This document provides an overview of chapter 3 from the textbook BIOL 201: Invertebrate Zoology. It discusses the phylum Protozoa, which includes over 215,000 described species of protists that are incredibly diverse in ecology, structure, and function. Key points covered include protozoan roles in nutrient cycling and primary productivity, structures like the pellicle and contractile vacuoles, modes of asexual and sexual reproduction, and important representative phyla such as Euglenozoa, Chlorophyta, Choanoflagellata, and Alveolata.

1. BIOL 201:
Invertebrate Zoology
Chapter 3:
Protozoa
Rob Swatski
Asst. Prof. Biology
HACC-York1

2. Protozoa
“First animals”
215,000 described
species (equal to the
# of described plants)
Incredibly diverse!
Major ecological
value
2

3. Protozoan
Ecology
Many are important
nutrient cyclers
Many photoautotrophic,
& make up 40% of all
primary productivity
Major component of
plankton communities
25% of the described
species live as
symbionts; many
parasitic
3

4. Protozoan
Structure &
Function
Pellicle: protozoan
body wall (cell
membrane &
cytoskeleton)
Cytostome: cell
mouth where food
enters a vacuole via
phagocytosis
Test (lorica, theca,
shell): internal or
external skeleton
Alveoli: vesicles
below cell membrane
4

5. 5
Osmoregulation
Hypotonic &
hypertonic
environments create
osmotic problems
for organisms
Osmoregulation =
the control of water
balance
Contractile
vacuoles

6. Contractile
Vacuoles
Network of vesicles or
tubules (spongiome),
that collect ions from
cytoplasm
Ions delivered to the
contractile vacuole
Vacuole contracts & its
contents are expelled
Rate of discharge
varies: every 6 sec to 15
min
6

7. 7
Contractile Vacuoles

8. 8

9. 9

10. Hypotonic
solution
Lysis Normal
Isotonic
solution
Shriveled
Hypertonic
solution
10
Tonicity

11. Asexual
(Clonal)
Reproduction
Most protozoa reproduce
asexually via mitosis
Binary Fission: splitting of
parent into 2 similar
daughter cells
Budding: portion of parent
splits off to form a new
smaller individual
Nuclear membrane stays
intact & spindle forms inside
(closed spindle)
11

12. Sexual
Reproduction
Widespread, but
not universal
Conjugation: fusion
of 2 individual cells
DNA
Areas of cell
membranes dissolve
& genes exchanged
Very diverse &
complex life cycles
12

13. Asexual Reproduction:
Pros/Cons
PRO:
Reproduction
can occur
without a mate
(good for
isolated species)
PRO: Produces
offspring
quickly; no
energy wasted
in gamete
production,
fertilization, or
development
PRO: Continues
identical
genotypes
(beneficial if
already well-
adapted to that
environment)
CON: Limited
genetic
possibilities;
constricts gene
pool & species
could die out if
environment
changes
13

14. Sexual Reproduction:
Pros/Cons
PRO: Increases
genetic variability via
crossing over,
independent
assortment, &
random fertilization
PRO: May improve
environmental
adaptability for
certain individuals &
the entire species
CON: Finding mates in
isolated or sessile
species
14

15. Encystment
Found in most FW
species: pumps water
out of cell & surrounds
itself with a cyst
Can survive harsh
environmental
conditions for years
Resists desiccation &
does not need food
Water, wind, & mud
dispersal
15

16. Phylum
Euglenozoa
Two main classes:
Euglenoidea &
Kinetoplastida
Flagellates
Solitary & free-living
Reproduce asexually
16

17. Class
Euglenoidea
(Phylum Euglenozoa)
1000 species
Two flagella: 1 long &
1 short
Euglenoid
movement: peristaltic
motion
Asexual reproduction
occurs via longitudinal
binary fission
17

18. Class
Euglenoidea,
cont.
Contractile vacuole
Pigmented eyespot shades a
photosensitive paraflagellar
body
Heterotrophic,
photoautotrophic, or
mixotrophic
Photosynthetic species rotate
on their longitudinal axis as
they swim toward light
18

19. Euglenoids 19

20. Class
Kinetoplastida
(Phylum
Euglenozoa)
600 species; most parasitic
Elongate cells with 1-2
flagella & undulating
membrane
Asexual reproduction
All contain a mass of
DNA (the kinetoplast),
located in a large
mitochondrion
20

21. Kinetoplast
Link between
kinetoplast &
parasitic lifestyle
Codes for
mitochondrial
morphogenesis
Parasites alternate
between aerobic &
anaerobic host
environments
21

22. Trypanosomes
(Class
Kinetoplastida)
Parasite causing African sleeping
sickness, transmitted by tsetse
fly
One large flagellum joining an
undulating membrane, which
runs the length of the cell
Pellicle’s protein composition
(antigens) controlled by roughly
1000 genes (40% of genome)
Invades CSF & brain, causing
lethargy, drowsiness, & mental
deterioration
22

