Taxonomy

The science of naming

and classifying organisms

Chapter 17

Carl Linnaeus developed the scientific naming system still used today

• 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

Tyto alba and Quercus alba

Are these species related?

Barn owl: Tyto alba

White oak:Quercus alba

• 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

• Ursus maritimus

Ursus maritimus Ursus arctos horribilis

(horribilis is the subspecies)

Match the Latin names with the descriptions

1. Big-horned sheep from Canada2. Bird with blue-green wings3. House sparrow4. Tree with large flowers5. Plant that has flower with six petals

(a) Cyanopica cyana(b) Passer domesticus (c) Ludwigia hexapetala(d) Ovis canadensis(e) Magnolia grandiflora

Scientific names help scientists to communicate.

• Some species have very similar common names.• Some species have many common names.

Linnaeus’ classification system has seven levels.

How can you remember these levels?

1. Kingdom __________

2. Phylum __________

3. Class __________

4. Order __________

5. Family __________

6. Genus __________

7. Species __________

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

-derived traits are shown with numbers 1-4- organisms are shown with letters A-D

Sample Cladogram

1) Which traits do the Sinornis and Velociraptor share?

2) Which animal has arms as long as legs?

3) Does the Allosaurus have down feathers?

Make a cladogram for quarter, dime, nickel, penny

Make a cladogram

Alligator: amniotic egg, bones, four limbs, jaws, vertebrae

Frog: bones, four limbs, jaws, vertebrae

Gull: amniotic egg, bones, feathers, four limbs, jaws, vertebrae

Lamprey: vertebrae

Shark: jaws, vertebrae

Swordfish: bones, jaws, vertebrae

Dichotomous keys

1 a) oval leaf: go to 2

b) lobed leaf: go to 5

2 a) leaf w/smooth edge: go to 3

b) leaf w/serrate or “sawtooth” edge: go to 4

3 a) leaf 10 to 15 cm long. . . . . magnolia

b) leaf 4 to 7 cm long . . . . . . . common pear

4 a) leaf 10 to 15 cm long . . . . Spanish chestnut

b) leaf 4 to 7 cm long . . . . . . white elm

5 a) four or five lobes: go to 6

b) many lobes: go to 7

1 a) oval leaf: go to 2

b) lobed leaf: go to 5

2 a) leaf w/smooth edge: go to 3

b) leaf w/serrate or “sawtooth” edge: go to 4

3 a) leaf 10 to 15 cm long . . . . . magnolia

b) leaf 4 to 7 cm long . . . . . common pear

4 a) leaf 10 to 15 cm long . . . . . Spanish chestnut

b) leaf 4 to 7 cm long . . . . . white elm

5 a) four or five lobes: go to 6

b) more than 5 lobes: go to 7

6 a) four pointy lobes . . . . . tulip tree

b) five pointy lobes: go to 8

7 a) lobes pointy . . . . . red oak

b) lobes rounded . . . English oak

8 a) star-shaped leaf . . . . sweetgum tree

b) leaf not star-shaped . . . Japanese maple

Common Latin noun endings

• -a, -us, -um, -ae, -i, -is, -o

Molecular clocks use mutations to estimate

evolutionary time.• Mutations add up at a constant rate in related species.

– As more time passes, there will be more mutations.

DNA sequence from ahypothetical ancestor

The DNA sequences from twodescendant species show mutationsthat have accumulated (black).

The mutation rate of thissequence equals one mutationper ten million years.

Mutations add up at a fairlyconstant 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

• Mitochondrial DNA is used to study closely related species.

grandparents

parents

child

Nuclear DNA is inherited from bothparents, making it more difficult totrace back through generations.

Mitochondrial DNA ispassed down only from the mother of each generation,so it is not subject to recombination.

mitochondrialDNA

nuclear DNA

– mutation rate ten times faster than nuclear DNA– passed down unshuffled from mother to

offspring

• Mitochondrial DNA

Evidence for molecular clockin Hemoglobin

Quoll = Large carnivorous marsupial

The current tree of life has three domains.

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

– Until 1866: only two kingdoms,Animalia and Plantae

– 1866: all single-celled organisms moved to kingdom Protista

AnimaliaProtista

Plantae

– Until 1866: only two kingdoms,Animalia and Plantae

– 1938: prokaryotes moved to kingdom Monera

– 1866: all single-celled organisms moved to kingdom Protista

AnimaliaProtista

Plantae

Monera

– Until 1866: only two kingdoms,Animalia and Plantae

– 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

– Until 1866: only two kingdoms,Animalia and Plantae

– 1938: prokaryotes moved to kingdom Monera

– 1866: all single-celled organisms moved to kingdom Protista

– 1959: fungi moved to own kingdom

– 1977: kingdom Monerasplit into kingdoms Bacteria and Archaea

AnimaliaProtista

Fungi

Plantae

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

• Domain Bacteria includes prokaryotes in the kingdom Bacteria.

– one of largest groups on Earth

– classified by shape, need for oxygen, and diseases caused

– known for living in extreme environments

• Domain Archaea includes prokaryotes in the kingdom Archaea.

– cell walls chemically different from bacteria

• Domain Eukarya includes all eukaryotes.– kingdom Protista

• Domain Eukarya includes all eukaryotes.– kingdom Protista– kingdom Plantae

• Domain Eukarya includes all eukaryotes.– kingdom Protista– kingdom Plantae– kingdom Fungi

• Domain Eukarya includes all eukaryotes.– kingdom Protista– kingdom Plantae– kingdom Fungi– kingdom Animalia

• http://www.peabody.yale.edu/exhibits/treeoflife/films.html