What is Life Efficiency? We now have a scientific overview of how an ecosystem works. Green plants share out the space available to the ecosystem among themselves and on professional lines. Each kind of plant has a separate niche, specializing in living on good soil or bad, being early in the season or late, being big or little. And these green plants trap some of the energy of the sun to make fuel. Some of this fuel they use, some are taken by animals, much goes to rot.
The fuel taken by the animals at the bottom of the Eltonian pyramid is mostly burned up by the herbivores themselves, but a portion is taken by their predators, and so on for one or two more links up the food chains. At each level in the pyramid, there are many species of animals, the numbers of each being set by its chosen profession or niche. All the animals and plants use much of their fuel to make as many babies as possible, and many of these babies are used as fuel by other animals.
Every animal and plant in this ecosystem have an appointed place defined both by its level in the pyramid and by its niche. All these living things are tied together in a great web of eating and being eaten, and an ecosystem is a complex community of energy-consumers, all straining to get the most and do their best with it. The result of all these individual efforts is the self-perpetuating mechanism of nature at which we wonder.
But how good is that mechanism really? It certainly works, and it undoubtedly is long-lasting, but is it efficient? This question has more than academic interests because the future of our human population depends on the fuel-gathering efficiencies of ecosystems. So, we ask whether the plants and animals of wild ecosystems are efficient converters of energy, and whether the agricultural ecosystems on which we depend are better or worse than the wild ones.
Once we know the answers to these questions, we want to know what sets the limits to efficiency and whether we can do anything to improve upon whatever it is. We first look at the plants, because they perform the most important task of subverting the sun to make fuel and ask how efficient they are as factories of fuel.
The plants that now exist must be “fit” plants, they must be able to leave more offspring than have plants that might have been, which in turn means that they must be able to win more food than could the might have been which means that they must be more efficient at trapping the sun than were the might-have-been. Thus, a Darwinian ecologist expects all plants to be superbly efficient.
We see that the green receptors and transducers of energy that we call “leaves” are indeed stacked up on the face of the earth in the formidable array. So far so good. But we expect the chemistry and thermodynamics of those green transducers to be as efficient as the leaves are abundant.
We hear engineers talk about the efficiency of automobiles or steam engines, by which they mean how much of the energy supplied as fuel is converted to useful work. They often talk of efficiencies of 20 or 30 percent. With these thoughts, we turn to the practical measurements of what plants and animals can really do.
The efficiency of plants were first determined by a fine piece of armchair scholarship. It was done by Nelson Transeau in an office of an old building of The Ohio State University in Columbus when he was seeking material for a presidential address to the local academy of sciences.
The plant on which this scholar mused was the humble com plant, so suitable for armchair scholarship because anything measurable about com can be found out from the library. No one had thought before how to measure its efficiency, but they had measured everything an ingenious man might need to calculate it.
A crop of com begins with the bare, ploughed ground, a place of zero production, zero efficiencies. The corn then grows, zealously defended by the farmer from browsing animals and pests, until maturity. During the intervening weeks, the com plants have been receiving sunlight and converting it first to sugar, then to all the other ingredients of the plant’s structure.
Every calorie these com plants trapped had one of two possible fates: either it was burned by the plant itself to do the work of growing and living or it was still there at harvest time, dormant as potential energy in that standing crop. Com plants have been weighed often enough, and an agricultural handbook readily gives average figures for the yield of grain, leaves, stem, roots, everything.
Also known is how many calories are in a gram of grain, leaves, roots and the rest; just as the number of calories in a gram of sugar or ice cream is known. So, one can add up the calories in a field of corn. Finding out how many calories the plants have burned during their lives is trickier, but, as we shall see, this can be discovered too.
Transeau mused about an acre of land in the state of Illinois, a good place to begin because someone had measured how many calories came onto the land of that state from the sun on a typical summer's day. A nice crop of good corn growing on that acre would constitute a population of ten thousand plants. These grew from germination to harvest, as it happened, in exactly one hundred days.
Now it was necessary only to go to the handbooks to find out how much poundage was represented by ten thousand well-grown com plants. Transeau did this, then did a little calculation to convert all the cellulose, protein, and other chemicals they represented back into the sugar from which they had originally been made. In his mind's eye, Transeau saw not a field of ten thousand yellowing, rustling plants but a beautiful pile of glistening white sugar. The sugar weighed 6,678 kilograms.
Now Transeau needed only to know how much sugar these ten thousand plants had burned in their hundred days of life, and his own notebooks gave him this figure. Transeau had pioneered the measurement of breathing in plants, and by the time of that presidential address of 1926 he had all the figures he needed. These had come from com plants that Transeau had grown in glass chambers to which he could control the air supply.
He measured the carbon dioxide going into the chambers and the carbon dioxide coming out. In total darkness his experimental plants would respire as an animal does, burning sugar to give them calories for work, disposing of the combustion gases into the air.
The excess carbon dioxide coming out of the glass chambers was thus a measure of the combustion, a measure of sugar burned. Transeau’s notebooks told him how much sugar typical com plants of varying ages would bum in a day.
It was simple now to work out how much sugar would have been burned by ten thousand plants in one hundred days, and soon Transeau could see a second glistening white pile beside the first, a pile of sugar the plants had first made and then burned. This the second pile weighed 2,045 kilograms, so the two piles combined weighed 8,723 kilograms.
This was all the sugar made by the cornfield that summer. Now the end was in sight. 8,723 kilograms of the sugar glucose represents 33,000,000 calories, but the man who had measured the sun streaming onto Illinois had found that one acre in a hundred days of summer received 2,043,000,000 calories, more than fifty times as much.
If you put one of these figures over the other and multiply by a hundred you get Transeau’s the result, which was that corn plants, on prime land in Illinois, where they were given every care and attention, were only 1.6 percent efficient.
And so, to our amazement we find, not the 20 or 30 percent efficiency of a steam engine, not some super efficiency suggested by ideas of survival of the fittest or the marvelous workings of nature, but a miserable 1.6. Could the scholar in his armchair have got his sums wrong? People have made all Transeau’s suggested measurements on real crops, not only com but other high-yielding plants such as sugar beets, and they have come up with the same general answer: about 2 percent.
They also measured the rates of sugar production in photosynthesis more directly, by monitoring the flow of raw materials and waste products to and from the plants, and numerous studies have confirmed the estimates from crops. Our rich productive crops on rich productive soil are only 2 percent efficient.
