In which of the following, do both pairs have the correct combination?

1.	Gaseous nutrient cycle Sedimentary nutrient cycle	Carbon and nitrogen Sulphur and phosphorous
2.	Gaseous nutrient cycle Sedimentary nutrient cycle	Carbon and sulphur Nitrogen and phosphorus
3.	Gaseous nutrient cycle Sedimentary nutrient cycle	Nitrogen and sulphur Carbon and phosphorous
4.	Gaseous nutrient cycle Sedimentary nutrient cycle	Sulphur and phosphorous Carbon and nitrogen

In an ecosystem, the rate of production of organic matter during photosynthesis is termed as:

1. net primary productivity

2. gross primary productivity

3. secondary productivity

4. net productivity

Most animals are tree dwellers in a:

Given below is a simplified model of phosphorus cycling in a terrestrial ecosystem with four blanks (A-D). Identify the blanks. 

If 20 J of energy is trapped at the producer level, then how much energy will be available to peacocks as food in the following chain? 
Plant → mice → snake → peacock

Pheretima and its close relatives derive nourishment from:

1. Sugarcane roots

2. Decaying fallen leaves and soil organic matter

3. Soil insects

4. Small pieces of fresh fallen leaves of maize

Which one of the following statements is correct for secondary succession?

Stability of ecosystem depends upon:

1. Primary

2. Interchange between producers and consumers

3. Number of producers

4. Number of consumers