Protozoa I
Protozoans
Over 50,000 known species
45 phyla (more than
metazoa!)
Relationship to Other Organisms

Two Kingdoms – Arististotle, Linnaeus
Relationship to Other Organisms

 Plants
 Plants
Metaphyta
 Protophyta
 Animals

 Protists
 Animals
Metazoa
 Protozoa



Lots of problems with this scheme
3 kingdoms of Haeckle/Darwin

Took care of the little stuff seen with the early
microscopes
Still has problems
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Relationship to Other Organisms

Copeland’s Four-Kingdom System (1938)
 Kingdom
 Kingdom
Monera.
Protoctista or Protista (priority?).
Protozoa
Red and brown algae
 Fungi


 Kingdom
Plantae
Green algae
 Fungi

 Kingdom
Animalia
Relationship to Other Organisms

Whittaker – 1960’s
 Added

Kingdom Fungi
5 Kingdoms
 Kingdom
Animalia
Plantae
Eukaryotes
 Kingdom Fungi
 Kingdom Protista
 Kingdom Monera - Prokaryotes
 Kingdom
Kingdoms and Domains

Carl Woese - U. of
Illinois (1970’s-present)
 Studied
gene sequences
of bacteria, archaea, and
eukaryotes
 Found
fundamental
differences (major!)
Relationship to Other Organisms

Carl Woese – late 1970’s
 Archaea
NOT Archaebacteria
Biochemistry is different from bacteria
 More closely related to animals than they are to
bacteria
 Briefly had six kingdoms with Archaea and Eubacteria
replacing the Monera
 Changed to three domains
 Eubacteria
Prokaryotes
 Archaea
 Eukarya

2
6 Kingdoms of Life
3 Domains of Life
Figure 1: All organisms are connected by
the passage of genes along the branches of
the phylogenetic Tree of Life.
Relationship to Other Organisms

Protista or Protoctista
 Some
algae (red, most green algae are not included)
 Protozoa
Traditionally classified based on how they move:
amoebae, flagellates, ciliates, sporozoans
 Has changed recently to also contain:
 Some slime molds
 Aquatic “molds”

Figure 2: Living organisms sit like leaves
at the tips of the branches of the Tree of
Life. Their evolutionary history is
represented by a series of ancestors which
are shared hierarchically by different
subsets of the organisms that are alive
today.
Old system classified by
locomotion

Ciliophora (=Ciliata, ciliates) a clade
Hypotrichs, holotrichs, heterotrichs, suctorians

Apicomplexa- (=Sporozoa) a likely clade
Gregarina, Coccidia – includes many important parasites

Mastigophora (=flagellates) a functional group
Excavates, Kinetoplastids, Parabasalids,
Choanoflagellates, Dinoflagellates (some are important
parasites)

Protozoan Phylogeny

Problem
 Protozoa
is a polyphyletic group
 Multiple
ancestors rather than a single
ancestral protozoan
 Aim
is to establish monophyletic groups that
have a single ancestor
Sarcodina (=amoebas) a functional group Amoebozoa,
Foraminifera, Actinopoda (Radiolaria, Heliozoa)
(many are important geologically)
3
Protozoan Phylogeny

Reclassification based on
History
 Ultrastructure
 Biochemistry
 Molecular data including DNA sequencing
 Most trees are being constructed based on
molecular data
 May or may not be the “best” way to go
 Dissenting camps: role of lateral gene transfer,
choice of genes for sequencing, convergent
evolution, etc.
Relationship to Other Organisms

 Life
Eukaryote classification is in flux

The major clades are not yet sorted out –
but there is rapid progress

Based on cell structural features, there are
about 60 different named eukaryote taxa
according to Patterson (Tree of Life)

These have been sorted into 8 clades based
on molecular & structural data by Baldauf
2003 (Science 300:1703)
Protista – still used as teaching tool.
 Grades
7-12?
intro bio (with reservations)
 Undergrad

