How are living things classified?

Aristotle classified organisms over 2,000 years ago!

Why do we classify? Easier to identify Classification: Grouping organisms or items based on similarities

Taxonomy The branch of science that classifies organisms.

Look at Question on page 19.

Carolus Linnaeus 1. Introduced a system based on similar structures of organisms. 2. Organisms are given a two-part name, BINOMIAL NOMENCLATURE

Binomial Nomenclature The first word identifies the genus, or group of similar species. The second word tells something about the species---what it looks like, where it was found, or who discovered it.

Example of Scientific Names Ovis dalli Marmota monax Pinus palustris

Ovis dalli Did you notice? The first word (Genus) is capitalized. The second word (species) is not. The scientific name should be written in italics or underlined. Ovis dalli

Organisms of the same species can mate and produce fertile offspring.

Look at Questions on page 20.

Why use scientific names? To avoid mistakes To show relationships among organisms To give descriptive information To allow information to be easily organized

Look at Questions on page 21 Assess your Understanding, page 21

Today’s classification system separates organisms into six (or five) kingdoms.

Note Kingdom Monera- This was before the six kingdoms.

Levels of Classification

Classification Levels The more classification levels two organisms share, the more characteristics they have in common and the more closely related they are.

The smallest classification category is a species.

How can I remember classification? Dear King Phillip came over for grandma’s spaghetti.

Look at Levels of Classification, page 22 Assess Your Understanding, page 23

Cartoons How did the cartoons apply to your reading?

Taxonomic Key Dichotomous Key These are useful in identifying organisms. Keys are paired statements. These statements describe a physical characteristic. These keys key “down” to a single organism.

Turn to Textbook We will go over the key on page 25.

How are evolution and Classification Related Charles Darwin explained that changes occur to organisms over time. This is the theory of evolution. Natural Selection is the process of change in organisms over time. A brief explanation will follow of Darwin’s observations of Natural Selection. (Standard 5)

According to Darwin… There are variations within a species. (This is random and a difference in DNA/mutation.) Sometimes the variation is favorable to conditions. Not all offspring will survive (non-favorable trait). Those with favorable DNA will pass this DNA on to offspring and over time there are changes in the species.

Continued Now scientist understand that similarities in organisms are because of a common ancestor. Species with similar evolutionary histories are classified more closely together. This often seen in a diagram. See next slide.

Branching Tree Examples: Cladogram or phylogenic tree These show probable evolutionary relationships among organisms and order in which characteristics may have evolved. The oldest ancestor or trait is located at the base.

FYI: Clade A clade is a group of organisms, comprised of all the evolutionary descendants of a common ancestor.

Look at the Tree

Textbook See Page 31,Summarize and Figure 1 See Page 32, Apply It and Finding a New Species

Showing Evolutionary Relationship Used to Determine Placement on a Cladogram: Fossils Similarities in Body Structure Early Development DNA in More “Modern” Organisms

Where would they be? Convergent Evolution ---- Organisms that are not related, yet share a characteristic. Look at the body types below. Do you think these organisms would be close on a cladogram? Explain.

Textbook See Page 33 Figure 3 Assess Your Understanding

Tools for identifying organisms: Field Guides----descriptions and illustrations of organisms to use in the field. Dichotomous Keys---detailed lists of identifying characteristics that include scientific names