Sir David Frederick Attenborough is a broadcaster and naturalist. His career as the respected face and voice of natural history programmes has endured for more than 50 years. He is best known for writing and presenting the nine “Life” series, in conjunction with the BBC Natural History Unit, which collectively form a comprehensive survey of all life on the planet. He is also a former senior manager at the BBC, having served as controller of BBC Two and director of programming for BBC Television in the 1960s and 1970s.  He expresses his fascination with the phenomenon of photosynthesis in the following words:

Leaves are the food factories of a plant. The raw materials they use are of the simplest. Carbon dioxide, water and a few mineral ingre­dients. The first, a gas, is all around them in the air and they absorb it through tiny pores in their surface. Water, and the minerals dis­solved in it, is collected by the roots from the ground in which the plant grows. The agents within the tissues of the leaves that process these raw materials are small grains containing that remarkable green substance, chlorophyll. Powered by the energy of the sun, this is able to combine these elements and produce starches and sugars, the foods from which the plant builds its various tissues. The proc­ess is called photosynthesis. Its by-product is oxygen. That gas drifts through the leaf pores into the atmosphere to the benefit of animals. For them it is the very breath of life.

Since daylight is essential for this process, every plant must, as far as possible, position its leaves so that each collects its share without interfering with any others the plant may have. This may require changing the posture of the leaves throughout the day as the sun moves across the sky. The accuracy with which a plant can position them may be judged simply by gazing up at the canopy in a wood.

In an environment where many species live crowded together, as they do in an English hedgerow, plants may have to jockey with their neighbors and rivals for exposure to the sun. Watching them do so on time-lapse film shot over several days is like watching the faces of a packed crowd at a tennis match, where each person is anxious to get a good view of the ball as it passes from one side of the court to the other. In the morning, they face eastwards. As the sun rises, so they crane upwards; and as it sets, so they turn west­wards. Overnight, some may fold up, but all realign themselves to be ready to face the sun when it appears once more at dawn in the east.

On the floor of a well-established forest, the light may be very dim indeed. Some plants deal with the problem by growing ex­tremely large leaves. The biggest undivided leaf of all belongs to a giant edible aroid that grows in marshy parts of the tropical rain forest in Borneo. One of its heart-shaped leaves may be ten feet across and have a surface area of over thirty square feet. Other members of the same family do not grow such monstrous leaves but maximize the meager light that falls on them in a different way. They coat the underside of their leaves with a purple pigment. This catches the light after it has passed through the thickness of the leaf and reflects it back into the leaf tissues so that the chlorophyll has the second chance to utilize what is left of it. Begonias, which also grow on the floor of these Asiatic forests, have an additional trick. Some cells in the upper surface of their leaves are transparent and act as tiny lenses, gathering the feeble light and focusing it on to the grains of chlorophyll within.[1]

David Attenborough showing his typical fascination with animals and plants

The technique of focusing light through lenses is also being lately used in solar cells to enhance the yield of the solar panels.   Professor Richard Dawkins confesses in one of his books:

Whenever humans have a goodidea, zoologists have grown accustomed to finding it anticipated in the animal kingdom. Examples pervade this book; including echo-ranging (bats), electro location (the Duckbill’s Tale), the dam (the Beaver’s Tale), the parabolic reflector (lim-pets), the infrared heat-seeking sensor (some snakes), the hypodermic syringe (wasps, snakes and scorpions), the harpoon (cnidarians) and jet propulsion (squids).[2]

Water supply to the leaves for photosynthesis

For photosynthesis in addition to light and carbon dioxide water is needed.  David Attenborough describes in his special style how water is pumped up effortlessly and noiselessly upto more than 400 feet by the mountain ash trees:

The mountain ash’s scientific name is Eucalyptus regnans which means, accurately enough, the ruling eucalypt. That indeed would certainly be a much better English name for such a magnificent giant. Walking through a forest of them it is difficult to appreciate just how gigantic they are, for the relative proportions of their trunks and branches are very much like those of smaller eucalypt species. In fact they stand over three hundred feet high. The current record holder is said to be one in the Styx Valley of Tasmania which has been measured as reaching 325 feet. Even this is not the tallest that has ever existed. The forests of Australia, like those almost everywhere else, have been plundered for timber ever since Euro­peans first entered them. Back in 1880, a surveyor measured a mountain ash in Victoria that stood 375 feet high. It was, of course, immediately cut down. Around the same time, an official inspector of forests reported a fallen trunk of one that was 435 feet long. That may well be the tallest tree ever measured.

