Truth That Matters

"What will it profit a man if he gains the whole world, and loses his own soul?" - Jesus Christ

Change in organisms

This article will examine the various types of change that occur in organisms, some features of that change, and the conclusions that can be drawn from these features. Classifying types of changes in organisms is a bit messy because there are two ways to define change: you can define change in terms of how the organisms look (the phenotype) or on how their genes are (the genotype). Change in the genotype often results in change in the phenotype, but not always, and sometimes the connection is not clear.

Changes in phenotype without a change in the genotype

Change in population due to environmental pressure: Black peppered moths are likely to survive better in areas where the tree barks are black, and white ones will survive in localities where the tree barks are white (this is due to camouflage, which protects the moths from being seen by birds - see image). If the tree barks change in color, so will the relative numbers of the moths. In pre-industrial England, the tree barks were white, and so the moth population was mostly white. When the trees got covered with black soot, the moth population became mostly black. Here there is no change in a given organism, just a change in the population. This change is due to different traits having different survival value.

Change in population due to cultural factors: The environment directly affects the development of the organs in an organism. For instance, if a plant becomes extinct in an area, so its soft seed is no longer available for rodents, and they have to do with hard seeds (or the soft seeds are still there but the rats think hard seeds are tasty), the rodents will develop harder, more muscular jaws. There is no change in the genes here, but the flexibility within the genes is being exploited to produce this change.

Varied offspring: Here I'm referring not so much to a change in an organism, just the fact that offspring are not identical to their parents. Traits in an organism are coded for by genes. Each human mother and father contributes 35,000 genes to the offspring. In many cases, one gene always dominates over the other, or both have a combined effect, but there are about 2345 heterozygous loci, that is gene locations where there is an appreciable probability for either the father's or mother's genes to be selected. Thus, a given father and mother can produce 2 raised to 2345 different children. That's 1 followed by 706 zeroes. Thus, there is a lot of scope for variation among humans today. Similar arguments apply for other animals. Since specialization increases with the number of generations, the original animals would have a much higher potential for variation. [The information here is taken from Francisco Ayala, The Mechanisms of Evolution, Scientific American 239(3):48-61, September 1978]. Hybrids are a special case of this type of change. If you cross a lion and tigress, the offspring has some tiger genes and some lion genes, and looks a little different from both its parents.
 
Note that in all these cases, no new information is being added to the gene pools of the organisms involved.

Changes due to point mutations

Mutations are changes in genes that take place while they are being copied during reproduction. Point mutations are mutations involving a change in just one nucleotide (a "letter" in DNA language). The following are the changes due to point mutations.

Sickness and malfunction: Most mutations lead to serious illnesses and deformities.
 
Bigger and better organisms: The protein yield of wheat can increase. This has been found to be due to mutations in genes that control the making of proteins. [Konzak, C. F. (1977). "Genetic control of the content, amino acid composition and processing properties of proteins in wheat", Advances in Genetics, vol 19, pp 407-582]. There are genes responsible for making the protein, and regulatory genes that inhibit the production of the protein after it reaches a certain value. Due to mutations, the regulatory genes are degraded successively, and this prevents them from playing their inhibiting role - thus, higher and higher levels of protein are obtained. The degradation of regulatory genes involves a loss of information, and thus has negative side effects (less starch per seed and less grain per planting - see Brock R. D (1980). "Mutagenesis and Crop Production" in Carlson, P.S., the Biology of Crop Productivity, New York: Academic Press pp. 383-409).

