Unicellular
Eukaryotes:
Protozoan Groups
(Kingdom Protista)
Origin of Eukaryotes
• First eukaryotic organism thought to have
evolved about 3.5 billion years ago
• Protozoans possible evolved from the 1st
eukaryotes by Endosymbiosis
– process where one prokaryote lives inside
another becoming dependent upon each other
Origin of Eukaryotes
 Endosymbiosis
Origin of Eukaryotes
ENDOSYMBIOSIS
Origin of Eukaryotes
Endomembrane infolding
Infolding of membrane system
forming nucleus and ER
Endosymbiosis Hypothesis
A
A prokaryote ingested some aerobic bacteria. The
aerobes were protected and produced energy for
the prokaryote
A
Aerobic bacteria
C
B
Mitochondria
D
Cyanobacteria
N
N
Chloroplasts
N
Plant cell
Prokaryote
N
Animal Cell
Endosymbiosis Hypothesis
B
Over a long period of time the aerobes
became mitochondria and no longer able
to live on their own
A
Aerobic bacteria
C
B
Mitochondria
D
Cyanobacteria
N
N
Chloroplasts
N
Plant cell
Prokaryote
N
Animal Cell
Endosymbiosis Hypothesis
C
Some primitive prokaryotes also ingested
cyanobacteria which contain photosynthetic
pigments
A
Aerobic bacteria
C
B
Mitochondria
D
Cyanobacteria
N
N
Chloroplasts
N
Plant cell
Prokaryote
N
Animal Cell
Endosymbiosis Hypothesis
D
Cyanobacteria became chloroplasts and
unable to live on their own
A
Aerobic bacteria
C
B
Mitochondria
D
Cyanobacteria
N
N
Chloroplasts
N
Plant cell
Prokaryote
N
Animal Cell
Prokaryotic Cells
Eukaryotic Animal Cell
Mitochondria
Typical Animal Cell
Eukaryotic Plant Cell
Typical Plant Cell
Secondary Endosymbiosis and
Origin of Algal Diversity
Secondary endosymbiosis is the merging of
two eukaryotic cells into one cellular unit
Algae AB
N
Secondary
endosymbiosis
N
N
Algae ABC
Heterotroph C
Many membrane
layers
Plastid
Secondary Endosymbiosis
Secondary
endosymbiosis
Cyanobacterium
Dinoflagellates
Apicomplexans
Red alga
Primary
endosymbiosis
Stramenopiles
Heterotrophic
prokaryote
Over the course
of evolution,
this membrane
was lost.
Secondary
endosymbiosis
Plastid
Euglenids
Secondary
endosymbiosis
Green alga
Chlorarachniophytes
Origin of Eukaryotes
•
Eukaryotic cell is more complex than prokaryotic cell:
•
Membrane-bound nucleus and organelles
•
Chromosomes consist of DNA and histone proteins
and occur in pairs.
•
Protists, fungi, plants & animals are composed of
eukaryotic cells.
Origin of Eukaryotes
Cladogram showing two major prokaryotic branches and diversification of eukaryotes
• Eukaryotic
• Mostly unicellular
• A very heterogeneous group include both
heterotrophic and photoautotrophic forms
• 11 phyla
• Lots of disagreements
• 64,000 species have been named
• 250,000 species in total
Classification based on nutrition:
•
Animal-like protists
•
•
Heterotrophic - obtain organic molecules
synthesized by other organisms
Plant-like (algal) protists
•
Autotrophic - synthesize their own
organic constituents from inorganic
substrates
Classification based on modes of locomotion:
•
Sporozoa - No distinct locomotive
structures
•
Flagellates - Use flagella
•
Ciliates - Use cilia
•
Amebas - Use pseudopodia
Flagellates
Cilliates
Amoeba
Cilia and flagella
•
Contains 9 pairs of longitudinal
microtubules arranged in a circle
around a central pair
•
Another microtubule joins each of
the 9 pairs & form a short tube
extending from the base of the
flagellum into the cell
(kinetosome)
•
Functions:
•
For locomotion
•
Create water currents for
feeding & respiration
Pseudopodia - extensions
of the cell cytoplasm
• Endoplasm
• more granular
• more fluid and is in
the sol state
• Ectoplasm
• more transparent
(hyaline)
• more rigid and is in
the gel state of a
colloid
Holozoic nutrition (phagocytosis)
• An area of the plasma membrane forms a
pocket that engulfs solid material
Ciliates, flagellates and apicomplexans
• Cytosome: site of phagocytosis is a definite
mouth structure, the cytostome
Amebas
• Phagocytosis can occur
at almost any point by
envelopment of a particle
with pseudopodia
Saprozoic nutrition
•
Ingestion of soluble food
•
May be by pinocytosis
(areas of the surface
membrane invaginate into
cells to form tiny vesicles)
•
May be by direct transport of
solutes across the outer cell
membrane such as diffusion,
facilitated transport, or active
transport
Protists reproduce asexually and sexually.
Fission is cell multiplication process that
produces more individuals
• Binary fission - two essentially identical
individuals result
Binary fission
The two nuclei of Arcella divide as some of its
cytoplasm is extruded and begins to secrete
a new test for the daughter cell
Budding - When a progeny cell is considerably
smaller than the parent and then grows to adult
size
Budding
Multiple fission - Division of the cytoplasm
(cytokinesis) is preceded by several nuclear
divisions, so that a number of individuals are
produced almost simultaneously
Nuclear
division
Cytokinesis
Sexual processes
• Important as a means of genetic recombination
• Gamete nuclei (pronuclei) fuse in fertilization to
restore the diploid number of chromosomes
• Isogametes - all gametes look alike
• Anisogametes - two dissimilar types
Isogametes of
Cladophora
Anisogametes
of Fucus
• Fertilization
• Syngamy - Fertilization of an individual
gamete by another
• Autogamy - Gametic nuclei arise by meiosis
and fuse to form a zygote within the same
organism that produced them
• Conjugation - An exchange of gametic
nuclei occurs between paired organisms
(conjugants)
Autogamy
Conjugation
Major Protozoan Taxa
Major Protozoan Taxa

