Carbon Cycle

This article is modified from an essay on the Internet.

The series of chemical, physical, geological, and biological changes by which carbon moves through the Earth's air, land, water, and living organisms is called the carbon cycle.

Carbon makes up no more than 0.27% of the mass of all elements in the universe and only 0.0018% by weight of the elements in the Earth's crust. Carbon occurs in many different chemical combinations, including calcium carbonate (CaCO₃), carbon dioxide (CO₂), methane (CH₄), and a huge diversity of organic compounds. In contrast to carbon's relative scarcity in the environment, it makes up 19.4% by weight of the human body. Along with hydrogen, carbon is the only element to appear in every organic molecule in every living organism on Earth.

The most abundant mineral forms of carbon in the rocks and soil of the Earth's crust are limestone (CaCO₃) and dolomite [CaMg(CO₃)₂]. These mostly occur in sedimentary rocks, which were formed in ancient marine environments through biological influences that resulted in the precipitation of limestone and dolomite from ions of calcium (Ca²⁺), magnesium (Mg²⁺), and bicarbonate (HCO₃^-) dissolved in water. The amount of carbon stored in sedimentary rocks has not yet been accurately estimated, but is thought to be much larger than that occurring in any other compartment of the carbon cycle.

Carbon also occurs in spaces within sedimentary crustal rocks in the form of fossil fuels. Fossil fuels are extremely important, but non-renewable, natural resources used as sources of energy and for the manufacturing of plastics and other materials. Wherever mining and drilling technology can access fossil fuel deposits, these deposits are being rapidly used up. Fossil fuels are derived from the partially decomposed biomass of ancient plants and other organisms, which became buried deep beneath marine sediment and were transformed very slowly (under intense pressure and heat in the absence of oxygen) into their present forms.

In the atmosphere, carbon exists almost entirely as gaseous carbon dioxide (CO₂). Its global concentration is about 360 parts per million (ppm), or 0.036% by volume. This makes carbon dioxide the fourth most abundant gas in the atmosphere after nitrogen, oxygen, and argon. Some carbon is also released as methane (CH₄) and carbon monoxide (CO) to the atmosphere by natural and human mechanisms. Carbon monoxide reacts readily with oxygen in the atmosphere, however, converting it to carbon dioxide.

Carbon returns to the hydrosphere when carbon dioxide dissolves in the oceans, as well as in lakes and other bodies of water. The solubility of carbon dioxide in water is not especially high, 88 milliliters of gas in 100 milliliters of water. Still, the Earth's oceans are so vast that they store approximately 36,000 billion tons of carbon. About 93 billion tons of carbon flow from the atmosphere into the hydrosphere each year.

Carbon moves out of the oceans in two ways. Some escapes as carbon dioxide from water solutions and returns to the atmosphere. That amount is estimated to be very nearly equal (90 billion tons) to the amount entering the oceans each year. A smaller quantity of carbon dioxide (about 40 billion tons) is incorporated into aquatic plants.

On land, green plants remove carbon dioxide from the air through the process of photosynthesis--a complex series of chemical reactions in which carbon dioxide is eventually converted to starch, cellulose, and other carbohydrates. Green plants fix about 100 billion tons of carbon each year, and a total of 560 billion tons of the element is thought to be stored in land plants alone.

The carbon in green plants is eventually converted into a large variety of organic (carbon-containing) compounds. When animals eat green plants, they use the carbohydrates and other organic compounds as raw materials for the manufacture of thousands of new organic substances. The total collection of complex organic compounds stored in all kinds of living organisms represents the reservoir of carbon in the Earth's biosphere.

The cycling of carbon through the biosphere involves three major kinds of organisms. Producers are organisms with the ability to manufacture organic compounds from inorganic materials. Green plants are the primary example of producers. Consumers are organisms that obtain their carbon from producers. All animals are consumers. Finally, decomposers are organisms that feed on the remains of dead plants and animals. They convert carbon compounds in these organisms to carbon dioxide and other products. The carbon dioxide is then returned to the atmosphere to continue its path through the carbon cycle.