Perhaps there is something wrong with agriculture. Perhaps it is only planted, grown in unnatural conditions that are so abysmally inefficient. But there is no escape this way either. It is harder to measure the efficiency of wild plants than of crops, but it can be done.
You cannot harvest a field of wild plants all the same age, as you can with com plants, but it has proved to be not beyond the wit of computer-minded man to make samples and calculate the potential wild crop. We now know that wild plants do about as well as tame plants. A very rough figure of 2 percent describes the efficiency of them all when they grow in very favorable circumstances.
Most wild plants achieve nothing like the 2 percent of agriculture because they do not have it so good. So, it is ours to reason why. What curious circumstance prevents 98 percent of the sun’s energy from getting into the living things staked out to wait for it in such an eager array?
What we know of these things has been told us by laboratory people. A plant is grown in a glass chamber, with rigid controls on all the conditions of its life so that it is comfortable and not disturbed; like a baby in an incubator. The breathing of the plant is monitored by measuring the gases it takes and gives to its chamber.
When it is busy converting energy by making sugar from carbon dioxide and water, it releases the oxygen that sensors can detect; when it is respiring in the dark it releases carbon dioxide. You can do wet chemistry on samples; you can make a plant use a radioisotope of carbon then measure activities, or you can wire the container to the fine expensive electronics of a modem analyst’s laboratory.
But, whatever way the measurements are taken, one can infer the rate at which the laboratory plant makes the sugar “glucose,” and hence the rate at which it fixes energy. Using a water-plant, such as a tiny green alga, makes things easier because the water simplifies the chemistry. Then you shine lights of known intensity into its glass incubator, recording precisely what it does.
First startling discovery is that half the kinds of light shone on the plant have no apparent effect on its chemistry. Half the total energy of sunlight is in the red end of the spectrum; what we call infrared light. We cannot see this light, but it floods down on us as warm rays, of low intensity it is true, but together adding up to half the energy getting to us from the sun. If red lamps are shone on the plant in its water bath, the chemistry of the water does not change. Plants cannot trap the energy of the far-red wavelengths any more than we can see them. Plants use only “visible” light.
We have obviously found one of the reasons for the inefficiency of plants, but we give a Darwinian biologist a curious question to answer while we are at it. Why should plants be made like people’s eyes so that they only make use of “visible” light? Plants must operate according to the rules of our Darwinian game, striving to wrest the largest possible number of calories from their surroundings so that they can turn them into babies.
They have been refined by natural selection to do this for a few thousand million years and should be very good at it. And yet they seem incapable of using half the energy pouring down on them. When this discovery was first made, an ingenious idea was put forward to explain it.
Plants, it was noted, had all first evolved in the sea, and red light does not penetrate very far through water but is rapidly absorbed. Any skin diver knows that everything looks blue down below the surface. A plant growing in an underwater place never has the redder rays shining on it and must do all its work of living with the bluer half of the spectrum.
So, it was argued, the ancestors of all plants evolved to be able to use only the energetic rays that penetrate water, essentially the visible light. Plants, however, have now lived on the land for several hundred million years, and it is very difficult for a biologist to believe that in all that time they could not adapt to this new brighter world with its red light. Fortunately for our peace of mind, modem physical chemists have come up with a better explanation.
The process of fixing energy (what we call “photo-synthesis,) involves violent disturbance to electrons as they spin in their orbits around atoms, and it takes a fierce pulse of energy to do this. The radiations of visible light are intense enough to fix energy, but the radiations of the red are not. Life, not for the only time, bows before the harsh reality of physical laws and does what it can with only half of the energy coming from the sun.
The red light can warm plants and does; it also evaporates water from them; helping drive the plants' circulation systems, but that is all. Since the laws of physics let plants use only half the sunlight, we ought to amend our efficiency calculation accordingly. We double the calculated efficiencies of wild vegetation and crop plants alike; bringing them up from a miserable 2 percent to nearly as miserable 4 percent. Steam engines and automobiles still manage 20 percent or better, and the greater part of our question about the inefficiency of plants remains.
The next enlightenment to come from laboratory science is that the efficiency of plants depends on the strength of the light. If one shines a very dim light into the laboratory bottles containing the plants, say the light of the dawning or twilight, the plants do amazingly well.
If one calculates the the efficiency with which they are using the meager resource of light, one may well find that they are doing as well as 20 percent efficient or even more. This does not compare so unfavorably with steam engines and automobiles, particularly when one reflects that a plant must do its own maintenance as it works, whereas steam engines are made and looked after by others.
So, we learn that in dim light the efficiency of plants compares quite favorably with the efficiency of man-made machines. They are not very productive in dim light, of course, because the total energy available is so slight. Twenty percent of very little is still very little, and dim light means poor production of sugar.
But plants in dim light yet use what energy there is available to them with tolerable efficiency. Why then do they not maintain this high efficiency when light is abundant and the potential riches in sugar to be won are very large? If brighter and brighter lights are shone into the plant incubators, the rate of sugar production goes up. This we would expect.
But the efficiency progressively falls until it levels off, not at 2 or 4 percent, but at about 8 per cent. It is still at about 8 percent when the very highest rates of photosynthesis, of making sugar, are reached. Eight per cent of an optimum amount of light gives the highest flow of energy into living things that the bottled plants can be made to achieve.
If the plants are given still more light, both their efficiency and the rate of production fall, and a time comes when production ceases altogether. That too fierce a light should stop the plant working completely is not surprising. Presumably, the plant is being cooked. It is the low efficiency with which light of optimum brightness is used for which we must find an explanation.
At this stage in the research, our original problem has been compounded rather than solved. We began by asking why crops and vegetation were so inefficient at handling the sunlight with which Providence provided them, and we have not got an answer yet.
What we have done is to show that plants are much more efficient at handling dim light than they are at handling the noonday sun and that algal cultures in laboratory incubators may be twice as efficient in bright sunlight as is a field crop (8 percent as opposed to 2 percent or 4 per cent depending on the wavelengths supplied).
Why are all plants comparatively inefficient in bright light? Why are all plants more efficient in dim light? Why are algal cultures in laboratory incubators twice as efficient as wild vegetation? The last question is the easiest, and we will take it first.
An algologist once taunted his colleagues, and tempted the public, with the figures from laboratory experiments with algae. See! These plants are 8 per cent efficient—far, far better than the com and the other plants we eat! It is foolish to grow inefficient crops when we could all fatten on green algal scum instead! This theme recurs in newspaper articles about the world food crisis.