Clade
 Stramenopiles
 Viridiplantae
 Phylum Chlorophyta
 Euglenozoa
 Subphylum Euglenida
 Subphylum Kinetoplasta
 Retortamonad & Diplomonad
 Alveolata
 Phylum Ciliophora
 Phylum Dinoflagellata
 Phylum Apicomplexa
 Parabasalids
 Amebas
Clade Stramenopiles
• Have 2 different
flagella (heterokont)
inserted at cell
anterior
• Consists of:
• Plant-like form
• Animal-like form
(forward directed)
(trails
behind
cell)
Phylum Chlorophyta
 Included in clade Viridiplantae
 Photoautotroph
 Single-celled and colonial form
Single-celled
Colonial
Phylum Chlorophyta

Volvox

Hollow sphere

A single organism contains many
thousands of cells (up to 50,000)
embedded in the gelatinous surface
of a jelly ball

Coordinated action of the flagella
causes the colony to move by
rolling over and over

Division of labor
 Most cells are somatic cells - for
nutrition and locomotion
 Few germ cells - for reproduction
Phylum Euglenozoa

Subphylum Euglenida
 Euglena
 Spindle shaped
 Have proteinaceous strips and microtubules beneath the
outer membrane that form a pellicle
 A flagellum extends from a reservoir at the anterior end,
and another, short flagellum ends within the reservoir
 Have stigma that functions in orientation to light
Euglena viridis
Phylum Euglenozoa
 Subphylum Kinetoplasta
 Genus Trypanosoma
 Can
be pathogenic
 African sleeping sickness
 Caused by Trypanosoma
brucei gambiense and T.
brucei rhodesiense (in
human), and T. brucei
brucei (in domestic
animals)
 Transmitted by Tsetse fly
 10,000 new cases in
human - 50% fatality, 50%
permanent brain damage
Tsetse fly
Phylum Euglenozoa
 Trypanosoma cruzi
 Causes Chagas’ disease in humans in Central
America and South America
 Transmitted by “kissing bugs” (Triatominae)
 2-3 million people in South and Central America
show chronic Chagas’ disease - 45,000 of these
die each year
Triatominae bug
Phylum Euglenozoa
 Leishmania
 Causes diseases in human
 visceral disease
 disfiguring lesions in the
mucous membranes of nose
and throat
 skin ulcer
 Transmitted by sand flies
 Visceral and cutaneous
leishmaniasis are common in
parts of Africa and Asia
 Mucocutaneous form occurs in
Central America and South
America.
Sand fly
Phylum Diplomonads
 Giardia
 A Diplomonad
 Live in the human and animal digestive tract
 Causes non-fatal diarhea
 Cysts are passed in the feces, and new hosts are
infected by ingestion of cysts, often in
contaminated water
Clade Alveolata
 3 traditional phyla (presence of alveoli i.e.
membrane-bound sacs that lie beneath the
cell membrane)
 Ciliophora
 Dinoflagellata
 Apicomplexa
Phylum Ciliophora

