Prokaryotes Protists and Fungi
Transcript of Prokaryotes Protists and Fungi
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ProkaryotesProkaryotes
(Bacteria)(Bacteria)
Everythingelse
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Prokaryotic cells have a Prokaryotic cells have a variety of shapesvariety of shapes
The three most common of which The three most common of which are spheres (cocci), rods (bacilli), are spheres (cocci), rods (bacilli), and spiralsand spirals
1 m 2 m 5 m(a) Spherical (cocci) (b) Rod-shaped (bacilli) (c) Spiral
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Cell-Surface StructuresCell-Surface Structures
One of the most important features One of the most important features of nearly all prokaryotic cellsof nearly all prokaryotic cells Is their cell wall, which maintains cell Is their cell wall, which maintains cell
shape, provides physical protection, shape, provides physical protection, and prevents the cell from bursting in and prevents the cell from bursting in a hypotonic environmenta hypotonic environment
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Using a technique Using a technique called the Gram staincalled the Gram stain
Scientists can classify many bacterial Scientists can classify many bacterial species into two groups based on cell wall species into two groups based on cell wall composition, Gram-positive and Gram-composition, Gram-positive and Gram-negativenegative
Gram-positive. Gram-positive bacteria have a cell wall with a large amount of peptidoglycan that traps the violet dye in the cytoplasm. The alcohol rinse does not remove the violet dye,which masks the added red dye.
Gram-negative. Gram-negative bacteria have less peptidoglycan, and it is located in a layer between theplasma membrane and an outer membrane. The violet dye is easily rinsed from the cytoplasm, and the cell appears pink or red after the red dye is added.
PeptidoglycanlayerCell wall
Plasma membrane
Protein
Gram-positivebacteria
20 m
Outermembrane
Peptidoglycanlayer
Plasma membrane
Cell wall
Lipopolysaccharide
Protein
Gram-negativebacteria
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The cell wall of many The cell wall of many prokaryotesprokaryotes
Is covered by a Is covered by a capsulecapsule, a sticky layer , a sticky layer of polysaccharide or proteinof polysaccharide or protein
200 nm
Capsule
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Some prokaryotes have Some prokaryotes have fimbriaefimbriae and and sex pilisex pili
FimbriaeFimbriae allow them to stick to their allow them to stick to their substrate or other individuals in a colonysubstrate or other individuals in a colony
Sex piliSex pili allow two bacteria to join and allow two bacteria to join and exchange DNA during conjugationexchange DNA during conjugation
200 nm
Fimbriae
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MotilityMotility Most motile bacteria propel themselves Most motile bacteria propel themselves
by by flagellaflagella Which are structurally and functionally Which are structurally and functionally
different from eukaryotic flagelladifferent from eukaryotic flagellaFlagellum
Filament
HookCell wall
Plasmamembrane
Basal apparatus
50 nm
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The typical prokaryotic The typical prokaryotic genomegenome
Is a ring of DNA that is not surrounded Is a ring of DNA that is not surrounded by a membrane and that is located in a by a membrane and that is located in a nucleoidnucleoid region region
1 m
Chromosome
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Many prokaryotes form Many prokaryotes form endosporesendospores
Which can remain viable in harsh Which can remain viable in harsh conditions for centuriesconditions for centuries
Endospore
0.3 m
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Major nutritional modes in Major nutritional modes in prokaryotesprokaryotes
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Prokaryotic metabolismProkaryotic metabolismalso varies with respect to also varies with respect to
oxygenoxygen
Three types of oxygen metabolismThree types of oxygen metabolism Obligate aerobesObligate aerobes
Require oxygenRequire oxygen Facultative anaerobesFacultative anaerobes
Can survive with or without oxygenCan survive with or without oxygen Obligate anaerobesObligate anaerobes
Are poisoned by oxygenAre poisoned by oxygen
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Protists
Single-celled Eukaryotes (mostly)
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Overview: A World in a Drop of Water
• Even a low-power microscope– Can reveal an astonishing menagerie of
organisms in a drop of pond water
Figure 28.150 m
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Protists, the most nutritionally diverse of all eukaryotes, include
– Photoautotrophs, which contain chloroplasts– Heterotrophs, which absorb organic molecules
or ingest larger food particles– Mixotrophs, which combine photosynthesis
and heterotrophic nutrition
Chlorohyta phacus24.6
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Protist habitats are also diverse in habitat
• And including freshwater and marine species
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There is now considerable evidence
• That much of protist diversity has its origins in endosymbiosis
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Diversity of plastids produced by secondary endosymbiosis
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Objectives 24.7 and 24.8 will be covered in a class project
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Plasmodial Slime Molds• Many species of plasmodial slime molds
– Are brightly pigmented, usually yellow or orange
4 cm
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At one point in the life cycle– They form a mass called a plasmodium
Feedingplasmodium
Matureplasmodium(preparing to fruit)
Youngsporangium
Maturesporangium
Spores(n)
Germinatingspore
Amoeboid cells(n)
Zygote(2n)
1 mm
Key
Haploid (n)Diploid (2n)
MEIOSIS
SYNGAMY
StalkFlagellated cells(n)
The feeding stageis a multinucleateplasmodium that liveson organic refuse.
