The document discusses several key points about protozoa: 1. Protozoa are unicellular eukaryotes that are found in both aquatic and terrestrial environments. They display a wide diversity of shapes and methods of nutrition, locomotion, and reproduction. 2. The earliest protozoa evolved over 1.5 billion years ago from ancient archaea. They are divided into multiple phyla based on features like nucleus type and locomotion. 3. Important protozoan groups include the SAR supergroup, apicomplexans, ciliates, and dinoflagellates. Many protozoa are free-living but some are parasitic and can cause serious diseases in humans and other

1. The protozoa

2.  1. Fossil study of protozoans: The fossil record indicates
that all protists and animal phyla were present during the
Cambrian period, about 550 million years ago. Unfortunately,
only a few fossil evidence are available. Therefore, scientists
gather evidence by examining the structure and function of
living species.
 2. Origin of protists: Ancient Archaea were the first living
organisms on this planet. The Archaea gave rise to the
kingdom Protista about 1.5 billion years ago. The
endosymbiont hypothesis explains the mechanism of this
evolution of protista. Most scientists agree that the protists
probably arose from more than one ancestral Archaean group.

3.  3. Taxonomy of protozoans: Zoologists recognize
between 7 and 45 phyla of protists. These phyla
represent numerous evolutionary lineages. Therefore,
the protists are polyphyletic.
◦ Kingdom protista has two groups
 Plant like protista (Algae): These are primarily
autotrophic.
 Animal like protista (protozoa): These are
primarily heterotrophic.

5.  Protozoa (Gr. proto, first zoa, animal) have unicellular
organization, which does not necessarily imply that they are
simple organisms. In some protozoan phyla, individuals group
to form colonies, associations of individuals that are not
dependent on one another for most functions.
 Maintaining homeostasis in protozoans:
 Protozoans maintain homeostasis by following methods:
◦ Support
◦ Osmoregulation
◦ Ingestion of food
◦ Process of digestion
◦ Respiration and excretion
◦ Reproduction

6.  The body of protozoans are supported by pellicle and cytoplasm.
◦ 1. A regular arrangement of microtubules is called the pellicle. Pellicle
underlies the plasma membrane of many protozoa. The pellicle is rigid
enough to maintain the shape of the protozoan, but it is also flexible.
◦ 2. The cytoplasm of a protozoan is differentiated into two regions.
The portion of the cytoplasm just beneath the pellicle is called
ectoplasm It is relatively clear and firm. The inner cytoplasm, called
endoplasm , is usually granular and more fluid.
2. Osmoregulation
• Most marine protozoa have solute concentrations similar to that of their
environments.
• However, Freshwater protozoa must regulate the water and solute
concentrations of their cytoplasm. Water enters freshwater protozoa by
osmosis because of higher solute concentrations in the protozoan than in
the environment. Contractile vacuoles remove this excess water. These
contractile vacuoles are composed of collecting tubule.

8.  There are different methods of ingestion of food:
◦ Most protozoa absorb dissolved nutrients by active
transport.
◦ Some protozoa ingest whole or particle of food endocytosis.
It forms food vacoules.
◦ Some protozoa ingest food in a specialized region analogous
to a mouth, called the cytopharynx or gullet.
4. Process of digestion
• Digestion and transport of food occurs in food vacuoles that
form during endocytosis.
• Food vacuoles fuse with enzyme-containing lysosomes and
circulate through the cytoplasm, distributing the products of
digestion. After digestion is complete, the vacuoles are called
egestion vacuoles. They release their contents by exocytosis,
sometimes at a specialized region of the plasma membrane or
pellicle called the cytopyge.

9.  Protozoan have a large surface area in proportion to their
volume. Both gas exchange and excretion occur by diffusion
across the plasma membrane.
◦ Gas exchange involves absorption of oxygen and elimination of the
carbon dioxide.
◦ Excretion is the elimination of the nitrogenous by-products of protein
metabolism. By-product in protozoa is mostly ammonia.
Reproduction
• Both asexual and sexual reproduction occurs among the protozoa.
– Asexual reproduction
• Binary fission (mitosis produces two nuclei)
• Budding ( mitosis produces a small cytoplasm along with nuclei)
• Multiple fission or schizogony (parent cell divides into multiple no. of
small cells)
– Sexual reproduction ( gamete formation>zygote> meiosis>mitosis)
• Concern from the book. See page 106-107 of miller and harley.

