Script for video - The Biosphere

The Biosphere

Part 1: A Brief History of the Biosphere

You are a voyager from a far off star system. You cruise near the speed of light by billions of stars in billions of galaxies separated by billions of miles of dark space.

On your home planet there is science fiction about life on other planets of the universe. Still, most people consider your quest a bit like the fabled knight Don Quixote. "This is my quest, no matter how hopeless, no matter how far ... to dream the impossible dream."

After travelling for many years and finding nothing, imagine your excitement when by impossible-dream-come-true you come upon a small blue-white planet orbiting a medium sized star at the far edge of the millYou probably would not call this blue-white planet "earth." More likely you would name it "ocean" since over two thirds of its surface is covered by a constantly moving layer of deep blue water.

You might not notice it immediately but as you came in to land you would find that planet "ocean" was also covered and protected by another moving layer, a kind of membrane or fluid skin of transparent blue air. Over both ocean and earth this air is dappled with roving white clouds.

And most interesting of all, air, earth and water are teeming with life, with an incredible diversity of living things.

Quite a sight. Quite a reward. Quite an astonisgly improbable find. Indeed an impossible dream come true. Against all odds you have found a celestial body,a hunk of cosmic rock with a living skin, a biosphere.

"Biosphere" is a word you hear and read more and more these days, and a word you will hear more and more in days to come. "Bios" means life. "Sphere" stands for the surface of the earth. "Biosphere" means the sum total of living things now living in that thin outer shell, the surface of our planet earth.

Let's look at this earth biosphere more closely. How did earth come to be alive? How much has the biosphere changed in the past? How much is it changing today? What part has human life played in the biosphere? What part does it play today? What will happen in the biosphere tomorrow?

First things first. How did the biosphere happen?

If our imaginary space voyager had arrived four and a half billion years ago instead of today, he or she would not have found a biosphere on earth. Our sun was there. A bit cooler than today but about the same size.

Some astronomers today think that not too long before this four billion year ago time, a nearby older star-perhaps a sister star to our sun-had exploded. Some of the debris from this gigantic explosion was captured by our sun's gravity. The explosive debris that did not crash directly into the sun was sent spinning in motion around the sun in large elliptical orbits. These stellar sparks and ashes were made of all the elements, heavy and light, that would later make up our small planet and all the living things on it, including you and me.

In the fullness of time, ashes and chunks of this debris were pulled together by their own gravity and formed the planets and moons and comets that today make up our solar system.

In the beginning none of these planets had life. There were no biospheres. The energy released from this gravitational pulling together and from the presence of radioactive atoms in the stellar debris made all the planets very hot in those earliest days. Rocks were forming from the molten iava. The heavier ones sank towards the center of the growing planets. The light ones floated on top.

Periodically the planets were bombarded with more debris from outside-meteors. Volcanoes exploded from underneath the surfaces, continually spewing into the atmosphere large quantities of water vapor, volcanic dust and gases. A space voyager arriving four billion years ago would have predicted little hope for life in this remote solar system on the edge of the milky way galaxy.

But if the voyager came back a billion years later, around three billion years ago, surprise of surprises! Life was there. Life had taken hold on at least one of the solar system planets, the one our imaginary voyager would one day call planet "ocean" and we today call planet "earth."

We don't know exactly how it happened but we do know for sure that life did start in that ancient ocean somewhere between three and four billion years ago. Students of earth history have been able to piece together some of the fascinating details of the birth and growth of this biosphere.

Take the ocean itself. In the beginning when the earth was first formed there was no liquid water at all. The surface of the planet was far too hot.

Volcanoes constantly erupted from below and shot huge quantities of water vapor (among other things) into the new and growing atmosphere around the new and growing earth.

The most important of these other things were gases like hydrogen, ammonia, methane and carbon dioxide. No free oxygen though. Oxygen was there but being chemically active it was combined with other elements like carbon and hydrogen.

As cooling went on over long periods of time eventually the water vapor condensed to form droplets of rain, and it rained for thousands of years. This rain eventually filled up all the lower - spots on earth's surface and made the first oceans. Some scientists speculate it may have completely covered the surface of the earth leaving no dry land at all.

So now we have the cradle for life ready. A water covered planet of moderate temperatures with an atmosphere of ammonia, methane, carbon dioxide and hydrogen, and an energy-rich sun just far off to be safe and just near enough to be warm and nurturing.

A chemist at the University of Chicago in 1954 simulated just such a cradle in his laboratory. Stanley Miller shot sparks of electricity (to imitate the action of the sun's ultraviolet radiation) through sterilized water bubbling in an atmosphere like that of the early days of earth. He let the action go on for one week.

