Download - Unit 17a Scientific classification
17.1 The Linnaean System of Classification
KEY CONCEPT Organisms can be classified based on physical similarities.
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
17.1 The Linnaean System of Classification
• Binomial nomenclature is a two-part scientific naming system.– uses Latin words. Why? – scientific names always written in italics. Why? – two parts are the genus name and species descriptor.
Why?
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– always follows genus
name; never written alone
Tyto alba
17.1 The Linnaean System of Classification
• Scientific names help scientists to communicate. How? – Some species have very similar common names.– Some species have many common names.
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.
Ah yes, it’s time for another mnemonic device!
• How will you remember the order of classification groups? K-P-C-O-F-G-S
• Kingdom• Phylum• Class• Order• Family• Genus• Species
17.1 The Linnaean System of Classification
The Linnaean classification system has limitations.
• Linnaeus taxonomy doesn’t account for molecular evidence. Why?– The technology didn’t exist during Linneaus’ time.– Linnaean system based only on physical similarities.
17.1 The Linnaean System of Classification
• Physical similarities are not always the result of close relationships.
• Genetic similarities more accurately show evolutionary relationships.
17.2 Classification Based on Evolutionary Relationships
KEY CONCEPT Modern classification is based on evolutionary relationships.
17.2 Classification Based on Evolutionary Relationships
Cladistics is classification based on common ancestry.
• Phylogeny shows the evolutionary history for a group of species.– evidence from living species, fossil record, and
molecular data– shown with branching tree diagrams using a method
called Cladistics.
17.2 Classification Based on Evolutionary Relationships
• Cladistics is a common method to make evolutionary trees.
– species placed in order that they descended from common ancestor
17.2 Classification Based on Evolutionary Relationships
• 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.
17.2 Classification Based on Evolutionary Relationships
• Derived characters are traits shared in different degrees by clade members.
– more closely related species share more derived characters
– Derived characters are represented on cladograms as hash marks
– Oldest relatives are at the bottom of the cladogram.
FOUR LIMBS WITH DIGITS
Tetrapoda clade1
Amniota clade2
Reptilia clade3Diapsida clade4
Archosauria clade5
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
17.2 Classification Based on Evolutionary Relationships
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. In this example, the different clades are distinguished by different colors.
Tetrapoda clade1
Amniota clade2
Reptilia clade3Diapsida clade4
Archosauria clade5
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
17.2 Classification Based on Evolutionary Relationships
• Molecular data may confirm classification based on physical similarities.
• Molecular data may lead scientists to propose a new classification.
Molecular evidence reveals species’ relatedness. What would you expect to see when comparing the DNA of two closely related species?
• DNA is usually given the last word by scientists.
17.2 Classification Based on Evolutionary Relationships
If two organisms are in the same phylum, what other taxon do they have in common?
• A. class • B. kingdom • C. family • D. genus
17.2 Classification Based on Evolutionary Relationships
If two organisms are in the same phylum, what other taxon do they have in common?
• A. class • B. kingdom • C. family • D. genus • Correct Answer = B
What is a species? • A. a group of organisms that live in the same habitat • B. a group of organisms that have similar structures • C. a group of organisms that compete for the same food source • D. a group of organisms that can breed and produce offspring that can
reproduce
17.2 Classification Based on Evolutionary Relationships
If two organisms are in the same phylum, what other taxon do they have in common?
• A. class • B. kingdom • C. family • D. genus • Correct Answer = B
What is a species? • A. a group of organisms that live in the same habitat • B. a group of organisms that have similar structures • C. a group of organisms that compete for the same food source • D. a group of organisms that can breed and produce offspring that can
reproduce • Correct Answer = D
Review
• Taxonomy is the science of naming and classifying organisms
• Binomial nomenclature is a two-part scientific naming system
• The classification groups from largest to smallest = kingdom, phylum, class, order, family, genus, species
• Cladistics is classification based on common ancestry• Molecular evidence reveals species’ relatedness• DNA is usually given the last word by scientists