Protozoa I
Protozoans
Over 50,000 known species
45 phyla (more than
metazoa!)
Relationship to Other Organisms

Two Kingdoms – Arististotle, Linnaeus
 Plants
Metaphyta
 Protophyta

 Animals
Metazoa
 Protozoa


Lots of problems with this scheme
Relationship to Other Organisms

3 kingdoms of Haeckle/Darwin
 Plants
 Animals
 Protists


Took care of the little stuff seen with the early
microscopes
Still has problems
Relationship to Other Organisms

Copeland’s Four-Kingdom System (1938)
 Kingdom
Monera.
 Kingdom 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
 Kingdom
 Kingdom
 Kingdom
 Kingdom
Animalia
Plantae
Eukaryotes
Fungi
Protista
Monera - Prokaryotes
Kingdoms and Domains

Carl Woese - U. of
Illinois (1970’spresent)
 Studied gene
sequences of
bacteria, archaea,
and eukaryotes
 Found
major
fundamental
differences
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
6 Kingdoms of Life
3 Domains 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”
 “Protists” are now distributed among all kingdoms.”
pg 37 incorrect. No prokaryotic protists!
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)

Sarcodina (=amoebas) a functional group Amoebozoa,
Foraminifera, Actinopoda (Radiolaria, Heliozoa)
(many are important geologically)
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
Protozoan Phylogeny

Reclassification based on
 Life
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

Protista – still used as teaching tool.
 Grades
7-12?
 Undergrad intro bio (with reservations)

We will not discuss Protists!
 Instead,
note the following schemes:
First - breakdown of what used to be protists.
 Second - taxonomic relationships of organisms
covered in P. Ch 3 (pg 38).

 Only
cover those in text and/or lab
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)
8 major eukaryote clades
(mainly from Baldouf 2003)
1.
2.
3.
4.
Opisthokonts includes animals, fungi
 Single basal flagellum on reproductive cells, flat
mitochondrial cristae (most eukaryotes have tubular
ones).
Plants includes land plants, green algae, red algae
 Plastids with just two outer membranes (primary
plastids).
Heterokonts includes brown algae, golden algae,
diatoms, water molds
 Unique flagellum decorated with hollow tripartite
hairs (stramenopiles) and, usually, a second plain
one. Plastids have 4 membranes (secondary).
Cercozoa includes foraminifera (& radiolaria?)
 Amoebae with filose pseudopodia, often living
within tests.
5.
6.
7.
8.
Amoebozoa includes lobose amoebae, most slime
molds
 Mostly naked amoebae (lacking tests), often with
lobose pseudopodia.
Alveolates includes ciliates, dinoflagellates,
apicomplexans
 Have systems of cortical alveoli directly beneath
their plasma membranes
Discicristates includes many flagellates, some slime
molds
 Have discoid mitochondrial cristae
Amitochondrial excavates includes parabasalids,
diplomonads
 Most have an excavated ventral feeding groove, and
all lack mitochondria.
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”

General characteristics highly variable
 Size,
morphology, ultrastructure
 Nutritional mode, physiology
 Behavior, life history

Importance
 Disease
agents
 Model organisms in biological research

Most are probably unknown
 82,000
known species
 ½ of these are fossils (shelled forms)
Defining Characteristics
of “Protozoa”

Importance
 Disease
agents
 Model organisms
Ecology
 Genetics
 Physiology
 Development

Defining Characteristics of
“Protozoa”


Eukaryotic
Unicellular
 Mostly
small 5-250 μm (0.5 μm – 7 mm)
 Multicellularity in a few but this is a derived
character


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)
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
…
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
Stylonychia
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
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=85D
GyFzxvy8&feature=player_detailpage
Body Structure

Only one plasma membrane
 Everything
is inside that membrane
 Structure is identical to the plasma
membrane of all other multicellular
organisms
 High SA/V for protist cells

Membrane has fluid mosaic structure
 Lipids
and proteins can move about laterally
within the membrane
Membrane has fluid mosaic
structure
Body Structure

Internal structures
 Cytoskeleton
Shape
 Rigidity

Cytoskeleton
Myonemes
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
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
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

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
Body Structure

Special organelles
 Contractile

vacuoles
Osmoregulation in freshwater species
Contractile Vacuole
Osmoregulation in FW
Contractile Vacuole
Osmotic Regulation
Body Structure
Special
organelles
Trichocysts
Defense, prey capture
Gas Exchange

No circulatory system
 All
transport is by diffusion
Plasma membrane must
remain moist for gases to
diffuse
 Restricts protozoa to moist
habitats
