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Biology II
Chapter 20 Protista
Questions To Be Answered
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What characteristics put an organism in
the protist kingdom?
What are the four major groupings within
this kingdom?
What are the names of the main
organisms and why are they important?
Chapter 20 Protozoa
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20-1 Overview of Protozoa
20-2 Protozoan Diversity
Section 20-1 Overview of
Protozoa
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Characterisitcs of Protozoa
Reproduction
Classification
Adaptations
Evolution
Great Discoveries
Paramecium
Characteristics of Protozoa
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Single-celled, microscopic
Eukaryotes
Able to move independently
65,000 species identified
Stentor
Characteristics of Protozoa
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Inhabit many environments –
• Salt and fresh water
• Soil
• In bodies of other organisms (parasitic with
complex life-cycles)
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Heterotrophic: obtain nutrients by
ingesting small molecules or cells and
digest it in a food vacuole that contains
digestive enzymes.
Characteristics of Protozoa
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Zooplankton: a population of organisms
that constitute one of the primary
sources of energy in aquatic
ecosystems.
Reproduction
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Asexual reproduction by binary fission:
divides into 2 essentially identical
individuals
• Some by multiple fission: cell division that
results in a number of identical individuals
Reproduction
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Sexual reproduction in the form of
conjugation: individuals from opposite
mating strains pair and exchange
genetic material.
Classification
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Protozoa are members of Kingdom
Protista along with algae, slime molds,
and water molds
Classification
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Research into evolutionary relationships
is constantly yielding new information
and altering Protistan classification
Classification
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Sometimes classified into 4 phyla based
on means of locomotion
• Sarcodina (Sarcodines) – pseudopodia
• Ciliophora (Ciliates) – cilia
• Zoomastigina (Zooflagellates) – flagella
• Sporozoa (Sporozoans) – non-motile adults
Adaptations
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Many species have physiological
mechanisms for monitoring conditions in
their environment
• Eyespot: localized region of pigment that
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detects changes in the quantity and quality of
light.
Others can sense physical and chemical
changes or obstacles in their environment
Adaptations
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Cyst: a dormant form characterized by a
hardened external covering in which
metabolic activity has ceased.
• Form in response to nutrient deficiency,
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drought, and decreased oxygen
concentration, or pH or temperature changes.
Emerge when conditions improve
Evolution
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First life forms 3.5 billion years ago were
prokaryote (bacteria), then 1.5 billion
years ago the first eukaryotic organisms
evolved. Protozoa are the descendants
of these early eukaryotes
Evolution
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Probably evolved through
endosymbiosis: a process in which one
prokaryote lives inside another and
gradually both host and guest become
dependent on one another.
Great Discoveries: The Origin of
Eukaryotic Cells
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Lynn Margulis -Symbiosis of Cell
Evolution
Animation/tutorial
Mitochondria and chloroplasts
are:
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Self-dividing
Approximately the same
size as prokaryotes
Able to make proteins
and lipids
DNA within are similar to
bacteria DNA rather than
eukaryotic DNA
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Ribosomes within are
more similar to those in
prokaryotes in size and
are sensitive to
antibiotics like bacteria
Synthesize protein using
metabolic steps that
bacteria use
Chloroplast produce
energy in the same way
that some bacteria
produce energy
Great Discoveries: The Origin of
Eukaryotic Cells
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Kwang Jeon: infected a species of
amoeba with bacteria parasite. Cultured
amoebas that survived infection,
producing a line of amoebas dependent
on the bacteria for survival.
Protozoan Diversity
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Phylum Sarcodina
Phylum Ciliophora
Phylum Zoomastigina
Phylum Sporozoa
Phylum Sarcodina
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Amoeba
40,000 species – 100’s of species of
amoebas
Inhabit fresh water, salt water, soil
Ex. Pelomyxa carolinensis – live on mud
and rocks in shallow, slow-moving
streams or ponds.
Pseudopodia
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Large, rounded cytoplasmic extensions
(flexible cell membranes) that function in
movement.
Forms when the endoplasm (inner portion of
cytoplasm) pushes the ectoplasm (outer
portion) forward to create a blunt arm-like
extension.
Other pseudopodia retract and cytoplasm flows
in direction of new pseudopodium
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Referred to as ameboid movement: a form of
cytoplasmic streaming
Pseudopodia also used for feeding – engulf
other Protists by phagocytosis – surrounds
food with its pseudopodia and a portion of the
cell membrane then pinches together and
encloses the food vacuole in a process called
endocytosis, then enzymes from the cytoplasm
enter vacuole and digest the food.
Wastes leave cell in reverse process called
exocytosis.
Contractile vacuole
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An organelle that expels fluid from the
cell.
Freshwater organisms are usually
hypertonic relative to their environment
so water continually diffuses into them.
To maintain homeostasis, it must use
contractile vacuole to rid cell of excess
water.
Ecological Role: Foraminifera
and Radiolarians
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Test: protective shell made of calcium
carbonate (foraminifera) or silicon
dioxide (radiolarians). Slender
pseudopodia extend through opening in
test.
Foraminifera and Radiolarians
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Existed since Precambrian times leaving an
excellent fossil record. Tests of dead organisms
have been sinking to the bottom of the ocean for
millions and millions of years.
