• GCO: How are living things organized into groups for ease of study– SCO: Describe peer review and explain how

classification systems developed as new evidence concerning living things emerged (114-5, 115-7, 116-2)

– SCO: Identify questions, limitations, and alternatives inherent in a classification system (214-2, 214-7, 212-1)

– SCO: Describe and apply classification systems and nomenclatures used in species (214-1)

• We operate on a hierarchical system (Linnaeus).– Seven levels exist (largest to smallest)

KingdomPhylum

ClassOrderFamilyGenus

Species*King Phillip came over for good strawberries*

Kingdom PhyllumClassOrderFamilyGenusSpecies

Animalia

ArthropodaInsectaDiptera

MuscidaeMusca

domestica

• Species: A group of organisms, alike in many ways, that can interbreed under natural conditions to produce fertile offspring.

• In taxonomic nomenclature, or naming system, each of those levels is called a taxon.

• As you move down the seven levels of classification from kingdom to species, the organisms in each classification level are more closely related.

The Six Kingdoms include:•Monera•Eubacteria •Archaebacteria•Protista•Fungi•Plantae•Animalia

• Molecular analyses (RNA – exists in all living organisms) have given rise to a new taxonomic category that is now recognized by many scientists. The domain is a more inclusive category than any other, and is larger than a kingdom.

• Grouped according to how long they have been evolving independently.

• Bacteria – Eubacteria

• Archaea– Archaebacteria

• Eukarya– Protista– Fungi– Plantae– Animalia

• Dichotomous = divided into two parts• Choose your own adventure/fork in the road

– Respond to a series of questions/declarations which force you to make decisions/choose an option, eventually leading you to the name of the organism you are trying to identify.

• Series of couplets, each consisting of two separate statements. – Description of the absence or presence of a

particular characteristic.– Progress through the key from typically broad

characteristics to more narrow characteristics until only a single choice remains.

– That single choice is the identification of your unknown organism.

• Rules to Follow When Using a Dichotomous Key– Always read both choices, even if the first seems

to be the logical. – Understand the meaning of the terms involved in

the key.– When measurements are given, use a scale to

measure the specimen. Do not guess at a measurement.

– Living things are always variable, so do not base your organism identification in the field on a single observation.

Copyright © 2010 Ryan P. Murphy

• Please use the key to answer the questions below.– I have no feathers but have legs?___________– I have feathers but don’t swim?________– I have no feathers or legs?______– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim?________– I have no feathers or legs?______– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim?________– I have no feathers or legs?______– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim? Hen– I have no feathers or legs?______– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim? Hen– I have no feathers or legs?______– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim? Hen– I have no feathers or legs? Snake– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim? Hen– I have no feathers or legs? Snake– I have feathers and swim?____________

• Please use the key to answer the questions below.– I have no feathers but have legs? Lizard– I have feathers but don’t swim? Hen– I have no feathers or legs? Snake– I have feathers and swim? Duck

• The first step in the key will be organized the following way: • 1a. wings covered by an exoskeleton • 1b. wings not covered by an exoskeleton• Next, the statements need to lead the observer to the next step to

narrow the identification further: • 1a. wings covered by an exoskeleton ………go to step 2• 1b. 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:• 2a. body has a round shape ……….ladybug• 2b. 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: • 3a. wings point out from the side of the body ……….dragonfly• 3b. wings point to the posterior of the body ……….housefly• Notice that there were four organisms to be identified and it only

took three steps. There should be one less step than the total number of organisms to be identified in your dichotomous key.

TIME TO CREATE YOUR OWN!!

LION

HOUSE CATBENGAL

BOBCAT

LYNX

JAGUAR

PANTHER

TIGER

SNOW LEOPARD

• The true evolutionary history of an organism• Degree of similarity

• Hypothesis about the actual evolutionary history of a group

• Sharing of derived characters• Begins with an outgroup organism

“Without the discovery of uniformities there can be no concepts, no classifications, no

formulations, no principles, no laws; and without these no science can exist.”

– Clyde K.M. Kluckhohn