Science in Christian Perspective

Entropy in Relation to Genetics

WILLIAM J. TINKLE
Albany, Indiana

From: JASA 7 (December 1956): 18-20.

Thermodynamics, the mechanical theory of heat, dates from Sadi Carnot, 1824. It deals with the trend in the manifestation of energy when heat flows from one body to another, or is transformed to another form of energy.

The first law of thermodynamics usually is stated as a special wording of the law of conservation of energy, as follows: When energy is transformed, equal units of another form of energy appear. This principle, implying that energy at present is neither created nor destroyed, has of course been recognized a long time; and tit recent years, atomic investigation has added the principle that matter may be changed into energy and vice versa.

The second law of thermodynamics is not easily stated in few words, but in its simplest form it carries the idea that heat tends to pass, from a hotter body to a colder one, as water flows down hill. Clauisius in 1850 stated the law in these words: "It is impossible for a self-acting machine to convey heat from one body to another at a higher temperature." Lord Kelvin in 1851 used more exact and practical language as follows: "It is impossible by means of any continuous inanimate agency to derive mechanical work from any portion of matter by cooling it below the lowest temperatures of its surroundings."

To use a familiar example, it is when heat is flowing from the fire box to the flues in a steam engine that this machine can perform work. The heat changes the water around the flues into steam, which moves the piston and turns the wheels. If the temperature of the fire box were less than the temperature of the flues, beat would not flow to the flues and no work would be done.

Heat leaves the engine by radiation or convection into the atmosphere, or else is changed into friction in the bearings and belts of the machinery. In obedience to the first law of thermodynamics, this heat is not destroyed; while in obedience to the second law, it enters a body of such a low temperature that it can not flow into any cooler body, and thus, no longer can do any work. So far as man is concerned the heat has been lost, through its degradation.

Entropy is a measure of this degradation of heat or other energy. Since heat always flows from a higher to a lower temperature, a body that gains heat always gains more entropy than is lost by the body losing the heat; hence, with every flow of heat the total entropy

Thus the second law of thermodynamics describes a world which is running down, as illustrated by its available energy. Psalms 102: 25-27 is in broad treatrnent, for it describes a world which wears out: 

"Of old thou didst lay the foundation of the earth, and the heavens are the work of thy hands. They will perish, but thou dost endure; they will all wear out like a garment. Thou chang est them like rainment, and they pass away;
but thou art the same, and thy years have no, end."

Isaiah 50:9; 51 :6; and Hebrews 1 :10, 11 state the same principle.

In opposition to all that has been stated above, General Smuts made the claim that the trend of the universe is upward. "The evolution of the material universe, and of life on this globe seems to be, in part at least, a negation of the second law of thermodynamics, the law of the dissipation of energy."¹ Similarly, the present writer remembers a claim which was made in a class in the Ohio State University that living things are all exception to this law.

The late T. 1-1. Morgan does not wholly agree with General Smuts. He writes that when a plant leaf makes starch from carbon dioxide and water in the presence of chlorophyll, it can be shown that the sunlight used was a greater amount of energy than the chemical energy stored in the starch which was made.² While I do not know that such a test has been made, Morgan doubtless is correct. Plant and animal metabolism regularly follows the laws of chemistry and physics, including the second law of thermodynamics.

If, then, the physiological processes are not unique but involve the accumulation of entropy just as engines do, the supposed evolution of living things is claimed to be very unique. It is placed in a corner, in a class by itself.

The question under discussion is this: Is there a broad agreement between the organic realm and the principle of accumulation of entropy? Is the world of living things building up or running down? Answers might be received from different branches of science, but in this paper genetics is employed because it deals with heritable changes.

As originally postulated, the theory of organic evolution contained the idea that plants and animals have been built tip gradually from simple to complex forms. In recent years, inen such as Simpson, Goldschmidt, and Dobzhansky recognize that many observed changes restilt in greater simplicity and less adaptation,³ yet they include these changes in evolution.

Their frankness is to be admired, but these men are weakening their theory. For the idea of progress is an essential part of the doctrine of evolution and in the nature of the case it must be so, if one says that the present complex, symmetrical, well adapted living things started as simple slime in the sea.

