Explain the role of the following in increasing the soil fertility and crop yield :
(a) Leguminous plants
(b) Cyanobacteria
(c) Mycorrhizae

3

(a)

Name the two different categories of microbes naturally occuring in sewage water.Explain their role in cleaning sewage water into usable water.

3

(a)

Explain the role of baculoviruses as biological control agents. Mention their importance in organic farming

3

(a)

Explain the different steps involved in sewage treatment before it can be released into natural water bodies.

3

(a)

An organic farmer releies on natural predection for controlling plant pests and diseases. Justify giving reasons why this is considered to be holistic approch.

3

(a)

How are flocs produced in the secondary treatment plant of the sewage? Explain their role.

3

(a)

Why should biological control of pests and pathogens be preferred to the conventional use of chemical pesticides?Explain how the following microbes act as biocontrol agents:
(a) Bacillus thuringiensis
(b) Nucleopolyhedrovirus.

3

(a)

How do biofertilisers enrich the fertility of the soil?

3

(a)

Name any three organic acids and the bacteria that produce them.

3

(a)

Find out the role of microbes in the following and discuss it with your teacher.
(a) Single cell Protein (SCP)
(b) Soil

3

(a)

What are the advantages of biogas plant in rural.

3

(a)

Explain why some microorganisms are called biofertilizers.Give two examples.

3

(a)

microbes have various contributions to the human welfare. For example, lactic acid bacteria helps in checking disease causing microbes in our stomach. With reference to this fact, state the contributions of different microbes in the process of digestion in ruminants.

3

(a)

What are Methanogens? Name the animals they are present in and the role they play there

3

(a)