11. Contents under study
2. Protozoan taxonomy

12.  Many protozoa have symbiotic lifestyles. Symbiosis (Gr. syn, with bios,
life) is an intimate association between two organisms.
 There are following types of symbiosis in protozoans:
◦ Parasitism:
 An association in which one organism lives in or on a second
organism, called a host, and cause disease in the host is called
parasitism.
 Some parasites have multiple hosts. These hosts may be:
 Definitive host (sexual stages occur)
 Intermediate host (offsprings are enter into another host, and reproduce
asexually in it and passes into definitive host)
◦ Commensalism:
 The symbiotic relationship in which one member of the relationship
benefits, and the second member is neither benefited nor harmed.
◦ Mutualism:
 The symbiotic relationship in which both species benefit.

13. Zoologists who specialize in the study of protozoa are called
protozoologists.
 Most protozoologists now regard the protozoa as a
subkingdom, consisting of seven separate phyla within the
kingdom Protista.
◦ These are the phylum Sarcomastigophora, consisting of flagellates and
amoebae with a single type of nucleus.
◦ The phyla Labyrinthomorpha, Apicomplexa, Microspora, Acetospora,
and Myxozoa, consisting of either saprozoic or parasitic species.
◦ And the phylum Ciliophora, containing ciliated protozoa with two types
of nuclei.
 The classification of this subkingdom into phyla is based
primarily on types of nuclei, mode of reproduction, and
mechanism of locomotion
 Overall, the number of protozoan species exceeds 38,000.

14.  Kingdom protista
◦ Subkingdom protozoa: ( single celled eukaryotes, lacking collagen and cell wall)
 1. Phylum Sarcomastigophora (About 18,000 species)
 Subphylum Mastigophora
 Class Phytomastigophorea (Euglena, Volvox, Chlamydomonas)
 Class Zoomastigophorea (Trypanosoma, Leishmania, etc.)
 Subphylum Sarcodina (About 4,000+3000 species)
 Superclass Rhizopoda (Amoeba, Entamoeba, Arcella)
 Superclass Actinopoda (Marine radiolarians, Freshwater heliozoans)
 Subphylum Opalinata (Opalina, Zelleriella)
 2. Phylum Labyrinthomorpha (Labyrinthula.)
 3. Phylum Apicomplexa (Coccidians, Plasmodium) About 5,500 species.
 4. Phylum Microspora (Nosema). About 850 species.
 5. Phylum Acetospora (Paramyxa, Haplosporidium).
 6. Phylum Myxozoa ( The Myxozoans) About 1,250 species.
 7. Phylum Ciliophora (Paramecium etc.) About 9,000 species.

15.  CLASS PHYTOMASTIGOPHOREA
◦ Dinoflagellates
 Flagella – 2 (1 wrap around the body & other is trailing flagellum)
 Pigment ( Xanthophylls)
 Toxins ( Red tide – Bloom )
◦ Euglena
◦ Paramecium

20.  Members of the class Zoomastigophorea lack
chloroplasts .
 They are heterotrophic.
 Some members of this class are important parasites of
humans.
 One of the most important species of zoomastigophoreans
is Trypanosoma brucei. This species is divided into three
subspecies:
◦ T. b. Brucei (Parasite of nonhuman mammals of Africa.
◦ T. b. Gambiense (Cause sleeping sickness in humans).
◦ T. b. Rhodesiense (Cause sleeping sickness in humans).
 Tsetse flies (Glossina spp.) are intermediate hosts and
vectors of all three subspecies.
 Disease cycle.

