What is the major source of nitrogen in the nitrogen biogeochemical cycle?

What is the trophic level of an herbivore such as a cow that eats only grass? 

Poverty, population growth and desertification and drought are three of the 10 key factors of Agenda 21 as listed in your text. List two more of these 10 key factors.

Bees, wasps and other stinging insects often have the same yellow and black coloration. This is an example of 

If a harmless frog has the same coloration as a toxic frog this is an example of 

An example of sympatric speciation would be the separation of two kinds of birds by their food preferences, because this is ____ isolation that could lead to the formation of two different species of the birds.

The chemical formula for sulfur dioxide is SO2.  This means there is/are __ sulfur atoms and __ oxygen atoms in this compound.

When describing the parts of a biogeochemical cycle the term “sink” refers to  

Which biogeochemical cycle is a slow cycle because the element is not found in gas form and because the main source is in rock formations, which take a long to make and to break down?

What is one reason that a certain percentage of land was preserved on islands such as Mauritius and Tobago during the 1700s when they were English and French colonies?