Main cause of eutrophication is

• fluctuation of temperature

• unusual growth of aquatic vegetations

• enrichment of nutrients

• abundance of microorganisms

Trophic levels in ecosystem is formed by

• only bacteria

• only plants

• only herbivores

• organisms linked in food chain

Pyramid of energy in ecosystems is

• always upright

• always inverted

• mostly upright

• mostly inverted

Which of the following is an example of man-made ecosystem

• Herbarium

• Aquarium

• Tissue culture

• Forest

The removal of 'Keystone' species will affect the

• producers

• consumers

• ecosystem

• decomposers

Identify the correct type of food chain

Dead animal > Blow fly maggots > Common frog > Snake

• Grazing food chain

• Detrital food chain

• Decomposer food chain

• Predator food chain

Which one of the following processes during decomposition is correctly described?

• Fragmentation - Carried out by organisms such as earthworm

• Humification - Leads to the accumulation of a dark coloured substance humus, which undergoes microbial action at a very fast rate

• Catabolism - Last step in the decomposition under fully anaerobic condition

• Leaching - Water soluble inorganic nutrients rise to the top layers of soil

When the two ecosystems overlap each other, the area is called

• habitat

• niche

• ecotone

• ecotype

Secondary productivity is rate of formation of new organic matter by

• producer

• parasite

• consumer

• decomposer

Acid rain is caused by

• NO₂

• SO₂ and NO₂

• SO₃

• CO₂