It is a myth that is probably as impossible to eradicate as the myth that Tyranosaurus rex was a ferociously active predator. But myth it is. Algae are not more productive than other plants. The catch about the algal culturing is that it is the culturing that leads to higher average efficiencies, not the algae. Any actively growing plant that can be introduced to one of the small laboratory cultures will do as well as the algae.
A whole seedling can be put in a small laboratory container, made comfortable, and it will convert the energy of light to the energy of glucose with an efficiency of 8 percent or so, depending on the wavelengths supplied. A piece cut out of a leaf can be made to do the same on its own in the nutrient solution, away from its parent plant. When conditions are the same, algae are no more and no less efficient than the crop plants with which they were so favorably compared.
We now know that any healthy young plant, com included, which grows in a well-watered field with enough fertilizer, does as well as the algae (or any other plants) in the incubators. Its efficiency is that same rough 8 percent of the laboratory cultures. But the special thing about the plant in the field is that it grows old. When it is old it feels its age and does not work very well. So, the average efficiency over its lifetime has to be much less than the 8 percent efficiency of its youth.
At the start of Transeau’s hundred days, his Illinois acre was bare of plants and there was no production. At the end of a hundred days, there were ten thousand senile individuals who were not doing very much. Somewhere in the intervening time the field was nicely covered with fresh green leaves turning in their 8 percent, but the average for the whole hundred days had to include the beginning and the end, which brought the average efficiency down to 2 per cent. Wild vegetation in temperate latitudes faces the same harsh reality: a spring without leaves, autumn with pretty colors but diminishing green.
The great deception concerning algal culture came very largely from the accidental circumstance that it was convenient for plant physiologists to use fresh-water algae in their experiments. Such cultures are not good ways of producing food (even if we wanted to eat green scum) because culturing requires massive amounts of work and energy compared with conventional crop husbandry.
If these inputs of the energy was fed into the efficiency equation, we would find that the calculated efficiency was drastically lowered. Algae are no more efficient than any other kind of plant. The answer to our third question is that crops and wild vegetation is less efficient “over-all” than cultures or growing seedlings because of the physical vicissitudes of life, of bare ground in spring, of old age before the winter, of shortage of water and nutrients, of the debilitating presence of neighbors.
Now we must solve the mystery of the dim-light efficiency and the failure of even the favored young to do better than 8 percent. We can find a plausible answer to both questions by pondering the supply of raw materials a plant uses in the essential chemistry of photosynthesis. Plants make sugar out of carbon dioxide and water.
When water is in short supply the plants grow miserably, as we all know. But when water is abundant it is available to plants in virtually unlimited amount. The other raw material, carbon dioxide, however, is always scarce, even though it is always present.
Carbon dioxide is a rare gas. It is present in the atmosphere at an average concentration of about 0.03 percent by volume, a quite tiny proportion. And carbon dioxide is the essential raw material out of which plants must make sugar. Plant leaves are thin and pierced with multitudes of tiny breathing holes (stomates) for they must suck in carbon dioxide from as many directions as possible if they are to keep their sugar factories going.
Even so the rate at which they can soak up the precious gas is strictly limited. It seems reasonable to suggest that it is this shortage of raw material that sets a limit to the sugar-producing powers of plants growing on even the most favorable sites. Plants are inefficient as machines for converting sunlight because they face a shortage of raw materials.
When a plant is grown in dim light, its energy factories cannot work very fast, this being the simple consequence of lack of their light ‘‘fuel.” In dim light they have carbon dioxide to spare, and only considerations of thermodynamics and plant chemistry inhibit the rate of photosynthesis. The plants in this case turn out to be highly efficient.
But as such plants are given lighter, their demand on the carbon dioxide supply quickly grows, until they soon are using it as fast as it can be extracted from the air. At this moment plants are working as fast as their factories can be made to run. They are then about 8 percent efficient. If they are given more fuel still, as by shining the noonday sun on them, they can only waste the surplus, degrading it to heat, pouring it away.
We can test our the hypothesis that carbon dioxide limits the productivity of plants by pumping a little extra into our plant incubators and seeing what happens. If we do this, the rate of sugar-production goes up and the efficiency of energy conversion in bright light is slightly increased.
If we give the plants too much carbon dioxide, we suffocate them; but this need not disturb us. Plants have evolved in a world in which carbon dioxide is scarce, and their chemistry has adapted accordingly. Yet the dependence of sugar production on the carbon dioxide supply is clearly shown by these experiments.
It is well to insert a small word of caution about the generality of this result. The logic that so scarce a commodity as carbon dioxide ought to limit the rate of production is sound, and the experimental data are convincing demonstrations that we are on the right lines. But some of the consequences of a shortage of carbon dioxide are very complex and may impose second-order restrictions on photosynthesis.
Plants must “pump” large volumes of gas as they extract their carbon and this pumping may introduce its own restraints. Flooding the plant tissues with oxygen in the flux of air will have its own consequences for reactions dependent on chemical oxidations and reductions. Opening the stomates must result in the escape of water.
And so on. All operations that boost production in the plant factories must involve their own constraints and we can expect many fresh limits to appear as plants evolve to make the most of the carbon dioxide supply in different circumstances.
These possibilities are reflected in many modem debates about alternative “pathways” of chemical synthesis in plants. But with this bit of mealy-mouthing we can yet say that plants are generally inefficient as converters of energy because carbon dioxide is a rare gas in the terrestrial atmosphere.
This finding is of great significance to practical people for it means that there is a very narrowly defined limit to the possibilities for growing human foodstuffs. Our ultimate yields are set by the carbon dioxide in our air, and there is nothing we can do to push plants to do better. Our so-called high yielding strains of wheat and the rest are in fact no more efficient than the wild plants they replace, whatever the gentlemen of the green revolution may claim.
All that the agriculturalists have done is to make plants put more of their total capital of sugar into parts that people like to eat. A high-yielding wheat makes more grain at the expense of stalk, roots, and the energies to defend itself against pests and weeds. The finest efforts of science have not made any plant one jot more efficient than those nature made.
To a biologist brooding on the great conundrums of life, the inefficiencies of plants have a different message. The fuel supply for all life is restricted to some small fraction of what comes from the sun. A theoretical upper limit is about 8 percent, but this will be reached only for very short periods in very small places. All plants face youth and senescence, and virtually all face the changing seasons.
