.

Convergent Evolution: Two or more different species evolve similar features (analogous structures) because they live in or occupy similar environments/niches.

Cladistics: • A method of classification in which the relationships between organisms are based on selected shared characteristics.

• Can be used to hypothesize the sequence in which different groups of organisms evolved. • Reconstructs evolutionary history. • Ancestral character: characteristic that evolved in a common ancestor of both groups.

• Derived character: characteristic that evolved in one group but not the other. • Cladistics based on the principle that shared derived characters/traits provides evidence that two groups are relatively closely related.

• Cladogram: branching diagram that shows the evolutionary relationships among groups of organisms. Objective.

• Evolutionary Systematics: Phylogenetic tree. Demonstrates varying degrees of importance to characters/traits. Subjective. • Both cladograms and phylogenetic trees represent a hypothesis of evolutionary history.