Eukaryotes – General
= “true nucleus”
appeared in fossil record about 1.2-1.5BY ago
(2.1 - 2.5 Billion years ago)??? ck
larger cells (100-500µm vs 1-5µm):
100x’s larger than prokaryotes
only one cell produces all the tasks essential for life
(same as bacteria but much more efficiently since eukaryotes)
compartmentalization
nucleus, organelles
makes them much more efficient than bacteria
Origin of Eukaryotes
eukaryotic cells probably arose from two processes:
1. infolding of cell membrane to form membrane
bound nucleus and possibly the endoplasmic reticulum and golgi bodies
2. endosymbiosis of other prokaryotes probably
produced mitochondria and chloroplasts and possibly the eukaryotic
flagellum
evidence:
there are examples today of such
endosymbiosis
chloroplasts and mitochondria are the size of
most bacteria
chloroplasts and mitochondria have bacterial
chromosome (circular ring of DNA)
they also have bacterial RNA and bacterial
enzymes
and replicate by binary fission as do bacteria
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006
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Kingdom Protista – General
~65,000 species described up to 200,000 species probable
simplest eukaryotic organisms
(the other kingdoms are mainly multicellular.
very efficient cells compared to procaryotic cells
most metabolically diverse group of eucaryotes
(but not more so than bacteria)
diverse group of organelles with highly developed
division of labor
found anywhere there is water or moisture:
freshwaters,
marine environments,
damp soil,
leaf litter,
snow,
ice
important part of plankton:
organisms that drift with currents
most unicellular, some colonial, filamentous, some (seaweeds) multicellular
multicellular forms with specializations of cells for
different functions:
reproduction
photosyn
attachment
reproduction
flotation
etc
autotrophs and heterotrophs
most aerobic
a few lack mitochondria and are anaerobic
Movement
most protists are motile
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 5 x’s faster
(but only ~5x’s body length, vs bacteria 10-50x’s body
length at 50µm/s)
eg. Paramecium 2700 µm/s
eg. Chlamydomonas 200µm/s
use
cilia
flagella
amoeboid motion
gliding
nonmotile
Reproduction and Life Cycles
highly varied reproduction and life cycles
true mitosis and meiosis to produce gametes
reproduce asexually and sexually
asexually:
budding
fission & multiple fission
sexually:
some by conjugation (eg. Spirogyra)
some by syngamy
isogamy = similar gametes
anisogamy = similar shape but
one is larger
oogamy =
female is larger, nonmotile
male is smaller, motile
some produce gametes in single celled
gametangium
many have both a feeding and a resistant stage in
their life cycle
some have alternation of sexual and asexual
generations
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200,000 species described
polyphyletic ie. not a natural grouping, some divide protists into 5 or 6
separate kingdoms
and 50 phyla
major types of organisms (Note: these are not
evolutionary groupings, they are groupings of convenience, an not
necessarily the same groupings as in your text, or in other books):
1. Algae (22,000 species + fossils)
mostly single celled, colonial, some
multicellular photosynthetic protists, most
with cell wall
2. Protozoa (31,000 species + fossils)
mostly single celled or colonial,
heterotrophs, non photosynthetic, mostly
motile
3. Slime Molds (1,100 species)
mostly complex life cycles
involving amoeba-like stage and fungal spore-like stage,
alternating sexual and asexual reproduction, heterotrophs
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Protists - Algae
~22,000 species
diverse group of mostly photosynthetic protists
almost all are photosynthetic autotrophs
=use sunlight as energy source to make organic
food
then store food as starch, leucosin, laminarin,
paramylon, lipids
contain same pigment for photosynthesis as do plants
 chlorophyll
most also have additional “accessory” pigments
restricted to damp or wet environments:
oceans,
hot springs
ponds,
atmosphere (droplets)
lakes,
snow,
rivers,
bark,
soil,
etc.;
most are aquatic and form phytoplankton
base of food chain in aquatic environments
density only few 1000/liter
but ocean area is so great that their
total productivity is:
3 x’s production of all worlds grasslands and
4 x’s all croplands
the larger, multicellular algae are found closer to
shore usually attached to substrate in shallow water
they provide both food and shelter for many other
organisms
a few are terrestrial
found on tree trunks and damp soil
many are symbiotic with fungi and animals
classification based on:
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1. type of accessory photosynthetic pigment
2. type of energy reserves
3. cell wall composition
Classification
Phylum: Pyrrophyta
Phylum: Chrysophyta