On a hot day, a tree the size of a mountain ash can lose several hundred gallons of water as vapour from its leaves. If those leaves are not to wilt, that water has to be continuously replaced. The tree has to gather it with its roots, raise it several hundred feet in its trunk and send it along its branches and stalks into the leaves themselves. A fireman, perched on top of his tallest ladder, can only get water into his hose if it is pumped up by a huge vibrating engine roaring away on the ground beneath. Yet a tree manages to do a similar thing with no visible movement and in total silence. How?

It is only able to do so because the tensile strength of water is very great indeed; that is to say, an enclosed column of it will not break into separate droplets except under enormous tension. The vessels up which the water travels were initially formed by extremely elon­gated cells. As they grew, these not only thickened their sides with lignin but ultimately broke down the dividing wall where they met, tip to tip, so that together they formed long continuous tubes unin­terrupted by any divisions. That done, the cells died. The pipes they created are thus inert and dead. They are also full of water. As the cells in a leaf lose water by evaporation, so it is replaced by water from the top of the tubes and the whole water column is pulled upwards.  This, of course puts a huge strain on the sides of the tubes within a tall tree, but their woody walls are rigid enough to withstand it, and the tensile strength of water normally prevents it from fragmenting.[3]

Imagine pumping water to a height of 435 feet through human technology and that should make us stand in awe of the mountain ash because of its or shall we say its Creator’s magic of noiselessly pumping several hundred gallons of water every day for years and decades on end, without fail, a miracle in durability still unmatched by human technology, despite centuries of boasting and tall claims!

Mountain ash trees

David Attenborough has captured his fascination with different phenomena in the plant kingdom in a documentary, titled, the private life of plants.  Some parts of it are available on Youtube:

The miracle of photosynthesis and evolution

The miracle of photosynthesis needs to be understood in the three billion year history of evolution on the planet earth. The first to come were the algae and with their particular form of chlorophyll that other plants adapted slightly. When animals evolved from the plants it appears that chlorophyll was adapted into myoglobin and hemoglobin for the different needs of the animals, a creative miracle that the atheists choose to attribute to blind chance or nature and theists have the frame of mind to attribute such a wonderful and ubiquitous adaptation to the Creator of our life.

Encyclopedia Britannica offers us basic information about the structure of chlorophyll:

Chlorophyll is any member of the most important class of pigments involved in photosynthesis, the process by which light energy is converted to chemical energy through the synthesis of organic compounds. Chlorophyll is found in virtually all photosynthetic organisms, including green plants, prokaryotic blue-green algae (cyanobacteria), and eukaryotic algae. It absorbs energy from light; this energy is then used to convert carbon dioxide to carbohydrates.

Chlorophyll occurs in several distinct forms: chlorophylls a and b are the major types found in higher plants and green algae; chlorophylls c and d are found, often with a, in different algae; chlorophyll e is a rare type found in some golden algae; and bacterio-chlorophyll occurs in certain bacteria. In green plants chlorophyll occurs in membranous disklike units (thylakoids) in organelles called chloroplasts. The chlorophyll molecule consists of a central magnesium atom surrounded by a nitrogen-containing structure called a porphyrin ring; attached to the ring is a long carbon–hydrogen side chain, known as a phytol chain. Variations are due to minor modifications of certain side groups. Chlorophyll is remarkably similar in structure to hemoglobin, the oxygen-carrying pigment found in the red blood cells of mammals and other vertebrates.[4]

Chlorophyll and hemoglobin: complex yet elegant

Giant water lilies in the Amazon have a very dramatic strategy to capture light for photosynthesis, by covering large surfaces of water.  The leaves looking like huge circular trays may be as large as 6 feet in diameter, here is some excellent footage by David Attenborough, demonstrating this beautiful miracle of nature:

Giant water lillies from the Amazon easily supporting the weight of a young girl

As animals evolved from the plants, the molecule of chlorophyll was very creatively adapted to serve as oxygen carrying blood chemicals, hemoglobin and like, including myoglobin that is used for storage of energy in the muscles.  In 1913 Dr. Richard Willstätter, a German chemist, discovered the role of chlorophyll in plant functions, and noted the structural similarity between chlorophyll and heme, the red pigment in blood responsible for transporting oxygen to all parts of the body. Both molecules have complex structures, called porphyrin rings, consisting of carbon, hydrogen, oxygen, and nitrogen. Heme (the oxygen-carrying part of the hemoglobin molecule) differs from chlorophyll primarily by the central atom; iron (Fe) in heme and magnesium (Mg) in chlorophyll.