We will not discuss Protists!
 Instead,
note the following schemes:
First - breakdown of what used to be protists.
 Second - taxonomic groupings of organisms
covered in Ch 3 (pg 71ff).
 Focus on those covered in text and/or lab

Kingdom Chromista

The Alveolata
 Flattened
membranous
alveoli (sacs) under outer
cell membrane
The Alveolates

Phylum Ciliophora

Phylum Dinozoa (Dinoflagellata)

Phylum Apicomplexa
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The Rhizaria



Very diverse group based on molecular data
Tubular cristae
3 Phyla
The Heterokonta

 Heliozoans?
– probably polyphyletic
Opalinata
 Flagellated parasites of intestines of ectothermic
vertebrates
 Class
 Phylum
Foraminifera
Radiolaria
 Phylum Cercozoa
 Phylum
Kingdom Protozoa

The Amoebozoa
 Branching,
tubular cristae
 Lobose pseudopodia


Arcellanids
Xenophyophoreans
The Excavata



 Class
Mastigamoididae
 Phylum Eumycetozoa

Class Euglenida
 Order
Kinetoplastea
Disc-shaped mitochondrial cristae
Deep ventral feeding groove (hence excavate)
Phylum Parabasala – no mitochondria
 Class
 Phylum
Phylum Euglenozoa
Phylum Stramenophiles
Trichomonadida
Hypermatigia
Phylum Heterolobsea


The diplomonads – no mitochondria
The oxymonads
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The Opisthokonta





Phylum Choanomonada
Phylum Fungi
Phylum Microsporidia
The Myxozoans – probably degenerate
cnidarians
Phylum(?) Animalia
Defining Characteristics of
“Protozoa”


1674 Antonie van Leeuwenhoeke
Nearly ubiquitous –wherever there is water
 Soil
 Water
 On/in

plants and animals
Life styles
 Free-living
 Symbioses


Mutualists
Parasites
Antonie van Leeuwenhoeke
Things that animals do (and
protozoa too)







Move (at some stage in the life cycle)
Obtain food and digest it
Obtain oxygen
Maintain water and salt balance
Remove metabolic wastes
Reproduce
Sense and react to the environment
Defining Characteristics of
“Protozoa”

Haeckel coined the termed Protista
 Protist
was anything that wasn’t clearly plant or
animal
 Now it’s anything that isn’t plant, animal, fungi or
bacteria

Most are probably unknown
 Over
84,000 species
of these are fossils (shelled forms)
 No formal taxonomic category called Protista
½
6
Defining Characteristics of
“Protozoa”

General characteristics highly variable
 Size,
morphology, ultrastructure
 Nutritional mode, physiology
 Behavior, life history

Defining Characteristics
of “Protozoa”

 Disease
 Model
Ecology
Genetics
 Physiology
 Development

 Ancestral
to multicellular animals and plants
(polyphyletic): ex. Choanoflagellates and sponges
 Mutualists in other inverts: ex. dinoflag. in corals
 Disease agents: ex. Plasmodium in malaria


Eukaryotic
Unicellular
 Mostly
small 5-250 μm (0.5 μm – 7 mm)
in a few but this is a derived
character
 Multicellularity


No collagen or chitin in cell walls
Heterotrophic
 Ancestral
state is non-photosynthetic
 Photosynthesis in a few groups is a derived character

Most are motile (except Apicomplexa)
agents
organisms

Importance
Defining Characteristics of
“Protozoa”
Importance
Protist Bauplan - On Being
Unicellular

Strategies and constraints of a
Unicellular Bauplan
 Size
limitations
 Body
structure
 Excretion
 Gas
exchange
 Support
and locomotion
 Nutrition
 Reproduction
 Activity
and sensitivity
On Being Unicellular