Phylum: Euglenophyta
almost all single celled species
Phylum: Rhodophyta
Phylum: Phaeophyta
large multicellular species
(no true tissues though)
Phylum:
mixture of unicellular, colonial and
multicellular forms
Chlorphyta
1. Fire Algae (Dinoflagellates, Pyrrophyta)
~1000 sp
unicellular
most are armored
produce cell walls of fused interlocking cellulose plates
usually with spines
each species has a distinctive shape
2 flagella in grooves perpendicular to each other
=> cause organism to spin like a top while moving
foreward
photosynthetic pigment = Chlorophyll a and orange carotenoids
food storage as starch
many symbiotic in coral animals as zooxanthellae
blooms of dinoflagellates color water red or brown
= red or brown tides
some produce powerful toxins which can kill fish and
other organisms that eat them
eg. 100,000’s of fish may die
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eg. red tides in florida and tropical islands
eg. 1980, Maine coast – costs $7M losses
shellfish often not hurt by toxins but can accumulate
and concentrate them
 may make them dangerous to humans
some are bioluminescent
= “burning of the sea” at night
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2. Diatoms (glass algae, Chrysophyta, golden-brown
algae)
~10,000 sp
most abundant group of algae
major base of aquatic food chains (fw and marine)
=phytoplankton
single celled (unicellular)
very distinctive group
cell walls:
no cellulose, has protein = pectin
also contains silica
radial symmetry
CW in two parts (petri dish)
CW of large numbers of intricately shaped pits,
pores and passageways
pigments: chlorophyull a and fucoxanthin
food storage as leucosin
no cilia or flagella
some have gliding movement = slime trail
Reproduction:
asexual:
shell halves separate and
new smaller shell is secreted to fit into old shell
half
sexual:
male and female cells unite to form
zygote which secretes new shell
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Economic Impact
all oil reserves were formed mainly by diatom deposits
source of diatomaceous earth
= chalky rock composed of diatom shells (fossil)
(white cliffs of Dover)
silica in shells make them useful for:
filters
cement
plaster
paper
paint
pesticides
abrasives
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3. Euglenoids
~800 sp
small group
unicellular,
motile by flagellum
mostly freshwater
mainly in eutrophic ponds and pools
(=lots of nutrients and organic material, eg farm ponds)
most unusual feature is lack of cell wall
flexible pellicle covering instead
food stored as paramylon (a polysaccharide found nowhere else in
living world)
has stigma = photoreceptor => attracted to light
has chloroplasts but can survive without them as well
(lives in dark like protozoan)
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4. Green Algae
~7000 sp
most diverse group of algae in sizes and shapes
most are freshwater
some terrestrial
found in a wide variety of habitats including
snow
tree trunks
soil
diverse body forms,
some form lichens with fungi;
mostly unicellular and colonial,
some coenocytic siphonous,
filaments or sheets;
probably gave
rise to plant kingdom;
motile by flagella,
very similar cell structure to plants:
pigments mainly chlorophyll a and b
food stored as starch
cell wall mainly of cellulose
plants probably evolved from a green alga
some with light sensitive “eyespot” = stigma
some multicellular filamentous forms and
small seaweeds (eg sea lettuce)
some chlamydomonas-like cells live in colonies of
4,8,16 or 32
they are connected by cytoplasmic strands
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most spectacular colonial form is Volvox:
500-60,000 cells
front and back ends
vegetative and reproductive cells
produce daughter colonies within adult sphere
 tendency toward multicellularity
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5. Brown Algae (phaeophyta)
~1500 sp
all multicellular seaweeds,
almost all marine
usually inhabit cooler, rocky shores, intertidal areas
most large seaweeds are in this group
giant kelp can grow 300 ft long
kelp beds can be so dense they are essentially
jungles
provide food and home for numerous sea
creatures
cell wall of cellulose
complex specializations of cells into structures of
specific functions:
blade
stipe (stalk)
floats
holdfast – attaches to solid surface
rapid growth rate: can renew tissues 1-5 x’s/yr
pigments: chlorophyll a and brown fucoxanthin
 gives them a dark brown or olive green appearance
stores foods as laminarin and lipids
life cycle usually involves
alternation of generations:
seaweed produces sporangium
sporangium produces male or female spores
spores grow into male or female sporophytes
sporophyte produces egg or sperm
zygote produces seaweed again
Sargassum
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=gulfweed, rockweed, seaholly
