Which of the following statement is incorrect?

1.	All the steps in decomposition operate simultaneously on the humus.
2.	Humus is an accumulated dark coloured amorphous substance.
3.	Humus is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
4.	Being colloidal in nature humus serves as a reservoir of nutrients.

Which of the following is the substrate in the process of mineralisation?

1. Detritus

2. Humus

3. Organic matter

4. None of the above

Which of the following does not affect rate of decomposition?

1. Substrate composition

2. Soil moisture

3. Temperature of soil

4. CO₂

Decomposition would be fast if the detritus contains-

1. Cellulose

2. Lignin and chitin

3. Nitrogen and water soluble sugars

4. Cellulose and pectin

Which of the following promotes the process of decomposition?

1. Warm and moist environment

2. low temperature

3. Anaerobiosis

4. Lignin and chitin-rich detritus

What is the source of energy for all ecosystems on Earth, except for the deep sea hydro-thermal ecosystem?

1. Sun

2. Hydrothermal vents

3. Lava

4. Water

What percentage of the incident solar radiation is photosynthetically active radiation (PAR)?

1. 50%

2. Less than 50%

3. More than 50%

4.10%

What proportion of the PAR (photosynthetically active radiation) is captured by plants?

1. 1 - 10%

2. 2 - 10%

3. 5 - 15%

4. 5 - 25%

Which of the following statement is incorrect?

Which are the primary consumers in a grazing food chain?

1. Carnivores

2. Herbivores

3. Detrivores

4. Omnivores