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CLASSIFICATIONMs. Moore
1/14/12
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.