Organizing Life’s Diversity Chapter 17 Organizing Life’s Diversity

Section 17.1 Classification FL Standard SC.912.L.15.4: Describe how and why organisms are hierarchically classified and based on evolutionary relationships. FL Standard SC.912.L.15.5: Explain the reasons for changes in how organisms are classified.

Organization of Organisms Why? It helps scientists better understand organisms

Organization of Organisms How? Classification The grouping of objects or information based on similarities

Taxonomy The branch of biology that groups and names organisms based on studies of their different characteristics. These scientists are called taxonomists.

Aristotle Grouped organisms into two groups: Plants Animals Herbs Shrubs Trees Animals Grouped based on their habitat and physical differences

Aristotle The problem: It didn’t group according to evolutionary history There are other organisms that aren’t plants or animals

Linnaeus System of classification based on physical and structural similarities of organisms Basis of modern classification system Gave organisms scientific names using a two-word naming system —binomial nomenclature First name—genus Group of similar species Second name—species identifier (a.k.a. specific epithet ) Often describes a characteristic of the organism

Scientific Names How it’s done: Example: Homo sapiens Written in Latin Genus name is capitalized Species identifier is lower case Italicized when typing Underlined when handwritten Example: Homo sapiens Homo means “man”, sapiens means “wise”

Subspecies Some organisms have subspecies, variations of a species that live in different geographic areas. Capable of interbreeding The subspecies’ name follows the species identifier

Examples of Subspecies Canis lupus familiaris (domestic dog) Canis lupus lupus (wolf) Canis lupus dingo (dingo)

Modern Classification Based on comparisons of external and internal structures, geographical distribution, genetic makeup Helps establish evolutionary relationships between living and extinct species

Example Are dinosaurs more closely related to birds or reptiles? Due to similarities in bone structures, taxonomists classify dinosaurs as more similar to birds than to reptiles.

How can organisms be identified? Scientists use a tool called a dichotomous key to identify organisms based on their external features

The first step in the key will be organized the following way:                                The first step in the key will be organized the following way: 1. a. wings covered by an exoskeleton b. wings not covered by an exoskeleton Next, the statements need to lead the observer to the next step to narrow the identification further: 1. a. wings covered by an exoskeleton ………go to step 2 b. wings not covered by an exoskeleton ……….go to step 3 Step 2 needs to consist of a pair of statements that will allow for the identification of the ladybug and the grasshopper: 2. a. body has a round shape ……….ladybug b. body has an elongated shape ……….grasshopper Step 3 needs to consist of a pair of statements that will allow for the identification of the housefly and dragonfly: 3. a. wings point out from the side of the body ……….dragonfly b. wings point to the posterior of the body ……….housefly

How Living Things are Classified A group of organisms is a taxon. Organisms are ranked in taxa from very broad characteristics to very specific ones Smallest taxon is species—organisms that look alike and can successfully interbreed

Taxa Genus—A group of similar species that have similar features and are closely related Family—Consists of a group of similar genera (pl. of genus) Order—A taxon of similar families Class—A taxon of similar orders Phylum—A taxon of similar classes --Division is used in plants & bacteria only

Taxa Kingdom—A taxon of similar phyla or divisions Domain—Contains one or more kingdoms

*Classifications have changed. Human Taxonomy Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Family: Hominidae* Genus: Homo Species: Homo sapiens *Classifications have changed.

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Why do classifications change? As more fossils and evolutionary relationships are discovered, changes to classifications are sometimes necessary.

New Human Classification Domain: Eukarya Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Primates Suborder Hominoids – gibbons, orangutans, chimps, gorillas, humans, relatives Family: Hominidae* (Hominids) – no gibbons Subfamily Homininae – no orangutans Tribe: Hominini (Hominins) – humans & extinct relatives Genus: Homo Species: Homo sapiens Subspecies: Homo sapiens sapiens (to distinguish it from H. sapiens idaltu, discovered in 1997)

A good way to remember Can you come up with a mnemonic device to help you remember the order? Domain-Kingdom-Phylum-Class-Order-Family-Genus-Species Did King Phillip cut off four giant sunflowers?