Biology Past Questions and Answers

In an experiment to estimate the volume of air in a soil sample using a measuring cylinder, it was found that:
initial volume of water .... = p cm₃
volume of soil before mixing with water = q cm₃
Final volume of water after adding soil = r cm₃
From the data above, which of the following deductions is correct?

An ecological succcession often leads to

Atmospheric nitrogen is converted to soil nitrogen for plant use by

I. High birth rate and high immigration rate II. Low birth rate and high immigration rate II. Low mortality rate and low emigration IV. High mortality rate and high emigration rate. Which combination of the above can cause rapid over-crowding in climax biotic communities and human settlements?

The soil becomes toxic to plants when the concentration of its essential elements is in the range labelled