Protists
Kingdom Protista
(The hodge-podge Kingdom)
Section 20-1
Kingdom Protista
Protist = any organism that is not a plant, animal, fungus, or
prokaryote
- this kingdom is mostly unicellular, but includes many
multicellular organisms as well
- this kingdom will be broken into several kingdoms based
on DNA analysis and other factors
- similar to the first eukaryotes
Classification of the Protists is based on Nutrition
A) heterotrophic = animallike protists = protozoa
B) autotrophic = plantlike protists
C) decomposers/parasites = funguslike protists
Endosymbiont Hypothesis – Lynn Margulis
- hypothesis that explains the evolution of the
first eukaryotic cells from symbiotic
prokaryotes
Animallike Protists = Protozoans
- Unicellular heterotrophs
- Four phyla based on locomotion:
a. Zoomastigina – swim using flagella
b. Sarcodina – move with pseudopodia
c. Ciliophora – swim with cilia
d. Sporozoa – no locomotion
B.
A.
C.
D.
Zoomastigina = Zooflagellates
- most have one or two flagella
- most absorb nutrients through cell
membrane
- often decomposers or parasites
- reproduce primarily by mitosis
- Trypanosomes – African Sleeping Sickness
- Trichomonas vaginalis – most common protozoan infection
in humans
Phylum Sarcodina – Sarcodines
- move and feed via pseudopods
- temporary cytoplasmic extensions
- ameboid movement
- surround and engulf food into food vacuoles, digested
nutrients are used, and undigested materials exit through
the cell membrane
- reproduce by mitosis and cytokinesis
- Amoebas are best known examples
- Foraminiferans
- sarcodines of warm oceans with calcium carbonate shells
- White Cliffs of Dover in England
Heliozoans
Ameba Feeding with Pseudopods
Phylum Ciliophora – Ciliates
- use cilia for locomotion and feeding
- very fast swimmers
- live in both fresh and salt water
- most are free-living
Internal Structures of Paramecium
- trichocysts – small defensive structures
- macronucleus – controls normal activities
- micronucleus – reserve copy of genes;
exchanged during conjugation
- gullet – oral groove into which food enters
- food vacuoles form around food and
lysosomes fuse with it to digest food
- wastes exit through anal pore
- contractile vacuoles keep water balance
Paramecium Anatomy
Paramecium Conjugation
- normally paramecia reproduce by mitosis and cytokinesis
- during stressful times they sometimes undergo conjugation
- exchange micronuclei with each other
- not reproduction because no new cells are formed, but it
helps produce and maintain genetic diversity
Phylum Sporozoa – Sporozoans
- do not move on their own
- parasitic
- often have complex life cycles with more than
one host
- reproduce by means of sporozoites
Animallike Protists and Disease
1. Malaria
- Plasmodium parasite kills up to 2 million people
per year
- Female Anopheles mosquitoes are the vector
- mosquito’s saliva enters a person with
sporozoites which get in person’s blood
- sporozoites enter liver and red blood cells
- when erythrocytes burst it causes severe chills and fever
- many strains of malaria have evolved resistance to the
drugs we use against the parasites
- best control is to control mosquitoes
sporozoites
sporozoites
merozoites
male gametophyte in
erythrocyte
2. African Sleeping Sickness
- Zooflagellate Trypanosoma
- spread by Tsetse flies
- damage the nervous system and can cause death
3. Amebic Dysentery
- causes severe diarrhea and intestinal bleeding
- Entamoeba
- spreads by contaminated drinking water
4. Giardia
- a flagellated protozoan that also causes diarrhea and
digestive system problems
Ecologically many protists are important decomposers and
symbionts with other organisms
- Trichonympha in termite guts digest cellulose
Sec. 20 -3 Plantlike Protists – Unicellular Algae
- often classified based on the type of
photosynthetic pigments they have
- have many different pigments to absorb the light
that can penetrate into deep water (blue)
- have chlorophyll a, b, and c
- accessory pigments absorb wavelengths that
chlorophylls can’t
Phylum Euglenophyta
- have two flagella, but no cell walls
- genus Euglena
- found in lakes and ponds
- eyespot allows them to swim toward light
- can live autotrophically or heterotrophically
Phylum Chrysophyta – Yellow-green + golden-brown
- means “golden plants”
- cell walls of pectin rather than cellulose
- golden algae often cause fish kills
Lake Wichita
Spring 2009
Phylum Bacillariophyta – Diatoms
- make shells of silicon (glass)
- shells of two parts like a petri dish
Phylum Pyrrophyta – Dinoflagellates
- half are heterotrophic; half autotrophic
- most have two flagella and a shell of thick cellulose
- many are luminescent
- Pyrrophyta means “fire plants”
Ecology of Unicellular Algae
1. Phytoplankton
- small photosynthetic organisms in the ocean
- perform about half of all photosynthesis on Earth
- are the base of the food chain – all sea-life
depends on these autotrophs
2. Algal Blooms
- happen when excess nutrients are in water and
algae grow very rapidly
- when nutrients are used up and the algae die,
their decomposition takes all of the oxygen out
of the water which causes many other
organisms to die
- “Red tides” can make shellfish poisonous
Plantlike Protists: Red, Brown, and Green Algae
- these groups are mostly multicellular
- most have cell walls and life cycles like plants
Phylum Rhodophyta = Red Algae
- can live at great depth (260 meters) due to their efficiency at
harvesting light energy
- contain chlorophyll a and reddish accessory pigments
called phycobilins which absorb blue light
- important in coral reefs
Phylum Phaeophyta = Brown Algae
- contain chlorophyll a and c and the accessory
pigment fucoxanthin
- largest and most complex algae
- mostly marine and often in cool, shallow
coastal water
- Kelp forests on west coast of U.S.
- Sargassum forms huge floating mats
on the ocean
- many have air-filled bladders that
help them float
Phylum Chlorophyta – Green Algae
- ancestors of green plants
- cellulose cell walls, contain chlorophyll a and b;
and store food as starch
- most are aquatic, but some live on moist land
- both unicellular, colonial, and multicellular
- Chlamydomonas
- unicellular
Volvox colonies
Ulva - multicellular
Zygote (cross-section)
Nuclear
Fusion
Diploid Stage
Haploid Stage
Meiosis and
Germination
Haploid
cell (strain)
Haploid
cell (+
strain)
ASEXUAL
REPRODUCTION
Cytoplasmic
Fusion
–
A thick-walled resistant
zygote develops.
Mitosis
More
spores
produced.
More
spores
produced.
SEXUAL
REPRODUCTION
+
+
Gametes of different
mating types meet.
ASEXUAL
REPRODUCTION
–
Life cycle of a species of Chlamydomonas
zygote
sporophyte (2n)
Fertilization
Diploid Stage
Haploid Stage
Meiosis
germinating
spore (n)
male
gametes
female
gametes
gametophyte (n)
10 cm
Human Uses of Algae
- algal chemicals are used to treat stomach ulcers,
high blood pressure, arthritis, and other health
problems
- many foods contain algae or algal products
- thickening agent in ice cream, salad dressing,
puddings, and candy bars
- industry uses algal chemicals to make plastics,
waxes, deodorants, lubricants, even artificial wood
- agar is used in biology labs to grow bacteria on