The Carbon Cycle:
Summary of Cycle
In the Carbon cycle, carbon moves everywhere! Carbon is taken from the atmosphere in
the form of CO2 and through photosynthesis produces glucose with the help of the Sun
for the plants to use. The carbon atoms are then transferred into animals as the plants are
eaten. Living animals release carbon back into the atmosphere by releasing carbon
dioxide in the process of respiration and eventually when the animals die, their bodies as
well as other detritus decay and put carbon into the ground where the carbon atoms can
become fossil fuels in millions of years. These burning of these fossil fuels by humans
release the carbon into the atmosphere as well. Though the oceans release carbon into the
atmosphere, it also absorbs some of the carbon from the atmosphere and the cycle repeats
itself over and over again as shown in this diagram.
Multiple Choice Questions
o
What is the purpose of a carbon sink? (e)
a)
b)
c)
d)
e)
o
Release carbon into the air
Absorb CO2 from the atmosphere
Create deposits for fossil fuels
Keep CO2 from accumulating at amore rapid rate in the atmosphere
Both b and d
Which option is not a description of part of the carbon cycle? (a)
a) Plants take CO2 from the soil where organic carbon in manure and fertilizer is
used to sustain soil using plants.
b) Animals gather the carbon atoms from eating plants and release it through
respiration
c) As dead animals and other detritus such as leaves or wood decays, the carbon
atoms enter the ground
d) The carbon atoms found in the ground become fossil fuels that is potentially
used by human, therefore releasing carbon back into the atmosphere
e) The ocean release and absorbs some of the carbon into or from the
atmosphere.
As animals release carbon in the form of carbon dioxide through respiration, the
producers or other primary producers take up carbon dioxide through photosynthesis.
More specifically, the carbon atoms from CO2 that are taken from the atmosphere become
carbon atoms of organic molecules through photosynthesis that eventually go into the
food webs and become part of the ecosystem. Through respiration, the organic carbon
atoms are released into the atmosphere. For the ocean ecosystem however, phytoplankton
and macroalgae removes CO2 from the huge pool of inorganic carbonates in seawater
through photosynthesis, and feeding moves the organic compounds through marine food
webs. And the carbon is returned to inorganic carbonates in the solution due to the
respiration of the biota.
Photosynthesis Equation: 6CO2 + 6H2O + Energy  C6H12O6 + 6O2
Cellular Respiration Formula: C6H12O6 + 6O2  6CO2 + 6H2O + Energy
B. Carbon is released into the atmosphere by the respiration of organisms, the burning of
fossil fuel, deforestation/ forest fires, and the release of carbon from the ocean.
C. CO2 is 0.03 percent of the atmosphere. Today we are at 387 parts per million of CO2.
The CO2 was at 298 parts per million in 1900.
D.Four carbon sinks are the oceans, terrestrial ecosystems, fossil fuel deposits, and the
atmosphere.
Phosphorus Cycle
Summary:
Phosphorus is one of the most important elements to living organisms. It is found
in DNA, phospholipids, and other majorly important molecules. It occurs in nature as
phosphate in ocean sediments and rocks. Weathering breaks it down into the soil so that
the plants are able to absorb the phosphates from the soil. Animals eat the plants, and
then when they die, the decomposers break down the tissue of the dead animals allowing
the phosphorus to be reincorporated into the soil. Ocean runoffs allow the phosphorus to
enter the ocean where it eventually sinks to the bottom to form new rocks.
In which of the following is phosphorus not important?
A) DNA
B) Phospholipids
C) ATP
D) RNA
E) H20
How are animals able to get phosphorus?
A) They eat plants which have absorbed the phosphorus from the soil.
B) They eat the rocks which contain phosphorus.
C) They are born with all the phosphorus they will need.
D) They produce it themselves.
E) They get it from the sun.
Question A:
The phosphorus cycle is different from the other cycles because it does not
include a gas phase.
Question B:
Mining, Fertilizing, Sewage Runoff can contribute to extra phosphorus which will
help some species like Algae take over.
Question C:
Fertilizers contain an abundant amount of phosphorus. Algae has a growth
advantage when there is a large amount of phosphorus contributing to its bloom problems
since a large amount of Algae limits the amount of other species that can survive.
Nitrogen Cycle
Summary:
Nitrogen is the most abundant elements on our planet; however the majority of
the earth’s life can not use nitrogen in its original form. Nitrogen is also a requirement for
life, as it exists in amino acids and various other essential aspects of life. In order to use it
nitrogen needs to be fixed into plants. This process, aptly named nitrogen fixation,
involves a free living enzyme called Nitrogenase which converts the nitrogen to
ammonia. This usually occurs is the legume family of plants. The fixing of nitrogen also
can occur during lightning strikes. Humans also have the ability to create ammonia and
use it as a fertilizer. The decay of dead animals also adds nitrogen to the soil through a
process known as ammonification in which the nitrogen in the animal is converted to
ammonium by decomposers.. However, plants still can't use pure ammonium and the
nitrogen must go through another step before becoming usable. Nitrification is the
process where bacteria convert the ammonium to nitrates which is then used by the plants
through the roots. In order to ensure that the nitrogen doesn't just build up in the ground
there is a process called denitrification, where bacteria in the soil convert the nitrates to
nitrogen gas and put it back into our atmosphere.