Drug resistance: Antibiotics work by attaching to the ribosomes (protein manufacturing molecular machines) in bacteria. The ribosome then cannot do its job, and the bacteria cannot multiply. If however a mutation occurs, the shape of the ribosome becomes different, and the antibiotic cannot attach to it. There is an important observation to make: several ribosome shapes prevent the antibiotic from attaching. Thus, the mutant ribosome is less specific than the original one, and this means that drug resistance involves a loss of information. Further discussion

New diets: In an experiment [Mortlock, R.P., "Metabolic acquisition through laboratory selection", Annual Review of Microbiology, volume 36, pp. 259-284], researchers denied soil bacteria their usual nutrients, namely, ribitol and D-arabitol, and tried to get them to eat xylitol, a similar molecule that however, does not occur in nature. At first the bacteria starved, but subsequently, a series of three mutants appeared that could digest xylitol with increasing efficiency!  Why did the bacteria starve initially? There are three reasons:-

Problem 1: The production of the digestive enzyme RDH is triggered only by the presence of ribitol, so it is not made when only xylitol is present.
Problem 2: Although RDH can help digest xylitol, its activity on xylitol is much less than that on ribitol.
Problem 3: Foreign molecules cannot penetrate through the bacteria's cell walls easily. Ribitol triggers the production of a "permease enzyme" that allows it entry. There is no transport system for xylitol.

So how did the first mutant bacteria work?
Problem 1: A mutation damaged the triggering mechanism for the production of RDH. So although ribitol was absent, RDH was produced uncontrolled.
Problem 2: The large amounts of RDH produced made up for the low activity on xylitol
Problem 3: Although xylitol has no transport mechanism, a small amount does get in by diffusion.

Now for the second mutant:
Problem 1: No further development
Problem 2: Another mutation changed the RDH and made it more active on xylitol. Further investigation showed that the mutant RDH is less specific - it is more active on xylitol and L-arabitol, and less active on ribitol. The original RDH is highly active on ribitol, and very less active on xylitol and L-arabitol
Problem 3: No further development

We also have the third mutant:-
Problem 1: No further development
Problem 2: No further development
Problem 3: A permease enzyme exists for D-arabitol, but its production is triggered only by the presence of D-arabitol. A mutation destroyed the control switch, and thus the enzyme was produced even though no D-arabitol was around. Although this enzyme is intended for D-arabitol, it works on xylitol also, and thus xylitol gets a free ride into the cell.

Notice that in all cases, the mutations involved a loss of information. [I've been very brief here. For a detailed and illuminating description, refer to Lee Spetner, Not by Chance, p148-159]

Change due to non-point mutations

Non-point mutations are substantial changes to the genome of the organism such as:-

  • Inversions: A precisely engineered inversion in a gene sequence can change the organism from one state to another.
  • Transposition: Segments of genetic material can shift from one location to another. As a consequence, several genes get turned on or off.
  • Deletions: Part of the genetic sequence is deleted. This can also turn several genes on or off.

What phenotypic change does this genetic change result in? The following are some examples from bacteria. More research will probably furnish more examples with other organisms.

Drug resistance: The salmonella bacterium demonstrates inversion about once in every 10 generations. This changes the proteins present in it. This helps it avoid the immune system of its host.  Drug resistance can also result from transposition.

New enzymes: John Cairns and his team at Harvard University kept some bacteria in lactose. These bacteria had a defect in the gene encoding for lactase (the enzyme that enables the digestion of lactose). So the bacteria starved. But a few of them managed to survive. Cairns concluded that there was a mutation that converted a gene to one that digests lactose. He wrote: "The cells may have mechanisms for choosing which mutations will occur....Bacteria apparently have an extensive armory of such 'cryptic' genes that can be called upon for the metabolism of unusual substrates....E coli turns out to have a cryptic gene that it can call upon to hydrolyse lactose if the usual gene for the purpose has been deleted. The activation requires at least two mutations...That such events ever occur seems almost unbelievable." [See Cairns, J, J. Overbaugh and S. Miller (1988). "The origin of mutants", Nature, volume 335, pp 142-145]

Note: Insertions, transpositions and deletions in the genome, and the switching on or off of sections of the genome amount to shuffling of information already present in the genome.

Is the change random or non-random?

