chapter 6a Flashcards
habitat of many numerous organisms
soil
source of carbon, energy, and nutrients for most organisms
organic matter
numbers, kinds, and activities of these organisms are influenced by
- OM in soil
- amount and kind of organic materials applied
- soil texture
- pH
- aeration
- salinity
zone of soil surrounding a plant root where the __ and __ of the soil are influenced by the root.
rhizosphere
biology
chemistry
size of rhizosphere
edge
1 mm
no distinct edge
shows the relationship among organisms and are constructed directly from comparisons of informational macro-molecules, rRNA
phylogenetic tree
bacillus
rod shaped cells
cocci
spherical cells
spirilla
twisted or spiral shaped rods
actinomycetes
slender, branching filaments
obligate aerobes
obtain energy exclusively by aerobic respiration
obligate anaerobes
grow in anaerobic conditions, obtain energy through fermentation
facultative anaerobes
can grow in presence or absence of oxygen
aerotolerant anaerobes
grows under aerobic and anaerobic conditions
bacteria on trophic level
decomposers, 2nd level
bacteria can rapidly metabolize
sugars
starch
simple proteins
bacteria decompose on slowly manner
lignin
waxes
oils
habitat: most bacteria are
mesophiles
mesophiles
grow optimally at temp. bet. 15-35 C
thermophiles
in excess of 40-50 C (even at 100 C)
acidophiles
low pH environment
alkalophic
high pH environment
halophiles
high salt concentrations
xerophiles
dry habitats
nitrogen-fixing bacteria
form symbiotic associations with the roots of legumes
nitrogen-fixing bacteria
form symbiotic associations with the roots of legumes
nitrifying bacteria
change ammonium to nitrite then to nitrate
denitrifying bacteria
convert nitrate to nitrogen or nitrous oxide
denitrifiers are
anaerobic
actinomycetes
special group of soil bacteria
resemble miniature fungus but aren’t fungus
have aerial mycelium, smaller than that of fungi
may produce asexual spores, powdery appearance
slow-growing organisms
produce antibiotics
asexual spores
conidia
actinomycetes are sensitive to
low pH, decrease at 6, disappear at 5
examples of important antibiotics
streptomycin, neomycin, erythromycin, tetracycline
fungi
most abundant organism in soil- mass basis
don’t contain chlorophyll
plant-like bc they have cell walls
non-motile
reproduced by means of spores
hyphae
long threads or strands
decomposers
saprphytic fungi: convert dead organisms into fungal biomass, carbon dioxide, organic acid
mutualists
mycorrhizal fungi: colonize plant roots
ectomycorrhizae
grows on surface layers of soil
endomycorrhizae
grows within root cells
pathogens
disease-causing, verticullum & phytium
mycorrhiza and agri
forms symbiotic relationship with plant roots
it links root cells to soil particles
vegetative body of fungus
thallus
chytrid cells
solitary globose cells with or without root-like filaments, “rhizoids”
yeast cells
spherical to ovoid cells
divide by budding
mycelia
filamentous network of hyphae that branch and grow only by atypical extension
protozoa
unicellular, eukaryotic organisms which represents a group in which mitosis and meiosis became established
flagellates
smallest member of protozoa
chlorophyll bearing
phytomastigophorea
non-chlorophyll bearing
zoomastigophores
amoeba
can move through protoplasmic flow, extensions called “pseduopodia”
ciliates
move by beating short, numerous cilia on the surface of their bodies
nematodes
multicellular, eukaryotic, non-segmented roundworms
float in fluid-filled cavity
do not have respiratory, endocrine, ciculatory
classification of nematodes
bacterial feeders
fungal feeders
predatory nematodes: eat nema and protozoa
omnivores: eat variety of organisms
what do nematodes do?
nutrient cycling
grazing
disperse microbes
food source
disease suppression and development
earthworms
tube-shaped segmented animal
major decomposers of dead and decomposing OM
derive their nutrition on fungi and bacteria on the OM
functions of earthworms
stimulate microbial activity
mix and aggregate the soil
increase soil porosity
increase water-holding capacity
provide channels for root-growth
bury and shred plant residue
arthropods
invertebrate and exoskeleton, segmented body and jointed appendages
classification of arthropods
shredders
predators
herbivore
fungal feeders
shredders
chew up on dead plant matter as they eat bacteria and fungi on the surface of plant
ex: millipede
predator
feed on other animals
ex: spider, beetle, centipede
herbivore
root-feeding insects
ex: cicadas, mole-crickets
fungal feeders
feed on fungi
ex: mites, silverfish
functions of arthropods
shred OM
stimulate microbial activity
mix microbes with their food
mineralize plant nutrients
enhance soil aggregation
burrow
control pests
virus particles
virions
classification of viruses
bacterial virus
fungal virus
plant virus
insect virus
animal virus
