Chapter 12
Characterizing and Classifying
Eukaryotes
Eukaryotes
• Four major groups
– Protozoa
– Fungi
– Algae
– Water molds and slime molds
• Include both human pathogens and organisms
vital for human life
Reproduction in Eukaryotes
• More complicated than that in prokaryotes
– Eukaryotic DNA packaged as chromosomes in the
nucleus
– Have variety of methods of asexual reproduction
(budding, fragmentation, spore formation, and
schizogony)
– Many reproduce sexually by forming gametes and
zygotes
• Algae, fungi, and some protozoa reproduce sexually
and asexually
Classification of Eukaryotic Organisms
Figure 12.4
Protozoa
• Diverse group defined by three characteristics
– Eukaryotic
– Unicellular
– Lack a cell wall
• With exception of the group apicomplexans,
they are motile by means of cilia, flagella,
and/or pseudopodia
Distribution of Protozoa
• Require moist environments
– Most live worldwide in ponds, streams, lakes, and
oceans; critical members of plankton
• Others live in moist soil, beach sand, and
decaying organic matter
• Very few are pathogens
Morphology of Protozoa
• Characterized by great morphologic diversity
• Some have two nuclei
– Macronucleus contains many copies of genome –
controls metabolism, growth, and sexual
reproduction
– Micronucleus – involved in genetic recombination,
sexual reproduction, and regeneration of
macronuclei
• Variety in number and kinds of mitochondria
• All produce trophozoites; some produce cysts
Life Cycle of Parasitic Protozoans
• consists of two stages:
trophozoite (motile
feeding stage) and cyst
(resting stage)
– under certain
adverse conditions,
some trophozoites
produce a
protective cyst.
• this cyst enables
parasitic species to
survive outside of a
host
Nutrition of Protozoa
• Most are chemoheterotrophic
• Obtain nutrients by phagocytizing bacteria,
decaying organic matter, other protozoa, or
the tissues of host
• Few absorb nutrients from surrounding water
• Dinoflagellates and euglenoids are
photoautrophic
Reproduction in Protozoa
• Most reproduce asexually only (binary fission or
schizogony)
• Few also have sexual reproduction
– Some become gametocytes that fuse with one another
to form diploid zygote
– Some utilize a process called conjugation
Characteristics of Protozoa
Table 12.2
Classification
•
Protozoans are often classified into four groups
based on mode of locomotion:
1. Sarcodina (pseudopodia)
2. Mastigophora (flagella)
3. Ciliophora (cilia)
4. Sporozoa (non-motile)
Sarcodina
• Move and feed by pseudopodia using amoeboid
motion
Entamoeba histolytica
•
•
•
•
lobe-shaped pseudopodia
no shell
some are disease causing
Ex. Entamoeba histolytica
– live inside animals
– cause of amebic dysentary
through the lysis of human intestinal cells
– infection occurs through ingestion of drinking
water with contaminated feces, hands, food, or
oral-anal intercourse
– Annual mortality of 100,000
Classification
•
Protozoans are often classified into four groups
based on mode of locomotion:
1. Sarcodina (pseudopodia)
2. Mastigophora (flagella)
3. Ciliophora (cilia)
4. Sporozoa (non-motile)
Mastigophora
• move by flagella
Giardia intestinalis
• Diarrhea-causing pathogen (giardiasis)
• Spread in the cyst form in fecal contaminated water,
food, soil.
Trichomonas vaginalis
• Most common protozoan disease (trichomoniasis)
• Transmitted via sex
• Occurs most frequently in people with a preexisting
STD
Trypanosoma
– Hemoflaggellates: blood parasite
• Ex. Trypanosome: causative agent of African
Sleeping sickness
• Transmitted by the tse-tse fly
• Life cycle of
Trypanosoma brucei,
causative agent of
African sleeping
sickness
Dinoflagellates
• Unicellular
• Photoautotrophs
• also considered
protozoans
• Freshwater and
marine plankton
• Two flagella of
unequal length
Red Tide
• Some dinoflagellates
produce red pigment
• An abundance of these
organisms produces
“red tide”
• Red tide blooms
produce neurotoxins
that are toxic to marine
life
Red Tide
Pfiesteria
• Dinoflagellate
• Poisons people who handle infected fish or
inhalation of microbes
BAD DINOFLAGELLATES:
PARALYTIC SHELLFISH
POISONING
Red Tide strikes again
DEP shuts down shellfish harvesting
in waters of Bay and Gulf counties
News Herald Staff Report
State environmental officials closed Bay County and Gulf
County waters to shellfish harvesting Thursday after
detecting unacceptable levels of red tide.
Water samples taken from Mexico Beach showed
medium levels of red tide - about 933,000 cells per liter.
DEP shuts down shellfish harvesting when levels reach
5,000 cells per liter.
