This document provides information on protists, including their characteristics, models of eukaryotic origins, evidence for the endosymbiotic hypothesis, candidate kingdoms of protists, life cycles of various protist groups, and the evolution of multicellularity. It addresses topics such as amoeboid movement, the life cycle of Plasmodium, conjugation in Paramecium, classification of algae, and differences between plasmodial and cellular slime molds.

1. 1. List the characteristics of protists.
They are the earliest eukaryotes 
showed up a billion years before the others
Age  2.1 billion years
There are 60,000 living species
Exist as unicellular, colonial, and
multicellular
Aerobic, cilia & flagella, asexual or sexual
Bottom line: a VERY diverse group 

2. 2. Explain why some biologists prefer to use
the term undulipodia for eukaryotic flagella
and cilia.
Because they appear to “undulate” or wave
while acting like feet or “podia” 

3. 3. Briefly summarize and compare the two major
models of eukaryotic origins, the autogenous
hypothesis and the endosymbiotic hypothesis.
• Specialization of the plasma membrane
invagination
 gave rise to the nuclear envelope, the
ER, the Golgi apparatus, etc…
3. Endosymbiotic associations may have
resulted in organelles
 mitochondria, chloroplasts, etc… 

5. 4. Provide three major lines of evidence for
the endosymbiotic hypothesis.
Similarities between organelles and
prokaryotes
Molecular systematics lends support 
rRNA of chloroplasts is more similar in
base sequence to RNA from certain
eubacteria than rRNA in eukaryotic
cytoplasm
9 + 2 flagella and cilia are analogous to
prokaryotes 

7. 5. Explain why modern biologists recommend
expanding the original boundaries of the
Kingdom Protista.
Observation that the Kingdom Protista is
polyphyletic
Current research groups protists into FIVE
candidate Kingdoms 

8. 6. Explain what is meant by the statement
that the Kingdom Protista is a polyphyletic
group.
Polyphyletic = ancestry from several
possible sources or directions
Example:
Protists are  animal-like
plant-like
fungus-like 

9. 7. List five candidate kingdoms of protists
and describe a major feature of each.
Archaezoa  lack mitochondria
Euglenozoa  are both autotrophic and
heterotrophic flagellates
Alveolata  have subsurface cavities
(alveoli)
Stramenopila  diatoms, golden brown
algae, and water molds
Rhodophyta  red algae; lack flagella 

10. 8. Describe amoeboid movement.
Amoebas move in a characteristic motion
use “pseudopodia”  form as cellular
extensions and function in feeding and
movement
The cytoskeleton of microtubules and
microfilaments functions in this amoeboid
movement 

12. 9. Outline the life cycle of Plasmodium.
It is the protist that causes malaria
The Anopheles mosquitos serve as the
intermediate host and humans are the final
host
The Plasmodium spends most of its life in
blood or liver cells 

13. 10. Indicate the organism that causes
African sleeping sickness and explain how it
spread and why it is difficult to control.
It is a species of Trypanosoma that causes
the disease and are spread by the bite of
the tsetse fly
It belongs in the candidate Kingdom
Euglenozoa, in the group Kinetoplastids 

14. 11. Describe the function of contractile
vacuoles in freshwater climates.
Contractile vacuoles allow
freshwater protists to:
1. Maintain water balance
and homeostasis
2. Expel accumulated
water from osmosis
3. Sometimes helps propel
protists 

15. 12. Distinguish between macronuclei and
micronuclei.
Macronuclei  large, over 50 copies of genome
- controls everyday functions of the cell by
synthesizing RNA
- necessary for asexual reproduction during binary
fission
Micronuclei  small, about 1 – 80 of these
- no function in growth, maintenance, or asexual
reproduction
- functions only in conjugation (sexual genetic
variation) 

16. 13. Using diagrams, describe conjugation in
Paramecium caudatum.
Page 530 in your book
• Two paramecium have diploid micronuclei which
go through meiosis to create haploid micronuclei
Through syngamy, the two paramecium exchange
a couple haploid micronuclei, and these fuse to
become a new, varied, diploid micronucleus
The new diploid micronuclei may also then follow
the cycle and exchange with another paramecium
throughout it’s life cycle 

18. 14. Explain how accessory pigments can be
used to classify algae and determine
phylogenetic relationships among divisions.
Diatoms  brown plastids cause brown/yellow
color
Golden algae  yellow and brown carotenoids and
xanthophyll
Brown algae  chlorophyll a, c and the carotenoid
fucoxanthin
Red algae  chlorophyll a, carotenoids,
phycobilins, and chlorophyll d
- color is due to accessory pigment phycoerythrin


19. 15. In a chart, distinguish among the following
algal groups based on their pigments, cell wall
components, storage products, reproduction,
number and position of flagella, and habitat:
a. Dinoflagellata b. Bacillariophyta
c. Chrysophyta d. Phaeophyta

20. 16. Describe three possible evolutionary
trends that led to multicellularity in the
Chlorophyta.
• Formation of colonies of individual cells
ex: Volvox
3. Repeated division of nuclei with no
cytoplasmic division (mitosis without
cytokinesis
ex: Caulerpa
5. Formation of true multicellular forms
ex: Ulva 

21. Life Cycle overview
Sporophyte  generally the adult form of
an organism; exists as a diploid (2n); makes
spores (ex: humans)
Gametophyte  generally an intermediate
step before fertilization; exists as a
haploid (n); makes gametes (ex: sperm &
eggs) 

22. 17. Outline the life cycles of Chlamydomonas,
Ulva, and Laminaria and indicate whether the
stages are haploid or diploid.
Chlamydomonas  at maturity it is a single
haploid cell
- asexual at first, then sexual only if stressed,
creating a diploid zygote
2. Ulva  diploid sporophyte and haploid
gametophyte
3. Laminaria  sporophyte (2n) with sporangia
makes zoospores (n) which make gametes (n) and
then fertilization to get diploid sporophyte again


23. 18. Distinguish between isogamy and oogamy;
sporophyte and gametophyte; and isomorphic
and heteromorphic generations.
Isogamy  when gametes are morphologically
indistinguishable
Oogamy  flagellated sperm fertilize the
nonmotile egg
Sporophyte  2n (diploid) generation
Gametophyte  n (haploid) generation
Isomorphic  gametophytes and sporophytes look
alike
Heteromorphic  gametophytes and sporophytes
are structurally different 

24. 19. Compare the life cycles of plasmodial and
cellular slime molds and describe the major
differences between them.
Plasmodial Slime Mold Cellular Slime Mold
Multinucleated mass Solitary haploid cells
Diploid nuclei Cells will aggregate
When stressed will when food supply is
form sexual low
reproductive Fruiting bodies
structures called (sporangia) function in
sporangia  asexual reproduction


25. 20. Provide evidence that the oomycetes are
not closely related to true fungi.
Have coenocytic (multinucleated) hyphae
(branching filaments) that are analogous to
fungal hyphae
Cell walls are made of cellulose rather than
the chitin in true fungi
Have biflagellated cells  fungi lack
flagellated cells 

26. 21. Give examples of oomycetes and describe
their economic importance.
Water molds  grow on injured tissue
but also will grow on the skin and gills of
fish
White rusts
Downy mildews
- both of these are parasitic on
terrestrial plants – act as pathogens 

27. 22. Explain the most widely accepted
hypothesis for the evolution of
multicellularity.
Multicellularity arose from unicellular
ancestors as colonies or loose aggregates
of interconnected cells
This involved cellular specialization and
division of labor among the cells
The End 