Transcript 17.1 The Linnaean System of Classification

17.1 The Linnaean System of Classification
KEY CONCEPT
Organisms can be classified based on physical
similarities.
How would you
classify this
animal?
This is a pangolin.
Pangolins are native to
Africa and Asia. They
can be found under the
Kingdom Mammalia.
Although they do not
have fur, they do
produce milk for young.
17.1 The Linnaean System of Classification
Why classify?
• Common names can be confusing:
Mud puppy
Firefly
Horned toad
Sea monkey
ringworm
Black bear
jellyfish
Sea horse
Spider monkey
crayfish
17.1 The Linnaean System of Classification
Why Classify continued….
• Only about 1.5 million
species have been named
on Earth
• 2-100 million species are
yet to be named on Earth.
17.1 The Linnaean System of Classification
Taxonomy is the science of naming and classifying
organisms.
• Taxonomy began with the ancient Greeks and Romans
– Aristotle classified organisms into two groups: plants
and animals.
• John Ray (1627–1705)
– Believed that each organism should have a set name.
– Otherwise, “men…cannot see and record accurately.”
• Gives scientists a standard way to refer to species and
organize the diversity of living things.
• Linnaean taxonomy classifies organisms based on their
physical and structural similarities.
• Organisms are placed into different levels in a hierarchy—
a multilevel scale in which each level is “nested” (included)
in the next-higher level.
17.1 The Linnaean System of Classification
Linnaeus developed the scientific naming system still
used today.
White oak:
Quercus alba
• A taxon is a group of organisms in a classification system.
(Plural = taxa)
• Under taxon system, species are most commonly defined
as a group of organisms that can breed and produce
offspring that can reproduce.
• Linnaeus’ system gives each species a scientific name.
17.1 The Linnaean System of Classification
• Binomial nomenclature is a two-part scientific naming
system that gives each species a two-part scientific name
– uses Latin words
– scientific names always written in italics
– two parts are the genus name and species descriptor
17.1 The Linnaean System of Classification
• 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.
– can be in italics or underlined, but
always lowercase
– always follows genus name; never
written alone (same word can be used
in other genera: alba means white and
is used in naming the white oak tree)
Tyto alba
– It can refer to a trait of the species
(white)
17.1 The Linnaean System of Classification
• Scientific names help scientists to communicate world-wide.
– Some species have very similar common names.
– Some species have many common names.
17.1 The Linnaean System of Classification
Linnaeus’ classification system has seven levels (taxa).
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Each level is “nested” or
included in the level
above it.
From the most general to
the most specific, these
levels are kingdom,
phylum (the term division
is often used instead of
phylum for plants and
fungi), class, order,
family, genus, and
species.
A kingdom contains one
or more phyla, a phylum
contains one or more
classes, and so forth.
The classification of the
gray wolf, Canis lupis, is
shown in FIGURE 17.3.
Moving down, the levels
represent taxa that
become more and more
specific, until you reach
the species level at the
bottom.
17.1 The Linnaean System of Classification
Getting familiar with the system
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What animals are dropped
as we move from kingdom
to phylum?
Invertebrates
What well-known
Australian animal is
excluded from the
Carnivora order, which
includes all true bears?
Koala bear
How can this be?
Sharing a common name
or having a similar name
means very little in terms
of actualrelatedness. An
animal called a bear may
not be a true bear.
From what you can infer
from the figure, what are
characteristics of animals
in the order Carnivora?
terrestrial, toothed, fourlegged, meat-eating
mammals
17.1 The Linnaean System of Classification
• Members of a Species
17.1 The Linnaean System of Classification
The Linnaean classification system has limitations.
• Linnaeus taxonomy doesn’t account for molecular
evidence.
– The technology didn’t exist during Linneaus’ time.
– Linnaean system based only on physical similarities.
– DNA and RNA is similar across all life forms
– Genes of many organisms show important similarities
at the molecular level
17.1 The Linnaean System of Classification
Apply what we just learned!