Then if evolution be proved, the organic world does contradict the second law of thermodynamics. But what do the careful and oft-repeated tests of genetics contribute as to the direction of the changes?

Genetics deals with changes which result in types of animal or plant life that reappear generation after .,eneration, a process such as growth, which affects but one generation at a time, without cumulative effect, does not affect the upward or downward tendency of living things, This subject was discussed in my paper, "The Principle of Growth as an Obsession", which was read at the 1953 Convention.

Pure lines of plants, which are developed by man's selection rather than appearing in nature, are significant indicators of the natural trend. Joharmsen's work⁴ with the Princess bean was discussed by the present author in "Modern Science and Christian Faith", second ed. p. 72f. Johannsen's method of starting a pure line was the saving of the progeny of a single bean seed. Since bean flowers naturally are self pollinated, this group or pure line of bean plants had identical ancestry. The genes of one plant were just like the genes of any other member of the pure line, and any difference between the plants was caused by their environment. Their likeness was proved by the fact that selection within a pure line was not effective, but small beans when planted produced the same size of seed as large beans, on the average.

Pure lines have been developed in other species of plants, with the same results. ]it a species which normally is cross pollinated, such as corn, Zen mays, the process takes longer but after six generations of inbreeding, strains of corn are developed which are nearly pure lines. In a pure line of any kind of plant there is so much hogogenity that selection makes no difference in the progeny. For instance, C. D. LaRue selected within a pure line of Pestalozzia gniphzi, a kind of ftingus.⁵ For ten generations he planted the longest spores, but the plants of the tenth generation bore spores of the same length as the plants of the first generation. He selected for length of spore appendages during twenty-five generations, but found this selection equally ineffective.

Stich stability in pure lines would not be observed if genes changed gradually, either for the better or for the worse. Genetics has demonstrated, however, that genes in all plants and animals have this stability. Pure lines are chosen as an illustration because of their simplicity; in them, extraneous factors do not confuse the picture. When a gene changes at all it suddenly mutates. Such changes do occur, although rarely, and will he discussed below.

Sometimes we hear farmers or gardeners say that a certain variety or strain "runs out". In many cases this is due to disease, and is most likely to occur in plants which are propagated by vegetative methods, such as cuttings, sprouts or bulbs. In such propagation the material connection between generations is larger than seeds or spores, with the result that bacteria or hyp hae of disease are carried readily.

A new connibination of characters such as usually follows a cross of two strains is a genetic change. Yet it does not involve a change in a gene nor even tit the number of genes, but brings genes together which formerly were in different plants or animals. In many instances a cross results in heterosis or hybrid vigor. But since this added vigor lasts but one generation, it has but little, bearing on our subject.

The discussion so far in this paper reveals a horizontal tendency in animate nature. It is true that the bodies of old animals and plants wear out but in the next generation the material and vigor of the new organism are built tip to the former standard, on the average.

But we must not overlook the exceptional occurrences, the heritable changes. In addition to the sudden change or reorganization of a gene called a mutation, there are changes which do not involve change in individual genes, but differences in their number or arrangements. Since a chromosome may be regarded as a row of genes, an unusual number of chromosomes results in an abnormal number of genes, and this makes changes in the characters of the plant. These exceptional forms have been observed in the primrose, Oenothera, the jimson weed, Datura, and the tomato, Lycopersicum. A plant having half the normal number of chromosomes, called a haploid, has greatly reduced vigor but with special care may live. If a haploid plant produces seeds (which it hardly would do in nature) these seeds become normal diploid plants and the haploid type ceases to be.

A few triploid plants have been observed to make their appearance, a type having three times as many chromosomes as the haploid or one and one half times as many as the normal diploid. It also has reduced vigor, and if it produces offspring they are not of its type.

Plants having an extra chromosome, the trisoinic or 2n + 1 type, havo less vigor than normal diploids. As for the 2n + 1 type, A. F. Blakeslee wrote the author that in his work with Datura at Cold Spring Harbor he observed only one such plant and was not sure of it. To produce such a plant, one gamete would have no chomosome of one of the pairs; but it seems that such a gamete could not live.

