CONTINUED FROM THE LAST POST
NOTE-An ode is a poem that pays tribute to a person or an object. What do you like? Your car? Your house? Your bed? Pounded Yam? Valentine Day? Christmas? There are billions of things you can write an ode to. And it shouldn’t take very long at all.
1.By The American Museum of Natural History
An Ode to O
Where would the world be without oxygen? Oxygen makes up 21 percent of the volume of Earth’s atmosphere and 30 percent of the mass of Earth as a whole. It turns iron to rust, causes a spark to burst into flame, and is the vital element in every breath we take. Oxygen is at once so omnipresent, essential, and utterly invisible, it is easy to forget how much it provides and hard to imagine an Earth without it.
And yet for nearly the first half of the planet’s 4.5-billion-year history, Earth had no free oxygen that is, no oxygen gas as part of its atmosphere. When free oxygen did begin to appear, sometime between 2.4 billion and 2.2 billion years ago, its effect on the planet was profound. Gradually released into the atmosphere by photosynthetic microbes, it formed two important gases new to fledgling Earth: breathable oxygen gas, or O2, and ozone, or O3. Together, the buildup of these gases enabled life to emerge onto land and evolve into the rich diversity of life-forms that inhabit Earth today.
“The appearance of oxygen in the atmosphere is extremely pivotal in terms of how the planet developed from there on in, particularly in relation to life,” says Grant Young, a professor of geology at the University of Western Ontario and one of the many Earth scientists currently working to pin down when this critical transformation occurred. “Oxygen is one of the things that renders our planet unique in the Solar System, and possibly in the Universe.”
That free oxygen should exist at all in Earth’s atmosphere is something of a wonder. Oxygen is highly reactive: it tends to quickly bind with other common elements like hydrogen (H), carbon (C), and iron (Fe) to form molecules and compounds such as water (H2O), carbon dioxide (CO 2), and the oxygen-containing mineral goethite, a component of rust. Combustion, or the process of burning, is simply a chemical reaction that occurs when a fuel like wood or charcoal interacts with oxygen to produce water, carbon dioxide, and some other byproducts. Human respiration works fundamentally the same way: We take in oxygen through our lungs and give off carbon dioxide and water. In our case, fortunately, the “fire” that results during respiration is carefully mediated by our cells, which utilize the energy in a manner that sustains us.
As elements go, oxygen is a social climber, associating with itself to form O 2 (oxygen gas) or O3 (ozone) only until a more influential element comes along. Respiration is common among organisms in part because O 2 is so ready to react. (Human blood gains its effectiveness from oxygen’s strong affinity for iron: red blood cells carry hemoglobin, an iron-containing protein, which binds with oxygen and transports it through the bloodstream.) In fact, today’s oxygen-rich atmosphere is nowhere near as fixed and permanent as it appears. Respiration and other ongoing chemical reactions are continuously breaking down O2 and O3, scavenging oxygen from the atmosphere and squirreling it away in other compounds.
Earth’s atmosphere would soon be stripped entirely of free oxygen were it not for a critical moderator: photosynthetic life. Microbes and plants pump out free oxygen in tremendous quantity, replenishing the atmosphere as quickly as it drains. Earth is unique among the known planets in no small part because it harbors the life essential to sustaining an oxygenated atmosphere.
2.Ode to Oxygen…By Dr. Hugh Ross
My seventh-grade science teacher asked the class to list “the three most essential needs of human life.” The “correct” answer—water, food, and sleep—illustrates how easily people take for granted the air we breathe, specifically its oxygen content. Most humans can live a few days without water, food, and sleep, and yet we can’t go more than a few minutes without oxygen. I understood that much in junior high, but at the time I had no idea that Earth’s oxygen-rich atmosphere represents—and facilitates—a miracle.
What’s so special about oxygen? In humans, as in any creature larger than about a millimeter in length, oxygen powers virtually all its life functions. Oxygen typically releases an abundance of energy when it attaches to another element or compound, and that’s how it fuels the metabolic process. Some life-forms called anaerobes do not rely on oxygen for their metabolism, but these creatures are tiny, no larger than unicellular filaments, with relatively low rates of metabolism. Organisms that approach even one millimeter in length require orders of magnitude more energy to survive. Their metabolism is aerobic, or oxygen-based, like our own, and with incremental increases in size come hugely increasing power demands. For example, species averaging about a meter in length (as adults) need at least 70% as much oxygen as we humans do for their bodies to do the “work” of living. Two other elements, fluorine and chlorine, also release significant amounts of energy, but they are relatively rare and highly volatile by comparison. Of the three reactive elements, only oxygen is sufficiently stable to accumulate in Earth’s atmosphere and provide for life’s metabolic needs. Today it constitutes about 20% of Earth’s atmosphere. (Nitrogen makes up most of the remaining 80%.)
How did oxygen get here? Inorganic chemical reactions and radioactivity passing through water produce only miniscule amounts. Nothing but photosynthetic life (such as cyanobacteria)—and lots of it—can possibly generate enough atmospheric oxygen to sustain aerobic life in any abundance. However, because oxygen is so highly reactive, most of what photosynthesis produced throughout Earth’s history lasted only briefly in the atmosphere. As soon as these tiny life-forms (powered by sunlight) converted carbon dioxide and water vapor into sugar and oxygen, the oxygen was swallowed up by enormous “oxygen sinks” (oxygen-absorbing chemicals and decaying organic matter) in Earth’s mantle and crust. Not until these oxygen sinks began to fill up could the atmosphere hold onto significant quantities of oxygen. The oxygen history of Earth’s atmosphere has been difficult to trace, but breakthroughs are coming. In a series of seven research papers, a team of chemists and physicists were able to write the early chapters of that history. They described two great oxygenation events: the first occurred roughly 2.4 billion years ago, and the second in three episodes between 635 and 545 million years ago.1 Additional research shows that these two events set the stage for a third event that occurred about 200 million years ago.2 While scientists continue to investigate the exact causes of these three great oxygenation events, they agree that catastrophic upheavals played a significant role. These disruptions buried large quantities of decaying organic matter, thereby preventing the carbon in this material from gobbling up oxygen. This circumstance would allow a major buildup in atmospheric oxygen if two crucial conditions were met. First, photosynthetic life would have to be extremely abundant and diverse to stay ahead of oxygen consumption by other oxygen sinks. Second, at least one of the other oxygen sinks would have to be filled up by the time the burials occurred.
What does science show? Both conditions appear to have been met with precise timing and with even more remarkable results. The earliest oxygenation event (2.4 billion years ago) provided for the sudden and widespread appearance of eukaryotic bacteria (cells with definite nuclei) existing both as individual cells and as mats of cells. The second oxygenation event (from 635 to 545 million years ago) precipitated the appearance of the first large animals. The last great oxygenation event (200 million years ago) coincided with the appearance of the first birds and mammals. This profile of available oxygen followed immediately by the appearance of creatures equipped to exploit it defies the assumptions of naturalism. A biblical creation model, on the other hand, can explain why the fossil record looks the way it does.3 The Creator of the universe orchestrated and timed these events on purpose, as part of a larger plan that includes you and me.