Protozoa vs metazoa
Protozoa are unicellular
 Thought
 BUT

to be simplest form of life
Urotricha globosa
Cothurnia annulata
Pseudodifflugia sp.
…
Protozoa are not simple!
A
protozoan is more complex than any single
metazoan cell
 Very complex internal structure
 Specialized organelles take the place of organs in
metazoans
Halteria grandinella
Ctedoctema acanthocryptum Vorticella aquadulcis
7
Stylonychia
Defining Characteristics of
“Protozoa”

Similarity of structures does NOT imply
relatedness

Various types of evidence are used in testing
hypotheses regarding evolutionary relatedness
 Could
 Gene
be convergent evolution
sequencing
ultratructure
 Cellular
Size limitations

Surface area to volume ratio
 SA
V
increases as radius squared
increases as radius cubed
 As
cell becomes larger, diffusion
becomes more and more difficult
(~1 mm limit)
 Need
to have lots of complex
projections etc. to increase SA
 Need
large SA/V
8
Body Structure

Cytoplasm has two regions
 Ectoplasm


Next to cell membrane
Clear, stiff, gelatinous
 Endoplasm



Inner portion
More fluid in nature
http://www.youtube.com/watch?v=85DGyFzxvy8
&feature=player_detailpage
Body Structure

Membrane has fluid mosaic
structure
Only one plasma membrane
 Everything
is inside that membrane
is identical to the plasma
membrane of all other multicellular
organisms
 High SA/V for protist cells
 Structure

Membrane has fluid mosaic structure
 Lipids
and proteins can move about laterally
within the membrane
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10
Body Structure

Internal structures
 Cytoskeleton


Cytoskeleton
Myonemes
Shape
Rigidity
Cytopharynx
Cytopharynx
Macronucleus
250 µm
Cirri
Body Structure

Outer coverings - give
shape/support/protection
 Pellicle
Interlocking strips of
protein below plasma
membrane in Euglenids
 Gives cell shape and
stability while permitting
flexibility

Eugloid movement = metaboly
11
Body Structure
 Lorica

Vase-shaped
protective shell
Body Structure
 Test

External “shell”

Usually many parts

Plates are below
plasma membrane
(cellulose plates in
dinoflagellates,
various materials in
testate amoebas)

CaCO3 foraminiferans

Silica in radiolarians
Body Structure

The usual eukaryotic organelles
 May be more than one macronucleus
 Runs everyday activities of cell
 May be one or more micronuclei
 Used for sexual reproduction
 Some




are anaerobes
Most have no mitochondria or cytochromes, and have
an incomplete TCA cycle (tricarboxylic acid cycle)
Some contain hydrogenosomes-small membranedelimited organelles containing a unique electron
transfer system that uses protons as terminal electron
acceptors to form molecular hydrogen
Trichonympha lives in the gut of termites
Giardia is an intestinal parasite
Mitochondria clockwise
Paramecium
Cryptomonad
Euglena
12
Body Structure




Some protozoa are anaerobes.
 Trichonympha lives in the gut of termites
 Giardia is an intestinal parasite
Most have no mitochondria or cytochromes, and have an
incomplete TCA cycle (tricarboxylic acid cycle).
Some contain hydrogenosomes-small membranedelimited organelles containing a unique electron
transfer system that uses protons as terminal electron
acceptors to form molecular hydrogen.
Some have symbiotic aerobic bacteria that do the job of
TCA cycle for the host.
Body Structure

Special organelles
 Contractile

Body Structure

Defense against predation
 Change
shape to become
harder to eat.

Euplotes detects presence of
predator
 Chemically
 Physically
 Euplotes swells in middle and
becomes too big for Lembadion
to swallow
Contractile Vacuole
Osmoregulation in FW
vacuoles
Osmoregulation in freshwater species
Contractile Vacuole
Osmotic Regulation
13
Body Structure

Special organelles
Trichocysts
Defense, prey capture
 Mucus
 Toxins
 Adherence to prey (Didinium)
Gas Exchange

No circulatory system
 All
transport is by diffusion
Plasma membrane must
remain moist for gases to
diffuse
 Restricts protozoa to moist
habitats

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