Classification
Linnaeus developed the scientific naming
system still used today
 Taxonomy is the science of naming and classifying organisms
Orcinus orca
• A taxon is a group of organisms in a classification system
 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
• 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
Callinectes sapidus
• Scientific names help scientists to communicate.
– Some species have very similar common names.
– Some species have many common names.
Dolphin, porpoise, dolphinfish, mahi mahi
http://www.foxnews.com/science/2013/07/23/hey-flipper-dolphins-use-names-to-reunite/
Linnaeus’ classification system has seven levels
 Each level is
included in the
level above it.
• Levels get
increasingly specific
from kingdom to
species.
The Linnaean classification system has limitations
Organisms can be classified based on physical similarities
 Linnaeus taxonomy doesn’t account for molecular evidence.
 The technology didn’t exist during 1700’s when Linneaus lived
 Linnaean system based only on physical similarities.
 Physical similarities are not always the result of close
relationships
 Genetic similarities more accurately show close relationships
Modern classification is based on genetic similarity
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
 Cladistics is a common method to make trees.
– classification based on common ancestry
– species placed in order that they descended from common ancestor
Horseshoe Crab
Living fossil - found in Ordovician strata 450 mya
• 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.
major-clades-of-animals-april-2013-5
KINGDOM Animalia
 1. Animal Clade
2. Unicellular Animals
 3. Multicellular Animals
4. Tissue-Level Grade
 5. Organ-Level Grade
6. The Radiate Animals
 7. The Bilaterians
8. The Nephrozoans
 9. The Deuterostomes
10. The Protostomes
 11. The Ecdysozoans
12. The Spiralians
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.
Mitochondrial DNA and ribosomal RNA
provide two types of molecular clocks
• Different molecules have different mutation rates.
– Mitochondria DNA higher mutation rate (10x faster than
chromosomal DNA,
– passed down unshuffled from mother to offspring
– better for studying closely related species
– Ribosomal RNA
– lower mutation rate than most DNA ,
– many conservative regions,
– better for studying distantly related species
Classification is always a work in progress
 The current tree of life has three domains
 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
Plantae
Animalia
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
Plantae
Animalia
Protista
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
Plantae
Animalia
Protista
– 1938: prokaryotes moved to
kingdom Monera
Monera
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
Plantae
Animalia
Protista
– 1938: prokaryotes moved to
kingdom Monera
– 1959: fungi moved to own
kingdom
Monera
Fungi
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
Plantae
Animalia
– 1866: all single-celled organisms
moved to kingdom Protista
Protista
– 1938: prokaryotes moved to
kingdom Monera
– 1959: fungi moved to own
kingdom
Fungi
– 1977: kingdom Monera
split into kingdoms Bacteria and Archaea
Archea
Bacteria
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
– kingdom Protista has been adjusted
The taxonomy of protists is still changing.
Newer classifications attempt to use ultrastructure,
biochemistry, and genetics.
(unranked): Archaeplastida
Division: Rhodophyta
Kingdom: Chromalveolata
Phylum: Heterokontophyta
The heterokonts or stramenopiles are a major line of
Protists. Currently containing more than 100,000
species. Most are algae, ranging from the giant
kelp to the tiny diatoms.
Originally the heterokont algae were treated as two divisions,
first within the kingdom Plantae and later the Protista
Division Chrysophyta Class Chrysophyceae (golden algae)
Class Bacillariophyceae (diatoms)
Division Phaeophyta (brown algae)
Domain Eukarya includes all eukaryotes
– kingdom Plantae
Green algae
Chlorophyta and charophyta
Marine Phyla –
27 members of Kingdom Animalia
 http://www.mesa.edu.au/phyla/
 Shows all new supergroups
http://comenius.susqu.edu/biol/202/taxa.htm