23. 23

24. Phylum
Chlorophyta
Marine & FW green
algae
Large, cup-like
chloroplasts with
chlorophylls a & b
(same as plants)
Synthesize & store
starch
Diverse nonmotile
(filamentous) &
motile forms
24

25. Phylum
Chlorophyta,
cont.
Motile solitary
flagellates
(Chlamydomonas)
Motile colonial
flagellates (Volvox)
Volvox is a hollow,
spherical colony of
1000’s of individual
cells
Cytoplasmic bridges
connect cells
25

26. 26

27. Volvox
Volvox displays some
cellular differentiation
Non-flagellated gonidia
(reproductive cells) can
reproduce sexually or
asexually
Volvox is closely related
to plants, but also
provides insights on
animal evolution
Shows how
multicellularity may
have evolved in the first
animals
27

28. Asexual
Reproduction
in Volvox
Gonidium undergoes
several rounds of
fission
Daughter colony forms
inside parent, but is of
opposite polarity
It will invert, so future
flagella will point out
Daughter colony
bursts out of the
parent colony
28

29. Phylum
Choanoflagellata
600 species; marine
& FW
Tiny - 10µm
Solitary or colonial;
free-living or sessile
Stalked, spherical,
or occur in sheets
29

30. 30

31. 31

32. Phylum
Choanoflagellata,
cont.
Closely related to
metazoans - resemble
collar cells of sponges
One large flagellum w/
base surrounded by a
collar of microvilli
Flagellum beats &
collar traps bacteria &
organic molecules
Particles ingested by
phagocytosis
32

33. Phylum
Retortamonada
Heterotrophic
flagellates, most living
anaerobically in guts of
insects & vertebrates
Mitochondria often
absent; survive on
glycolysis
Giardia lamblia possess
4 flagella & is a
common intestinal
parasite in US
Giardiasis is often
contracted by drinking
water from mountain
streams (“beaver
fever”) 33

34. Phylum
Axostylata
Heterotrophic
flagellate, closely
related to
Retortamonada
Trichomonas
vaginalis is the most
well-known
representative
Small parasite with
4 flagella that
infects the human
urogenital tract
Can be transmitted
sexually
34

35. Phylum
Alveolata
Consists of 3 subphyla:
Dinoflagellata,
Ciliophora, &
Apicomplexa
Have similar rDNA
sequences
Alveoli are located
deep to their cell
membranes
35

36. Subphylum
Dinoflagellata
4000 marine & FW
dinoflagellate species
Possess chloroplasts via
endosymbiosis & are
important primary
producers
Red-brown to gold-brown
in color, due to peridinin
pigment
Many contribute to
planktonic
bioluminescence
36

37. 37

38. Subphylum
Dinoflagellata,
cont.
Have a complex,
sculpted skeleton
(theca) made of
cellulose
Theca contains sulcus
& 2 flagella
Some have thick
theca made of several
plates
Reproduce via binary
fission & can also
encyst
38

39. 39

40. 40

41. Subphylum
Dinoflagellata,
cont.
Some are
endoparasites of
protozoa,
crustaceans, & fish
Certain genera cause
red tides (Pfiesteria)
May result in
massive die-offs of
shellfish & fish
Ciguatera food
poisoning in humans
41

42. Subphylum
Ciliophora
Ciliates are sophisticated
protozoans; 8000+
species in FW, SW, & soil
Most are motile &
solitary heterotrophs
Ciliate anatomy is
analogous to animal
tissues & organs
Many have specialized
somatic & oral ciliature
42

43. Ciliate Pellicle
43

44. Subphylum
Ciliophora,
cont.
Alveoli function in Ca+2
storage
Release of Ca+2 changes
ciliary beat & discharge of
extrusomes
Trichocysts: long
threadlike, barbed shafts
discharged as defense
Toxicysts: longs shafts
with toxin used to
capture prey
Mucocysts: release
mucus spray to create
sticky surface for prey
capture or to form
protective cysts 44

45. Locomotion in
the Ciliates
Ciliates are the fastest
protozoans (up to 2 mm per
sec)!
Paramecium changes
directions upon colliding with
solid objects (avoidance
reaction)
Depolarization (similar to
action potential) is due to
Ca+2 & K+ release from alveoli
Some are sessile & highly
contractile (Vorticella)
45

46. Vorticella
Sessile ciliates with coiled
stalk
Double row of cilia in
ciliary membrane at top of
cell
Each cell has a long stalk
with a spasmoneme (spiral
spasmin protein fiber)
Contracts rapidly to escape
from predators
46

47. 47

48. 48

49. Nuclei
Dimorphism
of Ciliates
Ciliates have 2 types of
nuclei
Macronucleus: genes are
actively transcribed for
daily synthesis activities
Micronucleus: master
copy of genome; inactive
except during cell division
Shapes & numbers of
nuclei vary across genera
Bean-shaped in
Paramecium; string of
beads in Stentor
49

