Unit 1
Taxonomy
Protozoa
Early Embryonic Development
Simple Metazoans
 1.
List the hierarchy of taxonomic ranks in
the modern classification system
 2. Compare & contrast concepts of species
identification
 3. Explain how taxonomic characters are
used to infer evolutionary relationships
 4. Define “clade”. Use shared and derived
characters to construct cladograms
 5. Identify characteristics that define the
Animal Kingdom
 Taxonomic
groupings are of human
design, and are organized in a way to
simplify our thinking about living
organisms
 Early taxonomic systems recognized two
Kingdoms, Plant and Animal
 As more varied organisms have been
discovered, many do not neatly fit into
either the Plant or Animal Kingdom
 Fungi
have cell walls and are sessile, but
cannot make their own food
 Many single celled organisms are
capable of photosynthesis, but have well
developed mechanisms for locomotion
 Cyanobacteria (formerly known as
Cyanophyta) are photosynthetic, but lack
organelles and a true nucleus
 Taxonomic
systems expanded from the
early 2 kingdom approach to the
recognition of 5 kingdoms: Monera (the
bacteria), Protista, Fungi, Plantae, and
Animalia
 Improvements in analytical techniques
have uncovered significant differences in
bacteria resulting in the recognition of 2
distinct types, Archaebacteria and
Eubacteria
 Modern
trends in taxonomy emphasize
ancestral relationships over convenience.
The addition of Domain above the Kingdom
level allows grouping of related Kingdoms.
There are 3 recognized Domains:
• Archaea – Includes the Kingdom Archaebacteria
• Eubacteria – The “true Bacteria”
• Eukarya – Eukaryotes:
 Includes Kingdom Protista, Fungi, Plantae and Animalia
 There
are different approaches to the
recognition of species. Each approach
has advantages and disadvantages
• Morphological Species Concept
 Based on body form characteristics
• Biological Species Concept
 Based on the ability to interbreed
• Evolutionary and Phylogenetic Species Concepts
 Based on ancestral/evolutionary relationships
 Based
on the ability to interbreed
 Some closely related species can
interbreed, but their offspring are sterile
(example: lion x tiger = liger)
 http://www.youtube.com/watch?v=CD6v
pheUoPE
 Accurate
interpretations of evolutionary
relationships require a variety of
evidence. The difficulty lies in
determining which similarities are
superficial and which reflect common
ancestry
• “Homology” reflects common ancestry
• “Analogous” traits are evolved independently in
separate lineages
 Modern
taxonomy is moving towards
greater emphasis on common ancestry
 Cladistics is based on identifying an
ancestral characteristic present in a
lineage
 Progressively smaller groupings are
formed as the result of “derived”
characteristics
 A “clade” includes all descendants of a
particular ancestral lineage
Cladogram
#1
moss conifer
fern
Chloro- Angiophyte sperm
multicellular
x
x
x
o
x
photosynthetic
produces
seeds
x
x
x
x
x
o
x
o
o
x
vascular
o
x
x
o
x
flowering
o
o
o
o
x
Cladogram #2 Bacteria Archaea Protozoa Animals
DNA
Plants
Algae
Fungi
x
x
x
x
x
x
x
some
some
o
o
x
x
o
Cell Wall
x
o
o
o
x
x
x
Multicellular
o
o
o
x
x
o
some
Peptidoglycan
x
o
o
o
o
o
o
Nucleus
o
o
x
x
x
x
x
Autotrophic
Osteichthyes
Aves
Mammalia
Reptilia
Amphibia
Urochordata
Chondrichthyes
Cladogram #3
paired limbs
o
o
x
x
x
x
o
feathers
o
o
o
o
o
x
o
amniote egg
o
o
o
x
x
x
o
mammary glands
o
o
o
o
x
o
o
vertebrae
x
o
x
x
x
x
x
notocord
x
x
x
x
x
x
x
bony skeleton
o
o
x
x
x
x
x
 Eukaryotic
 Multicellular
 Heterotrophic
 No
cell wall
 No Chloroplasts
 6.
Compare and contrast protozoans
with animals
 7. Describe means of locomotion
employed by protozoans
 8. Categorize major taxonomic groups
of protozoans
 Animal-like
protists. Unicellular, but:
• Heterotrophic
• Lack cell walls (usually)
• Motile (usually)
 http://www.youtube.com/watch?v=-
zsdYOgTbOk&feature=related
 Cilia
 Relatively
short and
densely
distributed
over the
surface of
the cell
 Flagellae
 Longer
and
less
numerous
than cilia, but
practically
identical in
internal
structure
 Internal
structure consists largely of bundles
of microtubules in a “9+2” arrangement
 9 pairs in a circular arrangement with 2 in the
middle
 http://www.youtube.com/watch?v=QGA
m6hMysTA
 Pseudopodia
 Literally “false
feet”
 Extensions of
the cytoplasm
used not only
for movement
but also for
feeding
 http://www.youtube.com/watch?v=pvOz
4V699gk
 http://www.youtube.com/watch?v=KeQ1
c6_Md1Q
 http://www.youtube.com/watch?v=TOPM
aNvGTvc
 http://www.youtube.com/watch?v=d_Bk
g8euB5Y
 Non-motile
 All
of these
types are
parasitic and
rely on a
“vector” for
movement to
a new host
 Since
motility is a trait generally
associated with Animals, categorizing the
protozoa by their locomotion was a
logical approach:
 Flagellates – use flagellae
 Ciliates – use cilia
 Sarcodines – use pseudopodia
 Sporozoans – are nonmotile
9. Discuss the colonial flagellate hypothesis of
metazoan origin
 10. Identify distinguishing characteristics of the
phylum mesozoa
 11. Identify distinguishing characteristics of the
phylum placozoa
 12. Identify distinguishing characteristics of the
phylum porifera
 13. Discuss the fundamental anatomy of sponges
 14. Relate variations in sponge canal systems to
feeding efficiency
 15. Categorize the classes of sponges