1 The plasmodiumtakes a weblike form.2
The plasmodium erectsstalked fruiting bodies (sporangia)when conditions become harsh.
3
Within the bulboustips of the sporangia,meiosis produces haploidspores.
4 These cells areeither amoeboid orflagellated; the twoforms readily convertfrom one to the other.
6 The cells unitein pairs (flagellatedwith flagellatedand amoeboid withamoeboid), formingdiploid zygotes.
7 The resistant spores dispersethrough the air to new locationsand germinate, becoming activehaploid cells when conditionsare favorable.
5
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Cellular Slime Molds
• Cellular slime molds form multicellular aggregates– In which the cells remain separated by
their membranes
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• The life cycle of Dictyostelium, a cellular slime mold
Spores(n)
Emergingamoeba
Solitary amoebas(feeding stage)
ASEXUALREPRODUCTIONFruiting
bodies
Aggregatedamoebas
Migratingaggregate
SYNGAMY
MEIOSIS
SEXUALREPRODUCTION
Zygote(2n)
Amoebas
600 µm
200 µm
Key
Haploid (n)Diploid (2n)
In the feedingstage of the lifecycle, solitary haploidamoebas engulf bacteria.
1 During sexual repro-duction, two haploidamoebas fuse andform a zygote.
2
The zygotebecomes a giantcell (not shown)by consuminghaploid amoebas.After developing aresistant wall, thegiant cell undergoesmeiosis followed byseveral mitoticdivisions.
3
The resistantwall ruptures,releasing newhaploid amoebas.
4
When food is depleted,hundreds of amoebascongregate in response to achemical attractant and forma sluglike aggregate (photobelow left). Aggregateformation is the beginningof asexual reproduction.
5
The aggregate migrates for awhile and then stops. Some of the
cells dry up after forming a stalk thatsupports an asexual fruiting body.
6
Othercells crawl
up the stalkand developinto spores.
7
Sporesare released.
8
In a favorableenvironment, amoebasemerge from the sporecoats and begin feeding.
9
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FungiFungi
Also pronounced “fun guy”Also pronounced “fun guy”
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Mighty MushroomsMighty MushroomsFungiFungi
Are diverse and widespreadAre diverse and widespread Are essential for the well-being of most Are essential for the well-being of most
terrestrial ecosystems because they break terrestrial ecosystems because they break down organic material and recycle vital down organic material and recycle vital nutrientsnutrients
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The Origin of FungiThe Origin of Fungi Molecular evidenceMolecular evidence
Supports the hypothesis that fungi and animals diverged from a Supports the hypothesis that fungi and animals diverged from a common ancestor common ancestor
Fungi probably evolvedFungi probably evolved Before the colonization of land by multicellular organismsBefore the colonization of land by multicellular organisms
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Fossil EvidenceFossil Evidence The oldest undisputed fossils of fungiThe oldest undisputed fossils of fungi
Are only about 460 million years oldAre only about 460 million years old
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Nutrition and Fungal Nutrition and Fungal LifestylesLifestyles
Fungi are heterotrophs (consumers)Fungi are heterotrophs (consumers) But do not ingest their foodBut do not ingest their food
Fungi secrete Fungi secrete exoenzymes that break down complex exoenzymes that break down complex
molecules and then they absorb the remaining molecules and then they absorb the remaining smaller compounds as nutrients.smaller compounds as nutrients.