The manganese gives chlorophyll the green color and iron gives hemoglobin its red color.

Mirza Tahir Ahmad, IV Caliph of Islam Ahmadiyya

Having examined the amazing significance of dry ringing clay at the preparatory stages of biotic evolution, let us pause and wonder for a while at the dazzling brilliance of the Quranic claim made over fourteen hundred years ago. The idea of the participation of dry ringing clay in the creation of man is so bizarre and unique, and is diametrically opposed to the then prevalent popular tale of the genesis of Adam. One can easily understand the workings of a simple mind, under the influence of such popular tales, to think of God as mixing earth with water, drying it up to a degree, until it achieved the consistency of modelling clay. What remained to be done was the simple exercise of moulding it into the shape of man. And Lo! Adam is raised from dust, complete with all his organic constituents! In that instant sprang into being the entire complex of his body cells furnished with DNA, RNA, chromosomes, genes, somatic cells, reproductive cells etc. Ears, nose and eyes were formed, blood vessels were created, and heart and lungs with all their complexities were completed and set in place. Also, of course, the central nervous and immune systems were completed that instant!

All that miracle was created, according to some naive readers of the scriptures, within the space of a single breath of life which, as they understand, the Creator blew into the statue of clay which He had moulded as Adam. This belief is as devoid of brain as blind evolution is devoid of sight. The evolutionists who believe in creation without a God, without a Conscious Supermind, may scorn at the naivety of those who take the account of the Old Testament over-literally. They forget however, that their stance is equally lamentable. If the scripture scenario is literally accepted, then the only conclusion one can draw is that God the Creator is Almighty, but not All-Wise! An All-Wise God could not have conceived such a brainless scheme of creation, in which even a skilful potter could beat Him at His own game!

The plan of evolution which antecedes the creation of man is a masterpiece of creative wonders and a work of beauty which knows no parallel. For such a Creator to have forgotten altogether the intricate laws of nature which He Himself had framed, and the bricks of life which He had so dexterously designed and moulded, and the profound wonders He packed into their tiny cells, is absolutely inconceivable. How could He have forgotten a billion years of the history of the evolution of life? Little did he remember, as he was engaged so seriously in shaping another Adam out of clay, all anew, that he had already created and perfected him a hundred thousand years before in a far more sensible manner. The earth was already abounding in Homo sapiens—and with what amazement they must have watched him engaged in this futile exercise in the garden of Eden!

However disdainfully one may reject this naive vision of the creation of man, as held by religious zealots, the case of the secular scientists is no less deplorable. They know full well the limitless intricacies involved in the scheme of creation and the most exquisitely executed plan of evolution. All the same they attribute this most wonderful masterpiece merely to ‘chance’ who is not only brainless, but is also blind, deaf and dumb! Little does it behove them to laugh and scorn at the religious zealots. The vision of their god, however senile he may have become—after executing his tremendous plan of creation—is out of all proportion superior to the evolutionist’s concept of the creative force at work. The most exquisite and unimaginably intricate plan of creation, they believe, was conceived and executed merely by a sightless brainless fashioner of man, the ancient thrower of dice.

The image of God as emerges from the Book of Genesis, when taken literally, presents Him no doubt as a doting senile but what the scientists would have us believe is even more exasperating. All through the journey of a billion years of biotic evolution, only a brainless phantom of chance occupied the driving seat, the naturalists insist, steering the wagon of evolution through the uncountable number of twists and turns it took before reaching its ultimate goal.

But unfortunately all their profound search for truth comes to a naught when they reach the point where life should begin to emerge in an oxygen-free atmosphere, which then existed, according to Haldane. In agreement with his theory, the scientists believe that a transformation did take place from a non-biotic era to a biotic era despite the absence of oxygen. We believe, on the other hand, that despite their denial of the existence of free oxygen, one must visualize its presence in the atmosphere somehow to the degree that it could support life. For this we have no alternative mechanism to suggest, but our failure to do so does not prove that it did not happen.