• If two species belong to the same order, what other
levels in the Linnaean system must they have in
common?
• class, phylum, kingdom
17.1 The Linnaean System of Classification
• Physical similarities are not always
the result of close relationships.
• The giant panda and the raccoon
have similar ears and snouts.
• Because of these similarities, they
have been placed in the same
family in the Linnaean system.
• Molecular biologists have found
that the giant panda is more
closely related to members of the
bear family than it is to raccoons.
• The red panda, shown in FIGURE
17.4, is more closely related to the
raccoon than to the giant panda.
• He’s cute, huh???? 
17.1 The Linnaean System of Classification
What do you think?
• What do you think bats are more closely related to?
• Birds or rodents and primates?
17.1 The Linnaean System of Classification
Dichotomous Keys
• A written set of choices that leads to the name of an
organism
• Scientists use them to identify unknown organisms
17.1 The Linnaean System of Classification
Consider the following animals, Biologous Piglitus. They
are all related, but each is a separate species. Use the
dichotomous key below to determine the species of
each.
1
Has aqua colored body ......go to 2
.
Has blue colored body ..... go to 4
2
Has 4 legs .....go to 3
.
Has 8 legs .......... Deerus octagis
3
Has a tail ........ Deerus pestis
.
Does not have a tail ..... Deerus magnus
4
Has a pointy hump ...... Deerus humpis
.
Does not have a pointy hump.....go to 5
5
Has ears .........Deerus purplinis
.
Does not have ears ......Deerus deafus
17.1 The Linnaean System of Classification
Exploring the Kingdoms
• Have you ever swum in a pond? Every drop of pond
water is teeming with single-celled organisms.
• At one time, scientists classified these organisms as
either plants or animals. Who said that?
• Classification schemes change. Single-celled eukaryotes
such as these pond dwellers now have a kingdom of their
own.
17.1 The Linnaean System of Classification
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,
Plantae
Animalia and Plantae
Animalia
17.1 The Linnaean System of Classification
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,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
17.1 The Linnaean System of Classification
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,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
Monera
17.1 The Linnaean System of Classification
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,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
– 1959: fungi moved to
own kingdom
Monera
Fungi
17.1 The Linnaean System of Classification
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,
Plantae
Animalia and Plantae
Animalia
– 1866: all single-celled
Protista
organisms moved to
kingdom Protista
– 1938: prokaryotes moved
to kingdom Monera
– 1959: fungi moved to
own kingdom
Archea
Fungi
Bacteria
– 1977: kingdom Monera
split into kingdoms Bacteria and Archaea
17.1 The Linnaean System of Classification
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
17.1 The Linnaean System of Classification
17.1 The Linnaean System of Classification
17.1 The Linnaean System of Classification
Activity: Draw the Domains with Kingdoms
17.1 The Linnaean System of Classification
Welcome Back!
Today in Biology we will
Continue Classification
notes!
Georgia Aquarium
“Creature
Presentations” for thirty
minutes.
17.1 The Linnaean System of Classification
Words to Know!
• Producer – organism that gets it’s energy from nonliving
organisms (Example: plants making their own food from
the energy provided by solar energy).
• Producers are also called autotrophs. Auto means self
(Greek); troph means nourishment.
• Consumer – organism that gets it’s energy by eating
(consuming) other living things or things that were once
living (plants and animals).
• Consumers are also called heterotrophs. Hetero means
what? Troph means what?
17.1 The Linnaean System of Classification
A look into the Three Domains and Six Kingdoms!
Domain Archaea
• includes Kingdom Archaebacteria (also
called Kingdom Archae – depends on the
textbook)
• contains single-celled (unicellular) prokaryotes
• cell walls are diverse but chemically different
from bacteria
• produce asexually
• differences discovered by studying RNA
• known for living in extreme environments
(methanogens in anaerobic swamps,
helophiles in salt lakes, thermacidophiles in
hot acidic environments)
• These guys to the right live without oxygen in
undersea hot vents or in sand around
volcanoes. They are called Pyrococcus
furiosus and grow in temps higher than boiling
17.1 The Linnaean System of Classification
Domain Eukarya
• Domain Eukarya includes all eukaryotes.