sargassum refers to ‘grapelike’ appearance of gas bladders
only seaweed that is not attached to a substrate
 it’s planktonic
sargasso sea
~2/3rd ‘s area of cont US
trapped in ring of currents in atlantic
sargassum can live for many years
reproduces mainly by fragmentation
when it becomes too encrusted it slowy sinks
to bottom
some weed is blown to gulf shores by winds
and currents
entire ecosystem of different organisms highly
adapted to it: crabs, shrimp, pipefish, “furry white” bryozoa,
sargassum fish “Histrio histrio”
lots of camoflage
Economic Impacts:
used as food especially in SE Asian countries;
Kelp
kelp forests in the pacific provide such products as Kombu, Barech and Seche.
Alginates
Alginates are derived from various species of brown algae including Macrocystis, Laminaria and Fucus.
About half of the ice cream in the US contains alginates.
It is used to produce a smooth consistency and eliminate ice crystals in icecreams. It is also used in some
cheeses and frostings.
alginates used to make a wound dressing that speeds healing of leg ulcers
Fertilizers:
seaweeds contain iodine, K, N, P
equivalent to manure
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6. Red Algae (rhodophyta)
~4000 sp
especially abundant in warm tropical waters,
(found in deeper waters than green algae)
mostly marine
body of filaments or sheets
most are multicellular seaweeds
some differentiation of cells into:
stalks, floats, blades in some species
often attached to substrate by holdfast
cell wall of cellulose but often has other
carbohydrates (eg. agar)
some can deposit calcium carbonate in their cell
walls
= coralline algae
 important component of coral reefs
pigments: include chorophyll a and red pigment = phycobilin (more
effective at capturing light in deeper water))
food stored as starch
Economic Impacts:
thick starchy cell walls yield commercial quantities of agar
Agar
Agar is extracted from several red seaweeds including Gelidium sp. and Gracilarid sp. It is used in the
manufacture of processed cheese, mayonnaise, puddings, jellies, baking products and canned goods.
agar:
capsules for pills
cosmetic base
culture media
jellies, puddings and desserts
mayonnaise
canned goods
some cheeses
Nori
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The red seaweed, Porphyra, is cultivated in Japan. There are several species that are roasted and
sometimes soaked in sugar and soy sauce for soup flavorings, wrapped rice crackers and to make other
oriental dishes
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Protists - Protozoa
~31,000 living species; ~10,000 of these are parasitic
animal like protists
share several animal-like traits:
lack cell wall,
most are motile
heterotrophic nutrition,
animals probably evolved from some kind of
protozoan
most are single cell (=solitary)
a few are colonial
most are microscopic (3-300µm)
have been found in all aquatic environments
form important part of plankton (=zooplankton)
some found in terrestrial habitats where moisture is
abundant:
sand
soil
decaying organic matter
some are parasitic or symbiotic in animals
most are motile by
cilia
flagella
amoeboid motion (form pseudopodia)
(found in amoebas and some flagellates)
can also use cilia or flagella to create water currents
for feeding
most have optimum temperature range of
36 – 40 º C (=96.8 – 104º F)
heterotrophs = feed by:
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1. absorbing dissolved organic nutrients
through cell membrane
2. ingest solid particles
through a mouth-like opening (=cytostome)
eat bacteria, algae, other protozoa, etc
some are saprophytic
(=eat decaying organic matter)
3. ingesting solids or liquids
through cell membrane (phagocytosis &
pinocytosis)
food becomes enclosed in vacuole which travels
through cytoplasm
digestive enzymes are injected into the vacuole
and digest the food
undigested material is expelled by a reverse
process (exocytosis) or through an “anal pore”
Life Cycles
a. most protozoa exist in a single form which feeds and
reproduces
b. some alternate between two stages in their life
cycle:
troph = active vegetative feeding form
cyst = more resistant stage,
low metabolic rate
may have wall of cellulose, silica or a
chitin-like substance
c. some parasitic forms have several different stages
in more than one host
Reproduction
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reproduce both asexually and sexually:
asexual: main form of reproduction
fission = divide in equal halves
(not same as bacterial fission)
eucaryotic fission involves mitosis
some split longitudinally (flagellages)
some split transversely (ciliates)
budding
= unequal fission
multiple fission = >2 daughter cells
(some flagellates, sarcodines, most sporozoans)
sexual:
involves some exchange of genes
