Protozoa
Animal like Protists
Evolutionary Perspective
• Protozoan is a complete organism in which all life
activities are carried on within a single membrane
• First fossil evidence of cells containing membrane
bound structures 1.5 billion years old
• Archaea and Eubacteria contributed to the origin of
protists
• Endosymbiont hypothesis explains how this could have
occurred
• Six phylogenitic protist Super groups are recognized
• All protist groups were present by the cambrian period
Life within a single cell
• Maintaining Homeostasis with organelles
• Pellicle- microtubules under the cell membrane, maintains
shape but is flexible
• Cytoplasm differentiated into two regions
– Ectoplasm- clear and firm
– Endoplasm- granular more fluid
• Contractile Vacuoles- expel excess water
• Nutrition
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Cytopharnyx- ingests larger food (mouth)
Endocytosis- thru membrane forms food vacuole
Smaller nutrients enter by active transport across membrane
Egestion vacuole expels undigested wastes
Single Cell
• Protozoa are so small they have high surface
area to volume ratio which facilitates difusion
• Gas exchange of oxygen and carbon dioxide
occurs easily
• Excretion of Nitrogenous wastes (ammonia) by
diffusion thru the cell membrane
Reproduction
• Both sexual and Asexual reproduction occur
• Binary Fission- simplest asexual, occurs by mitosis
producing two nuclei which separate when cytoplasm
divides. Two identical cells
• Some organelles duplicate as well to ensure each new cell
is complete
• Budding- mitosis produces new nucleus which is passed
into cytoplasm much smaller than parent
• Multiple Fission- mitosis produces many new nuclei which
are passed on to multiple daughter cells
• Sexual reproduction- sexually mature individual is haploid,
gametes produced by mitosis, meiosis follows union of
gametes
Super Groups
•
Excavata-Have feeding groove, flagellum or had one, feed by flagella generated
current
– Giardia- Anaerobic metabolism, causes waterborn disease in U.S
– Trichomonas- flagellated, causes sexually transmitted disease
– Euglena- flagella, posses chlorophyll, photosynthetic, pigment shield allows them to orient
towards the light
– Trypanosoma- cause African sleeping sickness from bite of Tsetse fly, attack central nervous
system, Death if not treated
•
Amebozoa- when feeding and moving they form temporary extensions called
pseudopodia, some lack a test or cell wall others have a test of calcium carbonate
or chitin
– Tubulinea- live anywhere they can remain moist, free living forms form tests of cemented
minerals, many are parasites of invertabrates, fish, and mammals
– Acanthamoebida- aerobic inhabitants of soil and water, two types are parasites of humans,
one attacks brain the other infects the eye
– Entamoebida- use pseudopodia to capture food, lack mitochondria, cause dysentery in
humans by ulceration and inflammation in lower intestinal tract, diarrhea contains blood and
mucus
Giardia
Trichomonas
Euglena
Trypanosoma
Tubulinea
Acanthamoebida
Entamoebida
Super Groups
•Rhizaria- related to amoeboid some have fine pseudopodia used for feeding
̶Foraminiferia- primarily marine, form test of calcium carbonate, resemble spiral shells from
beach, abundant in fossil record, formed chalk cliffs of Dover, planktonic
̶Heliozoans- some naked some have test with holes for axopodia, planktonic
̶Radiolaria- Planktonic, marine and fresh, radial symmetry test of silica, very porous for axopodia
•Chromalveolata- diverse group, autotrophic mixotrophic or heterotrophic, all have
plastids
̶Dinoflagellates- one flagellum that wraps around a central groove, spins on it axis, second
flagellum propels it, contain chlorophyll and xanthophyll (reddish), can become so numerous they
cause red tide and produce toxins that kill fish, Red sea was probably named after this
̶Plasmodium- tropical, causes malaria, 100 million people contract it yearly, is a bigger problem
with global warming, spread by mosquito
̶Cryptosporidium- causes chronic diarrhea, only known protozoan to resist chlorination
̶Toxoplasma- found in cats and birds, spread in cat feces, causes stillbirths and spontaneous
abortions in humans, fetuses that survive show mental retardation or epilepsy, keep cats away
from sand boxes, no raw meat.
̶Paramecium-cilia covered membrane, ciliated oral groove leads to food vacuole, sexual
reproduction with micronuclei, many live in the gut of hoofed mammals and contribute to
digestion