• Contains both unicellular and
multicellular organisms
• Cells with a membrane-bound
nucleus
• Sexual reproduction common
• Contains four kingdoms
1. Kingdom Protista
This is a Zooflagellate.
Why the name?
Did you know that there are
over 2000 species of
Zooflagellates?
Go tell a friend!
17.1 The Linnaean System of Classification
• Domain Eukarya includes all eukaryotes.
2. Kingdom Plantae
17.1 The Linnaean System of Classification
• Domain Eukarya includes all eukaryotes.
3. Kingdom Fungi
17.1 The Linnaean System of Classification
• Domain Eukarya includes all eukaryotes.
4. Kingdom Animalia
17.1 The Linnaean System of Classification
Domain Bacteria
• Includes Kingdom
Bacteria
• includes single-celled
prokaryotes
• One of the largest
groups of organisms
on Earth
• Beneficial or harmful
• There are more
bacteria in your mouth
right now than have
ever lived on Earth.
Really!
• Classified by many
traits: shape, need for
oxygen, disease
causing
Guess where these guys live?
17.1 The Linnaean System of Classification
Humans ARE the environment!
• Huh?
• Yes, not only do we share the environment, we ARE
home sweet home to many prokaryotes.
• Say ahhhhhhhhhhhh and hello to 500 types of
prokaryotes of which 25 types can be living in your mouth
right now!
• One milliliter of your saliva (spit) can have up to 40
million bacterial cells.
17.1 The Linnaean System of Classification
DOMAINS Bacteria and Archae
Bacteria and archaea are both single-celled prokaryotes.
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Prokaryotes are most abundant and
widespread organisms on Earth.
Prokaryotes can be grouped by their
need for oxygen.
– obligate anaerobes
are poisoned by
oxygen (can’t live with it)
Example: archae that produce
methane gas (live in intestines
in cows)
– obligate aerobes need oxygen
(can’t live without it)
Example: pathogens that cause
tubercolosis and leprosy.
– facultative aerobes can live with or
without oxygen
These are beneficial intestinal
bacteria. (Mutualism)
17.1 The Linnaean System of Classification
Bacteria and archaea are structurally similar but have
different molecular characteristics.
• Bacteria commonly come in three forms.
– rod-shaped, called bacilli
– spiral, called spirilla or spirochetes
– spherical, called cocci
Lactobacilli: rod-shaped
Spirochaeta: spiral
• Archaea have many shapes.
Enterococci: spherical
17.1 The Linnaean System of Classification
• Bacteria and archaea have similar structures.
– plasmid (small piece of genetic material that can replicate
separately)
– flagellum (used for movement)
– pili (help them stick to other surfaces)
pili
plasma
membrance
chromosome
cell wall
plasmid
This diagram shows the typical structure
of a prokaryote. Archaea and bacteria
look very similar, although they have
important molecular differences.
flagellum
17.1 The Linnaean System of Classification
• Bacteria and archaea have molecular differences.
– Bacteria have a polymer called peptidoglycan in their
cell walls; archae do not. Peptidoglycan is an important
defining characteristic for Bacteria.
– The amount of peptidoglycan within the cell wall can
differ between bacteria
– Archae have lipids (fats) in their membranes that no
other organism on Earth has.
GRAM NEGATIVE
GRAM POSITIVE
17.1 The Linnaean System of Classification
• Gram staining identifies bacteria into two types.
» Gram stain stains the polymer peptidoglycan in bacteria
» Used to diagnose infectious bacterial diseases
– gram-positive stains purple, more peptidoglycan
– gram-negative stains pink, less peptidoglycan
Gram-negative bacteria have a thin layer of
peptidoglycan and stain red.
Gram-positive bacteria have a thicker
peptidoglycan layer and stain purple.