1esc 590.soil biota.1
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Soil Biota PowerpointTRANSCRIPT
Soil BiotaSoil Biota
Reading AssignmentReading Assignment
Soil Microbiology: Soil Microbiology: An exploratoryAn exploratoryApproachApproach
Chapter 4, 5, 6 Chapter 4, 5, 6
The MacrofaunaThe Macrofauna
Examples Ants, Earthworm etc. Classified by » 1. Size» 2. Movement» 3. Time spent in soil or habitat» 4. What they eat
The MacrofaunaThe Macrofauna
Based on what they eat
- 1. Biophagous» Carnivores
» Herbivores
» Microvores
» Omnivores
The MacrofaunaThe Macrofauna
2. Saprophagous
» Detritivores
» Cadaveriocoles
» Copraphagous
The MacrofaunaThe Macrofauna
Earthworms:» Often constitutes the major portion of the
invertebrate biomass in the soil.» Active in processing litter and distributing
organic matter throughout the soil.» Activities result in the improvement of soil
aeration , drainage, and structure.
The MacrofaunaThe Macrofauna
Insects May be free-living, or may alternatively
live they may feed on plant roots
The MacrofaunaThe Macrofauna
Significance » Agricultural importance of the macrofauna
rests upon its contribution to soil fertility, soil structure, and plant disease.
» Important in leaf and litter decomposition» Soil structure
The MesofaunaThe Mesofauna
Nematodes:» The most numerous of all metazoa. » Their numbers may reach several millions per
square meter.» Both parasitic and free-living groups are
encountered.» Free-living groups use organic debris,
microorganisms and other substances as food.
MicrofaunaMicrofauna
Protozoa» Predators of the other forms of microbes.» Enumerated with plate method» Important to microscopically examine» Environmentally source of food is only
concern.
MicrofaunaMicrofauna
» No effect of soil pH, except effect of food source
» Reproduce usually by asexual means -binary fission
» Vast majority are saprophytes i.e. use soluble organic and inorganic substances or phagotrophic i.e. characterized by a direct feeding of microbial cells or particulate matter.
MicrofaunaMicrofauna
» A few are autothrophic
» When edible prey cells are no longer avialable or the environment in some way is unfavourable, the active protozoan enters a cyst stage.
» Mostly aerobic
MicrofaunaMicrofauna
» Exhibit no marked sensitivity to pH. Opt pH 6-8.
» Prefers found cool damp environments
» Trpophozoite Cyst feeding (resting)
» Feed a lot of rhizobia
MicrofaunaMicrofauna
Classification:Classified on basis of locomotion (4
categories)
»1. Mastigophora
»2. Sarcodina
»3. Ciliphora
»4. Sporozoa
MicrofaunaMicrofauna
a. Flagella –Mastigophora» most abundant in soil» 5-20 um in length» dominate the microfauna of terrestial
habitats» tolerant of low moisture
MicrofaunaMicrofauna
b. Cilia -Ciliata (ciliophora)» Movement by action of vibrating hairs
situated around the protozoan cell.» abundant in areas with high moisture status
MicrofaunaMicrofauna
c. Pseudopoda-Sarcodina
» size range from 10 mm to 80 mm
» move by means of temporary protoplasmic extrusions from the cell body e.g Amoeba
MicrofaunaMicrofauna
Significance in Soil.» 1. Serve to regulate soil bacterial population» 2. May also function by allowing different
competing bacteria to coexist in soil.» 3. They may participate in the decomposition
of plant materials.» 4. Some are pathogenic e.g Entamoeba
histolytica which cases amoebic dysentry
VirusesViruses
• These incluse nematodes, millipedes centipedes, mites, spiders, insects earthworms, flatworms etc.
Viruses • The are submicroscopic agents • Consist of DNA or RNA molecules within protein coats. • Viral particles are metabolically inert and do not carry out respiratory or bio-
synthetic functions. • They induce a living host cell to produce the necessary viral components • After assembly, the replicated viruses escape from the cell with the capability of
attacking new cells. • Viruses infect all categories of animal and plants, from humans to microbes. • Those parasitizing bacterial cells commonly are called bacteriophages, or simply
phages Significance in Soil • Little is known about the field ecology of viruses that infect soil organisms except
that they persist in soil as domant units that retain parasitic activities. • The ability of viral particles pathogenic to plants or animals to survive in soil and
move into the water table is of major concern to people.