8/29/2016
PowerPoint® Lecture
Presentations prepared by
Mindy Miller-Kittrell,
North Carolina State University
Modified by Ossi Turunen, Aalto University
CHAPTER
12
Characterizing
and
Classifying
Eukaryotes
© 2015 Pearson Education, Ltd.
General Characteristics of Eukaryotic
Organisms
• Eukaryotic microorganisms
• Protozoa (single celled organisms with many different shapes and sizes)
• Fungi (can be unicellular and multicellular)
• Algae (both unicellular and multicellular diverse group of photosynthetic
organisms)
• Water molds
• Slime molds
Mold is a fungus that
grows in the form of
multicellular filaments
called hyphae.
=> Include both human pathogens and organisms vital for human life
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General Characteristics of Eukaryotic
Organisms
• Reproduction of Eukaryotes
• More complicated than that in prokaryotes
• Eukaryotic DNA is packaged as chromosomes in the
nucleus
• Have variety of methods of asexual reproduction
• Many reproduce sexually by forming gametes and zygotes
• Algae, fungi, and some protozoa reproduce both sexually
and asexually
© 2015 Pearson Education, Ltd.
General Characteristics of Eukaryotic
Organisms
• Reproduction of Eukaryotes
• Nuclear division
• Nucleus has one or two complete copies of genome
• Single copy (haploid)
• Most fungi, many algae, some protozoa
• Two copies (diploid)
• Other fungi, algae, and protozoa
• Two types
• Mitosis
• Meiosis
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General Characteristics of Eukaryotic
Organisms
• Reproduction of Eukaryotes
• Nuclear division
• Mitosis
• Cell partitions that replicate DNA equally between two
nuclei
• Maintains ploidy of parent nucleus
• Four phases
© 2015 Pearson Education, Ltd.
Figure 12.1a The two kinds of nuclear division: mitosis and meiosis.
Mitosis
The major purpose of
mitosis
- increase the amount
of cells
- to replace worn out
cells
Diploid nucleus
(2n)
Mitosis and cytokinesis
together divide the parent
cell into two daughter
cells that are genetically
identical to each other
and to their parent cell.
DNA replication
1 Prophase
Centromere
Cytokinesis divides
the cytoplasm of a
parent cell into two
daughter cells
Chromosome
(two
chromatids)
2 Metaphase
Spindle
3 Anaphase
4 Telophase
Nuclear
envelope
© 2015 Pearson Education, Ltd.
Two diploid nuclei (2n)
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General Characteristics of Eukaryotic
Organisms
• Reproduction of Eukaryotes
• Nuclear division
• Meiosis
• Nuclear division that partitions chromatids into four nuclei
• Diploid nuclei produce haploid daughter nuclei
• Two stages – meiosis I and meiosis II
• Each stage has four phases
© 2015 Pearson Education, Ltd.
Figure 12.1b The two kinds of nuclear division: mitosis and meiosis (1 of 2).
Meiosis
Diploid nucleus
(2n)
DNA replication
Centromere
Tetrad
(two homologous
chromosomes,
four chromatids)
1 Prophase I
2 Late prophase I
Crossing over
MEIOSIS I
In meiosis a cell
divides twice to
produce four cells
that contain half the
original amount of
genetic information.
These cells are the
sex cells, sperm in
males, eggs in
females.
3 Metaphase I
Spindle
4 Anaphase I
Chromosome
(two chromatids)
5 Telophase I
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Figure 12.1b The two kinds of nuclear division: mitosis and meiosis (2 of 2).
6 Prophase II
Note:
No DNA
replication!
7 Metaphase II
MEIOSIS II
8 Anaphase II
9 Telophase II
Nuclear
envelope
Four
granddaughter
cells
Four haploid nuclei (1n)
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© 2015 Pearson Education, Ltd.
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General Characteristics of Eukaryotic
Organisms
• Reproduction of Eukaryotes
• Cytokinesis (cytoplasmic division)
• Typically occurs simultaneously with telophase of mitosis
• In some algae and fungi, is postponed or does not occur
at all
• Results in multinucleated cells called coenocytes
© 2015 Pearson Education, Ltd.
Figure 12.2 Different types of cytoplasmic division.