Land plants return carbon dioxide to the atmosphere during the process of respiration. In addition, animals that eat green plants exhale carbon dioxide, contributing to the 50 billion tons of carbon released to the atmosphere by all forms of living organisms each year. Respiration and decomposition both represent, in the most general sense, a reverse of the process of photosynthesis. Complex organic compounds are oxidized with the release of carbon dioxide and water--the raw materials from which they were originally produced.

At some point, land and aquatic plants and animals die and decompose. When they do so, some carbon (about 50 billion tons) returns to the atmosphere as carbon dioxide. The rest remains buried in the Earth (up to 1,500 billion tons) or on the ocean bottoms (about 3,000 billion tons). Several hundred million years ago, conditions of burial were such that organisms decayed to form products consisting almost entirely of carbon and hydrocarbons. Those materials exist today as pockets of fossil fuels. Estimates of the carbon stored in fossil fuels range from 5,000 to 10,000 billion tons.

The processes that make up the carbon cycle have been occurring for millions of years, and for most of this time, the systems involved have been in equilibrium. The total amount of carbon dioxide entering the atmosphere from all sources has been approximately equal to the total amount dissolved in the oceans and removed by photosynthesis. However, a hundred years ago changes in human society began to unbalance the carbon cycle. The Industrial Revolution initiated an era in which the burning of fossil fuels became widespread. In a short period of time, large amounts of carbon previously stored in the Earth as coal, oil, and natural gas were burned, releasing vast quantities of carbon dioxide into the atmosphere.

Between 1850 and 1998, measured concentrations of carbon dioxide in the atmosphere increased from about 280 ppm to about 360 ppm, an increase of 29%. Scientists estimate that fossil fuel combustion now releases about five billion tons of carbon dioxide into the atmosphere each year. In an equilibrium situation, that additional five billion tons would be absorbed by the oceans or used by green plants in photosynthesis. Yet this appears not to be happening. Measurements indicate that about 60% of the carbon dioxide generated by fossil fuel combustion remains in the atmosphere.

The problem is compounded by deforestation. As large tracts of forest are cut down and burned, carbon dioxide from forest fires is added to that from other sources, and the loss of trees decreases the worldwide rate of photosynthesis. Overall, it appears that these two factors have resulted in an additional one to two billion tons of carbon dioxide in the atmosphere each year.

No one can be certain about the environmental effects of this disruption of equilibria in the carbon cycle. Some scientists believe that the additional carbon dioxide will augment the Earth's natural greenhouse effect, resulting in long-term global warming and climate change. Others argue that we still do not know enough about the way oceans, clouds, and other factors affect climate to allow such predictions.

 

Nitrogen fixation by human processes now exceeds nonhuman sources.

Humans are injecting huge amounts of nitrogen into the biosphere

Global nitrogen transport

Global warming is a fact

Radiation Transmitted by the Atmosphere

Simplified Global Carbon Cycle

Language

In this step the content of your essay should be solid. If the idea itself needs discarding, you should not be tweaking the language; it would be a waste of time working on transitions if the organization and structure of your essay were in need of repair. Hence editing the language of your essay comes last. Here you are putting polish on a shoe that has already been sewn.

Editing the language can be tedious, but it is essential. You have got to proofread your essays many times to catch all the rough spots and language errors. As you proofread you will be checking for misspellings, poor mechanics, bad grammar, awkward word flow and numerous other linguistic details that you can improve. Proofreading the language may take hours as you attempt to polish your language to the point that it is pleasing to read and has literary style.

Give Your Eyes Rest

The more you read your essay, the more blind you become to it. Soon you stop reading the words on the page and only begin reading what's in your mind, which you falsely transpose onto the page. The actual letters could be Hebrew, or Greek, for all it matters at that point.

Do not keep reading hour after hour until your mind registers the entire text at a glance, without seeing the details. What you must do is rest your eyes; take a break. Give yourself a day or two between revisions. (This is why you should not procrastinate your assignments.) When you come back to your essay with fresh eyes and a renewed perspective, you will see with added clarity all the rough phrasings and strange ideas that your eyes once glided over.