24.  Members of the subphylum Sarcodina (sarko-dinah) are
the amoebae.
 When feeding and moving, they form temporary cell
extensions called Pseudopodia (Gr. Pseudes - false +
Podion - little foot).
 Pseudopodia exist in a variety of forms.
◦ Lobopodia – (mean little foot)
◦ Filopodia – (means thread)
◦ Reticulopodia – ( means netlike)
◦ Axopodia – (means axle)

25.  1. Lobopodia: They are broad cell processes containing
ectoplasm and endoplasm. They are used for locomotion and
engulfing food.
 2. Filopodia: They contain ectoplasm only. They
provide a constant two-way streaming movement, that delivers
food in a conveyor-belt fashion.
 3. Reticulopodia: They are similar to filopodia, except
that they branch and rejoin to form a netlike series of cell
extensions.
 4. Axopodia: They are thin, filamentous and supported by
a central axis of microtubules. The cytoplasm covering the
central axis is adhesive and movable. Food caught on
axopodia can be delivered to the central cytoplasm of the
amoeba.

27.  Subphylum Sarcodina>Superclass Rhizopoda>Class Lobosea.
 The most familiar amoebae belong to the superclass Rhizopoda, class
Lobosea, and the genus Amoeba.
◦ These amoebae are naked. They have no test or shell.
◦ They are normally found on shallow-water substrates of freshwater
ponds, lakes, and slow-moving streams.
◦ All amoeba are particle feeders, a few amoeba are pathogenic they feed
on other protists and bacteria.
◦ They engulf food by phagocytosis. The process phagocytosis involves
the cytoplasmic changes and food vacuoles are formed.
◦ Asexual reproduction takes place by Binary fission.
◦ Sexual reproduction is not present in them.
 Shelled Rhizopodans:
◦ Other members possess a test or shell. The shell may be:
 Made up of Calcium carbonate – Calcareous, Protein – Proteinaceous,
Silica – Siliceous, Polysaccharides – Chitinous or it may be form from
debris.

28.  Note: Tests are protective structures that the cytoplasm
secretes.

29. Arcella is a common freshwater,
shelled amoeba. It has a brown,
proteinaceous test that is flattened on one
side and domed on the other.
Pseudopodia project from an opening on
the flattened side.
Difflugia is another common
freshwater, shelled amoeba. Its test is
vase shaped and is composed of mineral
particles embedded in a secreted matrix.

30. Difflugia

31. Arcella

32.  It causes dysentery in humans. It causes Inflammation and
ulceration of the lower intestinal tract and a debilitating
diarrhea – It is a blood and mucus characterize dysentery.
Amoebic dysentery is a worldwide problem. It is caused due
to unsanitary conditions.
 A significant problem in the control of Entamoeba histolytica
is that an individual can be infected without experiencing
symptoms of the disease.
 Amoebae live in the folds of the intestinal wall, feeding on
starch and mucoid secretions. They pass from one host to
another in the form of cysts transmitted by fecal contamination
of food or water.
 After ingestion by a new host, amoebae leave their cysts and
take up residence in the host’s intestinal wall.

33. Entamoeba histolytica

36.  Foraminiferans (commonly called forams) are primarily a
marine group of amoebae.
 Foraminiferans possess reticulopodia and secrete a test that is
primarily calcium carbonate.
 The Foraminiferans grow and secrete new, larger chambers
that remain attached to the older chambers (figure 8.13). Test
enlargement follows a symmetrical pattern. It may form two
types of chambers:
◦ Straight chain of chambers
◦ Spiral arrangement that resembles a snail shell.
 Many of these tests become relatively large; for example,
“Mermaid’s pennies,”. It is several centimeters in diameter. It
is found in Australia.

37. Figure 8.13

38.  Their tests are abundant in the fossil record of
Cambrian period.
 They make up a large component of marine
sediments.
 Their tests accumulation on the floor of oceans
resulted in limestone and chalk deposits. The white
cliffs of Dover in England are one example of a
foraminiferan-chalk deposit.
 Oil geologists use fossilized forams to identify
geologic strata during oil exploration.

