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Todays Lecture
- Bacteria & Archaea: Similarities and differencesMetabolic
diversityEcological impact
- Fungi: General characteristicsStructureFeedingEcological
roles
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BACTERIA AND ARCHAEA
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Bacteria Vs. Archaea
Phylogeny- 2 major prokaryote branches: BacteriaArchaea
- First lineage to diverge = bacteria- Archaea and eukaryotes
more closely related.
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What Do They Have In Common?
* Structurally simple- Virtually all unicellular.- Small.
- All prokaryotic:
1.2.3.
*
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How Do They Differ?
* Fundamentally different in molecular structure andgenetic
machinery.
- External cell wallbacteria!unique polysaccharide
peptidoglycan
- Plasma membranearchaea!unique phospholipid (includes
isoprene)
- DNAarchaea!associated w/histones (like eukaryotes)
- DNA/RNA polymerases, ribosomes etc.distinct in bacteria
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Metabolic Diversity
* Masters of Metabolism!- Metabolic diversity prokaryotes >
all eukaryotes.- Can use almost anything as source of energy and
C.- Nearly all metabolic pathways originated in
prokaryotes!
evolved variations.
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!Explains ecological range; some extremophiles
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Ecological Impact Of Bacteria
1. Recycling Of Chemical Elements In Ecosystems
a) Decomposers- Break down large molecules in corpses and
waste.
b) Nitrogen Fixation- Converts atmospheric nitrogen
(N2) into NH4+!form organisms
(plants, algae) can use.
- Only certain prokaryotes possessenzyme.
- Free-living or in root nodules.
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2. Primary Production
- Photosynthetic and chemosynthetic bacteria make
organic compounds (food)!support food chains.
3. Mutualistic Relationships
Ex. Cellulose breakdown in ruminants
4. Historic Oxygen Revolution
- Cyanobacteria put all oxygen in atmosphere ~2.5billion years
ago.
- Allowed aerobic respiration.
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EUKARYOTES
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Whos Included In Eukarya?
- Largest, mostmorphologicallycomplex organisms.
- Plants, fungi, animals
= subgroups withinEukarya.
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The Eukaryotic Cell
Essence = large, compartmentalized cell.Membrane-bound nucleus
and other organelles.How are all these membranes useful?
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FUNGI
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General Characteristics
- Eukaryotic (chitin cell wall)- Mostly large and multicellular-
Non-motile* External heterotrophs- Filamentous bodies
Habitat
- Mostly terrestrial.
Anywhere organic material & moisture available.
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Structure
- 2 Growth forms:1. Multicellular filamentous mass = mycelium2.
Single-celled yeasts
- Note: Mushrooms are specialized reproductivestructures.
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- Individual very thinfilaments = hyphae- Divided by septa.
Incomplete - cytoplasm & organelles flow freely.
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Feeding
- Secrete digestive enzymes outside body at tips of
hyphae then absorb nutrients.- Mycelium grows toward food.
Dies back + release spores when food low.
Adaptations1. high surface area:volume - efficient absorption2.
grows under/in food tissue
How does high surface area explain habitat of fungi?
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Ecological Roles
1. Decomposition
- Saprophytic fungi = major decomposer in biosphere.- Digest
almost any organic substance.* Digest wood (lignin + cellulose)
completely!
- Speed up carbon cycle; C atoms locked in dead treesetc.
released for re-use.
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2. Mycorrhizae
- Mutualistic association between fungus and plant.- Fungi grow
on or in plants roots.- Extremely common (~90% of land plants).-
Fungus gains carbs; plant gains nutrients (P, N).
* Without mycorrhizae,host plants grow muchmore slowly or
starve.
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3. Parasitism
- Parasitic fungi cause death and disease amongplants and
animals.
Ex. Athletes foot, ringworm, thrush, diaper rash,
yeastinfections, Dutch elm disease, chestnut blight,
crop diseases
