Unit 13
Classification of Organisms
I. Isn’t everything living thing either a
plant or an animal?
A. Aristotle is credited with the first
true classification system. He
grouped all living things into two
basic groups: plant and animal.
OR
B Linnaeus further classified plants
and animals by dividing them into
related groups. He used the Latin
language, because Latin was not
longer spoken conversationally
and thus was less likely to change.
1. He first grouped related
organisms. He called this a
genus. For example, all of the
dog-like creatures were grouped
as the genus Canis.
2. He next gave every different type of
organism in the group a specific name,
which he called specie. For example,
the dog became
Canis familiaris and the wolf
Canis lupus. Notice the genus is
capitalized but the specie begins with
a lower case letter!
Both are italicized or underlined.
3. Thus, every organism was given a twoLoxosceles reclusa
word name, the genus and specie.
(Brown Recluse) This practice of binomial nomenclature
continues today, giving each organism
a “scientific name”.
4. The benefit of binomial nomenclature
includes eliminating confusion due to
What name
common names (ex. cottonmouth and
do you use
water moccasin are actually the same
for this
animal) and allows scientists around
organism?
the world to more easily communicate.
C. Even after the microbial
world was discovered,
the two “kingdom”
system continued.
(Yes, science can be
very slow to change.)
D. As knowledge of the
diversity of organisms
increased, Whittaker
(in 1969) expanded
classification to include
five kingdoms.
King
Phillip
Came
Over
For
Green
Soup
E. The science of classification,
taxonomy, now allowed scientists to
assign seven levels of taxa to living
organisms:
1. The kingdom is the most general of
these seven taxa, thus the kingdom
would contain the greatest number
of organisms.
2. Specie is the most specific of these
seven taxa, thus the specie would
contain only one type of organism.
A specie is defined as a group of
organisms which can interbreed and
produce fertile offspring.
F. Today, we use three domains, which
are divided into six kingdoms.
These domains are based on new
information about possible
evolutionary relationships.
II. What happens when you find an
organism and you are stymied?
A. Dichotomous keys are tools that use a series
of paired statements and the visible
characteristics of the organism. Of course,
a dichotomous key is only useful if the
organism has already been classified and
given a scientific name.
1. Always start at statement 1 (or the
beginning point)
2. Decide which path best describes the
organism (Statement A or Statement B)
3. Follow that path to find the next choice
(Go to …)
4. When you can go no further, you will find
the name!
B. If the organism has NOT been classified,
taxonomists must begin the process of
classification. In order to correctly classify
an organism, scientists use many modern
tools:
1. Morphology describes the physical
characteristics of an organism. Typically,
this is enough information to place the
organism within a domain and kingdom.
Example: Presence of a nucleus places the
organism in Domain Eukarya
2. DNA and biochemical analysis allow
scientists to test less visible, but
distinguishing, characteristics.
Example: Gram staining a bacteria cell
allows scientists to distinguish between
archaea and prokarya.
Gram-positive anthrax
bacteria (purple rods) in
cerebrospinal fluid
sample. If present, a
gram-negative bacterial
species would appear
pink. (The other cells are
white blood cells)
Gram-negative E. Coli
bacteria.
3. Comparing embryology allows scientists to
group organisms that share common fetal
development.
Example: The diagram below would
suggest the last two organisms are most
closely related.
4. Evolutionary phylogeny describes the
evolutionary relationships between
organisms. These relationships are
deduced based on shared traits that may
have been passed from ancestor to new
species. Traits may include physical traits
(ex. presence of jaws), or may be genetic
traits (shared genes). These relationships
can be illustrated in a phylogenetic tree or
cladogram:
Review Questions
1. Who first officially classified organisms?
Aristotle, then Linnaeus created our current
system
2. What was the contribution of Linneaus to
taxonomy?
He grouped related organisms and created
binomial nomenclature (every organism has
a two word name- genus and species)
3. What are the two parts of a scientific name?
Genus and species
4. What are the domains used in the current
classification system?
Prokarya, Archae, Eukarya
Review Questions
5. How many kingdoms are used in the
current classification system?
Six
6. What is a dichotomous key?
A key that uses paired statements and
visible characteristics to identify a known
organism.
7. What 4 modern tools are used to classify a
newly discovered organism?
Morphology, biochemical similarities,
embryology, and phylogeny (evolutionary
relationships)
III. Why am I not a fungus?
A. Kingdom Bacteria
1. Cellular Structure: Prokaryotic with
cell wall, unicellular
2. Metabolism:
a. Food getting: Very diverse –
some are photosynthetic, some are
chemosynthetic and some are
heterotrophic, taking in food by
active transport.
b. Cellular energy: Some are
aerobic for the production of ATP,
some are anaerobic.
WARNING-Mostly
X-Rated
Imagethrough
of
3. Reproduction:
asexual
Bacteria
Sexually
Reproducing
binary
fission;
may exchange
DNA using a
process called conjugation.
