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Unit 6: Classification and Diversity KEY CONCEPT Organisms can be classified based on physical similarities. Unit 6: Classification and Diversity Linnaeus developed the scientific naming system still used today. • Taxonomy is the science of naming and classifying organisms. White oak: Quercus alba • A taxon is a group (level) of organisms in a classification system. 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 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 Tyto capensis Unit 6: Classification and Diversity • Scientific names help scientists to communicate. – Some species have very similar common names. – Some species have many common names. 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. New sublevels have been introduced recently (30+) Unit 6: Classification and Diversity 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. What specific characteristics do these Canids share? Quadrapeds, walk on toes, non retractable claws, dew claw, baculum, young born blind, 42 teeth(most), nuchal ligament Unit 6: Classification and Diversity • Physical similarities are not always the result of close relationships. (Consider Convergent Evolution) • Genetic similarities more accurately show evolutionary relationships. Unit 6: Classification and Diversity KEY CONCEPT Modern classification is based on evolutionary relationships. 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 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 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. Unit 6: Classification and Diversity • Derived characters are traits shared in different degrees by clade members. 1 Tetrapoda clade – basis of arranging species in cladogram – more closely related species share more derived characters – represented on cladogram as hash marks 2 Amniota clade 3 Reptilia clade 4 Diapsida clade 5 Archosauria clade FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS BEHIND THE EYE EMBRYO PROTECTED BY AMNIOTIC FLUID FOUR LIMBS WITH DIGITS DERIVED CHARACTER Unit 6: Classification and Diversity • Nodes represent the most recent common ancestor of a clade. CLADE 1 Tetrapoda clade 2 Amniota clade 3 Reptilia clade 4 Diapsida clade • Clades can be identified by snipping a branch under a node. 5 Archosauria clade FEATHERS AND TOOTHLESS BEAKS. SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS BEHIND THE EYE EMBRYO PROTECTED BY AMNIOTIC FLUID NODE FOUR LIMBS WITH DIGITS DERIVED CHARACTER Unit 6: Classification and Diversity Molecular evidence reveals species’ relatedness. • Molecular data may confirm classification based on physical similarities. • Molecular data may lead scientists to propose a new classification. • DNA is usually given the last word by scientists. Unit 6: Classification and Diversity KEY CONCEPT Molecular clocks provide clues to evolutionary history. 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. (MCH) – As more time passes, there will be more mutations. 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 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. DNA sequence from a hypothetical ancestor http://evolution.berkeley.edu/evosite/evo101/IIE1cMolecularclocks.shtml 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 Unit 6: Classification and Diversity Mitochondrial DNA and ribosomal RNA provide two types of molecular clocks. • Different molecules have different mutation rates. – higher rate, better for studying closely related species – lower rate, better for studying distantly related species Unit 6: Classification and Diversity • Mitochondrial DNA is used to study closely related species. – mutation rate ten times faster than nuclear DNA – passed down unshuffled from mother to offspring grandparents mitochondrial DNA nuclear DNA parents Mitochondrial DNA is passed down only from the mother of each generation,so it is not subject to recombination. child Nuclear DNA is inherited from both parents, making it more difficult to trace back through generations. Unit 6: Classification and Diversity • Ribosomal RNA is used to study distantly related species. – many conservative regions – lower mutation rate than most DNA Unit 6: Classification and Diversity KEY CONCEPT The current tree of life has three domains. 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, Plantae Animalia and Plantae Animalia 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, Plantae Animalia and Plantae Animalia – 1866: all single-celled Protista organisms moved to kingdom Protista 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, Plantae Animalia and Plantae Animalia – 1866: all single-celled Protista organisms moved to kingdom Protista – 1938: prokaryotes moved to kingdom Monera Monera 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, Plantae Animalia and Plantae Animalia – 1866: all single-celled Protista organisms moved to kingdom Protista – 1938: prokaryotes moved to kingdom Monera – 1959: fungi moved to own kingdom Monera Fungi 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, Plantae Animalia and Plantae Animalia – 1866: all single-celled Protista organisms moved to kingdom Protista – 1938: prokaryotes moved to kingdom Monera – 1959: fungi moved to own kingdom Archea Fungi Bacteria – 1977: kingdom Monera split into kingdoms Bacteria and Archaea 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 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 Unit 6: Classification and Diversity • Domain Archaea includes prokaryotes in the kingdom Archaea. – cell walls chemically different from bacteria – differences discovered by studying RNA – known for living in extreme environments Unit 6: Classification and Diversity • Domain Eukarya includes all eukaryotes. – kingdom Protista Unit 6: Classification and Diversity • Domain Eukarya includes all eukaryotes. – kingdom Protista – kingdom Plantae Amorphophallus titanum Unit 6: Classification and Diversity • Domain Eukarya includes all eukaryotes. – kingdom Protista – kingdom Plantae – kingdom Fungi Unit 6: Classification and Diversity • Domain Eukarya includes all eukaryotes. – – – – kingdom Protista kingdom Plantae kingdom Fungi kingdom Animalia Unit 6: Classification and Diversity • Bacteria and archaea can be difficult to classify. – transfer genes among themselves outside of reproduction bridge to transfer DNA – blurs the line between “species” – more research needed to understand prokaryotes Unit 6: Classification and Diversity KEY CONCEPT Animal body plans and body organization Unit 6: Classification and Diversity Animal Body Plans • Animal Symmetry – Symmetry Correspondence of size and shape of parts on opposite sides of a median plane – Spherical symmetry Any plane passing through center divides body into mirrored halves Best suited for floating and rolling Found chiefly among some unicellular forms Rare in animals 9-37 Unit 6: Classification and Diversity Animal Body Plans – Radial symmetry Body divided into similar halves by more than 2 planes passing through longitudinal axis Usually sessile, freely floating, or weakly swimming animals No anterior or posterior end » Can interact with environment in all directions - Asymmetrical- random, having 2 sides that are not the same 9-38 Unit 6: Classification and Diversity Animal Body Plans – Bilateral Symmetry Organism can be divided along a sagittal plane into two mirror portions » Right and left halves Much better fitted for directional (forward) movement Associated with cephalization » Differentiation of a head region with concentration of nervous tissue and sense organs Advantageous to an animal moving through its environment head first Always accompanied by differentiation along an anteroposterior axis 9-39 Unit 6: Classification and Diversity Figure 3_01 Unit 6: Classification and Diversity Animal Body Plans • Regions of bilaterally symmetrical animals – Anterior Head end – Posterior Tail end – Dorsal Back side – Ventral Front or belly side – Medial Midline of body – Lateral Sides 9-41 Unit 6: Classification and Diversity Animal Body Plans – Distal Parts farther from the middle of body – Proximal Parts are nearer the middle of body – Frontal plane (coronal plane) Divides bilateral body into dorsal and ventral halves – Sagittal plane Divides body into right and left halves – Transverse plane (cross section) Divides body into anterior and posterior portions 9-42 Unit 6: Classification and Diversity Figure 3_02 Anatomical terminology Unit 6: Classification and Diversity Practice time! • Sketch a side view of an organism with bilateral symmetry (any organism, except a human) • Label: ventral, dorsal, anterior, posterior, medial, lateral • Label with dashed lines: transverse plane, frontal plane
