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Chapter 18
Finding Order in Diversity
Biologist have found and named over
1.5 million species so far
It is estimated that there are between
2 and 100 million species left to be
discovered
To study the diversity of life, biologist
use a classification system to name
organism and group them in a logical
manner
Finding Order in Diversity
Scientist discovered early that they could
not use common names to name
organisms…
Buzzard
In the UK means Hawk
In the US means Vulture
Cougar in the Mountain means:
Lion, Puma, Panther
Because early 18th century scientist all
understood Latin and Greek, this was
the language that was used to name
organisms
Binomial Nomenclature
A 2 word naming system
Each species is assigned a 2 part
scientific name
Always written italics
1st part of the name is capitalized, 2nd
part of the name is lowercase
Ursus arctos – grizzly bear
Binomial Nomenclature
The 1st part of the name is the genus
A group of closely related species
The 2nd part of the name is unique to a
particular species within a genus
A Latinized word often describing a
physical trait of the organism or a location
where it lives
Ursus maritimus refers to the sea where
polar bears live or pack ice in sea
Binomial Nomenclature
Taxon (pl. Taxa)
A group or level of organization
Linnaeus’ system of classification uses
7 Taxonomic Categories from smallest to largest
Species
Genus
Family
Order
Class
Phylum
Kingdom
Species
A population of organisms that can
breed with one another and produce
fertile offspring
Genus
A group of closely related species
Family
A group of genera that share many
characteristics
Order
A broad taxonomic category that is
composed or similar families
Class
Composed of similar orders
Phylum
Composed of many different
classes…includes many different
organism that nevertheless share
important characteristics
Kingdom
The largest of all taxons, i.e the kingdom
Animalia
A good aid for
remembering these
categories is the
mnemonic device:
Keep Plates Clean Or
Family Gets Sick.
Modern Evolutionary Classification
Originally, organism were grouped
and classified according to body
structure
There were problems with this
method though, i.e dolphins --fish or
mammals; and convergent evolution
made it difficult to distinguish between
related organism and unrelated
organism with similar body structures
Modern Evolutionary Classification
Scientist began to understand that
organism share certain traits because
they share an evolutionary history
Biologist now group organisms into
categories that represent lines of
Evolutionary Decent, not just physical
similarities– this is called Evolutionary
Classification
Many biologist now use Cladistic
Analysis
Identifies and considers only those
characteristics of organisms that are
Evolutionary Innovations:
New characteristics that arise as
lineages evolve
Derived characters are characteristics
that appear in recent parts of the
lineage but not in its older members
Claydogram
A diagram that shows the
evolutionary relationships among
groups of organisms
Uses Derived Characters to mark the
evolutionary change of a trait on the
diagram
A useful tool to help us understand
how one lineage branched from
another in the course of evolution
Claydogram
Similarities in DNA & RNA
All organism use DNA & RNA to pass on
information and to control growth and
development
DNA & RNA provide an excellent way of
comparing organism at a genetic (gene) level
The genes of many organism show important
similarities at the molecular level. These
similarities can be used as criteria to help
determine classification
i.e … genes of humans and yeast even show
similarities because both have a gene that codes
for Protein Myosin
In humans causes muscle constrictions
In yeast enables internal cell part to move
Similarities in DNA & RNA
DNA comparisons have shed light on
classification questions regarding just how
closely related 2 species are ..
i.e… the American Vulture and the Stork
American Vulture has peculiar habits
When they get over-heated they urinate on their
legs so that evaporative cooling removes some
body heat
Similarities in DNA & RNA
Storks also behave in the same manner as
American Vulture, but Storks looks quite
different from vultures and have always
been in a separate family
Scientists analyzed the DNA of these three
(African Vultures, American Vultures, &
Storks) birds revealed that American
vultures are indeed more closely related to
storks than they are to other vultures
Molecular Clocks
A model known as a Molecular
Clock uses DNA comparisons to
estimate the length of time that 2
species have been evolving
independently
Relies on a repeating process to mark
time--Mutations
Molecular Clocks
Mutations occur and accumulate in genes
at a steady rate causing slight changes in
the structure of DNA
Some mutations cause a change in
phenotype while others do not
The one that do affect phenotype are under
pressure form National Selection
The one that do not affect phenotype are
accumulated in DNA at about the same
rate
Molecular Clocks
A comparison of the DNA of 2 species can reveal
how dissimilar the genes are
The degree of dissimilarity is an indication of how
long ago the 2 shared a common ancestor
Molecular Clocks are complex while one gene
may be at one rate, another at a different rate, etc
like hands on clock –second, minute, hour, day,
week, month, year, etc
Researchers would use a different Molecular
Clock to compare modern bid species than they
would to estimate the age of the common ancestor
of yeasts and humans
Kingdoms and Domains
At first, there were only 2 kingdoms:
Plantae and Animalia
As scientist learned more about the natural
world, they realized that more kingdoms
were needed and added
Eubacteria
Archaebacteria
Protista
Fungi
These are the 6 Kingdoms use today
Three Domain System
Using a Molecular Clock based on
ribosomal RNA, scientist have grouped
modern organisms according to how long
they have been evolving independently
The Taxon that they are using for this
broad group is called the Domain
The Domain is more inclusive than any
other category– even larger than the
Kingdom
The 3 Domain
Bacteria
Corresponds to kingdom Eubacteria
Archaea
Corresponds to kingdom Archaebacteria
Eukarya
Corresponds to kingdoms Protista,
Fungi, Palantae, and Animalia
Eukarya
The kingdom Animalia is in this
domain
Members of this kingdom (Animals)
are Multicellular and Heterotrophic
The cells of animals have no cell
walls
Most animals move about for at least
some part of their life
Eubacteria
Have three basic shapes.
round
rod
spiral
Archaebacteria
Archaebacteria are found in extreme
condition.
Some are autotrophic
Photoautotrophs
Chemoautotrophs
Plantae
Multicellular
Photosynthetic
Cell walls contain cellulose
Non-motile
Protista
Mostly single celled
Very diverse group
Some multicellular (Seaweeds)
Eukaryotes
Many are autotrophic
Fungi
Heterotrophic
Have cell wall
Eukaryotes
Very diverse
Animalia
Heterotrophic
Eukaryotic
Motile
Chapter 18 Questions
1. What is taxonomy?
2. Explain Binomial Nomenclature
3. What are the 7 Taxonomic
categories form smallest largest?
4. What is evolutionary classification?
5. What are derived characters?
6. How and why do scientist use
Cladograms?
Chapter 18 Questions
7. How can genes be used in
classification?
8. What is a molecular clock?
9. What are the 6 kingdoms used in
modern classification?
10. What are 3 domains and which
kingdoms do they correspond with?
Chapter 18 Questions
11. What are 4 characteristics of the
domain Bacteria
12. What are 4 characteristics of the
domain Archaea?
13. What are the 4 kingdoms of
Eukarya and what are 2
characteristics of each?