4. Ecological/Economic Importance: Bacteria
are important to the environment because
they drive the nitrogen cycle and are
decomposers. Bacteria can be beneficial to
humans (ex. useful in making foods such as
yogurt) or harmful (ex. some may cause
disease such as syphilis)
B. Kingdom Archaea (Extreme bacteria!)
1. Cellular Structure: Prokaryotic with cell
wall, unicellular (different chemicals in cell
wall than Kingdom Bacteria)
2. Metabolism:
a.Food getting: Very diverse – some are
photosynthetic, some are
chemosynthetic and some are
heterotrophic, taking in food by active
transport.
Aerobic =
b. Cellular energy: Some are aerobic for
Oxygen used
the production of ATP, some are
Anaerobic =
anaerobic.
No oxygen
used
3. Reproduction: Mostly asexual through
binary fission; may exchange DNA using a
process called conjugation.
4. Distinguishing habitats: They are all
classified as “extremophiles” – they live in
extreme environments such as thermal
vents, swamps, guts of animals, and areas
of high salinity.
C. Kingdom Protista
1. Cellular Structure: Eukaryotic (some with
cell wall and some without), some are
unicellular (amoeba) and some are
multicellular (seaweed)
2. Metabolism:
a. Food getting: Very diverse – some are
photosynthetic (plant-like), and some are
heterotrophic (animal-like), taking in food
by active transport.
b. Cellular energy: All utilize aerobic
respiration for the production of ATP.
3. Reproduction: Asexual through binary
fission (in animal-like protists) and
fragmentation (in plant-like protists). Some
may exchange DNA though conjugation
(sexual).
4. Ecological/Economic Importance:
a. Plant-like protists (commonly called algae)
are the primary producers of oxygen used
for cellular respiration. They are also the
producers that form the base of all aquatic
food webs.
b. Animal-like protists (commonly called
protozoans) are important primary
consumers in aquatic food webs. Many
protozoans also cause diseases such as
malaria.
c. A specialized group of protists called slime
molds are important decomposers.
D. Kingdom Plantae
1. Cellular Structure: Eukaryotic with cell
wall, all multicellular
2. Metabolism:
a. Food getting: All are photosynthetic
(autotrophic).
b. Cellular energy: All utilize aerobic
respiration for the production of ATP.
3. Reproduction: All reproduce sexually
(using sperm and egg or spores); may
Each one of these buds can develop into a new plant
reproduce asexually (using vegetative
next year. In fact a whole row of potato plants can be
propagation
or good
spores)
started
from just one
tuber.
4. Ecological/Economic Importance: Plants are
exponentially more complex as compared
to algae, but perform many of the same
ecological roles (oxygen production, base of
food web). Plants are also used for
numerous products such as clothing
(cotton), paper, medicine (aspirin), and
lumber.
E. Kingdom Fungi
1. Cellular Structure: Eukaryotic with cell
wall, mostly multicellular (mushroom) with
some unicellular (yeast)
2. Metabolism:
a. Food getting: Heterotrophic with
extracellular digestion (fungi secrete
digestive enzymes and absorb nutrients
across the cell wall)
b. Cellular energy: Some utilize aerobic
Bird’s respiration
Nest Fungifor the production of ATP
(mushrooms), some are anaerobic
(yeast).
3. Reproduction: May be asexual (budding in
yeast and spore production in other fungi),
or sexual (spores).
4. Ecological/Economic Importance: Fungi are
important decomposers. Fungi can be
beneficial to humans (ex. used to make
food and alcohol), or harmful (cause
diseases such as ring worm and athletes
foot)
F. Kingdom Animalia
1. Cellular Structure: Eukaryotic with no
cell wall, all are multicellular
2. Metabolism:
a. Food getting: All are heterotrophic
and have diverse methods for acquiring
food.
b. Cellular energy: All utilize aerobic
respiration for the production of ATP but
some specialized cells can convert to
anaerobic respiration when oxygen is
scarce
3. Reproduction: All animals reproduce
sexually (egg and sperm), but some simple
animals may also reproduce asexually
(fragmentation in sponges, regeneration in
worms)
4. Ecological/Economic Importance: Animals
are important consumers in food webs.
Animals may be beneficial to humans (ex.
foods) or harmful (ex. worms may cause
disease)
Review Questions:
1. Which 2 kingdoms contain bacteria?
Archaebacteria and Eubactera
2. Which 2 kingdoms are prokaryotic?
Kingdom Bacteria and Kingdom Archae
3. The organisms of which kingdom do not have cell walls?
Kingdom animalia
4. Name the kingdoms that contain important
decomposers.
Bacteria and Fungi
5. Name the kingdoms that contain producers.
Plantae and Protista
6. Why are you not a fungus?
I am not a decomposer, do not get my food through
extracellular digestion, and do not reproduce asexually!