All suffer at times from a shortage of water or nutrients; none works at full efficiency for long. When we think of the average condition of life on earth, we think of deserts, mountainsides, and polar ice caps, as well as fertile flood plains. The average productivity of the earth must be very low, certainly much lower than that of 1.6 percent of Transeau’s cornfield. Probably only some fraction of 1 per cent of the solar energy striking the earth gets into living things as fuel for plants and food for animals.
When we try to explain the numbers and kinds of plants and animals, we must remember this great restriction in the fuel supply. Plant-eating animals, for instance, can get only a small portion of the sugar made by the plants on which they feed.
This is hard to measure, but practical people generally accept an upper estimate of about 10 per cent. We may think, therefore, that on good pasture land, herbivores get 10 percent of 2 percent of the sun. A tiger hunting those herbivores might theory get 10 percent of 2 percent of the sun. And so, on up the food chains.
We come then to the proposition that the numbers of the different kinds of plants and animals on earth are set by the amount of carbon dioxide in our air. Carbon dioxide sets the rate of plant production and is hence the ultimate arbiter of the food supply of all animals. If our earth had been forged with more carbon dioxide at its surface, the plants would have delivered more food and the opportunities for animals would have been greater.
We might even have had tiger-hunting dragons then, and the ferocious tyranosaur would have been less mythical. But the chemistry of the earth’s surface keeps the concentration of carbon dioxide low, by mechanisms quite out of reach of plants and animals. And so, the answer to many general questions about the numbers of animals as well as to the inefficiency of plants becomes, “Because it is very little carbon dioxide in our air.”
Why is Sea Blue? This is a very odd thing because the sea is also wet and spread out under the sun. It ought to be green with plants as is the land, but it is not. There are murky coasts and estuaries, the green hard waters of stormy channels, the fog-covered silvery- grey of ocean banks. But the deep sea, the open sea, most of the sea, is blue. This strange blueness of the sea can tell us many things.
An explanation for the color of the sea is simple enough. There are not enough plants in the sea to make it green, so we are left with the color of pure water under the sun. The light that passes through perfectly clear water is absorbed bit by bit, it's the energy dissipated as heat as it travels until at last all of it has flowed into the sink of heat and there is utter blackness.
But the colors of white light go progressively, one at a time. The low-energy wavelengths that we call “red” go first, then, in turn, the more intense parts of the spectrum orange, yellow, green and finally the various shades of blue. Only blue light reaches a few hundred feet down, and it follows that any reflected light that has made a double journey from the surface to the depths and back is blue. And so, the sea is blue.
But the real reason that the sea is blue is that there are not enough plants in it to make it green. And this is one of the oddest of the odd things about our world. Why are the great oceans not green with plants? We can get a first hint of where to look for our answer by reflecting on those few places in the sea that in fact are green, the shallow banks such as the Dogger Bank or regions of great upwellings such as those on the Peruvian coast.
These are the sites of the great fisheries, and the waters are murky green with plant life. The fisheries themselves attest to the rich productive qualities of these scattered places, and the green murk bespeaks high fertility. Indeed, high fertility, in the simple chemical sense, is the explanation of both the fisheries and the green murk.
The waters of banks and upwellings are well-supplied with chemical nutrients so that the tiny planktonic plants of the sea thrive abundantly, turning the water into a green soup in which animals wallow, to the eventual well-being of fishermen.
Where the sea is unusually fertile, tiny plants multiply and the water becomes green with their bodies. But most of the sea is not fertile; it is a chemical desert. Potassium, phosphorus, silicon, iron, nitrates and the rest are always present in sea-water, but in low concentrations.
By the standards of agriculture, the open sea is hopelessly infertile. And if the sea is infertile it is perhaps not unreasonable to expect that plants will not grow there very well, which is presumably why there are so few of them.
So far, we seem on safe ground, but there is a very large catch to the argument. Everything depends on the fact that the plants of the sea are tiny. In very fertile water (a polluted estuary is the best example) the tiny plants multiply until the water is pea-green with their bodies.
But if the water is a nutrient-poor desert like the great oceans, then there are only enough chemicals in the lighted upper layers of the sea to make a very few plants cells. The water is then essentially empty, the sun plunges down to the depths, and the water glows blue. But all these only follows//the plants are tiny.
Suppose there were large plants floating on the surface of the sea, plants that covered it with layers of leaves as the rain-forest trees cover the tropical land. These large plants would not have to worry about the thin supply of nutrients in the water any more than the rain-forest trees of the last chapter are stopped by the even thinner supply in the red tropical soils.
Large plants can collect, accumulate, and hoard nutrients. How easy it ought to be for a large plant in the sea. Deep down below the lighted surface of the sea, there are, in fact, almost unlimited nutrients, for the great oceans are some five miles deep in the middle. The fertilizer problem is one of concentration. In the few tens of meters at the top of the ocean, where the light reaches, and the plants must grow.
Hence, there is a local shortage of nutrients, but the potential supply underneath is truly enormous. A large plant at the surface would soak up nutrients, just like a large plant on land. More nutrients would then diffuse up from the depths to be similarly collected. And so on. Thus, if there were large plants in the open sea, the dilution of nutrients would not matter.
Now our inquiry comes close to Darwinian realities. The sea is blue, not so much because it is infertile but because there are no large plants growing there. Large plants would overcome the infertility of the surface water by gradually collecting nutrients as they filtered up from the depths below.
Large plants would become the dominant factor in the life of the sea as they are of the life of the land, making a massive shade of the spaces below them, forcing all food chains of animals to start with types that could bite out chunks from foliage. But no large plants live in the open sea. They can grow around coasts as do the kelps.
The giant kelps of the American Pacific, Macrocystis and Nereocystis, are said to be the longest vegetables in the world. But none of these large sea plants makes it out to a floating life in the open sea. For some reason, the niche or profession of “large-planting” is not possible in the open sea. Why? This is the fundamental Darwinian question behind the blueness of the sea.
Oceanographers have long known that there is something odd about the absence of big plants from the sea, but they have missed the grand Darwinian question. They never asked themselves, “Why can’t the plants be big?” Instead, they looked for the advantages of being small, counting the blessings of smallness and expecting to find their answers in this way. But you cannot get all of the answer like that.
Consider some of the so-called advantages of being small, particularly those based on the surface area. A small object has a much larger surface in proportion to its volume or mass than a big one. One result of this is less trouble with the sinking-problem, since the relatively large surface offers more friction, slowing the sinking rate. On the other hand, if you have a bladder of air or oil, you do not sink at all, so why bother being small?
