Chapter 17 Organizing Lifes Diversity Section 17 1

Chapter 17 Organizing Life’s Diversity

Section 17. 1 Classification n FL Standard SC. 912. L. 15. 4: – Describe how and why organisms are hierarchically classified and based on evolutionary relationships. n FL Standard SC. 912. L. 15. 5: – Explain the reasons for changes in how organisms are classified.

Organization of Organisms n Why? – It helps scientists better understand organisms

Organization of Organisms n How? – Classification n 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. n These scientists are called taxonomists. n

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

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

Linnaeus n n n 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 n Group of similar species – Second name—species identifier (a. k. a. specific epithet ) n Often describes a characteristic of the organism

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

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

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

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

Example n 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? n 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: 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. n Organisms are ranked in taxa from very broad characteristics to very specific ones n Smallest taxon is species—organisms that look alike and can successfully interbreed n

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

Human Taxonomy n n n n 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? n As more fossils and evolutionary relationships are discovered, changes to classifications are sometimes necessary.

New Human Classification n n 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 (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? n Domain-Kingdom-Phylum-Class-Order. Family-Genus-Species n Did King Phillip cut off four giant sunflowers? n