diversity eukaryotic microbes final
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Midterm results are graded, will beposted with key very soon
Average=56.6, top score=94, average of the top 6 scoreswas 89.3
We dont assign grades to individual midterms but IF thesame 6 students get the top scores overall, then cutoff forA = 90% of 89.3 =80.4B = 890% of 89.3 =71.5C = 70% of 89.3 =62.5D = 55% of 89.3 =49.1E below 49.1
If different students do well at different times (normallythe case), final cutoffs will be easier.
If you did really, really badly, when you pick up your exambooklet from Kaye Jays office, check that you bubbled theright version number.
Announcements
You must learn the material for the final exam
I encourage you to come to my office hours ifyou cant understand your mistakes
Also use the tutors for this, and to work outhow to study more effectively
I will not be here in the week or two beforethe final exam, so please seek help now.
Tuesday, Feb 21. Biological Evolution:What It Is and What It Isnt(Joanna Masel, EEB)
Tuesday, Mar 7. Cosmic Evolution:From Big Bang to Biology(Chris Impey, Astronomy)
Tuesday, Mar 21. Earth Evolution:The Formation of Our Planet(Joaquin Ruiz, COS Dean, Geosciences)
Tuesday, Mar 28. Social Evolution:Cooperation and Conflict FromMolecules to Society(Rick Michod, EEB)
Tuesday, Apr 11. Animal Evolution:Recycling Ancient Genes For New Uses(Lisa Nagy, MCB)
Tuesday, Apr 18. Human Evolution:Tracking Our Origins with DNA(Michael Hammer, ARL/EEB)
Tuesday, Apr 25. Disease Evolution:
The Example of HIV(Michael Worobey, EEB)
http://cos.arizona.edu/evolution/
Diversity ofEukaryotic Microbes
Where are microbes on tree of life?
Protists are eukaryotes that are not animals, plantsor fungi:
Yeast are unicellular fungi
Arch
aea
Bacteria
Eukaryote
s
Modified fromSimonson et al. (2005)PNAS 102, 6608-6613
Biology of protists
Most are unicellular, some are multicellular, afew are large
Some are heterotrophs, some are autotrophs,and some switch
Use membrane vesicles for many things Most reproduce both sexually and asexually
Protozoan and algae lump together manyphylogenetically distant protist groups
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Lots of endosymbiosis Lots of endosymbiosis
Evolutionary history of protists Diplomonads and Parabasalids
Giardia
Euglenozoans
Have flagella
2 clades
Euglenoids
Kinetoplastids
Euglenoids
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Various euglenoids collected fromstagnant ponds
Euglenoid Eutreptiamoves using flagella
Kinetoplastids parasitic
trypanosomes causesleeping sickness,leishmaniasis,Chagas disease,and East Coastfever
single largemitochondrion withkinetoplast housingmultiple, circularDNA molecules:edits own RNA
Alveolates
unicellular
cavities calledalveolijust belowtheir plasmamembranes
DinoflagellatesDistinctive appearance with two flagella
Dinoflagellates
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Dinoflagellates cause red tides When and why do dinoflagellatesbioluminesce?
Its like a burglar alarm against predators.
When a dinoflagellate is disturbed, it flashes. This attracts a secondary predator. The secondary predator is more likely to eat the
larger burglar than the smaller dinoflagellate. Often the threat alone is enough to scare off the
primary predator (burglar).
Breaking waves or stepping on sand also disturbdinoflagellates
Apicomplexans
Apical complex = mass of organelles at apicalend of spores
All are parasites: apical complex organelleshelp spore invade host tissue
Plasmodiumare the cause of malaria
Enters the human circulatory system by wayof the Anophelesmosquito
Extracellular parasite in the insect vector andan intracellular parasite in the human host
Life cycle of an apicomplexan
Liver
EVENTS IN MOSQUITO EVENTS IN HUMAN
Gametocytes
What part of the Plasmodiumlife cycledoes chloroquine interfere with?
erythrocytic stage
This treats the symptoms, butpersistent liver infection can leadto relapses
Ciliates have complex and variedbody forms with hairlike cilia
Almost allheterotrophic
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Large ciliate from termite gut movesusing thousands of synchronized flagella
Parameciumuses cilia to generatecurrent to carry prey to gullet
Ciliates have multiple nuclei
Cell life is run by products of macronucleus Micronuclei are involved in conjugation
Parameciumconjugation
Genetic recombination called conjugation Haploid micronuclei are exchanged
Fuse to form a new diploid micronucleus
Some protist body plans haveemerged multiple times
Amoebas
often live at the bottom of lakes, ponds etc.