Another is that the large surface to your little body can be used to soak up scarce nutrients. But there are ways of having a large surface area other than being tiny; by being convoluted or sponge-like, for instance. Rain-forest trees manage with a mat of hairs, even in mud and gravel let alone water. A spongy giant of an ocean plant would find soaking up nutrients easy; then it would be able to hoard its nutrients even as land vegetation does.
I have read in an oceanographic text that small entities use nutrients “efficiently.” This means that “turnover” is efficient if one thinks of the oceans as a banker thinks of a company that “turns over“ its capital quickly. But it is a strange sort of efficiency that keeps the oceans as a poorly productive desert.
If the ocean plants were large, they would soak up nutrients from below and make the ocean desert bloom like the lowland tropics. The “efficiency” of production would then be much greater. So why be small?
There must be some the advantage in being small, and we can best find what it is by looking for the the disadvantage of being big in the sea and whatever this disadvantage might be it surely must be overriding. There are big plants everywhere else, on all kinds of land surfaces and in every shallow patch of the sea along its coasts. It is only in the open sea, where they would have to float that there are no big plants. So, the answer to the problem must lie in a floating way of life.
Why do small plants make a success of floating in the sea whereas big ones do not? The answer stares us in the face. If a plant floats, it drifts, and if it drifts, it is soon blown away from where it wants to be. There must be some way to get back. A big floating mass kept up by air bladders or oil floats would never make it home after the first storm or the constant push of current had taken it away.
But it is easy to imagine ways in which tiny plants might arrange for their returns. The most obvious way is by letting themselves sink because the surface of the ocean is always being stirred. Water always moves into a patch of the sea as fast as water is taken away and for every leaving current there must be a current returning.
It seems likely that small plants can thrive in the open sea by following the currents round. It is possible, too, that they disperse in the air as well, being kicked out of the waves in spray and blown about the world oceans. Tiny plants can ride the currents to stay in home waters or travel the oceans to get back there. Large floating masses of vegetation cannot.
So, final hypothesis to explain the blueness of the sea is that large plants are excluded from it not by short commons in nutrients, but by the restless motion of the waters that would sweep them all away never to return. As it happens, fate has provided one intriguing test for the hypothesis in that there is one place in our contemporary ocean from which floating things are not swept away: the Sargasso Sea.
The Sargasso is at the center of a slow but enormous gyre, an oceanic whirlpool that gathers floating debris to its middle. This was so dangerous an area for sailing ships that legends have grown of ancient vessels, trapped by the remorseless swirling waters, rotting together far out in the Atlantic.
Columbus had his own grim meeting with the Sargasso, saving himself from the mutinous temper of his crew only by scooping a crab off the weed that floated alongside and claiming that the weed with its crab meant that land was near. But the land was a long way yet. The weed was the big floating brown alga we call Sargassum, and it floated thickly over the surface of the Sargasso Sea because the gyre held its population in place.
Sargasso weed floating about as straggling fragments can be found in many of the world’s oceans as can fragments of other species, oiFucus, and Ascophyllum, of any of the anchored coastal plants that bear floats and that might be tom up by storms. These floating fragments survive for a while as they drift, but they are all doomed.
They are not adapted to oceanic life; they cannot reproduce as they float about; they leave no offspring; and they die. But in the Sargasso Sea things are different. There the local species of Sargassum lives its whole life, reproducing, and persisting generation after generation.
Evidently this gyre in the oceans has persisted long enough for natural selection to produce from the chance debris of floating coastal algae a species able to carry on its life cycle as it floats. And the plant has done this in a patch of water notoriously unproductive in the sense of holding few nutrients.
The story of the sargasso weed leads us to believe that where it is possible for floating plants to stay put in the sea, we shall find large, floating plants. That we do not find them all over the oceans is because the oceans do not keep still. Natural selection then forces extreme smallness on the plants that are there, for the tiny ones are those best able to disperse about the seas.
If the surface waters are provided by conveyor-currents of nutrients in upwellings, or run-off from the land, or with delicious rivers of garbage like those that pour from the The Tiber, the Hudson, or the Medway, then the tiny plants will so multiply that the blue of the ocean is banished, and a green or turbid murk tells of vibrant life.
But if the sea is a nutrient-poor desert, like most of the world's oceans, then the tiny plants cannot be very numerous. There is then neither a canopy of floating vegetation nor a soup of tiny algae. Sunlight plunges deep into the water, it's fewer intensive rays being rapidly extinguished the while. Only the shorter wavelengths make the double journey to and from the depths. Which is why the sea is blue.
Reference: Paul Colinvaux
Why is Sea Blue? This is odd thing because sea is wet & spread out under the sun. It ought to be green with plants as the land but it is not.
Why Do We Grow Old? This question
often comes in mind, but no one has right answer. When Friends meet
after the passage of some years they probably remark, inwardly or
outspokenly. How time has altered the appearance if each. In the
ordinary way, people are not aware of growing older.
It is that sort of meeting that
makes them conscious of it. In each human body, physical and
psychological changes occur with increasing years. And a combination of a
number of these changes indicates the approach or presence of old age.
From about the age of 21 we begin to grow old. What causes; the gradual
changes, both external and inside the body. Which eventually lead to old
age?
Can Anything be Done to Delay this Process of Why Do We Grow Old?
The most familiar changes relate to
the external appearance of the body. The skin loses its elasticity and
bloom, becoming folded and wrinkled and flabby. The hair loses its
original color, becoming grey. Actual hair loss, producing baldness,
occurs more especially in men but also in women.
The muscles of the limbs and trunk
become weaker and thinner. It is causing a general appearance of weight
loss, while the bony parts of the skeleton become less dense with a
greater tendency to fracture. Wear and tear thins the discs between the
vertebrae of the spine, producing some shortening of stature.
The difference between three
generations of women is expressed not only in physical appearance but in
posture and style of dress.
A stooping posture, dim, sunken eyes, a wrinkled skin, grizzled
hair and beard such signs of age imprinted by a lifetime’s experience
nevertheless impart character to this head.
An elderly German obviously has no intention of resigning himself yet to becoming a mere spectator at the sports festival.
An old French woman concentrates on her knitting. Though the
joints may become stiff with age, long experience can make old people
very quick and deft at performing manual tasks. Poor muscle tone also
make an old person appeal shorter. A protruding abdomen or paunch may
result both from lack of tone in the voluntary muscles and excess fat in
the abdominal wall.
