Exam 22: Biogeochemical Cycles

Which of the following does NOT provide an input of nitrogen into ecosystems?

In gaseous biogeochemical cycles, the main pools of nutrients are the atmosphere and the ________.

Ammonium and nitrate are forms of nitrogen that can be directly used by plants.

Which of the following represents the largest natural source of sulfur gases released to the atmosphere?

Oxygen is produced during respiration.

All but a small fraction of the Earth's ________ is buried in sedimentary rocks and is not actively involved in a global cycle.

The atmosphere is the largest pool of nitrogen.

The main reservoirs of oxygen are water and ________.

Most plants obtain nitrogen directly from gaseous nitrogen in the atmosphere during respiration.

Which of the following nutrients has a cycle that does NOT contain an atmospheric phase?

The largest pool of nitrogen is

There are two basic types of biogeochemical cycles: gaseous and ________.

Atmospheric carbon dioxide concentrations are higher during summer than during winter.

In sedimentary biogeochemical cycles, the main reservoirs of nutrients are the atmosphere and the oceans.

In aquatic ecosystems, the phosphorous cycle moves through three states: particulate organic phosphorous, dissolved organic phosphates, and ________ phosphates.

Nitrogen can be returned to the atmosphere when certain bacteria convert it from nitrate into nitrogen gas, which is a process called ________.

Carbon cycles more quickly through cold and dry ecosystems than it does through warm and wet ecosystems.

Stratospheric ozone shields the planet from biologically harmful ultraviolet radiation.

Carbon dioxide occurs in both the atmosphere and in oceans.

The source of all carbon in living organisms is