CLASSIFICATIONMs. Moore1/14/12

WHY CLASSIFY? To study the diversity of life, biologists use a

classification system to name organisms and group them in a logical manner.

Taxonomy: the discipline where scientists classify organisms and assign each organism a universally accepted name

EARLY CLASSIFICATION SYSTEMS 350 B.C. Aristole set up 2 kingdoms:

Animal Plant

1600s John Ray recognized 2 kingdoms: Animal Plant

Classified by:

LandSeaAir

Classified by:

Similarities in body structure

COMMON NAMES MISLEADING John Ray noticed that common names were

misleading

So, he chose to name them in Latin because all scientists knew Latin and it is not spoken so translation is not a problem. Drawback: names were too long! Example: Carnation = dianthus floribus solitoriis

squamis calycinis subovatis brevissimis corollis crenatis

LINNAEUS TO THE RESCUE! 1700s Carolus Linnaeus developed a two kingdom

system Animal Plant

Agreed with Ray and used Latin, but gave every organism a two-part scientific name Genus – Species Ex. Homo sapiens

This system of classification is known as binomial nomenclature.

BINOMINAL NOMENCLATURE Genus: group of closely related species

Species: unique to each species within the genus

Ursus arctos Ursus maritimus Ailuropoda melanoleuca

LINNAEUS’S SYSTEM OF CLASSIFICATION Heirarchial system includes 7 levels/taxons:

Species Genus Family Order Class Phylum Kingdom

GENUS SPECIES Two smallest categories

Examples:Homo sapien

Canis lupus

Heterocephalus glaber

Sus scrofa

FAMILY/ORDER/CLASS/PHYLUM/KINGDOM Family: groups of genera

Ursidae family of bears Order: broad taxonomic category composed of

similar features Canidae (dogs) and Felidae (cats)

Class: composed of similar orders Mammalia: warm-blooded, have body hair, produce milk

Phylum: includes many different organisms that nevertheless share important characteristics Mammals groups with birds, reptiles, etc in the phylum

Chordata (backbone) Kingdom: largest and most inclusive of Linnaeus’s

taxonomic categories Animals and Plants

SIMILARITIES Species were grouped together in larger taxa

according to visible similarities and differences.

How would you have classified dolphins?

Evolutionary relationships are important in classification.

EVOLUTIONARY CLASSIFICATION Phylogeny is the study of evolutionary relationships

among organisms.

Organisms are now grouped into categories that represent lines of evolutionary descent.

Grouping organisms together based on their evolutionary history is called evolutionary classification.

Species within a genus are more closely related to one another than to species in another genus. This is because all members of a genus share a recent common ancestor.

USING CLADOGRAMS Cladograms are diagrams used to show the

relationship among organisms with evolutionary innovations—new characteristics that arise as lineages evolve.

Characteristics that appear in recent parts of a lineage, but not in its older members are called derived characters.

Just like a family tree shows the relationships among different lineages within a family, cladograms represent a type of evolutionary tree.

SHOWING RELATIONSHIPS

DNA AND RNA IN CLASSIFICATION How can DNA and RNA be used in classification?

The genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification and evolutionary relationships.

Humans and yeast related? Myosin

The more similar the DNA of two species, the more recently they shared a common ancestor. The more two species have diverged from each other, the less similar their DNA will be.

THE TREE OF LIFE EVOLVES As biologists learn more about he natural

world, they realize that Linnaeus's two kingdoms Plantae and Animalia did not represent the full diversity of life.

Changing Number of Kingdoms

First Introduced Names of Kingdoms

1700s Plantae Animalia

Late 1800s Protista Plantae Animalia

1950s Monera Protista

Fungi Plantae Animalia

1990s Eubacteria

Archaebacteria

Protista

Fungi Plantae Animalia

THREE-DOMAIN SYSTEM Eukarya (eukaryote = nucleus)

Protista include organisms that cannot be classified as animals, plants, or fungi.

Amoeba, Paramecium, slime molds, giant kelp, algae Fungi members are heterotrophs who usually feed on dead or decaying

matter. Mushrooms, yeasts

Plantae members are photosynthetic autotrophs and immobile. Mosses, fens, flowering plants

Animalia includes multicellular and heterotrophic organisms who have no cell wall.

Sponges, worms, insects, fishes, mammals

Bacteria (prokaryote = no nucleus) Bacteria are unicellular and prokaryotic. Cell walls contain peptidoglycan.

Archaea (prokaryote = no nucleus) Archaea are also unicellular and prokaryotic. Cell walls do not contain

peptidoglycan. Members of this domain live in some of the most extreme environments

you can imagine—volcanic hot springs, brine pools, etc.

Working in lab groups, complete the cladogram worksheets.