 Metazoans, in
contrast with Protozoans,
are truly multicellular (with some
differentiation of tissues)
 The most “primitive” of the metazoa are
barely more than colonies of cells, but
have some cells specialized for feeding,
or reproduction, or locomotion
2
hypotheses have been advanced as to
the protozoan ancestor to the animals:
• Amoeboid ancestor
• Flagellate ancestor
 Cells
resembling each of these protozoan
forms exist in some form within the
Animal kingdom
 The more accepted hypothesis is the
Flagellate ancestor hypothesis
Cells called “Choanocytes” in
sponges are identical in form and
behavior to Choanoflagellate
protists, which may be free living
or colonial
 Multicellular
organisms differ from
colonial organisms due to the
specialization of cells and the division of
labor that results.
 Groups of cells that are structurally and
functionally specialized are “tissues”
 Tissues that combine together for related
functions are “organs”
 Organs that perform a broad coordinated
function form a “system”
 All
animals share a common pattern of
embryonic development (suggesting a
common ancestry)
 Much of the phylogeny of Kingdom
Animalia can be traced back to variations in
early embryonic development
 Animal phyla generally considered
“primitive” only go through a few stages of
development, while the more “complex”
phyla go through additional stages
 The
zygote divides in two (“cleavage”), then 4,
then 8, forming a raspberry shaped “morula”
 Cleavage continues forming a hollow ball of
cells called a “blastula”
 Note
that there
are 2 different
patterns of
cleavage, Radial
and Spiral
 Spiral cleavage
results in
greater early
differentiation
of cells
 The
blastula caves in
on one end, forming
an inner layer
(endoderm) and an
outer layer
(ectoderm)
 The resulting space
(“Archenteron”) will
form the digestive
cavity
Mesozoa are basically an
elongated Morula – They
never reach the Blastula stage
 Mesozoans are at the
“cellular level” of
organization. No true tissues
exist
 The inner layer of cells are
specialized for reproduction
 All known forms are parasitic

 The
body form of
placozoans is a
flattened Blastula
 Placozoa are also at
the cellular level of
organization
 The “oral” surface is
specialized for
feeding and
locomotion
The name Porifera is
derived from many
pores (ostia) that
allow water to flow
through the channels
in the body wall,
allowing the sponge
to filter feed
 The flow of water is
driven by flagellated
“choanocytes” lining
the channels

ASCONOID
SYCONOID
LEUCONOID
 The
simplest canal system
 Choanocytes line the spongeocoel
 The
pouching
of the
spongeocoel
into radial
canals
increases the
surface area of
contact
between
choanocytes
and water flow
 Incurrent
canals direct water into specialized
chambers lined with choanocytes
 Excurrent canals direct water to the osculum to
be expelled
 Phylum
Porifera is divided into 3 classes
 Class Calcarea
• Calcium carbonate spicules
• All 3 canal system types represented
 Class Hexactinellidae
• 6 rayed, siliceous spicules
• Syconoid or Leuconoid canal systems
 Class Demospongiae
• Siliceous spicules (not 6 rayed), spongin
• Leuconoid canal systems