Bacteria
What is the primary role of decomposer bacteria in the soil?
a) Fix nitrogen
b) Produce antibiotics
c) Break down organic materials and recycle nutrients
d) Cause plant diseases
c) Break down organic materials and recycle nutrients
What is the primary function of fungi in soil?
a) Decomposition
b) Nitrogen fixation
c) Water retention
d) Pest control
a) Decomposition
What is the primary role of protozoa in soil ecosystems?
a) Regulate bacterial populations and release nutrients
b) Fix nitrogen
c) Suppress fungi
d) Consume nematodes
a) Regulate bacterial populations and release nutrients
What is the primary function of soil algae?
a) Photosynthesis and organic matter production
b) Pathogen suppression
c) Nematode control
a) Photosynthesis and organic matter production
What do earthworm casts contain?
a) Nutrients like nitrogen, phosphorus, and potassium
b) Antibiotics
c) Fungal spores
d) Actinomycetes
a) Nutrients like nitrogen, phosphorus, and potassium
Which bacterial genera are responsible for nitrogen fixation in symbiosis with legumes?
a) Pseudomonas
b) Rhizobium
c) Nitrobacter
d) Bacillus
b) Rhizobium
What type of fungi forms mutualistic relationships with plant roots?
a) Mycorrhizal fungi
b) Actinomycetes
c) Pathogenic fungi
d) Lichenized fungi
a) Mycorrhizal fungi
Which group of protozoa is the largest and most active in soil?
a) Ciliates
b) Amoebas
c) Flagellates
d) Actinomycetes
a) Ciliates
Which cyanobacteria fix nitrogen in rice paddies?
a) Clostridium and Thiobacillus
b) Rhizobium and Bradyrhizobium
c) Bacillus and Pseudomonas
d) Anabaena and Nostoc
d) Anabaena and Nostoc
How do earthworms improve soil aeration?
a) By decomposing cellulose
b) By consuming bacteria
c) By producing antibiotics
d) By creating burrows
d) By creating burrows
How do nitrifying bacteria contribute to soil fertility?
a) By oxidizing ammonia into nitrite and nitrate
b) By fixing nitrogen into ammonium
c) By converting nitrates into nitrogen gas
d) By decomposing cellulose and lignin
a) By oxidizing ammonia into nitrite and nitrate
What is the role of arbuscular mycorrhizal fungi (AMF) in plant nutrition?
a) They increase phosphorus and nitrogen uptake by expanding the root surface area
b) They break down lignin and cellulose
c) They suppress nematodes
d) They form biofilms on plant leaves
a) They increase phosphorus and nitrogen uptake by expanding the root surface area
What is the function of bacterial-feeding nematodes?
a) They decompose organic matter
b)They accelerate nitrogen cycling, making nitrogen available to plants
c) They suppress fungal populations
d) They reduce soil compaction
They accelerate nitrogen cycling, making nitrogen available to plants
How do algae help with soil stabilization?
a) They form biological soil crusts that bind particles together
b) They break down cellulose and lignin
c) They produce antifungal enzymes
d) They consume nematodes
a) They form biological soil crusts that bind particles together
What type of earthworms create deep burrows?
a) Epigeic worms
b) Anecic worms
c) Endogeic worms
d) Mycorrhizal worms
b) Anecic worms
Why do denitrifying bacteria thrive in waterlogged soils?
a) Because they require anaerobic conditions to convert nitrates to nitrogen gas
b) Because they use oxygen to break down nitrates
c) Because they help plants absorb phosphorus
d) Because they suppress fungi in the rhizosphere
a) Because they require anaerobic conditions to convert nitrates to nitrogen gas
Why are ectomycorrhizal fungi more prevalent in forests than in agricultural soils?
a) They form thick fungal sheaths around tree roots, facilitating nitrogen acquisition
b) They cannot survive in nutrient-rich soils
c) They require dry environments with low moisture
d) They only interact with grasses and annual crops
a) They form thick fungal sheaths around tree roots, facilitating nitrogen acquisition
How do plant-parasitic nematodes affect crops?
a) They convert nitrogen gas into ammonia
b) They decompose dead plant material
c) They pierce roots with a stylet, reducing water and nutrient uptake
d) They form symbiotic relationships with fungi
c) They pierce roots with a stylet, reducing water and nutrient uptake
What is the function of extracellular polymeric substances (EPS) secreted by cyanobacteria?
a) They break down organic matter
b) They fix atmospheric nitrogen
c) They bind soil particles and improve soil structure
d) They enhance fungal biofilms
c) They bind soil particles and improve soil structure
Why is earthworm mucus beneficial for soil structure?
a) It kills fungal pathogens
b) It fixes atmospheric nitrogen
c) It binds soil particles into stable aggregates
d) It decomposes lignin
c) It binds soil particles into stable aggregates
What role do plant growth-promoting rhizobacteria (PGPR) play in sustainable agriculture?
a) They enhance root growth, solubilize phosphorus, and produce antibiotics
b) They decompose lignin and chitin
c) They fix atmospheric nitrogen into nitrite
d) They form nodules on non-leguminous plants
a) They enhance root growth, solubilize phosphorus, and produce antibiotics
Which fungal genus is commonly used in biocontrol to suppress plant pathogens?
a) Trichoderma
b) Aspergillus
c) Fusarium
d) Laccaria
a) Trichoderma
What adaptation allows predatory nematodes to control soil pests?
a) They hunt and consume other nematodes and protozoa using specialized mouthparts
b) They produce antibiotics to kill harmful bacteria
c) They infect plant roots, causing wilting
d) They fix nitrogen into bioavailable forms
a) They hunt and consume other nematodes and protozoa using specialized mouthparts
Why do lichens (fungi + cyanobacteria) play a key role in barren ecosystems?
a) They fix nitrogen, decompose rock, and stabilize soil
b) They suppress fungal pathogens
c) They release antifungal antibiotics
d) They decompose lignin and cellulose
a) They fix nitrogen, decompose rock, and stabilize soil
How do earthworms enhance plant nutrient availability?
a) By releasing nitrogen, phosphorus, and potassium from organic matter in their casts
b) By fixing nitrogen directly into plant roots
c) By forming symbiotic relationships with fungi
d) By decomposing living plant roots
a) By releasing nitrogen, phosphorus, and potassium from organic matter in their casts