• Foraminifera have built up a calcium-rich layer
of sediment that has created limestone and
chalk deposits. Ex. White Cliffs of Dover,
England and the Great pyramids of Egypt
• Radiolarians formed a type of rock called chert
Human Diseases from Sarcodina
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Most are free-living, some live in the intestines
of humans or other animals
Entamoeba histolytica (amoebic dysentery):
• Enters body via contaminated food and water.
• Lives in the large intestine and secretes enzymes that
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attack the intestinal lining and cause deep ulcers.
Affected individuals feel intense pain and complications
arise when amoebas are carried by blood to the liver and
other organs.
Phylum Ciliophora
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Paramecium
8,000 species
Swim by means of cilia – short, hair-like
cytoplasmic projections that line the cell
membrane.
Example: Paramecium: abundant in
ponds, slow-moving streams that contain
plants and decaying organic matter
Phylum Ciliophora
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Zoothamnium
Cilia: beat in synchronized strokes that
pass waves across the cell causing the
protozoan to rotate on its axis.
Feed on bacteria, algae, and other small
organisms found in marine and fresh
water habitats.
Internal Structure
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Pellicle: clear, elastic layer of protein
surrounds the cell membrane
Oral groove: funnel-like depression lined
with cilia. Beating cilia create water
currents that sweep food down groove to
mouth pore and gullet where food
vacuole forms.
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Anal pore: where waste is expelled
Multinucleated: have at least one
macronucleus and one micronucleus.
• Macronucleus contains multiple copies of
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DNA and is responsible for metabolic and
developmental functions necessary for
asexual reproduction.
Micronucleus: participates in exchange of
genetic info during conjugation.
Reproduction in Ciliophora
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Asexual reproduction by binary fission
• Only the micronucleus divides by mitosis.
• Macronucleus which has up to 500x more
DNA than the micronucleus, simply elongates
and splits in half. One goes into each new cell
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Sexual reproduction by Conjugation
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Two organisms of opposite mating strains line up and
join together.
Macronucleus disintegrates
Each diploid micronucleus undergoes meiosis,
producing 4 haploid micronuclei. All but one
disintegrates.
Remaining micronuclei divides by mitosis producing 2
identical haploid micronuclei.
Two paramecium exchange 1 micronuclei
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The 2 micronuclei in each fuse to form one diploid
micronucleus in each paramecium.
Paramecium separate.
Macronucleus forms in each from products of mitotic
divisions of the micronucleus.
Although genetic material was exchanged no new
cells are produced.
Following conjugation, each paramecium divides,
producing a total of 4 genetically identical paramecia
which are genetically different from either of the
original paramecia.
http://www.vaxa.com/intestinal-protozoa.cfm
Phylum Zoomastigina
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Trichomonas
2500 species
Characterized by presence of one or
more flagella: long hair-like structures
that are made up of microtubules and
are used for movement.
• rapid whipping motion pushes or pulls
protozoan through water
Phylum Zoomastigina
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Many are free-living in ponds or lakes
and feed on small organisms.
Phylum Zoomastigina
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Example: Giardia lamblia
(giardiasis)
• Severe diarrhea, intestinal cramps.
• Several kinds of animal carry
parasite and contaminate water with
their feces.
Trichonympha live in the gut of
termites and help digest
cellulose.
Human Disease of Zoomastigina
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Genus Trypanosoma:
• live in blood of fish, amphibians, reptiles, birds,
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and mammals.
Carried from host to host by bloodsucking insects
African trypanosomiasis: sleeping sickness.
Transmitted by tsetse fly. Causes fever, lethargy,
mental disorientation, coma
Trypanosoma
Trypanosoma cruzi: Chagas’ disease.
Transmitted by “kissing bug”. Fever and
severe heart damage.
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Leishmania donovani:
• Transmitted by sand fleas.
• Causes leishmaniasis.
• Blood disease afflicts millions of people in
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Africa, Asia and Latin America.
Disfiguring skin sores, can be fatal.
Phylum Sporozoa
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6,000 species
No means of locomotion in adults
Plasmodium
Phylum Sporozoa
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Most species are parasitic
Have complex life cycles in which they
develop a spore
• Infective form protected by a resistant coat
• Carried in the blood and other tissues of their
hosts where they absorb nutrients and
destroy host tissues.
Example: Toxoplasma gondii:
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Found in birds, rodents, and domestic
cats.
Causes toxoplasmosis.
Few to no symptoms in healthy adults
but can cause damage to developing
fetus or newborn.
Example: Plasmodium
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Causes malaria.
Characterized by severe chills, fever,
sweating, fatigue, and great thirst.
Victims die of anemia, kidney failure or
brain damage.
Four species infect humans. All have life
cycles that involve the female Anopheles
mosquito.
Treating Malaria
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An effective way to reduce human deaths from
malaria is to control mosquito population and
interrupt the parasite’s life cycle.
Cured with drug derived from Cinchona tree,
native to Americas. Quinine used for over 500
years.
Sporozoan’s resistance to antimalarial drugs is
a significant worldwide problem. Possible
vaccination developed in the future.