THE "PROTISTA"
I.
CHARACTERISTICS
A. The "protist" refer to all unicellular eukaryotes as well as related multicellular algae
1. Unicellular eukaryotes
a) All life activities are carried on with in the limits of a single plasma membrane
B. Habitat
1. Wherever there is moisture
a) Fresh, brackish, and seawater
b) Commensualistic, mutualistic, and parasitic
II. TAXONOMY
A. Informal grouping
1. "Protozoa"
a) The phagotrophic unicellular eukaryotes
b) Many are not closely related to each other
c) Some members gave rise the animal and fungi kingdoms
2. "Algae"
a) The phototrophic unicellular eukaryotes
b) Many are not closely related to each other
c) Some members gave rise the plant kingdom
3. "Fungal-like protist"
a) A group of absorptive eukaryotes
b) Not related to the fungi (convergent evolution)
B. Current taxonomy is in a state of flux and we will use the classical classification
1. Phylum Apicomplexa
a) Non-motile organisms
b) Includes Plasmodium
2. Phylum Sarcomastigophora
a) Subphylum Sarcodina
(1) Motile by means of pseudopodia
(2) Includes Amoeba and forams
b) Subphylum Mastigophora
(1) Motile by means of flagella
(2) Includes Leishmania, Giardia, Trypanosoma, and Euglena
3. Phylum Ciliophora
a) Motile by means of cilia
b) Includes Paramecium
4. Phylum Chlorophyta
a) Includes the green algae
b) Gave rise to the plant kingdom
5. Phylum Phaeophyta
a) Include the brown algae
6. Phylum Rhodophyta
a) Includes the red algae
C. Evolutionary origin of the kingdoms
1. Fermenting prokaryotes
a) These were probably the first life forms on Earth
(1) Lived in an anaerobic environment (no oxygen) that was rich with nutrients
(energy source)
(2) They absorbed their nutrients from the surrounding environment and had a
fermentative type of metabolism (don't use oxygen)
b) They lacked a nucleus and other organelles
2. Photosynthetic bacteria
a) Nutrients on earth started to be used up and some bacteria evolved a
photosynthesis
(1) A group of these are now known as the cyanobacter
b) Photosynthesis changed the environment of the earth
(1) The waste product of photosynthesis is oxygen
(2) Oxygen started to accumulate on earth
3. Respiratory bacteria
a) Some bacteria evolved a respiratory type metabolism (uses oxygen) that was
more efficient than fermentation
(1) Aerobic respiration was possible due to the release of oxygen by the
phototrophs
4. "Protozoa" (Respiring unicellular eukaryotes)
a) Some bacteria with a respiratory metabolism formed symbiotic relationships with
eukaryotic cells
(1) Possible they were phagocytized by the eukaryotic cells or possibly they were
pathogens
(2) They eventually formed a permanent relationship with the eukaryotic cells and
have evolved in what we know today as mitochondria
(a) This is referred to as the endosymbiotic theory of the origin of the
mitochondria
b) Unicellular organisms with a nucleus & mitochondria are what we know today as
"protozoa"
5. "Algae" (Photosynthetic unicellular eukaryotes)
a) Some bacteria with photosynthetic metabolism (cyanobacteria) formed symbiotic
relationships with eukaryotic cells
(1) Probably ingested ancestors of cyanobacter
(a) They evolved and became what is know today as chloroplasts
(b) These organisms no longer needed to eat food and were free to develop
a outer cell wall made of cellulose
(2) This is known as the endosymbiotic theory of the origin of the chloroplast
b) These organisms were what is know today as the algae
6. Fungi
a) Some protozoa developed an absorptive type of nutrition
(1) Transporting in small molecules instead of phagocytizing large particles
(a) Since they no longer had to engulf organisms, they were free to develop a
cell wall
b) Cells began to specialize and these became multicellular eukaryotes with an
absorptive type nutrition we know today as the fungi
7. Animals
a) Some protozoa developed colonies and some cells started to specialize to form
truly multicellular organisms
(1) Some cells may be responsible for detecting prey, others for capturing it, and
still other for digesting it
b) These developed into multicellular organisms know today as animals
8. Plants
a) When algae invaded land resources were separated
(1) Water was below ground and light was above ground