conjugation = exchange of a few genes
(ciliates only)
syngamy = fusion of gametes
Classification
protozoa are classified according to presence and type
of motility:
amoeboid motion
flagella
cilia
nonmotile
Phylum: Sarcomastigophora
Subphylum: Mastigophora – 1 or more flagella
Subphylum: Sarcodina – amoeboid pseudopodia
Phylum: Ciliophora – ciliates
Phylum: Apicomplexa: - no cilia or flagella
non motile
all are parasitic
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1. Amoebas
amoeba = “to change form”
Include protozoa that move by pseudopodia
(=false feet)
related to changes in consistency of the cytoplasm:
ectoplasm = gel
endoplasm = liquid
organism can alternate between solid gel-like and
liquid cytoplasm to produce pseudopodia;
simplest protozoans relatively few organelles
may be naked or enclosed within shell or case:
only phylum of protozoan with extensive fossil
record
the shell may be composed of materials secreted
by cytoplasm or
foreign material embedded in cement like
secretion
two most important shelled forms:
radiolaria secrete a silica shell (SiO2), and
foraminiferans produce calcium carbonate shells (CaCO3)
reproduce mostly asexually
a few reproduce sexually
Human Impacts:
Human pathogens include:
1. Entamoeba hystolytica
amoebic dysentery
esp tropics and areas of poor sanitation
(5% infection in temperate areas)
humans only reservoir
spread by fecal/oral route
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invade intestinal mucosa
feed on RBC’s
90% are asymptomatic
can cause ulcerations and profuse bleeding in acute cases
cysts passed in feces
may spread to liver, lungs, brain, etc
2. Naegleria fowleri
causes always-fatal primary amoebic meningoencephalitis or
PAM
mature adults seem to be immune
prefers warm waters with a high iron content
may prefer areas where other organisms have been wiped
out by natural or man made disasters (eg Mt. St.
Helens)
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2. Flagellates
cell membrane surrounded by pellicle
move using one or a few long flagella
some have “sail-like” undulating membrane
(also used for food gathering and locomotion)
most are symbionts as either mutualists or
commensals
eg. such as those in the gut of termites
some are pathogens
eg. such as Giardia, Trypanosoma,
most flagellates are not closely related to other protozoans
 probably include several phyla
Human Impacts:
Human Pathogens:
1. Trichomonas
several species (esp. T. vaginalis)
human urogenital tract:
like acidity of female tract
one of most common infections in US
(2.5 M inf/yr: 3-15% US infected)
no cyst form  requires personal contact
occasionally spread in communal baths and mother to
child
both male and female infected
esp in promiscuous young women who are already
infected with other STD’s
~50% are asymptomatic carriers
symptoms: women -frothy, smelly green
discharge; painful urination
[T. tenax – 5-10% oral infections
esp with poor oral hygeine]
2. Giardia
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pear shaped
diarrhea
humans are final (definitive) host
no intermediate hosts
worldwide distribution
infect upper small intestine
no invasive ability – saprophytic
in large #’s can cause chronic diarrhea,
dehydration
cysts shed in feces
fecal/oral transmission
epidemics associated with contaminated water
3. Trypanosoma (African Sleeping Sickness)
esp in Africa
20,000 cases/yr (1988)
two hosts:
tsetse fly = definitive host
humans and other animals
intermediate hosts
moves into blood and lymphatic system
affects CNS: personality changes,
behavior changes, headaches, apathy, NM disorders,
sleepiness, emaciation
may result in death from coma,
malnutrition, secondary infections
4. Chagas disease (T. cruzi)
Mexico, Central America, So. America
only a few cases in extreme SW US
40-50% of population in So. America
reservoirs: rodents, possums, armadillos
vector: “kissing bug”: bites lips, defecates while
feeding and may be rubbed into wound by scratching
bite
most dangerous to children
symptoms somewhat similar to sleeping sickness
may also affects many organs; eg. brain, heart,
intestines
5. Leishmania
zoonosis
especially in equatorial areas
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transmitted by phlebotomid (sandfly) vector
injected directly into human host
reproduces inside WBC’s
two forms:
cutaneous form:
begins with skin ulcer at site of infection
may recur after healing
may spread to nose, lips, palate, throat
death from bacterial infection
systemic form:
produces high intermittant fever
enlarged spleen, liver and lymph glands
75-90% death rate
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3. Ciliates
The largest most diverse group of single celled
'protozoan' protists;
genetically as diverse as entire animal kingdom
mostly are freeliving
in a wide variety of habitats.