Slime molds
Amoeba moves via pseudopods usingactin microfilaments
25xrealspeed
Thisamoebahaseatengreenalgae
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Chitin
Production of chitin is a shared derived traitfor
How fungi live
All use absorptive nutrition, secretingdigestive enzymes and absorbing thebreakdown products
Most are saprobes Earths main decomposers (with bacteria)
principal decomposers of cellulose & lignin
Some are parasites A few are mutualists
Saprobic fungi and bacteriaCell structure of multicellular fungi
Vegetative body= mycelium(plural mycelia)
Composed ofthreadlikehyphae(singular hypha)
Incomplete division into cells
Cell-likecompartmentsseparated bysepta (singular
septum)
Freemovement oforganelles,sometimeseven nuclei,and othermaterialscoenocytic hypha septate hypha
Fungus structure
Hyphae may
disperse to look for nutrients
clump together to exploit a food source
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Fungal hyphae attack a leaf
Hyphae give a large surface:volume ratio, which helpswith absorptive nutrition
Symbiotic fungiLichens are symbiotic associations of a fungus with a
Symbiotic fungi
The fungus obtains organiccompounds, while the plantis provided with water andsoil minerals
Some plants cant growwithout them
Fungalreproduction
Life cyclesdistinguish 4 phyla
When sex has notbeen observed,provisionallyclassified asimperfect fungi ordeuteromycetes:currently 25,000
species
Yeast are fungi
All four fungal phyla have unicellular species
Those of the Zygomycota, Ascomycota, andBasidiomycota are calledyeasts
The yeast Saccharomyces cerevisiaemakesCO2 and ethanol during fermentation
Used for bread and beer
Asexual reproduction via sporesProduction ofhaploid sporeswithin sporangia
Production of naked sporesat the tips of hyphae (notwithin sporangia) calledconidia
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Fungal spores are everywhere
Every breath we take is full of fungal spores
Most humans only succumb to fungalpathogens when immunocompromised
Plants are notso lucky
Parasitic fungus Ustilagomaydis(corn smut)
Neither wasthis ant
Spores of thisfungus dontgerminate untilingested by anant
More asexual reproduction
Cell division by unicellular fungi
Sexual reproduction
Some fungi have more than 2 mating types
Mating types dont look different
Mating can only occur between different matingtypes, preventing self-fertilization
Sexual reproduction when hyphae (or motile cellsin chytrids) of different mating types meet andfuse
Haplontic life cycle
Often diploid only very briefly as a zygote
Meiosis produces haploid nuclei again
Haploid spores divide mitotically to form haploidhyphae
This type of life cycle is called a haplontic lifecycle. Some protists have it too.
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Basidiomycete life cycle Life cycle of the basidiomyceteCortenellus shiitake
Other 3 phyla alsohave complex and
distinctive life cyclesChytrid
Zygotefungus
Ascomycete(sac fungus)
Important points about sex andreproduction
Sex = 2 nuclei fusing and undergoing meiosis Reproduction = one individual giving rise to
multiple: can be sexual or asexual Genetic recombination = any gene exchange: not
just sex, also nonreproductive processes such asconjugation
Dikaryotic individuals include 2 fused individuals,but not fused nuclei
Spores can be sexual or asexual, reproductive ornot: normally a small, tough cell with potential to
become new organism. Often capable of latency.Can be plant, bacterial, protist or fungal.
Spores are
a. produced only by bacteria.
b. produced only by eukaryotes.
c. always a product of sexual reproduction
d. often a way for an organism to lie dormantand wait for better times.
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