At the end of that week he analyzed the water and though he did not find any living things, he did find some of the chemical molecules that are the stepping stones to life. These molecules included, for instance, some amino acids which we know are the building blocks for proteins. Proteins in turn are the building blocks for cells and cells are the building blocks for all living creatures.

Miller could not create life in one week in this simple experiment. Earth, however, had many millions of years to try. And however slowly it happened, it did happen in that ancient ocean. Molecules clumped together into large aggregates, large enough and complex enough to maintain and to reproduce their structure for another generation.

For anything to be living both maintenance and reproduction require a constant input of energy. Sunlight alone will not help. What do you do when the sun is no longer shining? Living things need some form of chemically stored energy that they can take in. We call this kind of chemically stored energy, food.

If Stanley Milleis flask made amino acids and other organic molecules in only one week, think how many organic molecules, and what an immense variety of them, the earth-sun-ocean system could make in a few million years. And make them it did.

By the time the first primitive aggregates that we could call living appeared, there was plenty of food around for them to eat. And eat they did. And reproduce. And eat. And reproduce. And over the years, the thousands and millions of years, these early thousands and millions of microscopic living things changed. Different varieties of aggregates appeared and experimented with better ways of staying alive and reproducing. So it was that evolution by natural selection began as well.

These first experiments in life on earth all happened in the ocean. And all in the absence of the gas we think so important to life, oxygen. There was oxygen of course on the earth's surface but it was all tied up in larger more stable molecules like carbon dioxide, carbon monoxide and above all, water itself, H20, two atoms of hydrogen to one atom of oxygen.

After about a billion years of this early ocean life there came a crises. Actually two crises, a natural resource crises and the first toxic waste crisis.

The natural resource crisis was a shortage of food. These early living things were not able to use sunlight directly for energy and the organic molecules created by chance collisions-as in Stanley Milleis flask-were getting scarce. So what happened?

Somehow the first varieties of living things came along that could use sunlight directly to make their own chemical-rich energy-captured food. This process of using sunlight directly to make food which could then be stored and later be eaten at leisure we call photosynthesis. Using the energy of the light (photo) to put together (synthesis) large energy-rich molecules.

This process of photosynthesis brought about a revolutionary change in the entire biosphere.

All the early life forms in the ocean were what we call today anaerobic. That is, they live only in the absence of air with free oxygen. To an anaerobic organism then and now, oxygen is a toxic waste, a deadly poison. The photosynthesis method of capturing and storing energy began to spread rapidly among a great variety of living things. Some of these microscopic living things of that ancient ocean developed a new and different form of photosynthesis that could and did thrive in the presence of free oxygen gas. They became the first aerobic life forms. They also became the progenitors of our modern plant world.

In the aerobic form of photosynthesis carbon dioxide and water are the raw materials and oxygen is produced as a waste product. As this waste product oxygen spilled out of the early aerobic photosynthesizers, life on earth took a violently different turn. Since oxygen was a deadly poison to anaerobic living things, anaerobic living things began to swiftly decline in numbers. Some anaerobic organisms did adapt to these new conditions by finding special niches where the free oxygen could not poison them-in mud and clay bottoms of early oceans, for instance, and later inside the tissues of larger aerobic creatures, plant and animal. Anaerobic organisms still occupy these niches today.

Once aerobic photosynthesis became common on earth, the way was clear for an explosion of plant life. Plants at the beginning were single celled but over time some began to clump together to form large multi-celled forms. In shallow arms and wetlands of the ocean some of these new plant forms learned to survive some of the time outside the water. Eventually some were able to leave the water altogether and live on land.

These pioneering plants pumped more and more oxygen into the water and into the early earth atmosphere and while this was deadly for anaerobic bacteria it was the breath of life for another fast growing style of living, animal life.

All of this took a long time. A very long time. According to the best estimates of scientists today the physical earth formed from stellar debris about four and half billion years ago. The first Iiving things appeared in the ancient ocean about four billion years ago. It took two billion years-almost half the time the biosphere has existed-for aerobic photosyntheis to begin to fill our atmosphere with oxygen. And then another billion years for many celled plants and animals to evolve.

During the most recent three-quarters of a billion years animals and plants have populated earth with an ever more impossible-dream-come true assortment of experiments. Algae, seaweeds, pondweeds and lotus blossoms. Grass, floweng plants, ferns and moss. Shrubs, vines, pine trees and oaks. Crab, octopus, anenome and trilobite. Insects, spiders, worms and lice. Bacteria, viruses, amoebas and molds. Fish, amphibians, reptiles, birds and mammals. Apes, monkeys, chimpanzees and human beings.