1. In what family of plants is nitrogen usually fixed.
a) Coniferous Trees
b) Sea Grass
c) Wheat
d) legumes
e) Deciduous Trees
2. Name the state where to many dissolved nutrients are in a body of water, such as when
excesses of human made ammonia run off into the seas causing algal blooms.
a) Hyperautophagy
b) eutrophication
c) Disequitable overload
d) Red algal blooms
e) Transhydrodiction
Question A
In the roots of legumes there live many bacteria who through their own metabolic
processes are able to convert the nitrogen gas in to ammonia or ammonium, depending of
the acidity of the soil. Converting nitrogen gas into a more usable form is extremely
difficult and is the reason that this process is so specialized. While ammonium may be
usable by a few plants, the majority cannot use it and another process is required.
Nitrifying bacteria oxidize the ammonia creating nitrite then nitrate allowing for the
nitrogen to be assimilated into the plants.
Question B
Ammonification is the process by which nitrogen stored in organic matter such as
animals and plants is converted into ammonium. Decomposers in the soil recycle the
nitrogen, creating ammonium which allows
for the nitrogen to enter the process of
nitrification. Nitrification is the conversion
of the ammonium to nitrites then nitrates
by aerobic bacteria. These nitrates are
usable by plants and are assimilated into the
plants system. The nitrates are used for
creating proteins as well as amino acids
within the plants. Animals can only
assimilate nitrogen through the
consumption of the plants or of other
animals. Not all of the nitrates are
assimilated and some enter a process known
as denitrification. Some bacteria use the
nitrates for oxygen for metabolism leaving
the nitrogen to be freed and return to the
atmosphere.
Sulfur Cycle
SO4
Formation
The weathering of
rocks or the eruption of a
volcano opens the sulfur to the
air allowing the sulfur to bind
with oxygen and create SO4.
Common source
Erosion of rocks and
eruption of volcanoes puts this
gas into the air and rain brings
it down to the plants and
microorganisms.
Ecological importance
Sulfate is converted
into organic forms by
microorganisms and plants to move sulfur through the food chain since sulfur is an
important element in amino acids in living organisms.
SO2
Formation
90% of Sulfur dioxide released into the air is a result of human action when we
burn coal, crude oil or other fuels.
Common source
Fossil fuel combustion, industrial processes and electricity generation
Ecological importance
Sulfur dioxide dissolves in water to form an acid which is harmful, especially in
the form of acid rain which can spread to many distance locations. Humans are adding
too much sulfur to the air SOx so the ecological impact is a negative one.
CH3 SCH3
Formation
Phytoplankton and bacteria produce this byproduct to the air.
Common source
Oceans and bacterial metabolism
Ecological importance
In terms of the sulfur cycle, this compound is one of the most abundant organic
sulfur molecules in the air.
H2SO4
Formation
Sulfuric acid forms when SOx dissolves in water, and over thirty million tons of
sulfuric acid are produced in the US every year.
Common source
Acid Rain and man
Ecological importance
Sulfuric acid is an important compound in many industries, but it is the main
constituent of acid rain.
H2 S
Formation
Bacteria produces this gas from their metabolism from the unusable sulfates in the
ground so that it can be put into the atmosphere where it later is rained on plants.
Common source
The most common source is metabolism of bacteria.
Ecological importance
This is extremely important because plants are unable to use the sulfate in the
ground unless bacteria are able to convert it into a more useable form.
The Water Cycle
During the water cycle the water will rise high into the atmosphere cooling the
warm water vapor down. This vapor turns into liquid as heat leaves it in the process
known as condensation. This new liquid in the atmosphere becomes too heavy for the
atmosphere and falls to earth as rain, snow, sleet, or hail, this is known as precipitation.
Once the precipitation lands on the ground some of the water will seep into the soil
joining earths ground water in a process known as infiltration. The water that does not
seep into the ground because of varying ground conditions becomes runoff, or water that
flows across the land into the rivers and oceans. In order for water to return to the
atmosphere evapotranspiration has to occur. This is a combination of two process known
as evaporation and transpiration. Evaporation is water heating up on the earth, turning
into water vapor and rising into the atmosphere. Transpiration occurs when plants take up
water through their roots, use it and release it through their leaves as water vapor.
Humans have the ability to alter these cycles through things like building dams to prevent
runoff, releasing pollution that combines with the water vapor to create acid rain, and
adding to many fertilizers to ground water for agriculture. In order to ensure clean
healthy water for all generations we must make preserving the water cycle one of our
utmost priorities.