Classification
"The incredible diversity of life on this
planet, most of which is microbial, can
only be understood in an evolutionary
framework" -- Carl Woese, 2000
What is Taxonomy?

How do we keep track of the some 1.7 million
species of living organisms have been
discovered?
Taxonomy is the science
dealing with the description,
identification, naming,
and classification of
organisms

Carolus Linnaeus
The classification
system used today
was developed
Swedish botanist
Linnaeus in the
1700s.
 Linnaeus used
structural similarities
as the basis of his
classification system.

Binomial Nomenclature



In order to identify organisms by a universal
name, Linnaeus devising a two name system in
which an organism is identified by its genus and
species.
For example, Homo sapiens is the scientific name
for man. The genus is capitalized and the species,
sapiens, is lower case.
The scientific name of an
organism is always italicized
or underlined.
Five Kingdom
Classification System
The five kingdoms,
from simplest to most
complex are:
--Monera (bacteria)
--Protista
--Fungi
--Plantae
--Animalia

Criteria for Classification
Kingdom Classification:
 Does the organism
have an organized
nucleus?
 Is the organism
unicellular or
multicellular?
 How does the
organism obtain its
food (autotroph or
heterotroph)?
Further Classification:
 Common ancestry
 Homologous
structures
 Comparative
biochemistry
 Fossil record
 Comparative
embryology
Terminology
Prokaryote
--does not have an organized nucleus
--genetic material is dispersed in the cytoplasm
--lacks most other organelles
 Eukaryote
--has a membrane bound nucleus
--has membrane bound organelles

New Discoveries




In the 1970s, scientists began to find evidence of an
unknown group of microbes that existed in extreme
environments.
These organisms were found in deep sea
hydrothermal vents, hot springs, acid lakes, and very
salty environments.
Because these microbes were thought to be
prokaryotic, they were called archaebacteria (ancient
bacteria)
Using DNA analysis and other biochemical
characteristics that these bacteria were more closely
related to eukaryotes than to modern bacteria and are
now officially called Archaea.
The Three Domains
By the 1990s, scientists
recognized that there were three
distinctly different lineages that
accurately describe the
relationships among living
organisms.

The super kingdoms or
domains include the Archaens,
the Protist, Fungi, Plant, and
Animal kingdoms, and divide
the Moneran kingdom between
the Archaens and Bacteria
domains.

Archaea



Methanogens: chemosynthetic
(make their own food using
inorganic molecules) releasing
methane gas. Live in swamps,
marshes, guts of cattle and
termites.
Halophiles: live in very salty
environments such as the Dead
Sea, the Great Salt lake or salt
evaporation ponds.
Thermophiles: live in hot sulfur
springs, deep sea hydrothermal
vents, in ocean waters around
Antarctica, and under the polar ice
caps.
Characteristics of Prokaryotes
Archaea
 No nucleus
 Ability to live in
extreme environments
 Cell wall and cell
membrane
 DNA in ringlike
structure in cytoplasm
 DNA/RNA more
similar to eukaryotes
 Few organelles
Bacteria
 No nucleus
 DNA loop in
cytoplasm
 Cell wall and cell
membrane
 Few organelles
 Have flagella for
locomotion
Eukarya
Includes Protists, Fungi, Plants, and
Animals
 membrane bound nucleus
 Organelles to carry on life functions
 DNA packaged into chromosomes found in
nucleus
 Depending on the kingdom, can be
unicellular, multicellular, heterotrophic, or
autotrophic.

Bacteria


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Includes simple bacteria and
blue-green algae.
Some bacteria are
chemosynthetic (make their own
food with inorganic molecules);
others heterotrophic
Bacteria
classified
by shape.
Examples of Bacteria
Samonella
E.coli
Streptococcus
Blue-Green Algae




Although called algae, they are actually a type of
bacteria known as cynobacteria.
They are found in rivers, lakes, damp soil, tree
trunks, hot springs, and snow.
Similar to algae, they are autotrophic and have
chlorophyll.
They exist as individual cells, in colonies, or in
filaments.
Protists

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Phyla include Algae, Protozoa, and Euglena
Algae are photosynthetic, have cell walls, and
chloroplasts
Kelp
Spirogyra
Protists: Protozoa & Euglena