(2) The organism's cells started to specialize
(a) Roots to get water and leaves to photosynthesize
b) They enveloped into multicellular photosynthetic organisms know today as plants
9. Evidence for the endosymbiotic theory of the origin of the mitochondria and
chloroplast
a) Size of bacteria
b) Membrane / enzyme systems similar to some bacteria
c) Divide by binary fission like bacteria
d) Circular DNA like bacteria
e) Ribosome structure like bacteria
f)
Genetic similarities with bacteria
III. LOCOMOTION
A. Pseudopodia
1. Mainly used in the Rhizopoda
2. Lobopodia
a) Rather blunt extension of the cell body with endoplasm and ectoplasm
3. Axopodia
a) Long, thin supported by microtubules
B. Flagella
1. Propels water parallel to the main axis of the flagellum
C. Cilia
1. No real structural difference from the flagella
a) Usually shorter and more numerous
2. Propels water parallel to the surface to which it is attached
IV. NUTRITION
A. Phototrophic
1. Use light energy
2. Referred to informally as algae
B. Chemotrophic
1. Osmotrophic
a) Transport soluble nutrients across membrane
2. Phagotrophic
a) Pseudopodia wrap around food
(1) When pseudopodia meet on opposite side of the food particle, they fuse
(2) The food particle ends up inside a cell in a vacuole called a phagosome
b) Lysosomes fuse with phagosome
(1) The lysosomes' enzymes digest the food particle
(2) The resultant vacuole is called a phagolysosome
V. KINGDOMS AND GROUPS
A. Phylum Apicomplexa
1. Characteristics
a) All are animal parasites
(1) Complex life cycle requiring two or more hosts
b) All have a complex at their apical end which aids in penetrating host cells, hence,
Apicomplexa
2. Plasmodium
a) Causes malaria
(1) Approximately 300 million infected
(2) Approximately 2 million deaths a year
b) Transmitted by mosquitoes
(1) The female Anopheles mosquito
c) Sexual reproduction in the mosquito
(1) Mosquito sucks up gametophytes when taking a blood meal
(2) Male and female gametophytes fuse and zygote undergoes many cell
divisions to produce a sporozoites.
(3) Sporozoite migrates to salivary gland
d) Asexual reproduction in humans
(1) Human is infected by infected mosquito
(2) Sporozoites migrates to liver
(3) Asexually merozoites that infect erythrocytes (red blood cells)
(4) Merozoites produced in erythrocytes lyse the cell and infect other erythrocytes
B. Subphylum Mastigophora
1. Giardia
a) Causes "backpacker's disease"
b) Transmitted fecal - orally
c) Many beaver serve as reservoir
2. Euglena
a) Phototrophic in the light, chemotrophic in the dark
3. Trypanosoma
a) T. brucei
(1) Causes African sleeping sickness
(2) Transmitted by the bite of a Tsetse fly
(3) About 150,000 infected with 20,000 new cases per year
(4) Also infects cows and horses
b) T. cruzi
(1) Causes Chagas disease in the Americas
(2) Transmitted by the bite of a kissing bug
4. Phylum Dinoflagellata
a) Red tides and paralytic seafood poisoning
(1) Blooms of dinoflagellates can make swimming uncomfortable and dangerous
due to released neurotoxins
(2) Accumulation of toxins in shell fish can lead to paralytic seafood poisoning
C. Subphylum Sarcodina
1. Characteristics
a) Have pseudopodia
2. Amoeba
a) Have blunt pseudopodia (lobopodia) for movement and phagocytosis
3. Forams
a) Slender pseudopodia (axopodia) reinforced with microtubules
b) Porous shells of calcium carbonate
(1) Large contributor to sedimentary rock
D. Phylum Ciliophora
1. Characteristics
a) Contain cilia
b) Contain two types of nuclei
(1) A macronucleus handles every day function
(2) The micronucleus is used only for sexual reproduction
2. Sexual reproduction (conjugation)
a) Paramecium partially fuse
b) All but one micronuclei disintegrate
c) The micronucleus undergoes meiosis
(1) Resulting in 4 haploid micronuclei
(2) Three of the resulting micronuclei disintegrate
d) The one remaining micronucleus undergoes mitosis
(1) Resulting in two haploid micronuclei
e) Paramecium swap one micronuclei each
(1) They retain their other micronucleus
f)
Swapped micronuclei fuses with one remaining micronuclei
g) Resulting diploid micronuclei undergoes several mitotic divisions
h) Macronucleus disintegrates
i)
Four micronuclei fuse, replicate, and become macronuclei
E. Four remain as micronuclei