Wall of parent cell
Nuclei of daughter cells
Vesicles forming cell plate
Cleavage furrow
Bud
Scar: Ring of chitinous scar tissue on the surface of the
mother cell, formed after the new daughter cell
separates from the mother cell. The scar marks the site
of cytokinesis and septation. The number of bud scars
accumulating on the surface of a cell is a determinant of
replicative age.
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Figure 12.3 Schizogony.
Merozoites
Schizont
Nucleus
Multiple mitoses
Cytokinesis
Some parasitic, single-celled organisms undergo a multiple fission-like
process to produce numerous daughter cells from a single parent cell.
-Wikipedia
© 2015 Pearson Education, Ltd.
• Eukaryotic microorganisms
• Protozoa (single celled organisms with many different shapes and sizes)
• Fungi (can be unicellular and multicellular)
• Algae (both unicellular and multicellular diverse group of photosynthetic
organisms)
• Water molds
• Slime molds
Mold is a fungus that
grows in the form of
multicellular filaments
called hyphae.
© 2015 Pearson Education, Ltd.
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Protozoa
Single celled organisms with many different shapes and sizes.
Nearly 20000 species.
• Diverse group defined by three characteristics
• Eukaryotic
• Unicellular
• Lack a cell wall
• Motile by means of cilia, flagella, and/or
pseudopods
• Except a subgroup: apicomplexans
© 2015 Pearson Education, Ltd.
Protozoa
• Distribution of Protozoa
• Require moist environments
• Most live 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, e.g. malaria and amebae.
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Protozoa
• Morphology of Protozoa
• Great morphological diversity
• Some have two nuclei
• Macronucleus
• Contains many copies of the genome
• Micronucleus
• Variety in number and kinds of mitochondria
• Some have contractile vacuoles that pump water out of cells
• Different stages in life cycle
• Motile feeding stage called a trophozoite
• Resting stage called a cyst
© 2015 Pearson Education, Ltd.
Figure 12.5 Contractile vacuoles.
Closed vacuole
Open vacuole
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Protozoa
• Nutrition of Protozoa
• Most are chemoheterotrophic (unable to fix carbon to form their
own organic compounds, grow using the carbon fixed by autotrophs)
• Food acquisition by absorption, ingestion
• 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 photoautotrophic
• Photoautotrophs synthesize their own food from inorganic substances (CO2)
using light as an energy source
© 2015 Pearson Education, Ltd.
Protozoa
• Reproduction of Protozoa
• Most reproduce only asexually
• Binary fission or schizogony
• Few also have sexual reproduction
• Some become gametocytes that fuse to form diploid
zygotes
• Some utilize a process called conjugation
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Protozoa
• Classification of Protozoa
• Classification of protozoa has shifted over the years
• Revised and updated based on 18S rRNA sequences
• One current scheme groups protozoa into six groups
• Parabasala
• Diplomonadida
• Euglenozoa
• Alveolates
• Rhizaria
• Amoebozoa
© 2015 Pearson Education, Ltd.
Protozoa
• Classification of Protozoa
• Parabasala
• Lack mitochondria
• Have a single nucleus
• Contain Golgi body–like structure called a parabasal body
• Important parabasalids
• Trichonympha
• Trichomonas
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Figure 12.7 Trichonympha acuta, a parabasalid with prodigious flagella.
© 2015 Pearson Education, Ltd.
Figure 12.8 Two representatives of the kingdom Euglenozoa.
Flagellum
Short second flagellum
"Eyespot"
Contractile vacuole
Paramylon granule
Nucleus
Chloroplasts
Pellicle
Kinetoplast
Nucleus
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Figure 12.10 A predatory ciliate, Didinium (on left), devouring another ciliate, Paramecium.
© 2015 Pearson Education, Ltd.
Figure 12.11 Gonyaulax, a motile armored dinoflagellate.
Cellulose
plate
Transverse
flagellum
Longitudinal
flagellum
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Figure 12.12 Rhizaria called foraminifera have multichambered, snail-like shells of calcium carbonate.
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Figure 12.13 Rhizaria called radiolarians have ornate shells of silica.
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© 2015 Pearson Education, Ltd.
Fungi
• Chemoheterotrophic
• Have cell walls typically composed of chitin
• Chitin is a long-chain polymer of N-acetylglucosamine, a
derivative of glucose.