39.  Heliozoans are aquatic amoebae.
 They are either planktonic or live
attached by a stalk to some substrate.
 The plankton of a body of water consists
of those organisms that float freely in the
water i.e., phytoplanktons &
zooplankton.
 Heliozoans are either naked or enclosed
within a test. The tests contains openings
for axopodia (figure 8.14a).

40. Figure 8.14a
Heliozoans

41.  They are marine and freshwater amoebae.
 They are planktons.
 They are relatively large; some colonial forms may
reach several centimeters in diameter.
 They possess a test (usually siliceous).
 It is composed of long, movable spines and needles.
Sometimes, it forms highly sculptured and
ornamented lattice (figure 8.14b).
 When radiolarians die, their tests settle down in the
ocean floor. Some of the oldest known fossils of
eukaryotic organisms are radiolarians.

42. Radiolarians
Figure 8.14b

43.  The very small phylum Labyrinthomorpha.
 They consists of protozoa with spindle-shaped, nonamoeboid,
vegetative cells.
 In some genera, amoeboid cells use a typical gliding motion to
move within a network of mucous tracks.
 Most of the members are marine, and either saprozoic or
parasitic on algae or seagrass.
 Several years ago, Labyrinthula killed most of the “eel grass”
on the Atlantic coast.
 Many ducks that feed on the grass face the starvation.

45.  Members of the phylum Apicomplexa are all
parasites.
 Characteristics of the phylum include:
1. They have apical complex for penetrating host cells.
2. They have single type of nucleus.
3. They have no cilia and flagella, except in certain
reproductive stages.
4. The life cycles that typically include asexual stages;
schizogony, sporogony and sexual stages;
gametogony.

46.  The most important species in the phylum Apicomplexa are
members of the class Sporozoea. The class name derives from
most sporozoeans producing a resistant spore or oocyst
following sexual reproduction.
 Some members of this class, including Plasmodium and
coccidians, cause a variety of diseases in domestic animals and
humans.
 Life cycle: Many coccidian are intracellular parasites, and
their life cycles have three phases.
◦ Schizogony or Merogony – Mesozoites formed by asexually.
◦ Gametogony – Merozoites undergo gametogony (the sexual phase),
Microgametocytes + Macrogametocytes = Zygote; enclosed by oocyst.
◦ Sporogony – Zygote undergoes meiosis than mitosis.

47.  1. Malaria : Plasmodium causes malaria. It was present back
in 1550 A.D. Malaria contributed significantly to the failure of
the Crusades during the medieval era, and along with typhus.
These diseases destroy the armies. Now over 100 million
humans are annually infected by malaria.
 Life cycle of plasmodium:
◦ The Plasmodium life cycle involves vertebrate and mosquito
hosts (figure 8.15).
◦ Schizogony occurs first in liver cells and later in red blood
cells.
◦ Gametogony also occurs in red blood cells.
◦ A mosquito takes in gametocytes during a meal of blood,
and the gametocytes fuse and form zygote.
◦ The zygote penetrates the gut of the mosquito and
transforms into an oocyst.
◦ Sporogony forms haploid sporozoites that may enter a new
host when the mosquito bites the host.

49.  Symptoms:
◦ The symptoms of malaria recur periodically and are called paroxysms.
◦ Chills and fever correlate with the maturation of parasites,
◦ the rupture of red blood cells, and the release of toxic metabolites.
 Species of Plasmodium :
◦ P. Vivax : Its paroxysms recur every 48 hours. This species occurs in
temperate regions and has been nearly eradicated in many parts of the
world.
◦ P. Falciparum : It causes the most virulent form of malaria in
humans. Its Paroxysms are irregular. It is present in mainly tropical and
subtropical regions. It remains one of the greatest killers of humanity,
especially in Africa.
◦ P. Malariae: It is worldwide in distribution and causes malaria
with paroxysms that recur every 72 hours.
◦ P. Ovale: It is the rarest of the four human malarial species and
is primarily tropical in distribution.

