Eukaryotes have cell membranes and nuclei - All species of large complex organisms are eukaryotes, including animals, plants and fungi, although most species of eukaryotic protists are microorganisms.
Prokaryotes lack nucleus
Tiny (1 μm width), one-celled - Tiny (1 μm width), one-celled
- Single cell division
- In lab: 1 can produce 5 billion in 12 hours
- (In real world limited by predators, water & food availability)
Abundant in rhizosphere - zone surrounding root
- dead root cells and exudate stimulate microbial growth
1. Decomposers Organic chemicals in big complex chains and rings - Bacteria break bonds using enzymes they produce
- Create simpler, smaller chains
Immobilize nutrients in their cells; prevents loss of nutrients from rooting zone 2. Mutualists form partnerships with plants (e.g. Rhizobium and legumes) 3. Pathogens cause plant galls 4. Chemoautotrophs get energy from compounds other than compounds
Make “earthy” smell Make “earthy” smell adaptable to drought usually aerobic heterotrophs break down “recalcitrant” compounds - Hard-to-decompose (chitin, cellulose)
Produce antibiotics, like Streptomycin
Unicellular; larger than bacteria Unicellular; larger than bacteria Amoeba, ciliates, flagellates Heterotrophic - Eat bacteria
- Bacteria have more nitrogen than protozoa need, so protozoa release the excess
- mineralize
e.g., flagellates in termite guts; digest fibers Require water - Go dormant within cyst in dry conditions
Filamentous, colonial, unicellular Filamentous, colonial, unicellular Photosynthetic - Most in blue-green group, but also yellow-green, diatoms, green algae
- Need diffuse light in surface horizons; important in early stages of succession
- Form carbonic acid (weathering)
- Add OM to soil; bind particles
- Aeration
- Some fix nitrogen
Grow as long threads (hyphae) Grow as long threads (hyphae) - Push through soil particles, roots, rocks
Often group into masses called mycelium (look like roots) Higher fungi have basidium : club-shaped structure , bearing fruiting body
Break down OM, esp important where bacteria are less active; low pH Break down OM, esp important where bacteria are less active; low pH attack any organic residue - feed by absorbing nutrients from organic material ; no stomachs;d igest food before it can pass through the cell wall into the hyphae.
- Hyphae secrete acids and enzymes that break the surrounding organic material down into simple molecules they can easily absorb.
chemosynthetic: adsorb dissolved nutrients for energy
Like bacteria: immobilize nutrients in soil Like bacteria: immobilize nutrients in soil Produce organic acids; increases humic-acid-rich OM that is resistant to degradation - Lasts in soil for 100s of years
Mycorrhizae: symbiotic absorbing organisms infecting plant roots, formed by some fungi Mycorrhizae: symbiotic absorbing organisms infecting plant roots, formed by some fungi - Mutualists
- Get carbon from plant
- Give to plant:
- Solubilize P; bring soil nutrients to plant
- normal feature of root systems, esp. trees
- increase nutrient availability in return for energy supply
- plants native to an area have well-developed relationship with mycorrhizal fungi
Grow on surface layers of roots Grow on surface layers of roots
Grow within root cells Grow within root cells - Grasses, crops, vegetables, shrubs
(Macrofauna: > 1 cm long) (Macrofauna: > 1 cm long) ANNELIDS several types: epigeic (litter) anecic (burrow) endogeic (in soil)
CHORDATES (vertebrates) mammals, amphibians, reptiles PLATYHELMINTHES (flatworms) ASCHELMINTHES (roundworms, nematodes) MOLLUSKS (snails, slugs) ARTHROPODS : (insects, crustaceans, arachnids, myriapoda)
Squirrels, mice, groundhogs, rabbits, chipmunks, voles, moles, prairie dogs, gophers, snakes, lizards, etc. Squirrels, mice, groundhogs, rabbits, chipmunks, voles, moles, prairie dogs, gophers, snakes, lizards, etc. Contribute dung and carcasses Taxicabs for microbes
Nonsegmented, blind roundworms Nonsegmented, blind roundworms > 20,000 species Eat bacteria or fungi or plants (stylet) - And protozoa, other nematodes, algae
Specialized mouthparts - Can sense temperature and chemical changes
nematode
¾ of all living organisms Exoskeleton, jointed legs, segmented body Insects Crustaceans Arachnids Myriapoda
Shredders Shredders Microbial taxis
Feeding Habits Feeding Habits Carnivores : parasites and predators Phytophages: eat above ground green plant parts, roots, woody parts Saprophages: eat dead and decaying OM Microphytic feeders: eat spores, hyphae, lichens, algae, bacteria
Distribution with depth Distribution with depth most active biotic horizons correspond with amount of OM: Roots: - Rhizosphere: zone surrounding root
- dead root cells and exudate stimulates microbial growth
- Most microbiotic population in A and rhizosphere
ACTIVE fraction: ACTIVE fraction: - Organic compounds that can be used as food by microorganisms
LABILE: - OM that’s easily decomposed
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