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Vocabulary
Prokaryote – unicellular organisms without a nucleus
Eukaryote – unicellular or multicellular organisms with a nucleus
Vocabulary
Autotrophs – “self feeder” organisms that can make their own food through photosynthesis
Heterotrophs – “other feeder” organisms that must ingest (eat) their food
Why Do We Classify Things?
Placing items in categories is natural for humans.
Wild animals: domesticated animals
Edible plants: poisonous plantsFresh water fish:salt water fishThere are numerous examples of
classification systems.
The First Classification System
The first classification system developed 2,500 years ago by Aristotle.
Organisms were separated into two groups, Plants and Animals.
A statue of Aristotle, 384 – 322 BC
Aristotle He further placed animals into three
groups, those that fly, those that walk, and those that swim.
Linnaeus
But, more divisions were needed, and scientists would name organisms whatever they wanted.
A better system was needed that everyone could use.
In 1760 Carolus von Linnaeus published his book on classification.
Carolus von Linnaeus
(1707-1778)
Swedish scientist who laid the
foundation for modern
taxonomy
Binomial Nomenclature
Binomial “two names”Nomenclature is a system
of namingCarolus von Linnaeus Two-word naming system
– GenusNoun, Capitalized,
Underlined or Italicized– Species
Descriptive, Lower Case, Underlined or Italicized
Why Do We Classify Organisms?
Biologists group organisms to represent similarities and proposed relationships.
Classification systems change with expanding knowledge about new and well-known organisms.
Tacitus bellus
Why a Scientific Classification System?
Ambiguity of terms– All scientists use the same system.
Latin “dead language”– The Latin terms will not change over
time Categorization of relationships:
– Evolutionary– Structural– Biochemical
Classification
Classification starts at the largest division that includes the most organisms.
Classification consists of three domains and six kingdoms.
BacteriaArchaea Eukarya
The Three Domains
The Six Kingdoms
How are organisms placed in kingdoms?– Cell type, prokaryotic or eukaryotic– The number of cells in their body, unicellular or
multicellular– Their ability to make food, autotrophs or
heterotrophs
EubacteriaArchaea Protist
aPlantaeFungi Animalia
The six-kingdom system
The farther you go down the classification system the more specific the name becomes for that particular organism.
What is classification based on?
Classification Criteria
BiochemistryGenetic System, DNA and RNAEvolutionary HistoryNutritionMolecular Make-upA Dichotomous Key is used to
classify organisms
Classification System for Lynx and Bobcat
Kingdom: AnimaliaPhylum: ChordataClass: MammaliaOrder: CarnivoraFamily: FelidaeGenus: LynxSpecies: Lynx canadensis Lynx
rufus lynx bobcat
The same to this point, the animals share the same characteristics
Family or Genus Relations?
Family:Less closely
relatedLarger groupGenus:More closely
relatedPrecedes
species=interbreeding
Family:FelidaeLions, tigers,
leopardshouse
cats,cheetahs, ocelots
Genus: PantheraLeopards
(pardus)Lion (leo)Tigers (tigris)
The First Cat
Most authorities agree that the domestic cat descended from the Caffre cat, a small breed of African wildcat. The Caffre cat was domesticated in ancient Egypt, possibly as early as 2500 BC.
Evolutionary History
The evolutionary history of a species is called its phylogeny.
Cladistics is a system of taxonomy that reconstructs phylogenies by inferring relationships based on similarities.
Taxonomic Diagrams
Biologists group organisms into categories that represent common ancestries, not just physical similarities.
Early naturalists used physical characteristics and later, fossil data, attempting to represent evolutionary relationships among organisms.
Taxonomic Diagrams
Today, modern classification systems use fossil data, physical characteristics and DNA/RNA information to draw increasingly more accurate branching diagrams.
Two types of diagrams are Cladistic and Phylogenic diagrams
Cladistics
Cladograms are based only on characteristics observable in existing species.
The branching patterns in a cladogram are defined by the presence of unique, characteristics shared by all members of the group.
Cladistics
A branching diagram to show an evolutionary family tree is known as a cladogram.
Cladistics hypothesize that every phylum originated from a single group of organisms that has branched into today’s species.
Cladograms
Each branch point or fork in the cladogram, shows a point in evolution where a unique characteristic developed to separate one group from another.
Cladograms are concerned with the order structural differences happened.
Taxonomic Diagrams
Phylogenetic trees, or phylogenies, represent hypothesized evolutionary relationships among organisms and may include extinct as well as modern species.