50.  2) Coccidiosis : Coccidians cause coccidiosis. It is a
disease of poultry, sheep, cattle, and rabbits. Two genera,
Isospora and Eimeria, are particularly important parasites of
poultry.
 3) Cryptosporidium : It causes chronic diarrhea in
AIDS patient. It resist chlorination. It is most virulent in
immunosuppressed individuals.
 4) Toxoplasmosis :
 Toxoplasmosis is a disease of mammals, including humans, and
birds.
 Sexual reproduction of Toxoplasma occurs primarily in cats.
 Infections occur when oocysts are ingested with food
contaminated by cat feces, or when meat containing encysted
merozoites is eaten raw or poorly cooked.
 Most infections in humans are with out any symptoms and once
infection occurs than an effective immunity develops.

51.  4) Toxoplasmosis :
◦ If a woman is infected near the time of pregnancy, or during
pregnancy, congenital toxoplasmosis may develop in a
fetus.
◦ Congenital toxoplasmosis is a major cause of stillbirths and
spontaneous abortions.
◦ Fetuses that survive frequently show signs of mental
retardation and epileptic seizures.
 Precaution or cure measures:
◦ Congenital toxoplasmosis has no cure.
◦ Toxoplasmosis also ranks high among the opportunistic
diseases afflicting AIDS patients.
◦ Steps to avoid infections by Toxoplasma include keeping
stray and pet cats away from children’s sandboxes; using
sandbox covers.
◦ We should not eat raw mutton or beef.

52. Phylum MYXOZOA

53.  The parasites of insects.
 Members of the phylum Microspora
commonly called microsporidia.
 They are small, obligatory intracellular
parasites.
 Included in this phylum are several species
that parasitize beneficial insects.
 Nosema bombicus parasitizes silkworms
(figure 8.16), causing the disease pebrine, and
N. apis causes serious dysentery (foul brood)
in honeybees.

54.  The movement is also shown as well.

55.  These parasites have a possible role as
biological control agents for insect pests.
For example, the U.S. Environmental
Protection Agency has approved and
registered N. locustae for use in residual
control of rangeland grasshoppers.
 Recently, four microsporidian genera
have been implicated in secondary
infections of immunosuppressed and
AIDS patients.

57.  Acetospora is a relatively small phylum
that consists exclusively of obligatory
extracellular parasites characterized by
spores lacking polar caps or polar
filaments.
 The acetosporeans (e.g., Haplosporidium)
primarily are parasitic in the cells,
tissues, and body cavities of molluscs.

59.  The phylum Myxozoa are commonly called
myxosporeans.
 They are all obligatory extracellular parasites
in freshwater and marine fish.
 They have a resistant spore with one to six
coiled polar filaments.
 The most economically important
myxosporean is Myxosoma cerebralis, which
infects the nervous system and auditory organs
of trout and salmon, causing whirling or
tumbling disease.

60. Myxosoma cerebralis

61. fish infected by Myxosoma cerebralis

62.  The phylum Ciliophora includes some of the most complex
protozoa (see table 8.1).
 Characteristics of the phylum Ciliophora include:
1. Ciliates are widely distributed in freshwater and marine
environments.
2. A few ciliates are symbiotic.
3. They have cilia for locomotion. Cilia are also used for the
generation of feeding currents in water.
4. They have rigid pellicle. It keeps their shapes has fixed.
5. They have distinct cytostome (mouth) structure.
6. They have dimorphic nuclei, typically a larger
macronucleus and one or more smaller micronuclei.

63.  Cilia:
◦ Cilia are generally similar to flagella, except that
they are much shorter, more numerous, and widely
distributed over the surface of the protozoan.
◦ Ciliary movements are coordinated so that ciliary waves
pass over the surface of the ciliate. Many ciliates can reverse
the direction of ciliary beating and the direction of cell
movement.
◦ Some ciliates have evolved specialized cilia. Cilia
may cover the outer surface of the protozoan. They
may join to form cirri, which are used in
movement. Alternatively, cilia may be lost from
large regions of a ciliate.

