1. Nitrogen Cycle
N cannot be used by organisms in its gaseous form. For Nitrogen to be useful, it has to undergo nitrification (Nitrogen gas being changed into a usable form) by special bacteria (blue-green algae).  Once the nitrogen is used by the plant and makes its way to an animal, it can be released through decomposition or urination.  Once it is back in the soil, another type of bacteria cause denitrification, which turns it back into nitrogen gas. 
Nitrogen is essential to living organisms. However, atmospheric nitrogen is not usable. It has to be changed or fixed before it can be used
Atmospheric nitrogen becomes part of living organisms in two ways. The first is through bacteria in the soil that form nitrates out of nitrogen in the air The second is through lightning. During electrical storms, large amounts of nitrogen are oxidized and united with water to produce an acid that falls to Earth in rainfall and deposits nitrates in the soil. -Plants take up the nitrates and convert them to proteins - then travel up the food chain through herbivores and carnivores. -When organisms excrete waste, the nitrogen is released back into the environment. -When they die and decompose, the nitrogen is broken down and converted to ammonia. - Plants absorb some of this ammonia; the remainder stays in the soil, where bacteria convert it back to nitrates The nitrates may be stored in humus or leached from the soil and carried into lakes and streams. Nitrates may also be converted to gaseous nitrogen through a process called denitrification and returned to the atmosphere, continuing the cycle Similarities:  Both of these are biogeochemical cycles, meaning that the chemicals spend a portion of the cycle in living things (hence the bio) and a portion in the nonliving environment (geo). They are also similar in that they both recycle nutrients that are essential to all organisms.  Finally, they both move from the soil into plants via the roots, and then to animals through ingestion, and they can be returned to the environment via decomposition.
Differences:  They are different in the manner that they cycle.  Nitrogen gas is quite abundant (78% of the air around us is nitrogen).  It cannot be used by plants or animals in its gaseous form though. In order for it to be useful, it has to undergo nitrification (Nitrogen gas being changed into a usable form).  This is carried out by bacteria that live in nodules on the roots of some plants (like beans).  Once the nitrogen is used by the plant and makes its way to an animal, it can be released through decomposition or urination.  Once it is back in the soil, another type of bacteria cause denitrification, which turns it back into nitrogen gas. 
Carbon, on the other hand, requires no special processing by bacteria prior to plants and animals being able to use it.  Plants take in carbon dioxide and use it to make sugar.  Animals eat this sugar and incorporate it into their body.  Some of it is released as the carbon dioxide that we exhale.

2. Environmental zones
Ocean zones are defined by their physical characteristics; temperature, depth and light penetration
Intertidal- boundary between land and sea
Splash Zone- never underwater. Exposed to salt spray

3. Intertidal Zone
As the tide comes in-and-out, the intertidal region divides into zones.  The splash zone and high-tide zone are exposed to air the most.  Here most of the animals have hard shells that close or they hide in crevices at low tide. Barnacles are an example of organisms living here. The mid-tide zone has a higher diversity of animals and seaweeds. They are not exposed to air as much. The low-tide zone (furthest from land) is exposed to air only at lowest tides (a few hours each month).  Here, top predators like sea stars and fish are more abundant than in any other zone. 

4. Inner Shelf Below intertidal. Always under water. Goes as deep as
light can reach.

5. Benthic – organisms that live on the bottom
Inner shelf
Outer
shelf
Benthic – organisms that live on the bottom
Pelagic- organisms that live in the water column