Do not plagiarize

Your work must be your own, and that includes the language and style, not just content. Knowing that the work is your own, and that it represents your highest level of performance, you will feel a sense of achievement and personal growth that perhaps you have not experienced before. Each essay should seem to you that it is your best work to date. Only when you feel this way is the paper done.

Paragraphs

Choose a singular focus

Each paragraph should have a clear, singular focus to it. If there is an overriding error students make in writing essays, it is shifting topics within the same paragraph, rather than continuing to develop the same idea they began with. A paragraph is a discrete unit of thought that expands one specific idea, not three or four. If you find yourself shifting gears to start a new topic, begin a new paragraph instead.

Someone once compared the beginning of a new paragraph to the changing angle of a wall. When the angle of the wall changes, a new wall begins. Let your paragraphs be like that wall: running straight along a certain angle, and beginning anew when the angle changes.

Begin with a topic sentence

Nothing will help you keep a tighter focus on your paragraphs than topic sentences. A topic sentence is generally the first sentence of the paragraph, and it describes the claim or point of the paragraph, thus orienting the reader to the purpose of the paragraph. When you use topic sentences, your reader will invariably find it easier to follow your thoughts and argument. As an example, look at the first sentences of each paragraph on this page. The entire paragraph is focused around the stated topic sentence.

Develop the idea

Invariably students shift topics and lose focus within their paragraphs because they do not know how to adequately develop their ideas. They usually know the paragraph needs to be longer, but they do not know how to expand their idea to fill that length. To develop your ideas, you can:

• illustrate your idea with examples
• give an authoritative quotation
• anticipate and respond to counterarguments
• back your ideas with more evidence
• offer another perspective to the idea
• brainstorm more insights about the idea
• elaborate on causes/effects, definitions, comparison/contrasts

 

 

Outline

Can you imagine a construction manager working on a skyscraper without a set of blueprints? No way! Similarly, writers construct essays using sets of blueprints or outlines to guide them in the writing process. Of course writers do not have to use outlines, but the effect is about the same as a construction worker who builds without blueprints. 

Drawing up an outline allows you to think before you write. What use is there in writing the entire paper only to realize that, had you done a little more planning beforehand, you would have organized your essay in an entirely different way? What if you realize later, after free-writing the essay, that you should have omitted some paragraphs, restructured the progression of your logic, and used more examples and other evidence? 

You can go back and try to insert major revisions into the essay, but the effect may be like trying to add a thicker foundation to a building already constructed. The outline allows you to think beforehand what you are going to write so that when you do write it, if you have done your planning right, you will not have to do as much rewriting. (You will still, of course, need to revise.)

Make your points brief

When you construct your outline, keep it brief. The titles, headings, and points in your outline should be about one line each. Remember that you are only drawing an outline of the forest, not detailing each of the trees. Keep each line under a dozen words. If you cannot compress your point into a one-liner, you probably do not have a clear grasp of what you are trying to say. 

When you describe the point of each paragraph, phrase the point in a mini-claim. If the point of a paragraph is that soft drugs should be legal because they are relatively harmless, do not just write "soft drugs" as the point of the paragraph in your outline -- it is too brief and vague. Instead, write "drugs should be legal b/c soft drugs are harmless." This description is still brief, as it should be (one line or less), but it makes a claim that gives it purpose in the outline.

Choose an appropriate arrangement

Drawing up an outline allows you to see at a glance how each of the paragraphs fits into the larger picture. When looking at your paragraphs from this perspective, you can easily shift around the order to see how a reorganization might be better. Remember that each paragraph in the essay should support the position or argument of your paper.

As you are shifting paragraphs around, you will probably begin to wonder what the best arrangement really is. In general, put what you want the reader to remember either first or last, not in the middle. Studies in rhetoric have shown the readers remember least what is presented in the middle of an essay. Hence, the middle is where you should probably put your weaker arguments and counterarguments. 

Some writers urge a climactic arrangement, one that works up to your strongest point, which is delivered as a kind of grand finale. Another successful arrangement is the inductive argument, in which you build up the evidence first, and then draw conclusions. A problem-solution format involves presenting the problem first and then outlining the solution — this works well for some topics because it is a soft version of the scientific method. Whatever your choice, choose an arrangement that presents a clear, logical argument. 