Classification
•
Protozoans are often classified into four groups
based on mode of locomotion:
1. Sarcodina (pseudopodia)
2. Mastigophora (flagella)
3. Ciliophora (cilia)
4. Sporozoa (non-motile)
Balantidium coli
• human parasite that causes
a rare type of severe dysentery
(Balantidiasis)
• ingested as cysts, they enter
the intestine and trophozoites are
released
• the trophozoites destroy host cells and feeds on the
host cell fragments
Classification
•
Protozoans are often classified into four groups
based on mode of locomotion:
1. Sarcodina (pseudopodia)
2. Mastigophora (flagella)
3. Ciliophora (cilia)
4. Sporozoa (non-motile)
Sporozoans (Apicomplexans)
• Animal pathogens
• Adults are non-motile
• Ex. Plasmodium (Genus) – causative agent of malaria
Eukaryotes
• Four major groups
– Protozoa
– Fungi
– Algae
– Water molds and slime molds
• Include both human pathogens and organisms
vital for human life
Fungi
• Chemoheterotrophic
– Decompose dead organisms and recycle their
nutrients
• Have cell walls typically composed of chitin
• Related to animals
– Important research tools
Significance of Fungi
1. Form beneficial associations with roots of
vascular plants that help plant absorb water
and minerals
2. Used for food and in manufacturing of foods
and beverages
3. Produce antibiotics
4. 30% cause diseases of plants, animals, and
humans
5. Can spoil fruit, pickles, jams, and jellies
Nutrition of Fungi
• Acquire nutrients by
absorption
• Most are aerobic;
some are
anaerobic; many
yeasts are
facultative
anaerobes
Fungal Morphology
•
the body of fungi is termed thallus (non-reproductive)
• The thalli of yeast are small, globular and are single
celled
• The thalli of mold are composed of long, branched
tubular filaments called hyphae.
Fungal Morphology
• Within multi-ceullar
hyphae of molds, the
can either be
separated (septae)
or continuous
(aseptate)
Fungal Morphology
• Some members of fungi are dimorphic.
– They take either a globular form or filamentous form
depending on environmental conditions.
Reproduction of Fungi
• All have some means of asexual reproduction
– Yeasts bud in manner similar to prokaryotic
budding
– Filamentous fungi produce lightweight spores that
differ in mode of development
• Most also reproduce sexually
Budding and Asexual Spore Formation
• Budding:
Asexual Spores of Molds
• Some asexual spores are enclosed in sacs
called sporangium at the end of the hyphae.
Figure 12.19a
Asexual Spores of Molds
• Some asexual spores are located in the middle
of the hyphae and enclosed in a thick wall
(chlamydiospores).
Asexual Spores of Molds
• Some asexual spores called conida are not
enclosed in sacs at the end of the hyphae.
Asexual Spores of Molds
• The type of asexual spore produced by a mold
is often used clinically to identify the identity
of the mold pathogen.
Sexual Spores Formation
Eukaryotes
• Four major groups
– Protozoa
– Fungi
– Algae
– Water molds and slime molds
• Include both human pathogens and organisms
vital for human life
Algae
• Simple, eukaryotic, phototrophic organisms
that carry out oxygenic photosynthesis.
• Reproduce asexually and sexually.
• Differ widely in distribution, morphology,
reproduction, and biochemical traits
Distribution and Morphology of Algae
• Most are aquatic, living in the photic zone of
fresh, brackish, and salt water
• Unicellular, colonial, or have simple
multicellular bodies (thalli)
Classification of Various Algae
Table 12.4
Red Algae
Figure 12.29
Diatom
• Single-celled
• Silicon in cell walls
composed of two halves
• Major component of
phytoplankton
• Major source of world’s
O2
Figure 12.32
Brown Algae
Figure 12.31
Parasitic Helminths and Vectors
• Parasitic worms have microscopic infective
and diagnostic stages – usually eggs or larvae
• Vectors are animals such as ticks, lice, and
mosquitoes that carry and transmit
microscopic pathogens
The Helminths
• Helminths (parasitic worms)
– Multicellular eukaryotes
– Consumers
– Common intestinal parasites
– Kingdom: Animalia
• Phylum: flatworms
– Class: flukes
– Class: tapeworms
• Phylum: roundworms
Table 12.1
Flatworms
•
•
•
•
Structurally simple
Most are parasitic
Hermaphrodites
Two classes:
– Fluke
– tapeworms
Liver Fluke
Flatworm: Flukes
• flat, leaf shaped bodies
• contain oral and ventral suckers that allow for
attachment to the host
Clonorchis
(Chinese Liver Fluke)
Flukes
• Complex life cycle
– Multiple hosts
• Intermediate host
• Definitive host
– Multiple Stages
Flatworm: Tapeworms
• flat, segmented,
intestinal parasites
• Scolex
– Small attachment
organ
– Contains suckers
and hooks
• Proglottid
– Irradiate from the
neck
– Grow continuously
– Contains
reproductive organ
(monoecious)
Tapeworms – life cycle
Roundworms
• Long, cylindrical; tapered at each end
• Complete digestive tracts
• Dioecious (females are larger)
Life Cycle of Trichinella spiralis
Arthropods as Vectors
• Kingdom: Animalia
– Phylum: Arthropoda
• Class: Insecta (6 legs)
– Lice, fleas, mosquitoes
• Class: Arachnida (8 legs)
– Mites and ticks
– May transmit diseases
(vectors)
Figure 12.31, 32