Download Chapter 17 Classification

Chapter 17
Classification
Why Classify?
 To study the diversity of life, scientists use a
classification system to name organisms and
group them in a logical manner
 The discipline known as taxonomy is the
science of naming and classifying organisms
Scientific Names
 By the 18th century, scientists realized that
referring to organisms by their common names
is confusing
 Common names vary by language and even by
geographical location
 For example, in America, the buzzard is a
common name for a vulture
 In England, the buzzard is a common name for
a Hawk
Early Naming Efforts
 First attempts at naming organisms gave
names that were too long and detailed
 For example, an early name for a human
might be: tall, bipedal mammal with a
highly developed brain and opposable
thumb
Binomial Nomenclature
 Carolus Linnaeus developed a two-name
system called binomial nomenclature
 In binomial nomenclature, each organism is
given a two-part scientific name
 The name is always written in italics
 The name is in Latin
 The first word is uppercase (genus) and the
second word is lowercase (species)
 The scientific name for human is: Homo
sapiens
Linnaeus’s System of
Classification:
 Kingdom (largest)
 Phylum
 Class
 Order
 Family
 Genus
 Species (smallest)
(King Philip Came Over For Great Spaghetti)
Dichotomous Key
 A dichotomous key is a tool that allows the
user to determine the identity of items in the
natural world, such as trees, wildflowers,
mammals, reptiles, rocks, and fish.
 Keys consist of a series of choices that lead
the user to the correct name of a given item.
 "Dichotomous" means "divided into two parts".
Therefore, dichotomous keys always give two
choices in each step.
Example
Problems with Traditional
Classification
 Classifying organisms by their physical
characteristics is not always feasible
 For Example, would you classify a dolphin as a
fish because they have fins and live in the
water?
 Sometimes, organisms have characteristics in
common with organisms they have little in
common with
Evolutionary Classification
 Biologists now classify organisms by their
line of evolutionary descent
 Organisms are grouped by their
similarities in DNA and not their physical
characteristics
 A cladogram is a diagram used to show
the evolutionary relationship between
organisms
Kingdoms and Domains
 Biologists now use a six kingdom system:
Archaebacteria, Eubacteria, Protista, Fungi,
Plantae, Animalia
 This replaced a five kingdom system where
Archaebacteria and Eubacteria were both in
the Kingdom Monera
 Bacteria are still sometimes called “monerans”
 Domains are groups that are even larger than
Kingdoms
Three Domain System
 Domain Archaea- Kingdom
Archaebacteria, all bacteria that live in
harsh conditions
 Domain Bacteria- Kingdom Eubacteria,
run-of-the mill bacteria that can help or
harm
 Domain Eukarya- all other Kingdoms
Domain Eukarya
 Kingdom Protista- Uni and Multi Cellular,
Eukaryotic organisms that can’t be
classified in any other kingdom. They
are like fungi, plants and animals and can
be auto or heterotrophic (algae, amoeba)
 Kingdom Fungi- Heterotrophic
Eukaryotes that have cell walls made of
chitin (mushrooms, yeasts)
Eukarya, Cont.
 Kingdom Plantae- Multicellular,
Autotrophic Eukaryotes that have cell
walls made of cellulose (trees, grass,
rose)
 Kingdom Animalia- Multicellular,
heterotrophic eukaryotes whose cells do
not have cell walls (humans, cat, sponge,
lobster)
Cladograms
 A cladogram is a branching diagram that
represents the proposed phylogeny or
evolutionary history of a species or group
 It shows how many characters species
have in common
 The general idea is that the more
characters they have in common, the
more recently they shared a common
ancestor
A Cladogram
Use the table below to
construct a cladogram