Sub-Kingdom
Protozoa
General Characteristics
• Single-celled or unicellular organisms; some live in
colonies;
• Size = microscopic (3 to 1,000 microns).
• No germ layers, tissues, or organs;
• However, specialized intracellular "organelles" are
present
• Over 64, 000 species have been described; about 50,
000 are free-living
• Locomotion by pseudopodia, flagella, or cilia.
• Symmetry = all types (bilateral, radial,
spherical, or asymmetrical)
• Free living, commensal, parasitic, or
mutualistic
• Mostly naked, but few have simple protective
exoskeletons (tests), E.g. Arcella and Difflugia
• Nutrition = autotrophic (holophytic), saprozoic,
saprophytic, or holozoic.
• Reproduction: asexual = longitudinal and transverse
binary fission, budding, multiple fission (sporogony,
schizogony)
• Sexual = syngamy, autogamy, conjugation
List of Phyla
Phylum Sarcodina
– Amoeba-like organisms (e.g. Amoeba, Entamoeba, Arcella)
• Phylum Mastigophora
– Phytomatigophorans (e.g. Euglena, Chlamydomonas)
– Zoomastigophorans (e.g. Trypanosoma, Giardia,
Trichonomas, Trichonympha)
• Phylum Chlorophyta (e.g. Volvox)
• Phylum Ciliophora (e.g. Paramecium, Balantidium,)
• Phylum Apicomplexa (e.g. Plasmodium, Eimeria,
Toxoplasma, Isospora)
Phylum Sarcodina
• Organisms move by pseudopodia, flagella, or a
combination
• Single nucleus, or monomorphic nuclei
• Genera
– Amoeba - without a test, naked (free-living)
– Arcella - with a calcareous test (free-living)
– Entamoeba - without a test (parasitic)
Figure 11.10
Amoeba
Pseudopod
Food Vacuole
Contractile Vacuole
Nucleus
Phagocytosis
Hyaline Cap
Amoeba hunting
food
Arcella
Test
Nucleus
Arcella
Pseudopod
Phylum Mastigophora
• Organisms move by one or two flagella
• Single nucleus, or monomorphic nuclei
• Some are capable of photosynthesis; chloroplasts usually
present
• Others are either mutuals or parasites
• Common symmetry is bilateral
Subphylum Euglenoidea
• Plant like organisms; photosynthesis
• Solitary
• Symmetry is usually bilateral
• Presence of stigma for light detection
Euglena
Euglena
Chloroplasts
Contractile Vacuole
Flagellum not
visible
Stigma
Kinetoplastida
• Organisms are only
heterotrophic
• No chloroplasts present
• all parasitic
Red Blood Cells
Organism
Trypanosoma smear – cause of sleeping sickness
Trypanasoma sp.
Trypanosoma
Red Blood Cells
Leishmania sp
Giardia sp
Phylum Chlorophyta
• Flagellated single or colonial organisms
• All members are autotrophic, chloroplasts with
chlorophyll
• Genetically different from Euglenozoa
Volvox life cycle
Zygote
Egg
Mother
Colony
Volvox
Phylum Apicomplexa
• organisms do not have
locomotor structures;
• all species are parasitic
• asexual reproduction
involves multiple fission
(schizogony, sporogony)
Plasmodium smear – cause of Malaria
Plasmodium – agent
For malaria
Vector
Final Host
Ring stage
trophozoite
merozoite
Red blood cell
Trophozooite
Ring stage in red blood cell
Ring stage – Early Trophozoite
Schizont with merozoites in red blood cell
Red blood cell
Merozoites in the Schizont
Female
Male
Gametocytes
Phylum Ciliophora: The Ciliates
• Organisms move by cilia
• Usually two sizes of nuclei ; Macronucleus and
micronucleus
• Reproduction usually by transverse binary fission
• Sexual reproduction by conjugation
Paramecium
Binary Fission – Asexual Reproduction
Conjugation – sexual reproduction
Vorticella
Stentor
Protozoa: Ecological Importance
• Unicellular level of organization
• Highly specialized organelles for various
physiological processes
• Prominent members of the aquatic food chain,
especially detritivores and
• Symbiosis is highly developed among
members i.e. Commensals, parasites, mutuals,
and detritivores with multicellular organisms