The fact that biological systems have very special requirements, and that these requirements are happily, met by nature, has been commented upon at least since the seventeenth century. It is only in the twentieth century, however, with the development of biochemistry, genetics, and molecular biology, that the’ full picture has emerged. Already in 1913 the distin­guished Harvard biochemist Lawrence Henderson wrote: ‘The properties of matter and the course of cosmic evolution are now seen to be intimately related to the structure of the living being and to its activities; … the biologist may now rightly regard the Universe in its very essence as biocenteric.’ Henderson was led to this surprising view from his work on the regulation of acidity and alkalinity in living organisms, and the way that such regulation depends crucially upon the rather special properties of certain chemical substances. He was also greatly impressed at how water, which has a number of anomalous properties, is incorporated into life at a basic level. Had these various substances not existed, or had the laws of physics been some what different so that the substances did not enjoy these special properties, then life (at least as we know it) would be impossible. Henderson regarded the ‘fitness of the environment’ for life as too great to be accidental, and asked what manner of law is capable of explaining such a match.

In the 1960s the astronomer Fred Hoyle noted that the element carbon, whose peculiar chemical properties are crucial to terrestrial life, is manufactured from helium inside large stars. It is released therefrom by supernovae explosions, as discussed in the previous sec­tion. While, investigating the nuclear reactions that lead to the for­mation of carbon in the stellar cores, Hoyle was struck by the fact that the key reaction proceeds only because of a lucky fluke. Carbon nuclei are made by a rather tricky process involving the simultaneous en­counter of three high-speed helium nuclei, which then stick together. Because of the rarity of triple-nucleus encounters, the reaction can proceed at a significant rate only at certain well-defined energies (termed ‘resonances’), where the reaction rate is substantially ampli­fied by quantum effects. By good fortune, one of these resonances is positioned just about right to correspond to the sort of energies that helium nuclei have inside large stars. Curiously, Hoyle did not know this at the time, but he predicted that it must be so on the basis that carbon is an abundant element in nature. Experiment subsequently proved him right. A detailed study also revealed other “coincidences” without which carbon would not be both produced and preserved inside stars. Hoyle was so impressed by this “monstrous series of accidents,” he was prompted to comment that it was as if ‘the laws of nuclear physics have been deliberately designed with regard to the conse­quences they produce inside the stars.’ Later he was to expound the view that the universe looks like a ‘put-up job,’ as though somebody had been ‘monkeying’ with the laws of physics.

These examples are intended merely as a sample. A long list of additional “lucky accidents” and ‘coincidences’ has been compiled since, most notably by the astrophysicists Brandon Carter, Bernard Carr and Martin Rees. Taken together, they provide impressive evi­dence it depends very sensitively on the form of the laws of physics, and on some seemingly fortuitous accidents in the actual values that nature has chosen for various particle masses, force strengths, and so on.[5]

Allah is He Who created the heavens and the earth and caused water to come down from the clouds, and brought forth therewith fruits for your sustenance; and He has subjected to you the ships that they may sail through the sea by His command, and the rivers too has He subjected to you.  And He has also subjected to you the sun and the moon, both performing their work constantly. And He has subjected to you the night as well as the day.  And He gave you all that you wanted of Him; and if you try to count the favours of Allah, you will not be able to number them. Verily, man is very unjust, very ungrateful.  (Al Quran 14:33-35)

This is a Book (the Quran) which We have revealed to thee, full of blessings, that they may reflect over its verses, and that those gifted with understanding may take heed. And We bestowed on David, Solomon who was an excellent servant. He was always turning to Us. When there were brought before him at eventide steeds of noblest breed and swift of foot, he said, ‘I love the love of horses because of the remembrance of my Lord.’ So great was his love of them that when they were hidden behind the veil, he said, ‘Bring them back to me.’ Then he began to pass his hand over their legs and their necks. (Al Quran 38:30-34)

As life began on earth, all vegetative growth which contains a green pigmented material—chlorophyll—entrapped the incident sunlight, converting it to chemical energy to synthesize organic compounds from inorganic compounds. During this process they manufactured carbohydrates from carbon dioxide and water releasing oxygen simultaneously:

6CO2 + 6H2O ——-> C6H12O6 + 6O2

Chlorophyll is of two types, chlorophyll a (C55H72MgN4O5) and chlorophyll b (C55H70MgN4O6). The composition of these formulae has the exact placing of each element in a certain sequence which is reminiscent of the composition of haemoglobin—being no less wonderful in its complexity. Thus writes Steven Rose in his book The Chemistry of Life:

