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Unit 6: Classification and Diversity KEY CONCEPT Organisms can be classified based on physical similarities.

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Presentation on theme: "Unit 6: Classification and Diversity KEY CONCEPT Organisms can be classified based on physical similarities."— Presentation transcript:

1 Unit 6: Classification and Diversity KEY CONCEPT Organisms can be classified based on physical similarities.

2 Unit 6: Classification and Diversity 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 Unit 6: Classification and Diversity Binomial nomenclature is a two-part scientific naming system. –uses Latin words –scientific names always written in italics –two parts are the genus name and species descriptor

4 Unit 6: Classification and Diversity 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 –always follows genus name; never written alone Tyto alba

5 Unit 6: Classification and Diversity Scientific names help scientists to communicate. –Some species have very similar common names. –Some species have many common names.

6 Unit 6: Classification and Diversity Linnaeus classification system has seven levels. Each level is included in the level above it. Levels get increasingly specific from kingdom to species.

7 Unit 6: Classification and Diversity The Linnaean classification system has limitations. Linnaeus taxonomy doesnt account for molecular evidence. –The technology didnt exist during Linneaus time. –Linnaean system based only on physical similarities.

8 Unit 6: Classification and Diversity Physical similarities are not always the result of close relationships. Genetic similarities more accurately show evolutionary relationships.

9 Unit 6: Classification and Diversity KEY CONCEPT Modern classification is based on evolutionary relationships.

10 Unit 6: Classification and Diversity 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

11 Unit 6: Classification and Diversity Cladistics is a common method to make evolutionary trees. –classification based on common ancestry –species placed in order that they descended from common ancestor

12 Unit 6: Classification and Diversity 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.

13 Unit 6: Classification and Diversity 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

14 Unit 6: Classification and Diversity 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

15 Unit 6: Classification and Diversity Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. Molecular evidence reveals species relatedness. DNA is usually given the last word by scientists.

16 Unit 6: Classification and Diversity KEY CONCEPT Molecular clocks provide clues to evolutionary history.

17 Unit 6: Classification and Diversity Molecular clocks use mutations to estimate evolutionary time. 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

18 Unit 6: Classification and Diversity 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

19 Unit 6: Classification and Diversity 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.

20 Unit 6: Classification and Diversity 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

21 Unit 6: Classification and Diversity Ribosomal RNA is used to study distantly related species. –many conservative regions –lower mutation rate than most DNA

22 Unit 6: Classification and Diversity KEY CONCEPT The current tree of life has three domains.

23 Unit 6: Classification and Diversity 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

24 Unit 6: Classification and Diversity 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

25 Unit 6: Classification and Diversity 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

26 Unit 6: Classification and Diversity 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

27 Unit 6: Classification and Diversity 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 Bacteria and Archaea Animalia Protista Fungi Plantae Archea Bacteria

28 Unit 6: Classification and Diversity The three domains in the tree of life are Bacteria, Archaea, and Eukarya. Domains are above the kingdom level. –proposed by Carl Woese based on rRNA studies of prokaryotes –domain model more clearly shows prokaryotic diversity

29 Unit 6: Classification and Diversity Domain Bacteria includes prokaryotes in the kingdom Bacteria. –one of largest groups on Earth –classified by shape, need for oxygen, and diseases caused

30 Unit 6: Classification and Diversity –known for living in extreme environments Domain Archaea includes prokaryotes in the kingdom Archaea. –cell walls chemically different from bacteria –differences discovered by studying RNA

31 Unit 6: Classification and Diversity Domain Eukarya includes all eukaryotes. –kingdom Protista

32 Unit 6: Classification and Diversity Domain Eukarya includes all eukaryotes. –kingdom Protista –kingdom Plantae

33 Unit 6: Classification and Diversity Domain Eukarya includes all eukaryotes. –kingdom Protista –kingdom Plantae –kingdom Fungi

34 Unit 6: Classification and Diversity Domain Eukarya includes all eukaryotes. –kingdom Protista –kingdom Plantae –kingdom Fungi –kingdom Animalia

35 Unit 6: Classification and Diversity Bacteria and archaea can be difficult to classify. –transfer genes among themselves outside of reproduction –blurs the line between species –more research needed to understand prokaryotes bridge to transfer DNA


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