Biology 110 Section 11
J Greg Doheny
NOTES: Protists (Chapter 28)
Quiz Questions:
1. What do you call a sudden, localized population explosion of dinoflagellates that ultimately
leads to toxic mollusks and shellfish?
2. What is the general term used to describe a sudden, localized population explosion of
phytoplankton which is not necessarily toxic.
3. What do you call an elevated container sitting atop a stalk that contains many spores?
(Usually produced by a fungus or a slime mold).
4. Collective name given to the various types of photosynthetic plankton in the ocean.
5. Name for a thin, microscopic filament made by some fungi, slime molds and water molds.
6. Genetically speaking, which of these protists most closely resembles land plants:
chlorophytes, Charophytes, or brown algae?
7. Genetically speaking, which of these protists most closely resembles fungi: Slime molds,
water molds, or Diatoms?
8. Genetically speaking, which of these protists most closely resembles animals: Slime molds,
water molds, or Dinoflagellates?
9. Which organisms cause ‘red tides?’
Some new terms and concepts that will be introduced in this section:
Terms:
Amoeba: is a descriptive term. An amorphous (shapeless) blob that moves using
‘amoeboid movement.’
Amoeboid Movement: amoeba move by producing a ‘pseudopod’ (plural: pseudopodia)
at the front end (leading end) of the cell, and cannibalizing (recycling) the materials from
the back end (trailing end) of the cell.
Benthic: (Benthic zone) refers to the floor of a body of water (ie-the ocean floor), and
the organisms that live there.
Bloom: a sudden, dramatic increase in the number of phytoplankton (usually
dynoflagellates).
Desiccation: to dry out.
Endosymbiosis: One organisms ‘swallowing’ (engulfing) and keeping another.
Fecal: refers to feces (excrement).
Fruiting body: a ball full of spores sitting on top of a stalk. Used to disperse spores into
the air or water.
Germinate: to start growing. (ie-when a spore germinates)
Hypha(e): Long tube full of spores.
Marine: Something that lives in or on the water. (ie-Marine Protists. Marine
Mammals.)
Mixotroph: Photosynthetic, but also eats things.
Model Organism: A specific organism that researchers do research on. (ie-people who
do research on genetics often use fruit flies [Drosophila melanogaster] as a model
organisms.)
Phytoplankton: photosynthetic planktonic organisms
Pigments: Coloured proteins or chemicals present in an organism.
Pseudopod (Pseudopodia): a ‘false foot’ produced by an amoeba in front of itself.
Pseudopodia are produced in front of a amoeba (the advancing end) with materials
‘cannibalized’ from the trailing end.
Spore: Dormant form of an organism enclosed in a desiccation-resistant shell.
Concepts:
Advanced eukaryotes like humans are multicellular. Primitive eukaryotes like amoebas are
unicellular. The Protists are a bridge between single-celled eukaryotes and more complicated
multicellular eukaryotes. Some protists are single-celled, some are ‘colonial’ and some are
multicellular.
Endosymbiosis: One organisms engulfing (‘swallowing’) and then keeping another organisms.
It is believed that the Eukaryotes arose when a Prokaryote developed a nuclear membrane
(developed a nucleus). This early Eukaryote then engulfed an alpha-proteobacterium capable of
Aerobic Respiration. The engulfed proteobacterium then became what we now call mitochondria
(the bean-shaped, energy producing organelles inside Eukaryotes). Some of these cells then
engulfed a cyanobacterium (another type of bacteria capable of photosynthesis) and became
photosynthetic protists (ie-green algae). This is called secondary endosymbiosis (when an
organisms that already has one endosymbiont [a mitochondrion] then engulfs a second type of
endosymbiont [cyanobacterium]). It is believed that organisms like this then developed from
single-celled photosynthetic eukaryotes into multicellular plants!
Single-celled vs. Colonial vs. Multicellular: In single celled organisms (ie-Bacteria) the cells are
all alike, and all live as individuals. In colonial organisms, the organisms is composed of many
individual cells that are all alike, but are ‘stuck together’ in a specific pattern. (ie-the fresh water
algae Dinobryon.) In a multicellular organisms, the organism is composed of many cells that are
‘specialized’ to perform slightly different things. (ie-Humans, composed of different types of
cells, such as kidney cells, heart cells, brain cells.)
Cell Differentiation: The process of turning from a ‘general’ cell into a specialized cell. Some
of the protists, such as the slime molds are able to convert back and forth from being single-celled
organisms to being multicellular organisms, and may represent an ‘evolutionary bridge’ between
simple single-celled organisms like amoeba, and complicated multicellular organisms like
humans.
Mitosis vs. Meiosis: Haploid organisms have only one copy of their genome. Most Eukaryotes
have more than one copy. Some are diploid (two copies), some are triploid (three copies), some
are tetraploid (four copies) and so on. (Which are humans?) Mitosis refers to cell division where
there is no reduction in the number of copies of the genome. (Diploid cells remain diploid.)