A number of tetraploids, plants having twice the normal number of chromosomes, have been observed, and superficially they represent an improved type. Such a plant has a stocky appearance because of the thick stems and leaves but the height is no greater than the diploids and it bears fewer seeds. While it usually reproduces its type, it tends to die out in nature if competition with the normal type is keen.

A typical group of tetraploids are the ones produced in muskmelon, Cucionis melo, by Batra, using 0.4 per cent of colchicine, which he applied upon the seedlings in the cotyledon stage.⁶ The tetraploids formed thus had larger leaves, flowers, stomata, pollen, and stem diameters than the diploid plants. But the fruits were smaller, the entire plants only half as large, and" characteristically they bore only 24.3 per cent as many plump, viable seeds. While the taste of the tetraplo4l is preferred, the plants are inferior from the standpoint of getting along in nature.

It is commonly mentioned that tetraploids and other polyploids are found in nature. For instance, the three common species of whcat have 7 pairs, 14 pairs, and 21 pairs of chromosolm-, , respectively. In chrysanthemums the numbers range from 9 pairs through 18, 27, 36, and 45 pairs in different species. But since we do not know how these types arose we can not state whether the changes- -if such occurred-resulted in, improvement or detriment. The changes in chromosome number which have been observed to occur have not been beneficial to the plants.

Concerning gene mutation and the resultant mutant types which are formed, there Las been much discussion. Geneticists are agreed that the majority of mutant types are inferior to their normal ancestors from the standpoint of getting along in the world. Of course some mutant strains are prized by man, for instance seedless oranges, stringless beans, and hornless cattle. At the Connecticut Agriculture Experiment Station a mutant tobacco plant⁷ appeared which grew so tall that it produced twice the normal number of leaves. But since this added growth was accomplished by a postponement of seed bearing, the lack of seeds was more of a loss to the plant itself than the added leaves were of gain. While it may be that some mutations confer neither an advantage nor a disadvantage, they characteristically reduce the vigor and often subtract some character.

There is no space in this paper to give a list of harmful mutations nor even to give a critical evaluation of the few which have been claimed to be beneficial. The best that can be done is to discuss the nature of such changes.

H. J. Muller, who won the Nobel prize for his work on mutations, at Washington was cornered by a group of newspaper men who asked him to discuss the outlook of improving the human race. He answered, "Most mutations are bad. In fact, good ones are so rare that we can consider them all as bad.⁸"

Now it might be said that beneficial mutations are being overlooked; that it is not enough to say that we have not found them. But Austin Clark of the U. S.

". . . a suotraction of something. Those differing National Museum says they naturally are defective; widely from the normal can not develop past the embryo."⁹ Dobzhansky also states that mutations which differ most from the normal are the least viable.¹⁰ It should be apparent that if the biggest changes are the worst, it must be that mutation is naturally a deleterious process, and we are not simply overlooking the good ones. That is, the general tendency of mutation is unfavorable, and a plant or animal is better off if none occurs. Julian Huxley also agrees, stating that the larger the change the less likely it is to be an improvement.

Conclusions

0bservation of the working of heredity in plants and animals shows that there is broad agreement between the organic realm and the second law of thermodynamics. There is not strict agreement, for while the loss of energy in a mechanical system 1 s gradual and continuous, just as a garment wears out, the loss of vigor in a living strain is noted only when a genetic change occurs. An animal such as the bracbiopod, Lingida, which has not manifested any change since the Silurian Period probably never has suffered any loss of vigor.

The improvement of plants and animals by man agrees with thermodynamic laws. This improvement has its counterpart in the refrigerator, which is cooled by forcing heat out of it by means of an electric motor, If left to itself, heat would flow into the refrigerator from the surrounding warm air. In like manner, the improved breeds and varieties developed by man lose their identity if left to reproduce in wild areas.

The facts cited above indicate that creation was a unique process, building up a universe which has been running down since that divine event. The Bible, the laws of physics, and the laws of genetics agree that the universe is running down, except as conscious human effort or divine intervention reverse the decline. The organic realm is not an exception.