Kingdom Protista
12. Discuss the rationale for taxonomic reorganization of
the kingdom protista
13. Contrast the use of taxonomic “supergroups” with the
traditional approach to classifying protists
14. Identify characteristics used to distinguish groups of
protists. Give some common examples
15. Identify the protistans most closely associated with
Fungi, Plants, and Animals
 Dating back to the 2 kingdom approach to taxonomy,
some protists (“protozoa”) were classified with animals
due to their ability to move, where other protists
(“algae”) were classified as plants due to their ability to
photosynthesize
 Following that logic, the protozoa were further
subdivided based on their means of locomotion, while
the algae were largely categorized by their
photosynthetic pigments
 Ciliates – use cilia
 Flagellates – use flagellae
 Amoeboids – use pseudopodia
 Sporozoans – have no means of locomotion
 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=QGAm6hMysTA
 Pseudopodia
 Literally “false
feet”
 Extensions of the
cytoplasm used
not only for
movement but
also for feeding
 http://www.youtube.com/watch?v=pvOz4V699gk
 http://www.youtube.com/watch?v=TOPMaNvGTvc
 http://www.youtube.com/watch?v=d_Bkg8euB5Y
 Non-motile
 All of these
types are
parasitic and
rely on a
“vector” for
movement to a
new host
 Different frequencies of light penetrate water differently, so






red, yellow and brown pigments allow photosynthesis in
deeper water, where green is restricted to shallower water
Blue-green Algae - actually prokaryotic cyanobacteria
Golden Algae – contain yellow and brown carotenoids
Yellow Algae (diatoms) have silaceous cell walls
Red Algae – contain phycoerythrin . Some are
multicellular (note “nori” used to wrap sushi)
Brown Algae – contain brown and olive colored
carotenoids. All are multicellular (note “kelp”)
Green Algae – c0ntain chlorophyll A and B and have cell
walls made of cellulose
 The phylogenic approach to taxonomy demands that
organisms are classified based on real ancestral
divergences, and that the characteristics we use to
distinguish the taxa are Homologous, not Analagous
(“homoplasy”, or “homoplastic” in some textbooks)
 Characteristics are homologous if they are derived
from a common ancestry, even if they are modified to
adapt to different functions or circumstances, or even
diminished to the point of lacking a function
(vestigial)
 Analagous traits or structures are superficially similar,
but evolved independently
 Modern technology in biochemistry and electron
microscopy reveals patterns impossible to observe by
scientists of earlier generations
 Many traits traditionally used for protist taxonomy are
actually analagous. Photosynthesis has evolved
independently in several lineages, as have
pseudopodia for locomotion. In some lineages
ancestral characters have diminished significantly,
concealing the relationship between apparently
distinct groups of organisms.
 A number of cellular organelles appear to be derived from
ancient endosymbiosis events.
 Organelles originating by endosymbiosis are recognized by
several factors:
 One or more additional membranes
 Independent reproduction within the host cell
 DNA within the organelle itself (resembling bacterial DNA)
 These organelles are believed to be the result of
endosymbiosis:
 Mitochondria
 Centrioles
 Plastids (Chloroplasts)
 Primary
 Secondary
 Resulted from the
 Resulted from the
engulfing of a
prokaryotic cell which
was retained as an
organelle
 Mitochondria and
centrioles are the result
of primary
endosymbiosis
 The chloroplasts of Red
and Green Algae are
primary endosymbionts
engulfing of a primitive
eukaryotic cell which
was retained as an
organelle.
 Simply, it is like an
organelle with
organelles of its own
 Chloroplasts of
chromalveolates are
secondary
endosymbionts
See page 577, figure 28.2
1. Cite at least four examples of structural and
functional diversity among protists
2. Summarize the role of endosymbiosis in eukaryotes
 The supergroup approach eliminates the Kingdom
Protista, and instead subdivides the Domain Eukarya
into 5 ancestral lineages, each of which contains some
members of the former Protist kingdom.
 3 of the 5 supergroups contain only protists
 1 of the supergroups includes the Plants and their
closest protist relatives
 1 of the supergroups contains both Animals and Fungi,
and closely related protozoans
 As endosymbiosis events created the cellular
organizations we recognize as Eukaryotes, variations
in these fundamental structures form the differences
between the supergroups
 Variations in mitochondria, centrioles, cilia &
flagellae, plastids and pseudopodia represent ancestral
characters
 These variations are more difficult to recognize than
characteristics traditionally used for classification, but
appear to be the real result of common ancestry – so
it’s better, but harder to grasp at our level of study
 Have diminished mitochondria that can function
anaerobically and flagellae with additional crystalline
rods
 The name “excavate” comes from a groove (excavation)
in the cell body
 Familiar excavates include:
 Euglenoids – “mixotrophic” flagellates that can
photosynthesize, consume food by phagocytosis, and
swim using flagella
 Trypanosomes – parasitic flagellates that cause African
Sleeping Sickness
 Appear to have originated as a result of a secondary
endosymbiosis involving red algae
 Some have chloroplasts resembling red algae
 Some lack plastids, but have some residual
DNA homologous to plastid DNA
 The chromalveolata are very diverse. One subtaxon
consists of traditional protozoans : ciliates, sporozoans
and dinoflagellates (which are photosynthetic). The other
subtaxon consists of a variety of algae: diatoms, golden
algae and brown algae as well as the “water molds” which
superficially resemble fungi
#2. Would you expect the plastid DNA of
photosynthetic dinoflagellates, diatoms, and golden
algae to be more similar to the nuclear DNA of
plants (Domain Eukarya) or to the chromosomal
DNA of cyanobacteria (Domain Bacteria). Explain
 Originally classified with the sarcodina (amoebae) due

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to the presence of pseudopodia
DNA analysis shows these organisms to be distinct
from the amoebae
Pseudopodia in the Rhizaria are threadlike, rather
than lobe shaped
Many have a cell wall or exoskeleton made of calcified
organic material (the foraminiferans) or silica (the
radiolarians)
Some also have flagellae, and may even be
photosynthetic
 As implied by the “plastida” suffix, these organisms
share a similar chloroplast structure.
 The chloroplasts of these organisms originates from an
ancient endosymbiosis with a cyanobacterium
 This supergroup includes the red algae, green algae,
and Kingdom Plantae
 The plants appear to be descended from an ancestral
green alga
#1. Contrast Red algae and Brown algae
#2. Why is it accurate to say that Ulva is truly
multicellular but Caulerpa is not?
#3. Suggest a possible reason why species in the green
algae lineage may have been more likely to colonize
land than species in the red algae lineage
 Unikonts include Kingdom Animalia, Kingdom Fungi,




and their closest protozoan relatives
Unikonta is divided into 2 subtaxa, the Amoebozoa
and the Opisthokonta
The Amoebozoa include the familiar amoebae (those
with lobe shaped pseudopodia) and the slime molds
The Opisthokonta include the Kindgom Fungi, the
Choanoflagellate protists, and the Kingdom Animalia
The animals appear to be descended from a
choanoflagellate ancestor
#1. Contrast the pseudopodia of amoebozoans and
forams
 Start individually and progress to small group (3)
 Construct a matching set using the 5 supergroups as
choices. Write 10 questions based on examples,
structural features, etc.
 Quiz the other members of your small group
 Condense your question set and quiz a second group
 The second group will also quiz your group.
 Do page 599 #1-6 and #8