• Do not perform photosynthesis
• Lack chlorophyll
Structure of sterols with carbon numbers
• Fungi have sterols in their cell membrane
• All, except yeasts, are multicellular
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Fungi
• The Significance of Fungi
• Decompose dead organisms and recycle their nutrients
• Help plants absorb water and minerals
• Used for food, in religious ceremonies, and in
manufacture of foods and beverages
• Produce antibiotics and other drugs
• Serve as important research tools
• 30% cause diseases of plants, animals, and humans
• Can spoil fruit, pickles, jams, and jellies
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Figure 12.15 Fungal morphology.
Septate hypha
Aseptate hypha
Bud
Yeastlike
form
Moldlike
(filamentous)
form
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Figure 12.16 A fungal mycelium growing on a leaf.
© 2015 Pearson Education, Ltd.
Fungi
• Nutrition of Fungi
• Acquire nutrients by absorption
• Most are saprobes (an organism that lives on decaying organisms)
• Some trap and kill microscopic soil-dwelling nematodes
• Haustoria allow some fungi to derive nutrients from
living plants and animals
•
In botany and mycology, a haustorium (plural haustoria) is the appendage or portion of a parasitic fungus
(the hyphal tip) or of the root of a parasitic plant (such as the broomrape family or mistletoe) that
penetrates the host's tissue and draws nutrients from it. - Wikipedia
• Most fungi are aerobic
• Many yeasts are facultative anaerobes
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Fungi
• Reproduction of Fungi
• All have some means of asexual reproduction involving
mitosis and cytokinesis
• Most also reproduce sexually
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Fungi
• Reproduction of Fungi
• Budding and asexual spore formation
• Yeasts bud in manner similar to prokaryotic budding
• Some yeasts produce long filament called a pseudohypha
• Filamentous fungi produce lightweight spores that
disperse over large distances
• Sexual spore formation
• Fungal mating types designated as "+" and "–"
• Four basic steps
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Figure 12.18 Representative asexual spores of molds.
Sporangiophore
Sporangiospore
Sporangium
Conidiophore
Conidia
Chlamydospore
A sporangium (pl., sporangia[1]) (modern Latin, from Greek
σπόρος (sporos) ‘spore’ + αγγείον (angeion) ‘vessel’) is an
enclosure in which spores are formed.[2] It can be composed of a
single cell or can be multicellular. All plants, fungi, and many
other lineages form sporangia at some point in their life cycle.
Sporangia can produce spores by mitosis, but in nearly all land
plants and many fungi, sporangia are the site of meiosis and
produce genetically distinct haploid spores.
Conidia, sometimes termed asexual chlamydospores, or
chlamydoconidia [1] are asexual,[2] non-motile spores of a fungus,
from the Greek word for dust, konis.[3] They are also called
mitospores due to the way they are generated through the
cellular process of mitosis. The two new haploid cells are
genetically identical to the haploid parent, and can develop into
new organisms if conditions are favorable, and serve in biological
dispersal.
-Wikipedia
© 2015 Pearson Education, Ltd.
Figure 12.19 The process of sexual reproduction in fungi.
Tips fuse
–
+
Dikaryotic
stage
(n+n)
–
+
1 Dikaryon
Mitoses
and cell
divisions
Two nuclei
per cell
–
+
4
–
+
+
+
+
–
–
–
3 Meiosis
Diploid
stage
(2n)
2 Nuclei
fuse
Haploid
stage
(n)
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Fungi
• Classification of Fungi
• Division Zygomycota
• Division Ascomycota
• Division Basidiomycota
• Deuteromycetes
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Fungi
• Classification of Fungi
• Division Zygomycota
• 1100 known species
• Most are saprobes
• Others are obligate parasites of insects and other fungi
• Reproduce asexually via sporangiospores
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Figure 12.20 Life cycle of the zygomycete Rhizopus.
Sexual Reproduction
Asexual Reproduction
3 Spore germinates
to produce aseptate
mycelium (1n).
2 Sporangium
bursts to
release spores.
8 Zygosporangium
matures.
4 Vegetative
mycelium
grows.
9 Nuclear meiosis occurs
(not shown).
7 Zygosporangium
forms (2n).
6 Mating hyphae
join and fuse.
10 Zygosporangium
produces an
asexual sporangium (1n).
Dikaryon (n +n)
11 Spores (1n)
are released
from
sporangium.
Haploid nuclei (1n)
Sporangium
(1n)
Sporangiospores
Sporangiophore
1 Aerial hypha
produces a
sporangium.