Here's how we check if an event is random or not:-

  • Find the probability that the event occurs randomly.
  • This probability can be used to calculate the probability of the event occurring repeatedly or, the expected time before it occurs a specified number of times.
  • Compare these figures with the actual occurrences of the event. If it occurs far more often or sooner than predicted, it means that the event is not random. Someone or something is deliberately making the event happen.

We can now understand Cairns using the word "unbelievable". The probability of the mutations occurring randomly was so vanishingly small, that Cairns didn't expect to see it. But there it was - so soon. It is unbelievable if we assume that these mutations are random. On the other hand, there is nothing  unbelievable if we assume that the bacteria itself decides what mutation will take place depending on the environment. In another similar experiment, probabilistic calculations showed that it would take more than a hundred thousand years for the mutant bacteria to appear. However, within a few days, forty percent of the bacteria were mutants! [See Hall, B. G., "Evolution in a Petri dish: The evolved beta-galactosidase system as a model for studying acquisitive evolution in the laboratory", Evolutionary Biology, vol 15, pp 85-150.]

Conclusion: Most, if not all, non-point mutations are not random. Organisms have a variety of genetic states built into them - they decide which state to adopt based on the environment. This means that the change in question is being brought about by the use of genetic information that is already present in organisms.

Is the change slow or fast?

This question is related to the previous one. Remarkable events occurring randomly take place after a long time, but they take place quickly if they are being doctored. If there are a million lottery tickets in the annual lottery, your chance of winning is one in a million. This means you may have to wait a trillion trillion years to win four lotteries in a row. So if you win four times in the next four years, I'll suspect you're rigging the system.

As we've observed above, bacteria mutate extremely rapidly, and this strongly suggests that the mutations are not random. Here's another example of rapid change:-

About 100 finches (a class of birds) were transferred in 1967 from Laysan Island in the Pacific Ocean to a group of four closely spaced islands about three hundred miles away. Within 20 years, the finches had diversified into different species, depending on the island. The image illustrates a similar speciation that Darwin observed [he only saw the descendant species, not the ancestors]

How did this happen? We don't know, since no one was observing the birds closely enough for twenty years. But the high rate of change gives us possible explanations.

  • It could be that the variety in offspring is large enough to account for what is seen in the new habitats. That is, the same finch pair can give rise to offspring with a variety of traits, such as beak size. Offspring with large beaks survive better where the seeds are hard and large, while offspring with small beaks survive better where the seeds are small, and so on. This leads to different finches on different islands.
  • It could also be that a non-random mutation could have switched some genes on or off in response to the new environment, producing the variation (as happened with the bacteria).

Whatever be the case, one thing is sure: twenty years is far too small a time for natural selection and random point mutations to produce significant changes such as increased or decreased beak size.

To summarize: a lot of change in organisms occurs extremely fast.

Conclusion

We have seen that:-

  • Organisms undergo a lot of change, some beneficial, and some detrimental.
  • Some beneficial change is random, but it leads to a decrease in the information in the genome. [The first example of drug resistance above, and the bacteria that learned to live on xylitol]
  • Some beneficial change can be very fast, and it occurs just when needed [the non-point mutations].
  • This indicates that it is not random, but that the organism already has mechanisms inbuilt to control this change.
  • This means that the change does not occur due to the gradual accumulation of the information in the genome of the organism - it is rather due to the shuffling of already existing genetic information.


This means that the observed change is:-

  • not the kind of change that can make goo to a cell [this needs the generation of information, but goo doesn't have genes and doesn't reproduce; goo only undergoes chemical reactions, which don't generate information]
  • not the kind of change needed to turn bacteria into horses and people [this requires the generation of massive amounts of genetic information]
  • just the kind of change needed to convert the 8000 or so kinds of animals on Noah's ark  to the millions of species we see today!
  • just the kind of change needed to turn good micro-organisms into pathogens within a few thousand years
  • just the kind of change needed to make humans weaker and short lived compared to their ancestors a few thousand years ago

In other words, the observed change is:-

Thus, the change we see in organisms is strong evidence against evolution theory (the goo to you kind), and strong evidence in favor of the Bible.