Research

Assuming you have been given a topic, or have narrowed it sufficiently down, your first task is to research this topic. You will not be able to write intelligently about a topic you know nothing about. To discover worthwhile insights, you will have to do some patient reading.

Read light sources, then thorough

When you conduct research, move from light to thorough resources to make sure you are moving in the right direction. Begin by doing searches on the Internet about your topic to familiarize yourself with the basic issues; then move to more thorough research on the Academic Databases; finally, probe the depths of the issue by burying yourself in the library. Make sure that despite beginning on the Internet, you do not simply end there. A research paper using only Internet sources is a weak paper, and puts you at a disadvantage for not utilizing better information from more academic sources.

Take a little from a lot

You will need to read widely in order to gather sources on your topic. As you integrate research, take a little from a lot -- that is, quote briefly from a wide variety of sources. This is the best advice there is about researching. Too many quotations from one source, however reliable the source, will make your essay seem unoriginal and borrowed. Too few sources and you may come off sounding inexperienced. When you have a lot of small quotations from numerous sources, you will seem -- if not be -- well-read, knowledgeable, and credible as you write about your topic.

Writing An Essay

1 Research: Begin the essay writing process by researching your topic, making yourself an expert. Utilize the Internet, the academic databases, and the library. Take notes and immerse yourself in the words of great thinkers.

2 Analysis: Now that you have a good knowledge base, start analyzing the arguments of the essays you are reading. Clearly define the claims, write out the reasons and the evidence. Look for weaknesses and strengths of logic. Learning how to write an essay begins by learning how to analyze essays written by others.

3 Brainstorming: Your essay will require insight of your own, genuine essay-writing brilliance. Ask yourself a dozen questions and answer them. Meditate with a pen in your hand. Take walks and think and think until you come up with original insights to write about.

4 Thesis: Pick your best idea and pin it down in a clear assertion that you can write your entire essay around. Your thesis is your main point, summed up in a concise sentence that lets the reader know where you are going, and why. It is practically impossible to write a good essay without a clear thesis.

5 Outline: Sketch out your essay before straightway writing it out. Use one-line sentences to describe paragraphs, and bullet points to describe what each paragraph will contain. Play with the essay's order. Map out the structure of your argument, and make sure each paragraph is unified.

6 Introduction: Now sit down and write the essay. The introduction should grab the reader's attention, set up the issue, and lead in to your thesis. Your intro is merely a buildup of the issue, a stage of bringing your reader into the essay's argument. (Note: The title and first paragraph are probably the most important elements in your essay. This is an essay-writing point that does not always sink in within the context of the classroom. In the first paragraph you either hook the reader's interest or lose it. Of course your teacher, who is getting paid to teach you how to write an essay, will read the essay you have written regardless, but in the real world, readers make up their minds about whether or not to read your essay by glancing at the title alone.)

7 Paragraphs: Each individual paragraph should be focused on a single idea that supports your thesis. Begin paragraphs with topic sentences, support assertions with evidence, and expound your ideas in the clearest, most sensible way you can. Speak to your reader as if he or she were sitting in front of you. In other words, instead of writing the essay, try talking the essay.

8 Conclusion: Gracefully exit your essay by making a quick wrap-up sentence, and then end on some memorable thought, or an interesting twist of logic, or some call to action. 

9 Language: You are not done writing your essay until you have polished your language by correcting the grammar, making sentences flow, incorporating rhythm, emphasis, adjusting the formality, giving it a level-headed tone, and making other intuitive edits. Proofread until it reads just how you want it to sound. Writing an essay can be tedious, but you do not want to bungle the hours of conceptual work you have put into writing your essay by leaving slippy misspellings and poorly worded phrases.

Essay requirements

1. Arial style font.
   
2. 10 point font size.
   
3. 1.5 line spaced.
   
4. Spell-checked.
   
5. Grammar-checked.
   
6. Proofread.
   
7. About 450 words (400-500). A well-researched and structured essay cannot be any shorter. I have posted essay writing guidelines on this blog. Please read them very carefully.
   