‘Although chlorophyll is by no means the only photosynthetic pigment, it is the only essential one. … The polar head part of the molecule is in fact very similar in design to that of the haem of the cytochromes and haemoglobin. Like haem it consists of a linked series of four carbon-and-nitrogen containing rings (‘pyrrole rings’) joined together to form a sort of doughnut with a hole in the middle. This hole is filled in haem by the metal iron: in chlorophyll on the other hand the jam in the doughnut is made of magnesium. The ring structures contain a series of alternating double and single bonds, and the absorption of a given small amount of light (a quantum) of a particular wavelength causes a sort of vibration, or resonance around these bonds. Because of the close packing and stable orientation of the pigment molecules within the lamellae, this resonance energy can be transferred from one pigment molecule to another until it is eventually channelled into a slightly different chlorophyll molecule from which it cannot escape. This final energy-trapping type of chlorophyll can receive an input from as many as 300 of the standard chlorophyll molecules. The energy from the light is thus very highly concentrated at a single site, giving the second molecule the ability to transfer an electron to a non-pigment receptor which in turn passes it, via an intermediate set of carriers, to NADP…

In the most complicated huge molecule of chlorophyll, there is an immensely long chain of atoms precisely arranged in a sequence which if altered, at even a single link, will completely destroy the very function and significance of chlorophyll. Life in every form owes its existence to this fundamental trap of energy, but carbohydrates thus produced cannot be utilized by life directly. The chain of all chemical reactions that follow depend on ATP and ADP, chemicals which essentially contain three or two phosphate groups. In both these chemicals the phosphorus groups play the central role. It is this most important ingredient which is present in every living cell of both plants and animals. It runs the immensely vast factory which provides a multitude of organic chemicals needed by the living.

In the preceding discussion we have in fact touched upon three mysteries of creation which the routinely familiar eyes of the scientists do not register. But all the great scientists who have tried to unravel the mysteries of the origin of life register these facts and attempt to resolve them. Chlorophyll is an exception to the rule. Instead of attempting to solve the enigma presented by this pigment, they bypass the issue altogether and proceed on to discuss some other hurdles regarding which they have at least some partial solutions to offer.

They bypass the issue of chlorophyll because they must have fully realized that this extremely complex pigment could not have suddenly jumped into existence out of nowhere. If on the other hand it had evolved, it must have left behind a very long trail of its evolution. Most certainly it should not have begun to exist out of nothing. But it does exist, and hurls a challenge to all the atheists, philosophers and scientists to explain its sudden emergence and existence. It is easier to conceive the haemoglobin to have evolved. But it is next to impossible to justify the existence of this little pigment.

http://www.alislam.org/library/books/revelation/index.html

Prof. Richard Dawkins’ inability to appreciate the beauty of trees

“Eyes and nerves, sperm tubes, sinuses and backs are poorly designed from the point of view of individual welfare, but the imperfections make perfect sense in the light of evolution. The same applies to the larger economy of nature. An intelligent creator might be expected to have designed not just the bodies of individual animals and plants but also whole species, entire ecosystems. Nature might be expected to be a planned economy, carefully designed to eliminate extravagance and waste. It isn’t, and this chapter will show it.”

Prof. Richard Dawkins

Before he will make his thesis he begins by arguing against his case and shoots himself in the foot.  Let us read it in his own words as he analyzes the complexity, organization and beauty of photosynthesis:

“Much of the land surface of the Earth is covered by green leaves, which constitute a many-layered catchment for photons. If a photon is not caught by one leaf, it has a good chance of being caught by the one below. In a dense forest, not many photons make it to the ground uncaught, which is exactly why mature forests are such dark places in which to walk. Most of the photons that constitute our planet’s minute share of the sun’s rays hit water, and the surface layers of the sea swarm with single-celled green plants to catch them. Whether at sea or on land, the chemical process that traps photons and uses them to drive ‘uphill’ energy-consuming chemical reactions, manufacturing convenient energy-storage molecules such as sugars and starch, is called photosynthesis. It was invented, more than a billion years ago, by bacteria; and green bacteria still underlie most photosynthesis. I can say this because the chloroplasts – tiny green photosynthetic engines that actually do the business of photosynthesis in all leaves – are themselves the direct descendants of green bacteria. Indeed, since they still autonomously reproduce themselves after the manner of bacteria, within plant cells, we can justly say that they still are bacteria, albeit heavily dependent on the leaves that house them and to which they give their colour. It appears that originally free-living green bacteria were hijacked into plant cells, where they eventUally evolved into what we now call chloroplasts.”[6]

