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TaxonomyTaxonomy

Techniques of the past and Techniques of the past and presentpresent to provide information to provide information

about an organism.about an organism.

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Part OnePart One

How it all started.How it all started.

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TAXA• Greek word - means categories or groups .

• Singular form of the term is taxon.

• Taxonomy: the science that deals with the classification or grouping of living things.

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The first classification system

• 400 B.C. - Greek philosopher, Aristotle, developed a system for sorting living organisms.

• His system consisted of two kingdoms; the plant and animal kingdoms.

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Plants were grouped according to their stem structure and size. The 3 subgroups were:

Shrubs Trees6

AnimalsAnimals were grouped according to were grouped according to habitathabitat::

Water

Land

Air

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Gradually Aristotle’s system showed weaknesses. Can you identify any?

• not specific enough • too many organisms were being discovered • The microscope discovered many organisms that

would not fit into Aristotle’s classification system.• NOTE: despite its weaknesses this first

classification system was used for about 2,000 years.

• Who improved on this old system?8

Beginnings of Modern Taxonomy

• 1600’s• John Ray - introduced a term called

species. • Stated that a species was a group of

organisms that were:• similar in structure • able to mate and pass the traits to their

offspring.

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Founder of modern taxonomy

• Carolus Linnaeus (also in the 1600’s)

• Also used structural similarities as the basis for his taxonomic system

• Started with a large group or kingdom which he divided into subgroups

• Organisms could be sorted more precisely

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Today’s taxonomy still uses Linnaeus’ system

7 Taxa / Groups

1. Kingdom2. Phylum3. Class4. Order5. Family6. Genus7. species

Example: human

Animalia Chordata Mammalia Primates Hominidae Homo sapiens

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Today’s Modified System

8 Taxa / Groups1. Domain2. Kingdom3. Phylum4. Class5. Order6. Family7. Genus8. species

Example: human Eukaryota Animalia Chordata Mammalia Primates Hominidae Homo sapiens

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What Changed

Three Domains added (based on DNA)1) Archaea – extremophile bacteria, ex.- methanogens, halophiles, and thermoacidophiles2) Bacteria – all other bacteriaNote- Kingdom Monera no longer exists 3) Eukaryota – 4 other Kingdoms – Protista, Fungi, Plantae, and Animalia.

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Duh,KingPhilip Came Over For Green soup

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Scientific Naming System• There are always two Latin words to name each species.• Process is called binomial nomenclature.• Used world-wide to prevent confusion caused by various

languages.• Prevents confusion with common names.

Example: A puma, cougar and mountain lion are all the same animal. Its scientific name, world-wide is:

Felis concolor

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More about scientific naming• The scientific name is composed of the Genus and

the species.• Rules for writing scientific names.

• Genus is given first and must be Capitalized and underlined (or in italics)

• Species name is second and must begin with a lower case letter and must be underlined (or in italics)

Example: Homo sapiens or Homo sapiens

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Other examples of scientific names:

Cats

• Wildcat

• Cougar

• Housecat

Genus - Felis

• Felis sylvestris

• Felis concolor

• Felis domesticus or Felis domesticus

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Review of the key terms

• Taxa• Taxonomy• Latin names• Aristotle• John Ray• Carolus Linnaeus• Species

• Kingdom• Phylum• Class• Order• Family• Genus• Binomial Nomenclature

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Part TwoPart Two

Modern MethodsModern Methods

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Today most scientistsToday most scientists ……. …….

• recognize that recognize that organisms have organisms have changed over timechanged over time..

• accept accept evolutionevolution as theas the basis for basis for classificationclassification..

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PhylogenyPhylogeny(phy-log-e-ny)(phy-log-e-ny)

The field of biology whereThe field of biology where scientists scientists study the evolutionary history of living study the evolutionary history of living

organisms.organisms.

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1. Fossil Records1. Fossil Records:: Fossils provide Fossils provide evidenceevidence that show how that show how plants and animals are plants and animals are relatedrelated by by preserving structurespreserving structures that can be that can be studied and compared.studied and compared.

Phylogenists often study Phylogenists often study fossilsfossils..

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What is a fossil ?What is a fossil ? A A cast or moldcast or mold of of

an an organism organism preservedpreserved in rock in rock that formed where that formed where the organism died. the organism died.

Trilobite

Fish

Archaeopteryx

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A fossil may also A fossil may also consist of the consist of the organism itself organism itself preserved in ice, preserved in ice, amber, or in amber, or in volcanic glass. volcanic glass.

Cockroach in amber

Firefly

Can you guess what these are?

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A fossil may also consist of A fossil may also consist of tracks tracks (footprints), seeds, or skeleton(footprints), seeds, or skeleton preservedpreserved in in deposits (sediments)deposits (sediments)..

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2. Homologous Structures2. Homologous Structures…… … …are are parts in different animalsparts in different animals that that show show

similaritiessimilarities in theirin their structure.structure.

Ex.- a bat Ex.- a bat wing, a human wing, a human arm, a whale arm, a whale flipper and a cat flipper and a cat foreleg are all foreleg are all homologous homologous structures.structures.

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3. Comparative Embryology3. Comparative Embryology

Taxonomists study the patterns of developmentTaxonomists study the patterns of development before birth. before birth. Embryos of organismsEmbryos of organisms believed to believed to be closely related show similar patterns of be closely related show similar patterns of development. development.

Dolphin embryo Human embryo

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Modern Methods (cont’d)Modern Methods (cont’d)4. Comparative biochemistry:4. Comparative biochemistry: the study of the the study of the

chemistry of chemistry of blood, enzymes and other specific blood, enzymes and other specific substancessubstances produced by animals and plants. produced by animals and plants.

Example: Example: hemoglobin in the blood cells of gorillas hemoglobin in the blood cells of gorillas and humans are the same except for one amino and humans are the same except for one amino acid.acid.

5. Comparing sequences of amino acids5. Comparing sequences of amino acids in in organisms helps to organisms helps to reveal relationships.reveal relationships.

Q. What determines the sequence of these Q. What determines the sequence of these amino acids ?amino acids ?

A. DNAA. DNA30

Modern Methods (cont’d)Modern Methods (cont’d)6. Comparative DNA and RNA6. Comparative DNA and RNA:: Scientists now Scientists now

study DNA and RNA structure to see their study DNA and RNA structure to see their similarities among organismssimilarities among organisms. .

• DNA of humans and chimpanzees is 96% identical.DNA of humans and chimpanzees is 96% identical.

• DNA between humans and other mammals DNA between humans and other mammals (dog,horses,whales,bats,etc) is only about 80% (dog,horses,whales,bats,etc) is only about 80% identical.identical.

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Modern Methods Modern Methods (cont’d)(cont’d)

7. Function7. Function: what the : what the organism doesorganism does: its : its place in the ecosystem.place in the ecosystem.

8. Behavior8. Behavior: series of : series of activities performedactivities performed by an organism by an organism in response to stimuliin response to stimuli..

9. Nutrition9. Nutrition: what an organism : what an organism eatseats

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Final ThoughtsFinal Thoughts• It is important to recognize that a It is important to recognize that a

taxonomic classification system is taxonomic classification system is not not a facta fact. .

• Classification is Classification is based on educated based on educated opinionsopinions and as a result there are a and as a result there are a number of ways in which number of ways in which organisms can be grouped.organisms can be grouped.