Meiosis refers to cell division where there is a reduction in the number of copies of the genome
(ie-diploid cells divide without copying the genome first, and become haploid.) Gametogenesis is
when diploid cells undergo meiosis to become haploid gametes. Haploid gametes then fuse to
become diploid organisms again. (ie-Men and women are diploid. Men produce haploid
spermatozoa [sperms] and women produce haploid ova [eggs] using meiosis and gametogenesis.
Haploid sperms and eggs then combine to produce diploid human beings again. Most Eukaryotes
do some variation of this.
Plasmodium: In biology, many words are used to describe more than one thing, which often
leads to confusion. This is true of the word plasmodium. Plasmodium is both the name of a
genus (ie-Plasmodium vivax, a protist that causes malaria), and a descriptive term used to
describe one of the forms a slime mold can take. Slime molds do not cause malaria, and
Plasmodium vivax does not form a plasmodium shape.
DOMAIN EUKARYA, Groups and Sub-Groups
Domain Eukarya: Includes any organism with a nucleus. The Eukarya are further divided into
FIVE GROUPS. (These groups are not part of the Linnean classification system you’ve learned,
but don’t worry about that for the moment.) The five groups are divided into sub-groups.
GROUPS and Sub-Groups:
1.Excavata: This group includes many parasites that cause diseases in humans.
They have one or
more flagella, and are not photosynthetic.
A. Diplomonads: Heterotrophic. Actually have two nuclei. Many are parasites. Example:
Giardia lamblia (fecal-contaminated drinking water).
B. Parabasalids: Heterotrophic. Are motile with a flagella. Many are parasites. Example:
Trichomonas vaginalis, an STD. Can ‘swim’ up the urethra (urinary tract).
C. Euglenozoans: Heterotrophic. Have two flagella. Some are parasites. Example: the
Trypanosomes (ie-Trypanosoma brucei), carried by tsetse fly vector, causes African
Sleeping Sickness. Trypanosomes evade the immune system by switching surface proteins in
alternate generations.
Name means coloured (‘chroma’) pockets (‘alveola’). This group
includes many single-celled organisms important to the field of oil-exploration, as well as some
multicellular algaes. Most are photosynthetic, but some are not. The group also contains a few
parasites that are harmful to humans (ie-the Apicomplexans).
A. Dinoflagellates: Single-celled. Most are mixotrophic. Are found in the ocean. Made
of two cellulose hemispheres, with two flagella wrapped around the equator.
Dinoflagellate fossils are important to oil exploration. Cause toxic, ‘red tide’ blooms,
leading to toxic mollusks and crustaceans. Important part of phytoplankton.
B. Apicomplexans: Single-celled. Heterotrophic parasites. Example: Plasmodium vivax
(causes malaria). Sporozoites (wormlike) in the Anopheles mosquito (the vector) enter
human liver, form merozoites (round, asexual cells) that exit the liver and infect red
blood cells.
C. Ciliates: Single-celled. Free living, non-parasitic. Have multiple cilia (for propulsion)
on their surface. Example: Paramecium caudatum.
D. Diatoms: Single-celled. photosynthetic, unicellular algae. Have a ‘shoe box and lid’
structure. Important in oil industry. Body is made of silicon dioxide (very unusual!).
Important component of phytoplankton. Possible use to combat Global Warming by
creating Diatom ‘blooms.’
E. Golden Algae: Single-celled or colonial. Photosynthetic. Can be single-celled or
colonial.
F. Brown Algae: Multicellular. Photosynthetic. Form the largest algaes (‘sea weeds’).
Most are multicellular with specialized structures (Blade, Stipe and Holdfast).
‘Alternation of generations’ life cycle. (Diploid plant form has Sporangia in the blades.
2. Chromalveolata:
Haploid sporangia are dispersed, some become male and others female. Fertilization of a
female gametophyte by a male gametophyte leads to a diploid sea weed. Example:
Laminaria
G. Oomycetes: Multi-cellular, heterotrophic ‘water molds.’ Made of cellulose (like most
plants), form hyphae (thread-like structures) and ‘fruiting bodies’ (elevated containers
full of spores). In damp climates they can grow on damp land plants (ie-spoil corn or
potato crops).
3. Rhizaria: This group includes some interesting single-celled marine protists, but you won’t
be expected to remember any of them for this course.
A. Radiolarians: Single-celled. Heterotrophic. Impressive looking organisms with
‘spikes’ that are used to spear bacteria.
4. Archaeplastida: This group contains the land plants!
It also contains the red and green
algae that live in the ocean and in fresh water.
A. Red Algae: Multicellular. Have red photosynthetic pigments as well as green. Sushi!
B. Chlorophytes: Live in fresh water. Some are single-celled, others are muticellular.
Some are syncitial (many nuclei without distinct cells), forming a ‘supercell.’
