Download Classification:

Classification:
Georgia Performance Standards:
• Compare how structures and functions vary between the six
kingdoms (archaebacteria, eubacteria, protests, fungi,
plants, and animals).
• Examine the evolutionary basis of modern classification
systems
Essential Questions:
1. How does the evidence of evolution contribute to modern classification
systems?
2. Why classify?
3. On what criteria do Taxonomists base their classification of organisms?
4. In what way does scientific discovery lead to the development of a new
classification group?
Why Classify?
• To study the diversity of life, biologists use a
classification system to name organisms and
group them in a logical manner.
• In taxonomy, scientists classify organisms and
assign each organism a universally accepted
name.
• By using a scientific name, biologists can be
certain that everyone is discussing the same
organism.
Early Efforts at Naming Organisms
• The first attempts at standard scientific names
often described the physical characteristics of a
species in great detail.
• Results in long names
• Difficult to standardize the names of organisms
• Different scientists described different
characteristics.
Binomial Nomenclature
• Carolus Linnaeus developed a two-word
naming system called binomial
nomenclature.
• In binomial nomenclature, each species
is assigned a two-part scientific name.
– The scientific name is always written in italics.
– The first word (the genus) is capitalized
– The second word (the species) is lowercased.
Linnaeus's System of Classification
• A group or level of
organization is called
a taxonomic category,
or taxon
• The are 7 taxonomic
categories. (from
smallest to largest)
• species
• genus
• family
• order
• class
• Phylum
• kingdom.
The 7 taxonomic categories
• Species - a group of organisms that breed with one
another and produce fertile offspring.
• Genus - a group of closely related species.
• Family - genera that share many characteristics.
• Order - is a broad taxonomic category composed of
similar families.
• Class - is composed of similar orders.
• Phylum- several different classes that share important
characteristics.
• Kingdom - largest taxonomic group, consisting of closely
related phyla
Checkpoint Questions:
1. How are living things organized for study?
2. Describe the system for naming species that
Linnaeus developed.
3. What are the seven taxonomic categories of
Linnaeus’s classification system?
4. Why do scientists avoid using common names
when discussing organisms?
5. Which category has more biological meaning—
all brown birds or all hawklike birds? Why?
Modern Evolutionary Classification
• Organisms are grouped into categories that
represent lines of evolutionary descent, not just
physical similarities
• This strategy of grouping organisms together
based on their evolutionary history is called
evolutionary classification.
 Modern classification systems are based upon
biochemical and genetic evidence that indicates
evolutionary relationships
Classification Using Cladograms
• Cladistic analysis identifies and considers only the
characteristics that arise as lineages evolve over
time.
– Characteristics that appear in recent parts of a lineage but
not in its older members are called derived characters.
– Derived characters can be used to construct a cladogram,
a diagram that shows the evolutionary relationships among
a group of organisms.
Traditional Classification Versus Cladogram
Section 18-2
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Gastropod
Barnacle
Limpet
Molted
exoskeleton
Segmentation
Tiny free-swimming larva
TRADITIONAL
CLASSIFICATION
Go to
Section:
CLADOGRAM
Modern Evolutionary Classification
• Similarities in DNA and RNA
– The genes of many organisms show
important similarities at the molecular
level that can be used as criteria to help
determine classification.
Modern Evolutionary Classification
• Molecular Clocks
– Comparisons of DNA can • Comparison reveals
more DNA in common,
also be used to mark the
the more recent the
passage of evolutionary
common ancestor
time.
– A model known as a
molecular clock uses
DNA comparisons to
estimate the length of
time that two species
have been evolving
independently.
Checkpoint Questions:
1. How is information about evolutionary relationships
useful in classification?
2. How are genes used to help scientists classify
organisms?
3. What is the principle behind cladistic analysis?
4. Describe the relationship between evolutionary time and
the similarity of genes in two species.
5. How have new discoveries in molecular biology affected
the way in which we classify organisms compared with
the system used by Linnaeus?
Constructing a Chart
Kingdoms and Domains
• The six-kingdom system of classification
includes the following kingdoms:
– Eubacteria
– Archaebacteria
– Protista
– Fungi
– Plantae
– Animalia.
The Three-Domain System
• The domain is the most inclusive taxonomic
category; larger than a kingdom
• The three domains are:
– Bacteria : kingdom Eubacteria
– Archaea,: kingdom Archaebacteria;
– Eukarya :Kingdom protists, fungi, plants, and
animals.
Cladogram of Six Kingdoms and
Three Domains
Section 18-3
DOMAIN
ARCHAEA
DOMAIN
EUKARYA
Kingdoms
DOMAIN
BACTERIA
Go to
Section:
Eubacteria
Archaebacteria
Protista
Plantae
Fungi
Animalia
Key Characteristics of Kingdoms and Domains
Classification of Living Things
DOMAIN
Bacteria
Archaea
KINGDOM
Eubacteria
Archaebacteria
CELL TYPE
Prokaryote
Prokaryote
CELL
Cell walls with
STRUCTURES peptidoglycan
NUMBER OF
CELLS
MODE OF
NUTRITION
Cell walls
without
peptidoglycan
Unicellular
Unicellular
Autotroph or
heterotroph
Autotroph or
heterotroph
Streptococcus, Methanogens,
Escherichia
halophiles
EXAMPLES
coli
Go to
Section:
Eukarya
Protista
Fungi
Plantae
Animalia
Eukaryote
Eukaryote
Eukaryote
Eukaryote
Cell walls of
cellulose in
some; some
have
chloroplasts
Cell walls of
chitin
Cell walls of
cellulose;
chloroplasts
No cell walls
or
chloroplasts
Most
unicellular;
some
colonial;
some
multicellular
Most
multicellular
; some
unicellular
Multicellular
Multicellular
Autotroph
Heterotroph
Autotroph or
heterotroph
Heterotroph
Amoeba,
Paramecium,
slime molds,
giant kelp
Mushrooms
, yeasts
Mosses,
ferns,
flowering
plants
Sponges,
worms,
insects,
fishes,
mammals
Section 18-3
Living
Things
are characterized by
Eukaryotic
cells
and differing
Important
characteristics
which place them in
Cell wall
structures
such as
Domain
Eukarya
Prokaryotic cells
which is subdivided into
which place them in
Domain
Bacteria
Domain
Archaea
which coincides with
which coincides with
Kingdom
Eubacteria
Kingdom
Archaebacteria
Go to
Section:
Kingdom
Plantae
Kingdom
Fungi
Kingdom
Protista
Kingdom
Animalia
Checkpoint Questions:
1.
What are the six kingdoms of life as they are now
identified?
2.
What are the three domains of life?
3. Why was the kingdom Monera divided into two separate
kingdoms?
4. Why might kingdom Protista be thought of as the “odds
and ends” kingdom?
5. Which kingdoms include only prokaryotes? Which
kingdoms include only heterotrophs?