The major reservoir for phosphorous is 

(1) Aquifers

(2) Soil and rocks

(3) The atmosphere

(4) Clouds

Nitrogen gas makes up nearly 80% of Earth's atmosphere, yet nitrogen is often a limiting factor for plant growth. Why ?
1. The atmospheric form of nitrogen cannot be used by plants.
2. Nitrifying bacteria remove usable nitrogen from the soil more repidly than plants can absorb it.
3. Atmospheric nitrogen dissolves readily in the soil but is washed out with every rainfall.
4. Plants must absorb nitrogen through their roots, which are not in contact with the atmosphere.

The phosphorus cycle is unusual in that it is entirely:

1. Within aquatic ecosystems

2. Within terrestrial ecosystems

3. Sedimentary

4. Gaseous

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

Match the following and select the correct option.

     Column I                      Column II

A.  Earthworm                 1. Pioneer species

B. Succession                  2. Detritivore

C. Ecosystem service       3. Natality

D. Population growth        4. Pollination

      A          B         C         D

(1) 1           2         3         4

(2) 4           1         3         2

(3) 3           2         4         1

(4) 2           1         4         3