EuKaryotes—General & Protists, Ziser Lecture Notes, 2006 1 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
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polyphyletic ie. not a natural grouping, some divide protists into 5 or 6separate kingdomsand 50 phyla
major types of organisms (Note: these are notevolutionary groupings, they are groupings of convenience, an notnecessarily the same groupings as in your text, or in other books):
1. Algae (22,000 species + fossils)mostly single celled, colonial, somemulticellular photosynthetic protists, mostwith cell wall
2. Protozoa (31,000 species + fossils)mostly single celled or colonial,heterotrophs, non photosynthetic, mostlymotile
3. Slime Molds (1,100 species)mostly complex life cyclesinvolving amoeba-like stage and fungal spore-like stage,
alternating sexual and asexual reproduction, heterotrophs
most spectacular colonial form is Volvox:500-60,000 cellsfront and back endsvegetative and reproductive cellsproduce daughter colonies within adult sphere
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 essentiallyjungles
provide food and home for numerous sea creatures
cell wall of cellulose
complex specializations of cells into structures ofspecific functions:
bladestipe (stalk)floatsholdfast – 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 involvesalternation of generations:
seaweed produces sporangiumsporangium produces male or female sporesspores grow into male or female sporophytessporophyte produces egg or spermzygote produces seaweed again
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 UStrapped in ring of currents in atlantic
sargassum can live for many yearsreproduces mainly by fragmentationwhen it becomes too encrusted it slowy sinks
to bottomsome weed is blown to gulf shores by winds
and currents
entire ecosystem of different organisms highlyadapted 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 somecheeses and frostings.
alginates used to make a wound dressing that speeds healing of leg ulcers
Fertilizers:seaweeds contain iodine, K, N, Pequivalent to manure
especially abundant in warm tropical waters,(found in deeper waters than green algae)
mostly marine
body of filaments or sheets
most are multicellular seaweedssome differentiation of cells into:
stalks, floats, blades in some speciesoften attached to substrate by holdfast
cell wall of cellulose but often has othercarbohydrates (eg. agar)
some can deposit calcium carbonate in their cellwalls
= 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 themanufacture of processed cheese, mayonnaise, puddings, jellies, baking products and canned goods.
agar: capsules for pillscosmetic baseculture mediajellies, puddings and dessertsmayonnaisecanned goodssome cheeses
The red seaweed, Porphyra, is cultivated in Japan. There are several species that are roasted andsometimes soaked in sugar and soy sauce for soup flavorings, wrapped rice crackers and to make otheroriental dishes
invade intestinal mucosafeed on RBC’s90% are asymptomaticcan cause ulcerations and profuse bleeding in acute casescysts passed in fecesmay spread to liver, lungs, brain, etc
pear shapeddiarrheahumans are final (definitive) hostno intermediate hostsworldwide distributioninfect upper small intestineno invasive ability – saprophyticin large #’s can cause chronic diarrhea,
dehydrationcysts shed in fecesfecal/oral transmissionepidemics associated with contaminated water
3. Trypanosoma (African Sleeping Sickness)
esp in Africa20,000 cases/yr (1988)two hosts:
tsetse fly = definitive hosthumans and other animals
intermediate hostsmoves into blood and lymphatic systemaffects CNS: personality changes,
may result in death from coma,malnutrition, secondary infections
4. Chagas disease (T. cruzi)
Mexico, Central America, So. Americaonly a few cases in extreme SW US40-50% of population in So. Americareservoirs: rodents, possums, armadillosvector: “kissing bug”: bites lips, defecates while
feeding and may be rubbed into wound by scratchingbite
most dangerous to childrensymptoms somewhat similar to sleeping sicknessmay also affects many organs; eg. brain, heart,
transmitted by phlebotomid (sandfly) vectorinjected directly into human hostreproduces inside WBC’stwo forms:
cutaneous form:begins with skin ulcer at site of infectionmay recur after healingmay spread to nose, lips, palate, throatdeath from bacterial infection
systemic form:produces high intermittant feverenlarged spleen, liver and lymph glands75-90% death rate
ony ciliate that is a human parasitezoonosis: esp in sheep, cattle, pigs, horsesrare in USesp in hosts with weakened defensescan be asymptomaticcauses erosion of intestinal liningproduces nausea, vomiting, bloody diarrhea
most have fairly complex life cyclessame species exists in lots of different formsalternating 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/yrin some parts of world is chronic
relatively rare in US (usually travelers)4 species, all can infect humansrequires two hosts to complete life cycle:
sexual reprodoccurs in Anopheles mosquitoreproduces in salivary glands
asexual reproductionoccurs in humansconcentrates in liver
symptoms: cyclic chills/fever, headache every 3-4 daysif not treat may be self limiting but may be reservoir for up
to 3 yearscan produce irreversible damage to liver, spleen, kidneys
and brainmost effective prevention is elimination of mosquitoWHO has been trying to eliminate it but with little successmosquitoes have developed resistance to insecticideshas developed antibiotic resistanceexperimental vaccines being testedsome living in endemic areas have developed
Superficially resemble fungi;nonphotosyntheticbody 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 placeseg. 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, free-living mass of protoplasm up to several inches across that moves aroundand engulfs bacteria and organic matter
it is thick and slimy to the touch
after its feeding period it moves out of its normalhabitat and goes to a drier, more exposed location to produce a fruitingbody
fruiting bodies can also be produced by absence of food, changesin moisture, pH, temperature
once begun, it cannot be reversed
some can produced a hardened resistant sclerotiumto survive adverse conditions
life cycle has two major stages:feeding stage (nonreproductive)sporangia (reproductive)
feeding stage = plasmodiumwall-less amoeba-like masslarge single cellthin streaming masses of cytoplasmcreep along in amoeboid fashioncan cover an area of several square yards (to 30 g = ~ 1oz)growth continues as long as there is adequate food and
moisturewhen 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 initiatedplasmodium divides into numerous moundseach mound forms cells surrounded by cell wallsproduce multicellular fruiting body = sporangiumhas cell walls on cellsvery similar to those of fungiproduces very resistant reproductive spores
life cycle also involvesfeeding stagereproductive stage
feeding stage consist of individual amoeba-like cellswhen food or moisture runs out cells aggregateform a single multicellular organism = pseudoplasmodium
(=slug)the slug develops a stalked structure (the fruiting body) which