Most of these experiments in living-plants and animals who once lived and made up the biosphere-no longer live and make up the biosphere. Like the dinosaurs and mammoths and neanderthal humans, they are extinct. They have been replaced, however, by more than a few million different species that today alive and make up the rich biosphere of earth.

Despite all the change of living forms through the last billion years of earth history, one of the most surprising things about the biosphere as a whole is that the climate and the non-living environment have remained remarkably constant.

Volcanoes have erupted, meteors have hit, continents have drifted, earthquakes and hunicanes and tornadoes have come and gone. One kind of plant has been replaced by another kind millions of times. One kind of animal has been replaced by another millions of times. Not to mention the near infinite number of individual living things that have come and gone.

Despite all of this coming and going consider what has not changed. Since soon after oxygen first invaded the atmosphere its proportion in the air has remained at about one fifth. Nitrogen has remained at about four-fifths. Carbon dioxide, water vapor, inert gases, trace gases of ammonia, methane, all these have kept within very narrow limits, pretty much the same now as they were almost a billion years ago.

All of which is very fortunate! If oxygen were five percent more plentiful forest fires would quickly burn out of control. In fact fires would quickly make life impossible on land. If oxygen were five percent less plentiful most animal life on land would be impossible.

The ocean is no more and no less salty today than it was a billion years ago. This is as fortunate as the oxygen situation in the air. If the ocean were ten percent saltier, most life in the ocean would be impossible.

And finally, the climate on earth. For most of earth's biospheric history the climate has been somewhat, a few degrees; warmer on the average. During the long thirty million year time when dinosaurs dominated the earth's biosphere, for instance, there were no ice caps at the north and south poles, and tropical vegetation grew most places on the earth's surface.

In recent years, the past two or three million years that is, earth has been a few degrees colder on the average and we have had ice ages. Northern parts of America and Europe have been covered with ice sheets over a mile thick.

Still,when compared to Venus or Mars, our two neighboring planets, the temperature range on earth has been remarkably narrow. A temperature range it turns out that is just about right for life. For a biosphere.

What keeps earth's biosphere so constant?

We aren't sure. Some bold and imaginative scientists today like James Lovelock and Lynn Margulis have hypothesized a remarkable and controversial explanation for this constancy. They suggest we look on the biosphere itelf as a single living entity. Just as our own body is made up of a working aggregate of many kinds of living cells, tissues and organs, so too the biosphere of earth is a super living entity made up of a working aggregate of many kinds of living things, plant, animal and microscopic. They suggest we call this super living entity, Gaia.

Other scientists do not agree with this hypothesis, but they do agree that it is remarkable how constant our biosphere has been for so many millions of years past.

How constant it will be in years to come no one can be sure and it may depend at least partly on what we do.

Part Two: The Biosphere Today

The biosphere is the very thin outermost layer of planet earth where the only life we know of in this universe exists. The biosphere is you and me, as well as our friends the trees and flowers, the birds and fish, and yes, the bacteria and molds and other microscopic living things that live in such incredible numbers in each handful of soil, each glass of water and each breath of air.

The greenhouse effect, acid rain, global warming, new ice ages on the way, nuclear winter, pesticides in our food, toxic wastes in our lakes and oceans, rain forests disappearing-all these issues and more make headlines today. All in one way or another have to do with the existence and the health of what we call the biosphere.

Before we get into controversies about how to keep and even to enhance the health of the biosphere let's summarize what scientists know and don't know about the biosphere today.

One of the most striking things about the biosphere is how thin this hollow sphere of life is. Ninety-nine plus percent of living things live within a few thousand feet of the earth's surface. If you reduced earth to the size of an apple the biosphere would be thinner than the apple's skin.

Go down a mile or two in the ocean or out a mile or two in the atmosphere and you can find a few living things but not many. Further in or out than that, nothing. Nothing but rock and molten lava as we move toward the center of the earth. Nothing but the awe of lifeless space and stars as you move out ... for millions and millions of miles.

The second most striking thing about our biosphere-isolated and alone as it is in the vast stretches of cosmic space-is how stable and tough and life-nurturing this thin shell has been for the past three to four billion years.

How can we explain this remarkable life-nurturing stability?

