Ch. 17:

Classification

Who is Carolus Linnaeus?

• Linnaeus developed the scientific naming system

still used today.

What is…? • Taxonomy… –the science of naming and

classifying organisms.

• A taxon… –group of organisms in a

classification system.

Linnaean Taxonomy • Organisms are grouped based on physical

and structural similarities.

• Basic taxon is the species

–Defined as a group of organisms that can breed and produce offspring that can reproduce

• Each species is given a scientific name

Binomial Nomenclature • Two-part scientific naming system

–uses Latin words

–scientific names always written in italics

–two parts are the genus name and species descriptor

Binomial Nomenclature • 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

– (1) Genus (2) species

Seven Levels • Kingdom, Phylum, Class, Order,

Family, Genus, Species

• Each level is included in the level above it.

• Levels get increasingly specific from kingdom to species.

Taxonomy of Lions

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Carnivora

• Family: Felidae

• Genus: Panthera

• Species: leo

Taxonomy of Leatherback Sea Turtles

• Kingdom: Animalia

• Phylum: Chordata

• Class: Reptilia

• Order: Testudines

• Family: Cheloniidae

• Genus: Dermochelys

• Species: coriacea

Taxonomy of Humans

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Primates

Family: Hominidae

Genus: Homo

Species: sapiens

The Linnaean classification system has limitations.

• Linnaeus taxonomy doesn’t account for molecular evidence, only on physical similarities… – The technology didn’t exist during Linneaus’

time.

–Physical similarities are not always the result of close relationships.

–Genetic similarities more accurately show evolutionary relationships.

Dichotomous Keys • Used to identify objects or organisms that

have already been described by another scientist.

• Made up of paired statements.

– Pair of statements divides the objects to be classified into one category or the other, but not both.

• As you proceed from step to step, the classification is narrowed down.

http://cbe.wisc.edu/assets/docs/pdf/biolearn/Classification/WhatIsLife/dichotomous_key.pdf

Cladistics • is a common method to make

evolutionary trees. • classification based on

common ancestry

• species placed in order that they descended from common ancestor

Cladogram

• 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.

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

Cladogram

• Nodes represent

the most recent

common

ancestor of a

clade.

• Clades can be

identified by

snipping a branch

under a node.

FOUR LIMBS WITH DIGITS

Archosauria clade 5 Diapsida clade 4 Reptilia clade 3

Amniota clade 2

Tetrapoda clade 1

NODE

EMBRYO PROTECTED BY AMNIOTIC FLUID

SKULL OPENINGS BEHIND THE EYE

OPENING IN THE SIDE OF

THE SKULL

SKULL OPENINGS IN

FRONT OF THE EYE AND

IN THE JAW

FEATHERS AND

TOOTHLESS

BEAKS.

CLADE

DERIVED CHARACTER

Domains and Kingdoms • 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 • Domain Bacteria

includes single-celled prokaryotes in the kingdom Bacteria. – one of largest

groups on Earth

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

Domain Archaea • Domain Archaea includes single-celled

prokaryotes in the kingdom Archaea.

–cell walls chemically different from bacteria

–differences discovered by studying RNA

• known for living in extreme environments – Can live areas that lack oxygen, an area with

a high salt concentration, or extremely hot environments.

Domain Eukarya • Domain Eukarya includes

all eukaryotes (cells have a distinct nucleus and membrane-bound organelles).

• Eukarya may be: – Single-celled: protists

– Colonial: some algae

– Multicellular: You!!

• Domain includes the following kingdoms: • kingdom Protista

• kingdom Plantae

• kingdom Fungi

• kingdom Animalia