Facial appearance may be altered both by changes in the sheen of
the skin and by wrinkles but also by the presence of dentures replacing
decayed teeth. The individual’s own teeth may have been affected by
dietary habits and dental attention, but age does thicken the teeth,
producing a yellow appearance.
Glasses and Hearing Aids
Hearing aids and glasses are clues
to the fact that the senses are also affected by ageing. Changes in the
inner ear lead to a gradual loss of high tone hearing, making group
conversation difficult to follow. Whether a person is long sighted,
short sighted or normal sighted in younger years, advancing age alters
the eye lens and lens muscles.
This causes increasing difficulty in
reading small print, calling for correction by suitable glasses.
Sharpness of vision and night vision may also decrease because of age
changes in the light-sensitive cells in the retina at the back of the
eye.
The other senses of taste, smell,
touch and vibration become less efficient over the years but are never
completely lost unless disease of the nervous system supervenes. The
sense of pain is usually retained in old age, though its messages may
not be interpreted so efficiently by the brain.
Professional singers and political
orators become aware sooner than most that age affects the strength and
range and timbre of the voice. Thinning or the muscles of the voice box
and loss of tissue in its cartilages helps produce the change in voice.
Which may the universally felt dread
of old age finds harsh expression in a typically brutal caricature. Two
old people drinking soup become hoarse or high and piping. Dentures or
lack of teeth may also result in slurred speech. While brain changes can
affect what is said and slow the delivery.
Changes inside the body may be less
obvious but continue apace with advancing years. The linings of the
joints, particularly the weight-bearing joints like knees and hips, are
subject to wear and tear. This reduces the mobility of the joints, which
become stiffer, affecting walking and other movements.
In the digestive system there is
thinning of the stomach lining. But this has little influence on actual
digestion unless disease is present as well. Sometimes there is reduced
secretion of enzymes from the salivary glands and the pancreas, which
does interfere with digestion.
The kidneys produce urine normally
in old age, excreting the body’s waste products satisfactorily. There is
some gradual decline in the kidneys’ reserve function though, and the
old are vulnerable to any sharp decline in water intake. Such as may
occur in a debilitated old person living alone and neglecting diet and
fluid for some time.
With age, breathing becomes less
efficient, partly due to changes in lung capacity through loss of
elasticity. There may be thinning of the heart muscle with advancing
years and an associated reduction in working capacity. The actual heart
rate may be the same as in younger people or it may slow up, and there
is a greater tendency to irregular beats.
The shuffling or unsteady gait noted
when old people move about is one result of impaired co-ordination due
to changes in the 130 nervous system. This may he made worse by muscle
weakness and lack of tone and further exaggerated by disease.
In the female human body, the
ovaries cease to function at the menopause around the end of the fourth
decade of life. In the male human body, however, the testicles can
continue to function well into the seventh and even eighth decade.
This means that women cease to be
able to reproduce in middle age while men can continue to father
children into old age. In both sexes there is a gradual but steady
decline in sexual activity but the sexual urge can be well maintained
into old age.
Living in the past
The
overall physical picture of ageing in the human body is therefore one
of a general decline in vigor, in activity and in organ function.
Moreover, old people respond badly to extremes of external temperature
in particular, thin skin, poor muscle-shivering reflex and slower
blood-vessel contraction in the skin make them less able to tolerate
cold.
Contrary to popular notions, there
is no thinning of the actual blood with age. Where there is lack of
blood it is caused by dietary deficiency or disease. Changes in
mental powers have recently been studied more fully. Mental alertness
and fitness may be well preserved into later years.
There is a gradual and cumulative
deterioration in intellectual function as age advances. However
particularly with respect to new situations new ideas and new techniques
involving co-ordination and the power to adapt. The decline in memory
affects learned facts and recently occurring events especially, while
past incidents are well recalled. Artistic creativity is also likely to
fall off.
An important change in the
blood-vessels, known as arteriosclerosis (popularly called ‘hardening of
the arteries.), affects everyone as he grows older. The normally
elastic and supple arteries become narrowed rigid and twisted. As a
result the oxygen supply to the tissues through the blood is reduced and
degeneration and ultimate decay of cells. Tissues and organs ensues.
The actual age of onset of
arteriosclerosis is variable, some people may be affected in early
middle age. The severity of the condition also varies some people may be
affected more than others. Such factors as the presence of high
blood-pressure, or sugar diabetes are known to encourage the earlier
development of arteriosclerosis. When arteriosclerosis is associated
with etheroma degeneration of the inner lining of the arteries – it is
called atherosclerosis.
Doctors and scientists alike have
argued whether arteriosclerosis is a normal biological ageing process or
whether it is due to ill-understood disease factors. General opinion
favors the latter concept. And so further research may enlighten us on
its cause and treatment. What is certain, however, is that
arteriosclerosis speeds up normal tissue decay by depriving the ageing
tissues of an adequate blood and oxygen supply. This is especially true
in the case of the brain and heart.
While insurance companies can
calculate the expectation of life at birth for men and women,
calculation of the rate at which an individual ages overall is very
difficult. Different tissues and organs age at different rates in each
human body, and the rate of ageing of individual organs or the body as a
whole may in addition be altered by stress, disease, arteriosclerosis
or uncertain factors like radiation.
Looked at in biological terms, the
human body has several growth periods up to puberty. Followed by further
development in adolescence until the full peak is reached at the age of
21. At that age, for example, long-bone growth ceases and many consider
that true ageing begins shortly after this time. Since the expectation
of life at birth is around 68 years for men and 72 years for women. It
follows that men and women have a very long ageing period.
The social, cultural and
evolutionary value of this long-ageing period is immense. It allows
individuals to organize their lives in terms of studying and training
for different occupations. Then developing the knowledge and expertise
thus gained in their employment over many years. It allows the growth of
cultural group patterns – secular, ethnic and religious and long
periods of individual cultural attainment.
Moreover, it gives adequate time for
the development of social and sexual relationships, and consequently of
family units as the essence of stable societies. In an evolutionary
sense, wisents and grandparents are themselves it means that the
children born to parents potentially long-living. The maximum at
different periods in their lives will vary, human life wins, and we have
seen is about producing genetic mutation and adaptation.
Very few animals apart from turtles
which regulates length of life, however the bio tortoises, have a life
span greater than the logical time clock’. It appears to be built in 110
years which is the usually accepted genetically. When the individual
contribution are upper limit for a human being and many Man’s
evolutionary plan of pro-familiar animals, like dogs and horses, grass
is over, ageing and death arrive.