In ancient Greek mythology the life-nurturing earth goddess was called Gaia. Some scientists today have hypothesized that our biosphere is indeed a kind of super-organism which they call Gaia. Just as our bodies react to the environment in ways that will preserve and enhance our life, so too, Gaia, the biosphere as a whole, reacts to the cosmic environment in ways that will preserve its life and health.

The Gaia hypothesis is very controversial among scientists today. What is not controversial is the scientific notion of homeostasis.

The ability of our bodies, or of any living organism to respond to life-threatening challenges of the environment is called homeostasis. If the temperature around us gets warmer, our bodies respond by sweating, by opening up blood capillaries to our surface skin and by making other internal adjustments to take heat away. If the temperature gets colder our bodies respond by shivering, by shrinking the blood capillaries near the surface to keep heat inside and by other internal adjustments to keep heat inside.

If we go up a mountain where there is less oxygen our bodies respond by increasing the amount of red blood corpuscles in order to take in more oxygen. If we take too much salt in our food, our bodies respond to dilute and remove that salt. If a harmful bacteria, virus or poison invades our bodies, our immune system responds to neutralize ane make harmless these attacks.

All living things-microbes, plants, and animals-have similar capabilities. All living things are homeostatic.

Whether Gaia actually exists or not, the sum total of all living things that we call the biosphere also seems to be homeostatic.

Take temperature. Life can only exist in a relatively narrow range of temperatures. Temperatures above the boiling point of water or below the freezing point are obviously unsuitable for life. Thus as planets go, Venus is far too hot, and Mars is far too cold. Earth is just about right. And earth's biosphere seems to be able to maintain that just-right in-between temperature.

It does it by a combination of fail-safe mechanisms, only a few of which we have investigated. The most important is the way the biosphere helps to maintain the present composition of the atmosphere-approximately seventy nine percent nitrogen gas, twenty percent oxygen gas and the remainder a mixture of carbon dioxide, water vapor, inert gases and traces of gases like methane and ozone.

If it were not for the living biosphere earth would almost certainly have a very different kind of atmosphere and hence a very different temperature, a much much warmer one. Probably more like Venus, which has an average surface temperature of nine hundred degrees centigrade.

The reason Venus is so hot is not that it is that much nearer the sun than earth. It is because of what is called the "greenhouse effect." Here's how it works.

Some gases like carbon dioxide and water vapor act like the glass windows on greenhouses. That is, they let certain light rays from the sun penetrate, warm the air and soil, and provide the energy for green plants to photosynthesize. The air and soil and plants in turn eventually radiate equal amounts of energy back to space.

Note that if more energy came in than went out a planet, or a greenhouse, would simply get hotter and hotter. If less energy comes in than goes out the planet, or the greenhouse, would get colder and colder.

Some gases in the atmosphere like carbon dioxide and water vapor tend to trap heat energy inside. That is, they let radiation from the sun pass through but reflect back to the ground the lower wave length energy radiation coming from water, soil and living things. The more carbon dioxide and water vapor in the atmosphere, the more greenhouse effect and the hotter the surface of the planet will be.

Thus, a planet like Venus with an atmosphere of seventy percent carbon dioxide and water vapor is very hot indeed, far too hot to support any life at all.

In very early days four billion years ago earth too had an atmosphere with a much higher concentration of carbon dioxide and water vapor. Early life in the ocean gradually changed this situatiuon, taking carbon dioxide out of the air and replacing it with oxygen. Once the present proportion of oxygen and carbon dioxide was reached two to three billion years ago, there has been surprisingly little change in that proportion or in the temperatures on earth.

Then and now, the plant world and the microscopic world do the most important job in maintaining the biosphere's oxygen/carbon dixoide balance. There is, in other words, a natural recycling system that works well.

Green plants carry on photosynthesis. In this process they take carbon dioxide out of the air and replace it with oxygen. Plants and animals and microbes in turn carry on respiration and reverse this process, using oxygen in their cells to burn food and releasing carbon dioxide to the atmosphere.

The photosynthesis of plants in the ancient ocean waters started this process and ever since those days the plants in the ocean have been the most single important factor in keepking the oxygen/carbon dioxide cycles relatively constant. Scientists also think that the rich association of land plants such as you find in tropical rain forests may be key factors in maintaining this balance today.

There is concern among many scientists today that the very recent industrial activities of human beings may alter this balance. By burning fossil fuels, by cutting down tropical forests and in other ways putting more carbon dioxide into the air than we are taking out, we risk increasing the greenhouse effect and warming permanently the climates of planet earth.