–
+
5 Gamete
forms at
tip of
hypha.
12 Spore germinates.
© 2015 Pearson Education, Ltd.
Fungi
• Classification of Fungi
• Division Zygomycota
• Microsporidia (spore forming unicellular parasites)
• Once classified as protozoa
• More similar to zygomycetes by genetic analysis
• Obligate intracellular parasites
• Spread as small, resistant spores
• Nosema parasitic on insects
• Used as biological control agent for grasshoppers
• Several genera cause disease in immunocompromised
patients.
• Most infect insects.
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Fungi
• Classification of Fungi
• Division Ascomycota (sac fungi)
• 32,000 known species
There are 8 ascospores in each
ascus of Sordaria fimicola
(Wikipedia).
• Ascomycetes form ascospores in sacs called asci
• Also reproduce by conidiospores
• Includes most of the fungi that spoil food
• Some infect plants and humans
• Many are beneficial
• Penicillium
• Saccharomyces
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Figure 12.21 Ascocarps (fruiting bodies) of the common morel, Morchella esculenta, a delectable edible ascomycete.
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Figure 12.22 Life cycle of an ascomycete.
Sexual Reproduction (called Eupenicillium at this stage)
Asexual Reproduction
5 Hyphal tip undergoes
cytoplasmic fusion with
opposite mating type.
4 Vegetative
mycelium grows.
+
–
3 Conidiospore germinates
to produce
mycelium.
6
Dikaryon (n+n)
forms.
7
2 Conidiospores
are released
from
conidiophore.
Nuclei fuse in
terminal cells to
form 2n nuclei.
Dikaryon
11 Ascospores
germinate
to produce
mycelia.
Ascus
Ascospores
Conidiospore
Conidiophore
8 Meiosis produces
four haploid (1n)
cells.
1 Hypha produces
conidiophores and
conidiospores.
10 Ascus
opens to
release
ascospores.
Ascus
Ascospore
9 Mitosis produces eight
haploid ascospores
on each tip.
© 2015 Pearson Education, Ltd.
Fungi
• Classification of Fungi
• Division Basidiomycota
• 22,000 known species
Wikipedia
• Mushrooms and other fruiting bodies of basidiomycetes
called basidiocarps
• Basidiomycetes affect humans in several ways
• Most are decomposers that return nutrients to the soil
• Many mushrooms produce toxins or hallucinatory
chemicals
• Some cause expensive crop damage
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Figure 12.24 Sexual life cycle of Amanita muscaria, a poisonous basidiomycete.
Cross section of gill
showing hyphae.
5 Pair of haploid
nuclei fuse.
2n
6 Meiosis produces
four haploid
nuclei.
7 Four
basidiospores
(1n) develop.
Gills
Basidium
1 Basidiospore is
released.
2 Basidiospores germinate
to produce mycelia.
+
4 Dikaryotic mycelium
growing in soil produces
basidiocarp (mushroom).
–
Dikaryon
(n+n)
3 Hyphae of opposite mating
types fuse belowground
to produce dikaryotic
mycelium.
© 2015 Pearson Education, Ltd.
Figure 12.23 Basidiocarps (fruiting bodies).
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Fungi
• Classification of Fungi
• Deuteromycetes
• Heterogeneous collection of fungi with unknown sexual
stages
• Most deuteromycetes belong to the division Ascomycota
based on rRNA analysis
The Fungi imperfecti or imperfect fungi, also known as Deuteromycota, are fungi which do not fit
into the commonly established taxonomic classifications of fungi that are based on biological species
concepts or morphological characteristics of sexual structures because their sexual form of
reproduction has never been observed; hence the name "imperfect fungi." Only their asexual form of
reproduction is known, meaning that this group of fungi produces their spores asexually, in the process
called sporogenesis. - Wikipedia
© 2015 Pearson Education, Ltd.
Fungi
• Lichens
• Partnerships between fungi and photosynthetic microbes
• Fungus provides nutrients, water, and protection
• Photosynthetic microbe provides carbohydrates and oxygen
• Abundant throughout the world
• Grow in almost every habitat
• Occur in three basic shapes
• Foliose, crustose, fruticose
• Create soil from weathered rocks
• Some lichens provide nitrogen in nutrient-poor environments
• Eaten by many animals
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Figure 12.25 Makeup of a lichen.