“Look at a single tall tree standing proud in the middle of an open area. Why is it so tall? Not to be closer to the sun! That long trunk could be shortened until the crown of the tree was splayed out over the ground, with no loss, in photons and huge savings in cost. So why go to all that expense of pushing the crown of the tree up towards the sky? The answer eludes us until we realize that the natural habitat of such a tree is a forest. Trees are tall to overtop rival trees – of the same and other species. Don’t be misled when you see a tree in an open field or garden that has leafy branches all the way down to the ground. It has that well-rounded shape so beloved of sergeant instructors because it is in an open field or garden. You are seeing it out of its natural habitat, which is a dense forest. The natural shape of a forest tree is tall and bare- trunked, with most of the branches and leaves near the top – in the canopy which bears the brunt of the photon rain. And now, here’s an odd thought. If only all the trees in the forest could come to some agreement – like a trades union restrictive practice – to grow no higher than, say, 10 feet, everyone would benefit. The entire community – the entire ecosystem – could gain from the savings in wood, and energy, which are consumed in building up those towering and costly trunks.”[7]

“We are talking individual costs and benefits throughout this argument. The forest would look very different if its economy had been designed for the benefit of the forest as a whole. In fact, what we actually see is a forest in which each tree species evolved through natural selection favoring individual trees that out-competed rival individual trees, whether of their own or another species. Everything about trees is compatible with the view that they were not designed – unless, of course, they were designed to supply us with timber, or to delight our eyes and flatter our cameras in the New England Fall. And history is not short of those who would believe just that, so let’s turn to a parallel case, where the benefits to humanity are harder to allege: the arms race between hunters and hunted.”[8]

Recycling of elements: the carbon and the nitrogen cycles

Carbon cycle, in biology, circulation of carbon in various forms through nature. Carbon is a constituent of all organic compounds, many of which are essential to life on Earth. The source of the carbon found in living matter is carbon dioxide (CO2) in the air or dissolved in water. Algae and terrestrial green plants (producers) are the chief agents of carbon dioxide fixation through the process of photosynthesis, through which carbon dioxide and water are converted into simple carbohydrates. These compounds are used by the producers to carry on metabolism, the excess being stored as fats and polysaccharides. The stored products are then eaten by consumer animals, from protozoans to man, which convert them into other forms. All animals return CO2 directly to the atmosphere as a by-product of their respiration. The carbon present in animal wastes and in the bodies of all organisms is released as CO2 by decay, or decomposer, organisms (chiefly bacteria and fungi) in a series of microbial transformations.[10]

Nitrogen cycle, circulation of nitrogen in various forms through nature. Nitrogen, a component of proteins and nucleic acids, is essential to life on Earth. Although 78 percent by volume of the atmosphere is nitrogen gas, this abundant reservoir exists in a form unusable by most organisms. Through a series of microbial transformations, however, nitrogen is made available to plants, which in turn ultimately sustain all animal life. The steps, which are not altogether sequential, fall into the following classifications: nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and denitrification.

Nitrogen fixation, in which nitrogen gas is converted into inorganic nitrogen compounds, is mostly (90 percent) accomplished by certain bacteria and blue-green algae (see nitrogen fixation). A much smaller amount of free nitrogen is fixed by abiotic means (e.g., lightning, ultraviolet radiation, electrical equipment) and by conversion to ammonia through the Haber-Bosch process.

Nitrates and ammonia resulting from nitrogen fixation are assimilated into the specific tissue compounds of algae and higher plants. Animals then ingest these algae and plants, converting them into their own body compounds.

The remains of all living things—and their waste products—are decomposed by microorganisms in the process of ammonification, which yields ammonia. (Under anaerobic, or oxygen-free, conditions foul-smelling putrefactive products may appear, but they too are converted to ammonia in time.) Ammonia can leave the soil or be converted into other nitrogen compounds, depending in part on soil conditions.

Nitrification, a process carried out by nitrifying bacteria, transforms soil ammonia into nitrates, which plants can incorporate into their own tissues.

Nitrates also are metabolized by denitrifying bacteria, which are especially active in water-logged, anaerobic soils. The action of these bacteria tends to deplete soil nitrates, forming free atmospheric nitrogen.[11]

Epilogue