Have a life expectancy of less than a
third the improvement in the average expected the three score years and
ten which is the portion of life from 60 years in 1930 to over. There
appears to be no single main genes but to an environmental change the
cause of human ageing. What seems to better medical and surgical
treatment of happen is that a number of factors – disease and better
social and economic inherited physical, chemical, psycho conditions?
Logical and environmental varying
with there are several cellular theories of each individual – cumulate
to damage and ageing to explain some of the tissue and ultimately
destroy the cells and tissues. Organ changes already described. The end
result of ageing is therefore cells are capable of dividing indefinitely
inevitably death of the individual as a throughout life, the old cells
being shed as whole.
The nature of these ageing factors
scales while the new one, replace them it is understood in some
instances and still is known by analogy with what happen to the subject
of research in others. In cancer, that this capacity for dividing
Heredity appears to influence the in and renewing can be altered both by
dividable life span.
1 At nearly 90 years of age the many people retained his extraordinary vitality, creativity and influence in their profession.
2 In the stress-free atmosphere of a
rural immunity people may live to great ages. Accepted as a member of
society with an active part to play, this old Turkish farmer still finds
life good.
3 In old age there is some
stiffening of the limbs, allied with an insecurity in balance and
greater tendency to fall, which makes getting downstairs a hazardous
business needing help.
1 and 2 A full, strenuous and
momentous life has been responsible for the difference taken at the
beginning and end of any career.
3 Men can continue to father
children until late in life, and they are more like than women to marry
partners much younger than themselves. The ever-youthful film actor Care
Grant became a father for the first time at the age of 62.X-rays in the
case of the skin and by chance mutations.
As a result the new cells produced
by the ageing human during the division process are progressively
inexact copies of their predecessors, and their function is
progressively less satisfactory. Cells of the central nervous system are
unable to regenerate at all, and once lost at any time throughout life
are irreplaceable. Ageing of the brain and spinal cord can be thought of
as progressive loss of cells through ill health, infection or changes
in the blood supply.
A current theory of ageing is
derived from speculation about certain types of illness such as thyroids
and acquired hemolytic anemia. In these illnesses it is believed that
the body’s ability to distinguish its own tissues from foreign invaders
of the body, zilch as micro- organisms, is disturbed.
The breakdown in the
self-recognition mechanism results the production of antibodies rich at
ac the body’s own proteins. In tie diseases mentioned, is responsible
for the destruction of thyroid-gland tissue and blood-cell tissue. It is
thought that this auto-immune process could operate in ageing as well
as in cases of specific disease, gradual degeneration steadily extending
throughout the body.
The fact that a woman’s expectation
of life is greater by at least four years than a man’s has led to a
suggestion that sex hormones have an effect on ageing. While there is
some evidence that giving sex one to patients with chemical measurable
sex-hormone deficiency, makes them look younger.
It does not altogether fundamental
ageing process. Similarly, illnesses caused by hormone deficiency, like
hypothyroidism. Which produce illness with the features of old age, are
corrected by giving in this case thyroxin hormone, but do not alter the
basic ageing tendency.
An older idea, based on animal
experiments, relates the body’s metabolic act it sits or rate of living,
to the speed of the ageing process. Metabolism is related to hormone
function and also to temperature levels and diet. A famous experiment
with rat-showed that these creatures could be retarded in their growth
and development by persistent low-calorie feeding, and that they lives
could be abnormally prolonged in this way. This does not mean.
However, that human ageing can be
retarded in the same way; although the converse is true overeating
leading to obesity shortens life. There is no clear evidence that human
ageing is affected by temperature. Extremes of temperature however, act
as a stress factor adapted to them and stress is thought it to influence
ageing. Stress, pain, privation, and neglect may because of premature
ageing. Which is promoted by arteriosclerosis has noted earlier.
Why Do We Grow Old When Friends meet after the passage of some years they probably remark, inwardly or outspokenly.
As young as you feel the influence
of the mind on ageing is now being increasingly recognized. Apart from
the problems of adapting to the physical changes brought by age, such
causes of emotional disturbance as compulsory retirement from work,
bereavement, altered social role and economic anxiety may all contribute
to ageing. The absence of a positive function in old age can affect the
will to live and may accelerate the ageing process towards death.
From earliest times, Man has dreamed
of reversing the ageing process. Particularly with a view to sexual
rejuvenation, and of prolonging life indefinitely. The search for an
elixir of life by the medieval alchemists is one example of this
preoccupation.
The modern science of gerontology
studies the processes of ageing in animals and humans in order to
understand the difference between normal and disease-induced ageing. The
purpose is to determine the causes of normal ageing, and to see whether
the ageing processes can be retarded.
There has been no real progress in
the last-mentioned aim. Despite the widespread and uncritical use of so
called ‘anti-ageing’ drugs usually sex hormones, vitamins or procaine
derivatives no evidence of prolongation of the natural life span is
forthcoming.
The only real improvement has been
in the care and rehabilitation of the sick or disabled old person.
Nevertheless, some American enthusiasts are so sure of the success of
gerontology that they are considering suspended and by a ‘deep freeze
process called. Source: CP
For more than a decade, researchers trying to make sense of the mysterious degenerative brain disease afflicting football players and other contact-sport athletes have focused on the threat posed by concussions. But new research suggests that attention was misguided. Instead of concerning themselves with the dramatic collisions that cause players to become dizzy, disoriented or even lose consciousness, neuroscientists should be paying attention to routine hits to the head, according to a study that examines the root cause of chronic traumatic encephalopathy, better known as CTE.
“On the football field, we’re paying attention to the bright, shiny object — concussion — because it’s obvious,” said Dr. Lee E. Goldstein of Boston University, who led the study published Thursday in the journal Brain. But, he continued, “it’s hits to the head that cause CTE.” The disease is marked by abnormal deposits of calcium and proteins throughout the brain, as well as by neuropsychiatric symptoms that range from tremors and memory problems to depression and suicidal rage. For now, the only way to diagnose it is by examining a patient’s brain tissue after death. Some of the hits that cause CTE may result in concussion, Goldstein said. But his team’s findings show that concussion is not necessary to trigger the process. Indeed, the new research suggests that concussion and CTE are completely different medical problems.