66. Cilia and other Pellicular structures
 Basal bodies (kinetosomes) :
 It is the root of the cilia. Cilia arise from the basal bodies.
 Basal bodies of the adjacent cilia are interconnected.
 They form an elaborate network of fibers. These fibers
anchor the cilia and give shape to the organism.
 Trichocysts :
 Trichocysts are pellicular structures primarily used for
protection.
 They are rodlike or oval organelles oriented perpendicular
to the plasma membrane. In Paramecium, they have a
“golf tee” appearance.
 The pellicle can discharge trichocysts, which then remain
connected to the body by a sticky thread (figure 8.18).

68.  Mechanism of feeding:
◦ Paramecium: Some ciliates, such as Paramecium, have a
ciliated oral groove along one side of the body. Cilia of the
oral groove sweep small food particles toward the
cytopharynx, where a food vacuole forms. When the food
vacuole reaches an upper size limit, it breaks free and
circulates through the endoplasm and digestion takes place.
◦ Didinium: Some free-living ciliates prey upon other
protists or small animals. Prey capture is usually a case of
fortuitous contact. The ciliate Didinium feeds principally on
Paramecium, a prey that is bigger than itself. Didinium
forms a temporary opening that can greatly enlarge to
consume its prey.

70.  Suctorains : Suctorians are ciliates that live attached to
their substrate. They possess tentacles whose secretions
paralyze prey, often ciliates or amoebae. The tentacles digest
an opening in the pellicle of the prey, and prey cytoplasm is
drawn into the suctorian through tiny channels in the tentacle.
The mechanism for this probably involves tentacular
microtubules.

71.  Genome : Ciliates have two kinds of nuclei.
◦ A large, polyploid macronucleus regulates daily
metabolic activities.
◦ One or more smaller micronuclei are the genetic
reserve of the cell.
 Asexual reproduction:
◦ Ciliates reproduce asexually by transverse binary
fission and, occasionally, by budding.
◦ Budding occurs in suctorians and results in the
formation of ciliated, free-swimming organisms
that attach to the substrate and take the form of the
adult.

72.  Sexual reproduction: conjugation
◦ Ciliates reproduce sexually by conjugation. The partners
involved are called conjugants.
◦ Many species of ciliates have numerous mating types, not all
of which are mutually compatible.
 The steps are as follows:
Initial contact between individuals is apparently random,
and sticky secretions of the pellicle facilitate adhesion.
Ciliate plasma membranes then fuse and remain that way for
several hours.
The macronucleus does not participate in the genetic
exchange. The macronucleus breaks up and reforms from
micronuclei of the daughter ciliates.

73. The meiosis takes place in the conjugants and four haploid
pronuclei are formed.
The three pronuclei in each conjugate degenerate. The
remaining pronuclei divides by mitosis. Thus each conjugant
has now two pronuclei.
The conjugants exchange pronuclei mutually. The pronuclei
fuse with each other in each conjugant.
The conjugants separate from each other and they are now
called exconjugants.
Each exconjugants undergo a series of nuclear divisions. Thus
eight daughter nuclei are formed in each exconjugants. Two are
degenerated.
Four of the remaining six nuclei become macronuclei. Each
exconjugants divides at this stage. Now each daughter nuclei
has two macronuclei and one micronucleus.
Each micronucleus again divides. Cytoplasmic division occurs.
Thus four paramecia are formed from each exconjugant.

75.  Most ciliates are free living; however, some are commensalistic
or mutualistic, and a few are parasitic.
 Balantidium coli is an important parasitic ciliate that lives in the
large intestines of humans, pigs, and other mammals.
 At times, it is a ciliary feeder; at other times, it produces
proteolytic enzymes that digest host epithelium, causing a flask-
shaped ulcer. (Its pathology resembles that of Entamoeba
histolytica.)
 B. coli is passed from one host to another in cysts that form as
feces begin to dehydrate in the large intestine.
 Fecal contamination of food or water is the most common form of
transmission. It is most common in the Philippines.
 Large numbers of different species of ciliates also inhabit the
rumen of many ungulates (hoofed animals). These ciliates
contribute to the digestive processes of their hosts.