motile by means of cilia
= 1000’s oarlike projections
produce coordinated movements
fastest of the protozoans
a few are nonmotile: attached to substrate by stalk
use cilia for feeding, not movement
Wide variation in #’s and kinds of organelles:
more than one nucleus,
some macronucleus => vegetative chores
micronuclei (up to 80) => sexual reproduction
“mouth” and throatlike area,
most feed on microorganisms – have mouthlike cytostome;
opens into a throat; food vacuole forms at end of throat
contractile vacuoles, etc
some fw forms use to remove incomming water
trichocysts
some ciliates can steal chloroplasts from the algae
they eat
Reproduction:
asexual: binary fission
sexual: conjugation: portion of micronuclei are
exchanged between + and – forms
Human Impacts:
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Human Pathogens:
1. Balantidium coli
ony ciliate that is a human parasite
zoonosis: esp in sheep, cattle, pigs, horses
rare in US
esp in hosts with weakened defenses
can be asymptomatic
causes erosion of intestinal lining
produces nausea, vomiting, bloody diarrhea
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4. Apicomplexa (Sporozoa)
All members of this group are nonmotile
are endoparasites
most have fairly complex life cycles
same species exists in lots of different forms
alternating between forms that reproduce sexually
and those that reproduce asexually.
Human Impacts:
Human parasites include:
1. Plasmodium (malaria)
single most important disease hazard for
people traveling to foreign lands
(esp. Asia, Africa, Latin America)
worldwide infects 270M and kills 2M/yr
in some parts of world is chronic
relatively rare in US (usually travelers)
4 species, all can infect humans
requires two hosts to complete life cycle:
sexual reprod
occurs in Anopheles mosquito
reproduces in salivary glands
asexual reproduction
occurs in humans
concentrates in liver
symptoms: cyclic chills/fever, headache every 3-4 days
if not treat may be self limiting but may be reservoir for up
to 3 years
can produce irreversible damage to liver, spleen, kidneys
and brain
most effective prevention is elimination of mosquito
WHO has been trying to eliminate it but with little success
mosquitoes have developed resistance to insecticides
has developed antibiotic resistance
experimental vaccines being tested
some living in endemic areas have developed
genetic resistance to disease (sickle cell)
2. Toxoplasma
zoonosis
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cats are main reservoir and definitive host
humans contract by contaminated soil, cat feces (litter box),
infected meat
generally no human-human transfer
asymptomatic in adults
if pregnant can cross placenta and cause retardation,
blindness and convulsions in embryo or newborn
3. Pneumocystis
common secondary infection of AIDS victims
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Protists:
Slime Molds & Water Molds
~1100 species
Superficially resemble fungi;
nonphotosynthetic
body of threadlike filaments = hyphae
 fruiting body a sporangium producing spores
fungus like, but:
produce flagellate reproductive cells and
some have cell wall of cellulose,
others with cell walls of chitin
feeding stage is amoeba-like motile
common in cool, moist shady places
eg. crevasses of rotting wood
most easily found in summer and early fall
fruiting body is the most likely to be seen
 very small (~1-2mm)
 goblets, globes, plumules
 with or without a stalk
 often colored yellow, orange, red
for most of a slime molds life it exists as a thin, freeliving mass of protoplasm up to several inches across that moves around
and engulfs bacteria and organic matter
it is thick and slimy to the touch
after its feeding period it moves out of its normal
habitat and goes to a drier, more exposed location to produce a fruiting
body
fruiting bodies can also be produced by absence of food, changes
in moisture, pH, temperature
once begun, it cannot be reversed
