Classification of Organisms

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Write a definition for the word “classify”.

Isn’t every living thing either a plant or an

animal?• Aristotle is credited

with the first true classification system.

• He grouped all living things into two basic groups: plant and animal

OR

Carlos Linnaeus

• Linnaeus further classified plants and animals by dividing them into related groups.

• He used the Latin language, because Latin was no longer spoken conversationally and thus was less likely to change.

Carlos Linnaeus

• He first grouped related organisms.

• He called this a genus.• For example, all of the

dog-like creatures were grouped as the genus Canis.

Carlos Linnaeus

• He next gave every different type of organism in the group a specific name, which he called species.

• For example, the dog became Canis familiaris and the wolf Canis lupus.

• Notice the genus is capitalized but the specie begins with a lower case letter.

• Both are italicized or underlined.

Carlos Linnaeus

• Every organism was given a two-word name, the genus and specie.

• This practice of binomial nomenclature continues today, giving each organism a “scientific name”.

Loxosceles reclusa(Brown Recluse)

Carlos Linnaeus

• The benefit of binomial nomenclature includes eliminating confusion due to common names (ex. cottonmouth and water moccasin are actually the same animal) and allows scientists around the world to more easily communicate.

Microbes?

• Even after the microbial world was discovered, the two “kingdom” system continued.

• (Yes, science can be very slow to change.)

plant or animal?

Whittaker

• As knowledge of the diversity of organisms increased, Whittaker (in 1969) expanded classification to include five kingdoms.

Taxonomy

• The science of classification, taxonomy, now allowed scientists to assign seven levels of taxa to living organisms.

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MEMORY AID!K-P-C-O-F-G-S-

Taxonomy

• The kingdom is the most general of these seven taxa, thus the kingdom would contain the greatest number of organisms.

Taxonomy

• Specie is the most specific of these seven taxa, thus the specie would contain only one type of organism.

• A specie is defined as a group of organisms which can interbreed and produce fertile offspring.

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How are the terms “kingdoms” and “taxa” related?

Taxonomy

• Today, we use three domains, which are divided into six kingdoms.

• These domains are based on new information about possible evolutionary relationships.

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Draw a picture for each of the six kingdoms and label with the kingdom name:

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The History of Classification:Linnaeus had ____ kingdoms

Whittaker used ____ kingdoms

Today we use ____ kingdoms

Let’s Play …

1. Which level is the most general? The most specific?

2. At what taxonomic level do the dog and human become different?

3. What is the family name of the dog?

4. Which organism is most closely related to the dog?

5. What is the scientific name of the dog?

6. A genus is composed of a number of related ___?

7. A group of related phyla are called a ___?

8. Which taxon contains the largest number or organisms?

What happens when you find an unknown organism?

• Dichotomous keys are tools that use a series of paired statements and visible characteristics of the organism.

• Of course, a dichotomous key is only useful if the organism has already been classified and given a scientific name.

What happens when you find an unknown organism?

• Always start at statement 1 (or the beginning point).

• Decide which path best describes the organism (Statement A or Statement B)

• Follow that path to find the next choice (Go to …)

• When you can go no further, you will find the name!

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Answers:1.2.3.4.5.

What happens when you find an unknown organism?

• If the organism has NOT been classified, taxonomists must begin the process of classification.

• In order to correctly classify an organism, scientists use many modern tools:

What happens when you find an unknown organism?

• 1. Morphology describes the physical characteristics of an organism.

• Typically, this is enough information to place the organism within a domain and kingdom.

• Example: Presence of a nucleus places the organism in Domain Eukarya

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WORD HELP!“Morph” means ___________

“ology” means ___________

What happens when you find an unknown organism?

• 2. DNA and biochemical analysis allow scientists to test less visible, but distinguishing, characteristics.

• Example: Gram staining a bacteria cell allows scientists to distinguish between archaea and prokarya.

What happens when you find an unknown organism?

• 3. Comparing embryology allows scientists to group organisms that share common fetal development

• Example: the diagram below would suggest the last two organisms are most closely related.

What happens when you find an unknown organism?• 4. Evolutionary phylogeny

describes the evolutionary relationships between organisms.

• These relationships are deduced based on shared traits that may have been passed from ancestor to new species.

• Traits may include physical traits (ex. presence of jaws), or may be genetic traits (shared genes).

• These relationships can be illustrated in a phylogenetic tree or cladogram:

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In this cladogram, what kingdom is most closely related to animals?

What kingdom evolved first?

From what kingdom did plants evolve?

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The four things we can compare to classify:

1.2.3.4.

Check Yourself!

1. Who first officially classified organisms?2. What was the contribution of Linnaeus to

taxonomy?3. What are the two parts of a scientific name?4. What are the domains used in the current

classification system?5. How many kingdoms are used in the current

classification system?6. What is a dichotomous key?7. What 4 modern tools are used to classify a newly

discovered organism?

Check Yourself!

1. Who first officially classified organisms? ARISTOTLE

Check Yourself!

2. What was the contribution of Linnaeus to taxonomy?

GROUPED RELATED ORGANISMS CREATED BINOMIAL NOMENCLATURE

Check Yourself!

3. What are the two parts of a scientific name? GENUS + SPECIE

Check Yourself!

4. What are the domains used in the current classification system?

ARCHEA BACTERIA EUKARYA

Check Yourself!

5. How many kingdoms are used in the current classification system?

SIX

Check Yourself!

6. What is a dichotomous key? TOOL THAT USES A SERIES OF PAIRED

STATEMENTS AND VISIBLE CHARACTERISTICS TO HELP IDENTIFY UNKNOWN ORGANISMS

Check Yourself!

7. What 4 modern tools are used to classify a newly discovered organism?

MORPHOLOGY BIOCHEMICAL ANALYSIS EMBRYOLOGY EVOLUTIONARY PHYLOGENY