Ascocarp of fungus
Soredium
Algal cell
Fungal hyphae
Fungal hyphae
Phototrophic layer
Substrate
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Figure 12.26 Gross morphology of lichens.
Foliose
Crustose
Fruticose
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Algae
• Simple, eukaryotic phototrophs
• Carry out oxygenic photosynthesis using
chlorophyll a
• Have sexual reproductive structures in which
every cell becomes a gamete
• Differ widely in distribution, morphology,
reproduction, and biochemical traits
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Algae
• Distribution of Algae
• Most are aquatic
• Live in the photic zone of freshwater, brackish water, and
saltwater
• Have accessory photosynthetic pigments that trap
energy of short-wavelength light
• Allows algae to inhabit deep parts of the photic zone
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Algae
• Morphology of Algae
• Can have different morphologies
• Unicellular
• Colonial
• Simple multicellular bodies called thalli
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Algae
• Reproduction of Algae
• Reproduction in unicellular algae
• Asexual reproduction involves mitosis followed by
cytokinesis
• In sexual reproduction, individual gametes form zygotes
that undergo meiosis
• Reproduction in multicellular algae
• Reproduce asexually by fragmentation
• Reproduce sexually with alternation of generations
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Figure 12.27 Alternation of generations in algae, as occurs in the green alga Ulva.
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Algae
• Classification of Algae
• Classification is not settled
• Classification schemes are based on different features
• Differences in photosynthetic pigments
• Storage products
• Cell wall composition
• Various groups
• Division Chlorophyta
• Kingdom Rhodophyta
• Phaeophyta
• Chrysophyta
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Algae
• Classification of Algae
• Division Chlorophyta (green algae)
• Share numerous characteristics with plants
• Have chlorophylls a and b
• Use sugar and starch as food reserves
• Many have cell walls of cellulose
• 18S rRNA sequences are similar
• Most are unicellular and filamentous
• Live in freshwater
• Some multicellular forms grow in marine waters
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Algae
• Classification of Algae
• Kingdom Rhodophyta (red algae)
• Have the red accessory pigment phycoerythrin
• Use the storage molecule glycogen
• Cell walls composed of agar or carrageenan
• Both are used as thickening agents
• Nonmotile male gametes called spermatia
• Most are marine algae
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Figure 12.28 Pterothamnion plumula, a red alga.
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Algae
• Classification of Algae
• Phaeophyta (brown algae)
• Motile gametes have two flagella
• Produce chlorophylls a and c, carotene, and xanthophylls
• Most are marine algae
• Use laminarin and oils as food reserves
• Cell walls are composed of cellulose and alginic acid
• Alginic acid is used medically and as a thickening
agent
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Algae
• Classification of Algae
• Chrysophyta (golden algae, yellow-green algae, and
diatoms)
• Use chrysolaminarin and oils as storage products
• Some lack cell walls; others have ornate coverings
• Most are unicellular or colonial
• Diatoms
• Component of marine phytoplankton
• Major source of the world's oxygen
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Figure 12.31 Coscinodiscus, a diatom.
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Water Molds
• Differ from fungi in several ways
• Have tubular cristae in their mitochondria
• Cell walls are of cellulose instead of chitin
• Spores have two flagella
• Have true diploid bodies
• Decompose dead animals and return nutrients to
the environment
• Some species are pathogens of crops
• Phytophthora infestans caused the Irish potato famine
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Figure 12.32 An example of the important role of water molds in recycling organic nutrients in aquatic habitats.
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Other Eukaryotes of Microbiological Interest:
Parasitic Helminths and Vectors
• Parasitic worms have microscopic infective and diagnostic
stages
• Arthropod vectors are animals that carry pathogens
• Mechanical vectors
• Biological vectors
• Disease vectors belong to two classes of arthropod
• Arachnida
• Insecta
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Other Eukaryotes of Microbiological Interest:
Parasitic Helminths and Vectors
• Arachnids
• Adult arachnids have four pairs of legs
• Ticks are the most important arachnid vectors
• Hard ticks are most prominent tick vectors
• A few mite species transmit rickettsial diseases
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Other Eukaryotes of Microbiological Interest:
Parasitic Helminths and Vectors
• Insects
• Adult insects have three pairs of legs and three body
regions
• Include
• Fleas
• Lice
• Flies
• Mosquitoes
• Most important arthropod vectors of disease
• Kissing bugs
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Figure 12.33 Representative arthropod vectors.
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