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Fungi exhibit diverse lifestylesFungi exhibit diverse lifestyles DecomposersDecomposers ParasitesParasites Mutualistic symbiontsMutualistic symbionts
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BasidiomycetesBasidiomycetes
DecomposersDecomposers Breakdown organic Breakdown organic
material using material using enzymes to obtain enzymes to obtain nutrientsnutrients
(a) Fly agaric (Amanita muscaria), acommon species in conifer forests in the northern hemisphere
(b) Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat
(c) Shelf fungi, important decomposers of wood
(d) Puffballs emitting spores
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PathogensPathogens
About 30% of known fungal speciesAbout 30% of known fungal species Are parasites, mostly on or in plantsAre parasites, mostly on or in plants
(a) Corn smut on corn (b) Tar spot fungus on maple leaves (c) Ergots on rye
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Lichens Lichens (mutualistic)(mutualistic)
Are a symbiotic association of millions of Are a symbiotic association of millions of photosynthetic microorganisms held in a photosynthetic microorganisms held in a mass of fungal hyphaemass of fungal hyphae
(a) A fruticose (shrub-like) lichen
(b) A foliose (leaf-like) lichen (c) Crustose (crust-like) lichens
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Body StructureBody Structure The morphology of multicellular fungiThe morphology of multicellular fungi
Enhances their ability to absorb nutrients Enhances their ability to absorb nutrients from their surroundingsfrom their surroundings
Hyphae. The mushroom and its
subterranean mycelium are a continuous
network of hyphae.
Reproductive structure.
The mushroom produces
tiny cells called spores.
Spore-producing
structures
20 m
Mycelium
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Fungi consist ofFungi consist of Mycelia, networks of branched hyphae Mycelia, networks of branched hyphae
adapted for absorptionadapted for absorption Most fungi have cell walls made of chitin Most fungi have cell walls made of chitin
(polysaccharide - also found in the exoskeleton of many insects and (polysaccharide - also found in the exoskeleton of many insects and arthropods)arthropods)
24.12 Network of Hyphae
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Fungi propagate themselvesFungi propagate themselves By producing vast numbers of spores, either sexually By producing vast numbers of spores, either sexually
or asexuallyor asexually
24.13
LIFE CYCLE
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Many fungi that can reproduce Many fungi that can reproduce asexuallyasexually Grow as mold, sometimes on fruit, bread, Grow as mold, sometimes on fruit, bread,
and other foodsand other foods
2.5 m
Orange
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Other asexual fungi are yeastsOther asexual fungi are yeasts
That inhabit moist environmentsThat inhabit moist environments Which reproduce by simple cell divisionWhich reproduce by simple cell division
10 m
Parent cell
Bud
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Fungus-Animal SymbiosisFungus-Animal Symbiosis
Some fungi share their digestive services Some fungi share their digestive services with animalswith animals Helping break down plant material in the Helping break down plant material in the
guts of cows and other grazing mammalsguts of cows and other grazing mammals
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Practical Uses of FungiPractical Uses of Fungi Humans eat many Humans eat many
fungifungi And use others to And use others to
make cheeses, make cheeses, alcoholic alcoholic beverages, and beverages, and breadbread
The edible ascocarp of Morchella esculenta, the succulent morel, is often found under trees in orchards.
Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open.
24.15
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Antibiotics produced by fungiAntibiotics produced by fungi Treat bacterial infectionsTreat bacterial infections
Staphylococcus
Penicillium
Zone of inhibited growth
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Fairy RingsFairy Rings Folklore holds that fairy rings are doors into the fairies' Folklore holds that fairy rings are doors into the fairies'
world, transporting people to other places or making world, transporting people to other places or making
people appear in the same place in a different time.people appear in the same place in a different time.
Extra Credit – write 1/2 page describing how fairy rings form