Writing Assessment 6 Conventions

5 The writer demonstrates a good grasp of standard writing conventions (e.g., spelling, punctuation, capitalization, grammar, usage, paragraphing) and uses conventions effectively to enhance readability. Errors tend to be so few that just minor touch-ups would get this piece ready to publish.

A. Spelling is generally correct, even on more difficult words.

B. The punctuation is accurate, even creative, and guides the reader through the text.

C. A thorough understanding and consistent application of capitalization skills are present.

D. Grammar and usage are correct and contribute to clarity and style.

E. Paragraphing tends to be sound and reinforces the organizational structure.

F. The writer may manipulate conventions for stylistic effect—and it works! The piece is very close to being ready to publish.

 

3 The writer shows reasonable control over a limited range of standard writing conventions. Conventions are sometimes handled well and enhance readability; at other times, errors are distracting and impair readability.

A. Spelling is usually correct or reasonably phonetic on common words, but more difficult words are problematic.

B. End punctuation is usually correct; internal punctuation (commas, apostrophes, semicolons, dashes, colons, parentheses) is sometimes missing/wrong.

C. Most words are capitalized correctly; control over more sophisticated capitalization skills may be spotty.

D. Problems with grammar or usage are not serious enough to distort meaning but may not be correct or accurately applied all of the time.

E. Paragraphing is attempted but may run together or begin in the wrong places.

F. Moderate editing (a little of this, a little of that) would be required to polish the text for publication.

 

1 Errors in spelling, punctuation, capitalization, usage, and grammar and/or paragraphing repeatedly distract the reader and make the text difficult to read. The writing reflects more than one of these problems:

A. Spelling errors are frequent, even on common words.

B. Punctuation (including terminal punctuation) is often missing or incorrect.

C. Capitalization is random and only the easiest rules show awareness of correct use.

D. Errors in grammar or usage are very noticeable, frequent, and affect meaning.

E. Paragraphing is missing, irregular, or so frequent (every sentence) that it has no relationship to the organizational structure of the text.

F. The reader must read once to decode, then again for meaning. Extensive editing (virtually every line) would be required to polish the text for publication.

Writing Assessment 5 Sentence Fluency

5 The writing has an easy flow, rhythm, and cadence. Sentences are well built, with strong and varied structure that invites expressive oral reading.

A. Sentences are constructed in a way that underscores and enhances the meaning.

B. Sentences vary in length as well as structure. Fragments, if used, add style. Dialogue, if present, sounds natural.

C. Purposeful and varied sentence beginnings add variety and energy.

D. The use of creative and appropriate connectives between sentences and thoughts shows how each relates to, and builds upon, the one before it.

E. The writing has cadence; the writer has thought about the sound of the words as well as the meaning. The first time you read it aloud is a breeze.

 

3 The text hums along with a steady beat, but tends to be more pleasant or businesslike than musical, more mechanical than fluid.

A. Although sentences may not seem artfully crafted or musical, they get the job done in a routine fashion.

B. Sentences are usually constructed correctly; they hang together; they are sound.

C. Sentence beginnings are not ALL alike; some variety is attempted.

D. The reader sometimes has to hunt for clues (e.g., connecting words and phrases like however, therefore, naturally, after a while, on the other hand, to be specific, for example, next, first of all, later, but as it turned out, although, etc.) that show how sentences interrelate.

E. Parts of the text invite expressive oral reading; others may be stiff, awkward, choppy, or gangly.

 

1 The reader has to practice quite a bit in order to give this paper a fair interpretive reading. The writing reflects more than one of the following problems:

A. Sentences are choppy, incomplete, rambling or awkward; they need work. Phrasing does not sound natural. The patterns may create a sing-song rhythm, or a chop-chop cadence that lulls the reader to sleep.

B. There is little to no “sentence sense” present. Even if this piece was flawlessly edited, the sentences would not hang together.

C. Many sentences begin the same way—and may follow the same patterns (e.g., subject-verb-object) in a monotonous pattern.

D. Endless connectives (and, and so, but then, because, and then, etc.) or a complete lack of connectives create a massive jumble of language.

E. The text does not invite expressive oral reading.