In mice, head impacts that caused concussion and those that led to CTE had different effects inside the brain. In people, the symptoms tend to show up as different behaviors that became evident at very different times. In mice, the research documented immediate behavioral responses to head impact that ranged from zero to disability. And researchers captured what appeared to be the earliest moments of CTE in many mice that showed few if any immediate symptoms. That new research underscores that the kinds of “sub-concussive” blows to the head that many athletes routinely endure are far more worrisome than players, their parents and their physicians have been led to believe. Even as football programs from Pop Warner to the National Football League are adjusting their rules to reduce concussions, the findings suggest these efforts will not be enough to prevent long-term injury.
”You have to prevent head impact,” Goldstein said. The new work originated at Boston University’s Center for Chronic Traumatic Encephalopathy and drew in dozens of experts from a wide range of disciplines and institutions. The team began by inspecting the brains of four teenage athletes who died one day, two days, 10 days and four months after suffering serious head injuries. Those brains were compared with others belonging to teen athletes who died without a history of head injury. The researchers observed an abnormal buildup of a protein called tau — a hallmark of CTE — in two of the athletes who experienced head trauma. One, in fact, met the diagnostic criteria for early CTE.
That and other evidence led the researchers to hypothesize that early CTE may result from leaky blood vessels in the brain. In the deep recesses of the organ’s folds, these damaged blood vessels were letting proteins spill into nearby brain tissue, triggering inflammation, they surmised. To see whether they were right, they needed to study a population of subjects with greater rigor. So they built a machine to deliver calibrated blows to young male mice, subjecting them to a range of head impacts. The effects of these blows were recorded in imaging scanners, in test mazes and on pathology slides.
The researchers examined the animals’ brain chemistry, cortical structure and behavior. Finally, they performed computer simulations to repeat and extend their findings on how various brain tissues responded to head impacts. The results were all over the map. Delivered a powerful blow, some mice would reel from the injury for days but then recover. Upon dissection, their brains might even look fine. Other mice, including many who got a series of blows equivalent to participating in a single game or practice, would behave normally in the days following a head impact. But not much later, their brains would reveal early signs of tau protein accumulations.
Sure enough, these deposits appeared to start in the deep recesses of the brain’s folds, where the hallmarks of full-fledged CTE are most clearly seen in humans too. The results may explain why approximately 20% of athletes who were found to have CTE after they died had never received a concussion diagnosis when they were alive, Goldstein said. And they suggest that people who seem to bounce right back after getting their “bell rung” may well have sustained damage that will not be evident for years.
“The overwhelming majority of people whose brains are hurt are going right back in and doing the worst thing possible: getting hit again and again,” Goldstein said.The research was presented in New York City in conjunction with a new campaign from the Concussion Legacy Foundation to discourage the participation of kids under 14 in tackle football. Goldstein and foundation cofounder Chris Nowinski said that playing flag football before the age 14 would reduce injuries to young players while allowing them to learn the game’s fundamentals. They were flanked by NFL Hall of Famers Nick Buoniconti and Harry Carson and Oakland Raiders legend Phil Villapiano. Nowinski, a former professional wrestler who is now a neuroscientist at Boston University, noted that the U.S. Soccer Federation forbids kids younger than 11 from heading the ball, and that USA Hockey outlawed checking in the sport for kids younger than 13. Youth football leagues should follow that trend, he said.“Football has been open season on your child’s head from the time they’re allowed to play,” said Nowinski, who was an award-winning defensive tackle during his college days at Harvard.
Goldstein agreed. “We should be paying attention to all hits,” he said. “And in kids, all the hits should be no hits.” For some parents and coaches, that may be difficult to imagine. But studies like the one published Thursday should help drive the message home.
“Football coaches are coaching these kids to help them,” Nowinski said. “Their hearts are in right place. They just need to be educated about what scientists are finding. This is really preserving the future for football.”
The reliable Geminids meteor shower has returned to our sky and, with the Moon as an unobtrusive waning crescent before dawn, we are in for a spectacular display of meteors over the coming week.
Active between the 8th and 17th, the shower is expected to peak overnight on the 13th-14th, bringing more than 100 meteors an hour for an observer under perfect skies. Since high rates persist for more than a day, there should be an excellent show on the previous night, but probably less so on the next one.
The radiant point, from which the meteor paths appear to diverge, lies close to Gemini’s star Castor, which climbs from low in the NE at nightfall to pass high on the meridian at 02:00. Our chart spans some 100° from Leo to Taurus and is centred on Gemini, which stands to the NE of the unmistakable form of Orion. Of course, the meteors appear in every part of the sky – it is just their paths that point back to the radiant.
Travelling at 35km per second, Geminid meteoroids trace long sparkling paths as they disintegrate in the upper atmosphere. However, unlike some meteors, they rarely leave persistent glowing trains in their wake. The meteoroids are thought to derive from the 5km-diameter asteroid Phaethon, which is roasted every 523 days as it sweeps within 21 million kilometres of the Sun at perihelion – closer than any other named asteroid. Its rocks are thought to fracture in the heat, allowing splinters and dust to escape its tiny gravitational pull and spread out around its orbit.
Phaethon passes about 10 million kilometres from the Earth on the 16th in its closest approach since its discovery in 1983, though whether this will result in even more Geminids than usual is questionable. It should be a telescopic object of around the tenth magnitude as it speeds south-westwards from the vicinity of Capella in Auriga on the 11th, through Perseus and Andromeda to the Square of Pegasus.
Also plotted on our chart are Praesepe, the Beehive, in Cancer, and M35, at the feet of Gemini, which are both open star clusters just naked-eye-visible but easy through binoculars. Hydra the Water Snake, the largest constellation, stretches more than 100° around the sky from its head to the S of Cancer to the tip of its tail, which lies S of the conspicuous planet Jupiter in our SE predawn sky. The Moon stands above Jupiter and to the left of Mars on the morning of the 14th. Star-lovers and sky-enthusiasts can enjoy a meteor shower display on December 13 after 10 p.m., and in the early morning hours of December 14, if clouds and light pollution do not play spoilsport. Reach a spot without city lights, maybe the suburbs, and you can enjoy the Geminid meteor shower. Here, Dr. Debiprosad Duari, Director, M. P. Birla Planetarium, Kolkata explains meteors and the Geminid meteor shower.
The
overall physical picture of ageing in the human body is therefore one
of a general decline in vigor, in activity and in organ function.
Moreover, old people respond badly to extremes of external temperature
in particular, thin skin, poor muscle-shivering reflex and slower
blood-vessel contraction in the skin make them less able to tolerate
cold. 