50. Sexual Reproduction: Conjugation 50

51. 51

52. Subphylum
Apicomplexa
(Sporozoa)
5000 species; widespread;
common parasites of worms,
insects, & vertebrates
Apical complex attaches to or
penetrates host cell
Anterior conoid holds
digestive enzymes
Micropores (feeding pores)
located on side of cell
52

53. Plasmodium
Four species of
Plasmodium that
cause malaria
#1 human parasite,
infecting 300 million
people per year
1% die each year
Anopheles mosquito
is the vector
53

54. 54

55. The Complex Life
Cycle of
Plasmodium
Sporozoite: motile, infective
stage with apical complex
Merozoite: motile, reinfective
stage with apical complex
Gametocyte: male & female
reproductive stage that
releases gametes (sexual
reproduction)
Spore: protective capsule
secreted after gametes fuse
to form diploid zygotes
6-12 merozoites
55

56. Plasmodium Life Cycle
56

57. Stages of
Plasmodium Life
Cycle
Sporozoites injected into
blood by mosquito & attack
liver cells
Merozoites derived from
sporozoites & reinfect liver
cells or move to RBCs
Cyclical merozoite release
correlates with cyclical
nature of malaria symptoms
Chills, fever, fatigue (hgb
loss), serious damage due to
the blocking of capillaries by
infected RBCs
57

58. Stages of
Plasmodium Life
Cycle, cont.
Gametocytes form in RBCs,
but do not pair
After ingestion, release
gametes into the mosquito
gut
Form zygotes which
penetrate gut wall &
encyst to form spore
Sporozoites produced in
spore & later migrate to
salivary glands; released
with mosquito’s next
blood meal
58

59. Ameboid
Protozoa
Have many pseudopodia
for locomotion & prey
capture (heterotrophs);
complex cytoskeleton
Marine, FW, & terrestrial
species
Similar to certain animal
cells: archeocytes of
sponges, mammalian WBCs
3 main groups: Amebas,
Foraminifera, &
Actinopoda
59

60. Amebas
3 phyla that includes
important genera such as
Amoeba, Chaos, Arcella,
Difflugia
Naked or enclosed in a
test (lorica, theca)
Arcella has dome-shaped
test covering its top with
pseudopodia extending
underneath
Chaos: 5mm long &
multinucleated
60

61. Arcella
61

62. Chaos
62

63. Cellular
Features of
Amebas
Specialized
pseudopodia
Lobopodia: wide &
rounded
Filopodia: slender &
may be branched
FW species have 1
or more contractile
vacuoles (none in
marine species)
63

64. Phylum
Foraminifera
(“Forams”)
Most marine
Many branching
reticulopodia (specialized
filopodia) that
interconnect to form
reticulopodial network
Vesicular traffic gives
reticulopodia a granular
appearance
Locomotion is via
reticulopodial network:
extends, anchors to
substrate, & contracts
64

65. 65

66. 66

67. Foram
Structure
67

68. Single-chambered foram Multi-chambered foram
with test pores
68

69. Phylum
Foraminifera,
cont.
Forms a probing net
used to find food
Test made of calcium
carbonate
Most multi-chambered;
start life in 1 chamber,
but extend & secrete
new tests
Benthic & planktonic
forams have different
tests
69

70. 70

71. Phylum
Foraminifera,
cont.
Planktonic tests are
more fragile
Possess spines to
increase surface area
& buoyancy
Foram tests create
natural wonders in
the form of chalk &
limestone
Pink sands of
Bermuda, White Cliffs
of Dover, blocks of
pyramids
71

72. 72

73. Phylum
Actinopoda
Spherical, planktonic
group with a perforated
test
Posses many axopodia:
long, stiff, needle-like
pseudopodia
Have microtubule support
rods that can attach &
retract
Used for flotation,
locomotion, & hunting
73

74. Phylum
Actinopoda,
cont.
Distinct cellular regions due
to the presence of a layer of
pseudopodia (not
actinopods)
Cortex: shroud of
pseudopodia covering test
that digests prey & transfers
nutrients
Medulla: inner cell body that
contains the nucleus,
nutrients, or oil drops for
buoyancy
Divided into two classes:
Radiolaria & Heliozoa
74

75. Class Radiolaria
(Phylum Actinopoda)
Marine, mostly
planktonic
Spherical test of
silica (SiO2)
Large, up to 20 cm
in some colonial
species
Forms radiolarian
ooze
75

76. 76

77. 77

78. Radiolarian Heliozoan
78

79. Class Heliozoa
(Phylum Actinopoda)
Sun animalcules
Marine, FW, or
terrestrial (on
mosses)
Contractile vacuoles
in FW species
Similar to
radiolarians
79

80. 80

81. Heliozoan81

82. Phylogeny of Protozoa 82

83. 83
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