1. 17.1 The Linnaean System of Classification KEY CONCEPT Organisms can be classified based on physical similarities. Pangolian ↓

2. 17.1 The Linnaean System of Classification Linnaeus developed the scientific naming system still used today. Taxonomy is the science of naming and classifying organisms. A taxon is a group of organisms in a classification system. White oak: Quercus alba

3. 17.1 The Linnaean System of Classification Aristotle Grouped the types of creatures according to their similarities: animals with blood and animals without blood, animals that live on water and animals that live on land. Hierarchical classification. He assumed that creatures could be grouped in order from lowest to highest, with the human species being the highest.

4. 17.1 The Linnaean System of Classification Aristotle 384 BC – 322 BC Greek philosopher and a student of Plato. His writings cover many subjects, including poetry, theater, music, logic, linguistics, politics, government, ethics, biology, and zoology. In the zoological sciences, some of his observations were confirmed to be accurate only in the 19th century. All aspects of Aristotle's philosophy continue to be the object of active academic study today.

5. 17.1 The Linnaean System of Classification Carl Linnaeus 1707-1778 was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology.

6. 17.1 The Linnaean System of Classification Binomial nomenclature is a two-part scientific naming system. –uses Latin words –scientific names always written in italics or underlined –two parts are the genus name and species descriptor

7. 17.1 The Linnaean System of Classification A genus includes one or more physically similar species. –Species in the same genus are thought to be closely related. –Genus name is always capitalized. A species descriptor is the second part of a scientific name. –always lowercase –May refer to a trait of the species, scientist who first described it or native location Tyto alba White barn owl

8. 17.1 The Linnaean System of Classification Scientific names help scientists to communicate. –Some species have very similar common names. –Some species have many common names. Advantages

9. 17.1 The Linnaean System of Classification Linnaeus’ classification system has seven levels. Each level is included in the level above it. Levels get increasingly specific from kingdom to species.

10. 17.1 The Linnaean System of Classification Seven levels of classification Kingdom Phylum/Division Class Order Family Genus Species

11. 17.1 The Linnaean System of Classification The Linnaean classification system has limitations. Linnaeus taxonomy doesn’t account for molecular evidence. –The technology didn’t exist during Linneaus’ time. –Linnaean system based only on physical similarities.

12. 17.1 The Linnaean System of Classification Physical similarities are not always the result of close relationships. Genetic similarities more accurately show evolutionary relationships. Red panda → More related to raccoons

13. 17.1 The Linnaean System of Classification Cladistics is classification based on common ancestry. Phylogeny is the evolutionary history for a group of species. – evidence from living species, fossil record, and molecular data –shown with branching tree diagrams

14. 17.1 The Linnaean System of Classification

15. Cladistics is a common method to make evolutionary trees. –classification based on common ancestry –species placed in order that they descended from common ancestor

16. 17.1 The Linnaean System of Classification A cladogram is an evolutionary tree made using cladistics. –A clade is a group of species that shares a common ancestor. –Each species in a clade shares some traits with the ancestor. –Each species in a clade has traits that have changed.

17. 17.1 The Linnaean System of Classification Derived characters are traits shared in different degrees by clade members. –basis of arranging species in cladogram –more closely related species share more derived characters –represented on cladogram as hash marks FOUR LIMBS WITH DIGITS Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE DERIVED CHARACTER

18. 17.1 The Linnaean System of Classification FOUR LIMBS WITH DIGITS Nodes represent the most recent common ancestor of a clade. Clades can be identified by snipping a branch under a node. Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW FEATHERS AND TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE NODE DERIVED CHARACTER CLADE

19. 17.1 The Linnaean System of Classification Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. Clades can be identified by snipping a branch under a node. DNA is usually given the last word by scientists.

20. 17.1 The Linnaean System of Classification Molecular clocks use mutations to estimate evolutionary time. How they work Mutations add up at a constant rate in related species. –This rate is the ticking of the molecular clock. –As more time passes, there will be more mutations. DNA sequence from a hypothetical ancestor The DNA sequences from two descendant species show mutations that have accumulated (black). The mutation rate of this sequence equals one mutation per ten million years. Mutations add up at a fairly constant rate in the DNA of species that evolved from a common ancestor. Ten million years later— one mutation in each lineage Another ten million years later— one more mutation in each lineage

21. 17.1 The Linnaean System of Classification Scientists estimate mutation rates by linking molecular data and real time. –an event known to separate species –the first appearance of a species in fossil record

22. 17.1 The Linnaean System of Classification Different molecules have different mutation rates. –higher rate, better for studying closely related species –lower rate, better for studying distantly related species Mitochondrial DNA and ribosomal RNA provide two types of molecular clocks.

23. 17.1 The Linnaean System of Classification Mitochondrial DNA is used to study closely related species. grandparents parents child Nuclear DNA is inherited from both parents, making it more difficult to trace back through generations. Mitochondrial DNA is passed down only from the mother of each generation,so it is not subject to recombination. mitochondrial DNA nuclear DNA –mutation rate ten times faster than nuclear DNA –passed down unshuffled from mother to offspring

24. 17.1 The Linnaean System of Classification Ribosomal RNA is used to study distantly related species. –many conservative regions –lower mutation rate than most DNA

25. 17.1 The Linnaean System of Classification Classification is always a work in progress. The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae Animalia Plantae

26. 17.1 The Linnaean System of Classification Classification is always a work in progress. The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae –1866: all single-celled organisms moved to kingdom Protista Animalia Protista Plantae

27. 17.1 The Linnaean System of Classification Classification is always a work in progress. The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista Animalia Protista Plantae Monera

28. 17.1 The Linnaean System of Classification The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae Classification is always a work in progress. –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista Monera –1959: Fungi moved to own kingdom Fungi Protista Plantae Animalia

29. 17.1 The Linnaean System of Classification The tree of life shows our most current understanding. New discoveries can lead to changes in classification. –Until 1866: only two kingdoms, Animalia and Plantae Classification is always a work in progress. –1938: prokaryotes moved to kingdom Monera –1866: all single-celled organisms moved to kingdom Protista –1959: fungi moved to own kingdom –1977: kingdom Monera split into kingdoms Eubacteria and Archaebacteria Animalia Protista Fungi Plantae Archea Eubacteria

30. 17.1 The Linnaean System of Classification 1977: Carl Woese discovered two genetically different groups of prokaryotes, based on rRNA studies of prokaryotes He proposed creating 3 domains above the kingdom level. –domain model more clearly shows prokaryotic diversity