some can produced a hardened resistant sclerotium
to survive adverse conditions
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fossils of this group has the distinction of being the first
true fossil that actually shows an organism caught in the act of sexual
reproduction (65MY)
Classification:
three major Phyla:
1. plasmodial slime molds (Myxomycota)
2. cellular slime molds (Acrasiomycota)
3. water molds (Oomycota)
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1. Plasmodial Slime Molds
~700 species
life cycle has two major stages:
feeding stage (nonreproductive)
sporangia (reproductive)
feeding stage = plasmodium
wall-less amoeba-like mass
large single cell
thin streaming masses of cytoplasm
creep along in amoeboid fashion
can cover an area of several square yards (to 30 g = ~ 1oz)
growth continues as long as there is adequate food and
moisture
when in short supply they migrate away from feeding area
(often seen crossing roads, lawns, climbing trees, etc)
some species form extensive growths on lawns, croplands
 do little, if any, damage
eg. Fuligo septica plasmodium (shades of war of the
worlds)
1973 found in Dallas suburb & reported in paper
appeared on lawns as bright yellow masses
spread over large areas
described in paper as a “pulsating yellow blob”
blobs broke apart when sprayed with hose
but pieces continued to crawl around
caused local panic:
must be indestructible aliens from space
 or mutant bacteria that might take over
the earth
excitement soon dissipated once identified
 biologists “saved the world!”
when food supply dwindles reproduction is initiated
plasmodium divides into numerous mounds
each mound forms cells surrounded by cell walls
produce multicellular fruiting body = sporangium
has cell walls on cells
very similar to those of fungi
produces very resistant reproductive spores
spores are
haploid cells
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flagellated (=swarm cells)
or amoeba like (=myxamoeba)
this group is probably more closely related to amoebas
than to fungi
Economic Importance:
Veracruz Mexico:
some are collected, fried and eaten by indigenous
peoples
called “cacade luna”
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2. Cellular Slime Molds
~70 species
superficially resemble the plasmodial slime molds
also closely resemble amoeba
life cycle also involves
feeding stage
reproductive stage
feeding stage consist of individual amoeba-like cells
when food or moisture runs out cells aggregate
form a single multicellular organism = pseudoplasmodium
(=slug)
the slug develops a stalked structure (the fruiting body) which
produces spores
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3. Water Molds
~580 species
mainly soil and water borne organisms
once classified with fungi: have hyphae and mycelium
but differ significantly in fundamental structures and biochemistry
most commonly seen as the fuzzy filaments on dead
aquarium fish
hyphae are coenocytic (= 1 giant multinucleate, filamentous cell)
has both asexual and sexual reproductive stages:
asexual: zoosporangium producing zoospores
sexual: antheridium and oogonium producing oospores
Economic Impacts:
some are serious plant pathogens
eg. downy mildew
affects grapes
introduced into France in late 1800’s
almost destroyed the wine industry
problem was accidentally solved using copper
sulfate and lime
eg. Phytophthora infestans
Cause of Irish Potato Famine (1845-7)
in Ireland
virtually the entire Irish potato crop was wiped
out in one week
> 1 million deaths from starvation
began large scale emmigration of Irish to US
within a decade the population of Ireland
dropped 50%: 8M -> 4M
eg. other Phytophthora species
have caused widespread destruction of many
crops throughout the world:
pineapples
tomatoes,
rubber,
onions
strawberries
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006
34
apples
soybeans
tobacco
citrus
EuKaryotes—General & Protists, Ziser Lecture Notes, 2006
35