Biogeochemical Cycles

Oxygen enters seawater mainly

• through the respiration of animals

• as a byproduct of photosynthesis

• as a result of decomposition of plant and animal remains

• through the oxidation of metal ions in seawater

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Organisms that can exist with light as an energy source and an inorganic form of carbon and other raw materials:

• are called photoautotrophs.

• do not exist in nature.

• are called heterotrophs.

• are best classified as decomposers.

What goes in Box 5 of the food web in the picture?

• herbivores

• scavengers

• carnivores

• decomposers

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The ultimate source of energy for communities associated with hydrothermal vents is:

• chemicals contained in hot seawater

• sinking detritus from the surface waters

• energy derived from photosynthesis, as in almost all other communities

• chemical synthesis of organic molecules by bacteria

• algae

The nitrogen cycle is one of the most important and complex of the biogeochemical cycles. It is important because nitrogen:

• is a greenhouse gas

• is an essential part of biological molecules such as proteins and nucleic acids (DNA)

• is the most toxic element to living organisms

• dilutes the oxygen in the atmosphere causing respiratory problems

• is a crucial part of the process of photosynthesis

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The most abundant gaseous components of the Earth's atmosphere are:

• carbon dioxide and oxygen.

• nitrogen and hydrogen.

• nitrogen and carbon dioxide.

• nitrogen and oxygen.

• oxygen and carbon dioxide.

The major source of carbon dioxide in seawater is:

• from photosynthesis by marine plants.

• from rain falling into the ocean.

• from the respiration of marine animals and other organisms.

• from seafloor sediments.

• runoff from land

a chemical that provides what is needed for organisms to live and grow

• nutrient cycles

• nutrients

• reservoir

• source

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part of the abiotic phase of the nutrient cycle where nutrients can remain for long periods of time

• tree

• nutrient

• decomposer

• reservoir

the flow of water from land caused by precipitation

• run-off

• upwelling

• assimilation

• leaching

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