Possess cilia
 Cover the surface of the
organism or restricted to the
oral region or to certain bands
 Undulating membrane - Cilia
are fused into a sheet
 Membranelles - Small number
of cilia in neighboring rows
lean towards each other
making a 2-D pointed tooth
 Cirri - fused cilia forming
stiffened tufts
Phylum Ciliophora
 Symbiotic ciliates
 Can be harmful to their hosts
 Ichthyophthirius - causes disease in aquarium
and wild freshwater fishes
 Entodinium - lives in digestive tract of ruminants
 Balantidium coli - parasite of human and other
mammals
Phylum Ciliophora
 Free-Living Ciliates (Paramecium)
• Abundant in ponds Fecal material
or sluggish streams is discharged
containing aquatic
plants and decaying
Radiating
organic matter
canal
• Reproduction
•Binary fission
•Conjugation
•Autogamy
Undulating membrane
(keeps food moving)
(discharge fecal material)
Pellicle
Phylum Dinoflagellata

Covered by
cellulose plates
Forms:
 2 flagella
 one equatorial
 one longitudinal
 Naked or covered by cellulose
plates or valves
Naked
Phylum Dinoflagellata
Noctiluca is one of many marine
organisms that can produce light
Bioluminescence
Phylum Dinoflagellata
 Red tide
 Release of toxic substance
 Highly poisonous to fish and other marine life
 Causes human illness - ciguatera
Phylum Apicomplexa


All are endoparasite
 Hosts include many animal
phyla
Possess apical complex
 a certain combination of
organelles
 aid in penetrating the
host’s cells or tissues
Phylum Apicomplexa
 Class Coccidea
 intracellular parasites in
invertebrates and vertebrates
 Toxoplasma gondii
Toxoplasma gondii
 parasite of cats
 infect AIDS patients and
pregnant women
 infection through consumption
of infected meat (insufficiently
cooked)
Congenital toxoplasmosis
Phylum Apicomplexa

Plasmodium spp.
 causes malaria in human
 Global estimates of deaths caused by malaria
range from 700,000 to over 2 million (75% being
African children)
 Examples
 P. falciparum
 P. malariae
 P. vivax
 P. ovale
Phylum Apicomplexa
Schizogony
Carier: mosquitoes (Anopheles)
Clade Parabasalids

Contains phylum Axostylata
 Have a stiffening rod
composed of microtubules
(axostyle) that extends
along the longitudinal axis
of their body
 Trichomonas
 a disease-causing
organism for humans
and other animals
 Trichomonas vaginalis
causes vaginitis in
females but no symptom
in males
axostyle
Clade Amebas

Classified based on shape of pseudopodia
 Actinopods vs. Nonactinopods
Actinopods have axopodia that are
supported by axial rods of microtubules
Clade Amebas

Actinopod Amebas
 Has axopod pseudopodia
 Heliozoan (freshwater
amebas with or without
tests)
 Radiolarian (marine testate
amebas with intricate
specialized skeletons of
great beauty)
Types of radiolarian tests. In his study
of these beautiful forms collected on the
famous Challenger expedition of 1872 to
1876, Haeckel proposed our present
concepts of symmetry.
Amebas with axopodia
Clade Amebas
 Nonactinopod Amebas
 Types of pseudopodia
 Lobopodia - blunt,
fingerlike
 Filopodia - slender,
with pointed ends
 Rhizopodia branching filaments