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Protozoa are heterotrophic and are classified by
method of locomotion.
Euglena contain chlorophyll and are photosynthetic
Ameba: pseudopods
Euglena: flagellum
Paramecia: cilia
Fungi
Multicellular except
for yeast (unicellular)
 Heterotrophic
 Extracellular
digestion

Athlete’s Foot
Bread
Mold
Plants
Bryophytes: no vascular
tissue (no true roots,
leaves or stems
-- mosses, liverworts
 Tracheophytes: vascular
tissue (xylem and
phloem)
--ferns, conifers,
flowering plants

Moss
Ferns
Conifers & Flowering Plants
Animals
Evolutionary Relationships
Trends in Body Development
 As you move from simple organisms such as sponges
to more complex organisms, such as chordates we see
changes in:
Body organization (cells organized into tissues,
organs and organ systems)
Number of germ (embryonic) layers (tissues from
which more specialized tissues develop)
Body symmetry
A complete or incomplete digestive tract
Development (or not) of an internal cavity called a
coelom
Germ Layers
 Germ layers are the main
layers that form during
embryonic development.
 Once the sperm and egg
meet a fertilized egg,
known as a zygote is
formed.
 The zygote immediately
begins to divide through
a process called cleavage
eventually forming a solid
ball of cells called the
morula.
Germ Layers (cont’d)
 The morula hollows out to form a single layer ball of
cells called the blastula.
 The blastula indents (pushes inward) to form the
gastrula through the process of gastrulation.
 In simpler (dibobastic) animals, there are only 2 layers
formed – endoderm (inner layer) and the ectoderm
(outer layer)
 In more complex (triboblastic) organisms, 3 layers are
formed – endoderm (inner layer), mesoderm (middle
layer) and the ectoderm (outer layer)
Germ Layer Development
Body Symmetry

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In general simple animals exhibit radial symmetry
where body parts are arranged around a central axis.
Such a body arrangement allows the animal to
interact with its environments from all directions.
More complex animals exhibit bilateral symmetry
where the body is
organized along
a longitudinal
axis and the left
and right sides
are mirror
images.
Terms Associated with Bilateral
Symmetry
Dorsal: top or back of organism
 Ventral: belly or underside of organism
 Anterior: front portion of organism
 Posterior: rear portion of organism

Cephalization
Along with bilateral symmetry comes
cephalization or development of a head end
(anterior) and a rear end (posterior).
 Sensory cells, a brain or in simpler animals,
ganglia (bunch of nerve cells) are clustered at
the anterior end.
 Digestive, excretory, and reproductive
structures are located toward the posterior end.
 This allows animals to move faster to either
capture prey successfully or flee from predators.
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Coelom
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Coelom: a fluid-filled body cavity that is completely
surrounded by a middle layer of tissue called
mesoderm. The coelom is important in the
development of advanced animals because it provides
a space for complex organ systems to develop.
acoelomates: primitive animals such as flatworms do
not have a coelom
pseudocoelomates: animals such as nematodes and
roundworms have a fluid filled tube that is not
completely lined by the mesoderm.
coelomates: most complex animals – includes
annelids, mollusks, arthropods, and chordates.
Types of Coeloms
Animal Phyla

Porifera: filter
feeders (sponges)

Coelenterates:
hollow body cavity
with one opening
(hydra, jellyfish)
Hydra
Animal Phyla

Annelids: worms with segmented bodies, openings
at both ends, tube within tube body structure
(earthworms, leeches, sandworms)

Arthropods: segmented body, jointed appendages,
exoskeleton (grasshopper, lobster, spider)
Animal Phyla
Tree Frog

Vertebrates: animals with
true backbones
(fish, frogs, snakes, and
humans)
Parrot
Fish
Anaconda
Mammals
Warmblooded, have
hair, produce milk
 Monotremes:
--have common duct
(cloaca) for urination,
defecation, and
reproductive processes
--lay eggs, mothers do
retain eggs inside
bodies for some time
and provide eggs with
nutrients

Duckbill Platypus
Marsupials

Offspring born in an
immature state and
must make their way
into the mother’s
pouch on the ventral
side of body where
development will be
completed with
nourishment from the
mother’s milk.
Placental Mammals
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Offspring develop
inside female uterus,
nourished by the
placenta, an organ
made of maternal and
fetal tissue.
Offspring are born
when they are fully
developed
Infants have the most
parental care of any
living organisms.