C. Charophytes: Multicellular and leafy, are very similar to land plants.
D. Land Plants: (We’ll discuss these later.)
5. Unikonta: This group contains fungi (discussed next week) and animals!
The Unikonta
are divided into two sub-groups, the Amoebozoans and the Opisthokonts. The Opisthokonts are
more advanced, and contain humans and fungi. The Amoebozoans (amoebas) are primitive,
single-celled organisms that usually live as individuals, but sometimes (amazingly) join together
to form multicellular organisms.
5a.Amoebozoans: Single celled organisms that exhibit ‘amoeboid movement.’
A. Slime Molds: Heterotrophic, single/multicellular organisms that live in soils. The slime
molds are very interesting because they represent a ‘bridge’ between single-celled and
multicellular organisms. They live as individual organisms, but under conditions of
starvation they form a multicellular mass (‘aggregated amoebas’), and later fruiting
bodies to disperse spores. Are of two types:
i. Plasmodial slime molds: live individually. Under starvation
conditions they form a syncitial ‘feeding plasmodium,’ and
eventually a ‘mature plasmodium,’ and then form fruiting bodies full
of haploid spores.
ii. Cellular slime molds: Live individually, but under starvation
conditions form an aggregated mass, and later a migrating aggregate,
and finally a fruiting body full of haploid spores. Example:
Dictyostelium discoideum.
B. Entamoebas: Heterotrophic, individual amoeboid cells that live in fresh water. Some are
parasites. Example: Entamoeba histolytica (causes ‘amebic dysentery’ from drinking
contaminated water.
5b.Opisthokonts:
A. Fungi: (we’ll discuss fungi later.)
B. Animals: (we’ve already discussed these.)
PRACTICE QUESTIONS:
Match the term to the definition:
a) Amoeba
b) Benthic
c) Bloom
d) Colonial
e) Cyanobacterium
f) Endosymbiont
g) Fruiting body
h) Germinate
i) Heterotroph
j)
k)
l)
m)
n)
o)
p)
q)
Hypha
Merozoite
Mixotroph
Photoautotroph
Pseudopod
Red tide
Spore
Sporozoite
1. A thin, microscopic, multicellular filament or thread.
2. Name for the worm-like form of Plasmodium vivax.
3. A sudden localized increase of dinoflagellates in the ocean. Because the dinoflagellates contain
toxins, the mollusks that eat them (filter feeders) will be toxic to eat.
4. An elevated structure that sits atop a stalk, and contains many dormant spores. Used to disperse
spores into the air or water.
5. Name for the floor of a body of water (ie-the ocean floor) and the organisms that live there.
6. A sudden local increase in the number of phytoplankton in the ocean. Usually diatoms or
dinoflagellates.
7. Name for the round, asexual form of Plasmodium vivax.
8. An organisms (usually a bacterium) living inside another organisms cell. (An intracellular
symbiont living in a mutualistic relationship with its host.)
9. A primitive type of photosynthetic bacteria believed to be the precursor of modern chloroplasts.
10. An a non-photosynthetic organisms that must eat things to survive. (May eat other organisms, or
passively soak up complicated macromolecules from the environment.)
11. Term used to describe what happens when a dormant spore starts to develop into a living
organisms.
12. A ‘false foot.’ A temporary foot-like structure, built by an amoeba.
13. An organism that is both photosynthetic, but also eats things. (Believed to be the result of a
heterotrophic protist ‘engulfing’ and keeping a photosynthetic bacterium.)
14. An amorphous single-celled organisms that moves by building ‘psudopods’ in front of it.
Protist Clades: Match the question to the Protist Group:
a.
b.
c.
d.
Excavata
Chromalveolata
Archaeplastida
Unikonta
1. Three important human pathogens, Giardia lamblia (causes diarrhea from drinking fecalcontaminated water), Trichomonas vaginalis (an STD), and Trypanosoma brucei (causes
African Sleeping Sickness) are all members of the same protist group. Which one is it?
2. Which one contains the fungi?
3. Which one contains the animals?
4. Which one contains the cellular slime molds?
5. Which one contains land plants?
6. Which one contains the Diatoms and Dinoflagellates?
Pathogenic Protists and Humans: Match the protist to the human illness.
a.
b.
c.
d.
e.
f.
Dinoflagellates
Plasmodium vivax
Giardia lamblia
Trichomonas vaginalis
Trypanosoma brucei
Entamoeba histolytica
1.
2.
3.
4.
5.
6.
7.
Causes malaria.
Causes African Sleeping Sickness.
Causes a sexually transmitted disease infecting the urethra.
Causes red tide poisoning.
Causes diarrhea from drinking contaminated water (beavers).
Causes amebic dysentery.
Which is famous for being able to evade the immune system using surface-protein class
switching?