Classification of Organisms

Mrs. Wolfe

How do we keep track of them all?

• Estimated 10 – 30 million organisms on earth

• Taxonomy – the science of naming and classifying organisms– Scientists began using taxonomy in the middle

ages.

What is Taxonomy?

• We name organisms using a system called binomial nomenclature.

• Carolus Linnaeus– Swedish biologist

– Catalogued organisms

– Developed a way to name them

Binomial Nomenclature• A two-word naming system• Each organism has two words for its name and we

call this its scientific name.• Example:• Quercus ruba common name: Red oak acorn• First name is capitalized. This is the Genus of the

organism.• Second name is lowercase. This is the Species of

the organism.• Both words in italics or underlined.

More examples

• Erithacus rubicula– Great Britain robin

• Turdus migratorius– North American robin

• Homo sapiens– Human

• Remember:

Genus species or Genus species

Linnaes’ system

• How did he name all of those organisms?

• He first grouped them by likeness and named the groups.

• He continued to make smaller and smaller groups until he was down to a single species.

• Kingdom• Phylum• Class• Order• Family• Genus• Species

Species

• The final category, that cannot be divided further, is species.

• A species is a group of organisms that can interbreed with each other and cannot interbreed with other groups of organisms.

Suppose we found an organism in the woods…..

• What kind of organism is it?

• Scientists have several tools to identify the organism:

– Dichotomous keys– Field Guides

Dichotomous Key

• Example: Identify these objects1a. Long, tubular object…………….…..go to number 2 b. Short, non-tubular object ………..…go to number 42a. Constructed from plastic………..…..go to number 3 b. Constructed from wood…………….…..……pencil3a. Produces yellow color……………….….highlighter b. Produces a black ink…………………….…...…pen4a. Is rectangular with a metal blade….pencil sharpener b. Is made of silver metal…….………..……paper clip

However, …..

• A dichotomous key identifies the scientific name of an organism. Try to identify the organisms in your handout using your dichotomous key.

• Notice how you determine a SCIENTIFIC NAME for each organism!

Field Guides

• Books you can use to identify an organism while you’re out.

– You see an animal track. You can use the book to determine the organism that made the track.