It may not seem much to you but scientists point out that over two billion years earth's average temperatures from year to year have not varied more than five or six degrees centigrade. Careful studies have shown that just within the last four decades of industrial development the average temperatures on earth have risen one half a degree centigrade. If the present imbalance of carbon dioxide especially continues into the next century we may see an average rise of three to five degrees. This would not make us into a Venus to be sure, but it would be enough to cause very great changes everywhere on earth.

Ice caps would begin to melt at the north and south poles. More important, warmer ocean water would expand causing a significant rise in ocean levels around the world. Coastal cities like New York, Los Angeles and Miami might find themselves with severe flooding problems.

Rain patterns would shift dramatically with such a rise in temperatures. It is not easy to predict precisely which areas would get wetter and which would get dryer but most climatologists think the midwest USA-at present the source of a significant proportion of the nation's and the world's food-would become dryer, perhaps making the growing of corn and wheat much more difficult if not impossible. Northern Africa, southern Canada and parts of India and China, on the other hand, would become wetter and hotter.

Since the biosphere and the human place in the biosphere are so interwoven today changes like this have many other consequences difficult to predict. In many parts of this country and the world, for instance, electrical power is generated by water flowing from reservoirs over dams. If the change of climate resulted in less rain, the water now would lessen, electrical power would decrease. When this is combined, as it would be, with hotter days and nights, air conditioning would accelerate the demand for electrical power making matters worse.

Temperature is important but it is only one of the important factors for life in the biosphere. High on the list of other factors is the efficient cycling of life needed elements. You could put it another way-the efficient recycling of wastes.

All living things are made of the same basic raw materials, the same elements. Not surprisingly these life elements are among the most common elements in the universe. Over ninety nine percent of all living structures are built of just six key elements-hydrogen, oxygen, nitrogen, sulfur and phosophorus. Living cells also need small but important traces of some fifteen to twenty other elements like iron, magnesium, copper, sodium, chlorine and iodine.

All of these elements were forged in the center of an exploding star of over five billion years ago. The atoms in other words that make up our earth and all the living things of the biosphere are the very same atoms that came together to make up our five billion year old earth. In all that long history these same atoms have been recycled continuously as they are still recycling today.

Thus the atoms of carbon or hydrogen or oxygen or sulfur or phosphorus that today are combined in the molecules that are the cells in your brain once were a part of other molecules that made up the cells in the early ocean waters. And they are the same atoms that tomorrow will cycle into the air and water and soil and corn plant and child of the twenty first century.

Scientists have been able to figure out many of the details of the recycling of these atoms.

As mentioned before, carbon dioxide cycles into green plants where it combines with water. Oxygen is sent back to the atmosphere, the carbon is used to make energy-rich sugar in the process called photosynthesis.

Sugar (a molecule made of carbon, hydrogen and oxygen atoms) is used as an energy and matter source to make larger life-needed molecules, especially the all important enzymes, proteins and mucleic acids that are the actual building blocks of all living cells and organisms.

To make these enzymes, proteins and nucleic acids, cells need the other life necessary atoms of nitrogen, sulfur, phosophrus, etc.

Nitrogen, for instance, makes up seventy nine percent of the air. However, this free nitrogen is of little use to most living things in that form. Fortunately one particular variety of living things, a group of bacteria, are able to take in this free nitrogen and build it into a molecule that can then be used by the rest of the living world as a source of life-building nitrogen molecules which are then used to make proteins, enzymes and nucleic acids.

Thus we get a nitrogen cycle.

Each of the other life necessary elements has its own way of cycling through the biosphere.

Finally, besides cycling matter and energy, the biosphere has many protective structures. Just as our skin keeps out unwanted moisture, microbes and heat, so too the atmosphere protecs us from many life-threatening dangers. Meteors, for instance. They usually burn up when they hit the outer atmosphere before reaching the surface of the earth.

The ozone in the outer atmosphere protects us from ultra violet rays of sun which cause skin cancer and probably many other as yet unknown threats from cosmic space.

As you can see by now it is not simple. Life has existed as a biosphere for over three and a half billion years. These cycles of elements and energy have gone through many variations. Over ninety nine and nine tenths of the living species that have ever lived are now extinct. And yet there are now over five million species of living things that make up today's biosphere. And these five million species, which include Homo sapiens, still live as a part of a biosphere essentially the same as that of a billion years ago.

The scientists who claim this means the biosphere itself is a kind of super organism, Gaia, are a minority today. But all scientists who have studied the biosphere agree that we need to know more, much more, about its parts and its cycles.

And the more we know, the better we can predict and the better we can act to safeguard the future health of this biosphere, which, after all, includes you and me.