The Rebel Road…

I know you’ve come to kill me. Shoot, coward, you’re only going to kill a man. – Ernesto Che Guevara

Evolution explained.

with 3 comments

“When the views entertained in this volume…are generally admitted, we can dimly foresee that there will be a considerable revolution in natural history” — Charles Darwin, The Origin of Species (1859).

Evolution has, ever since its conception, proven to be the cornerstone of contemporary biological studies. It unites all the fields of biology on one platform. The theory of explaining what form we have acquired over the millennia and thus predicting, using intelligent resources, what could happen if certain conditions were allowed to prevail is extremely valuable. The layman is quite confused about the actual definitions of biological evolution. This is primarily attributed in large part to the inability of the scientists to communicate effectively to the general public and also to confusion among the scientists themselves about how to define such an important term.

When discussing evolution it is important to distinguish between the existence of evolution and various theories about the mechanism of evolution. And when referring to the existence of evolution, it is important to have a clear definition in mind. What exactly do biologists mean when they say that they have observed evolution or that humans and chimpanzees have evolved from a common ancestor?

In this regard, evolution has been defined by Mr Douglas J. Futuyma in his book Evolutionary Biology. He says:

“In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political systems all evolve. Biological evolution…is change in the properties of populations of organisms that transcend the lifetime of a single individual. The ontogeny of an individual is not considered evolution; individual organisms do not evolve. The changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest proto-organism to snails, bees, giraffes, and dandelions.”

Having defined evolution it must also be made clear how it functions in the lifecycles of living things. Plants and animals are the most basic categories in which we can classify any living organism, though of course more specific categories do exist.

The first organisms ever to appear in the oceans were single celled organisms that would probably fall under the classification of bacteria. As these bacteria evolved, perhaps some of them felt the need for more nutrition, or rather self-sufficiency in the nutritional department. It is thought that chloroplasts themselves were separate organisms that developed a symbiotic relationship with these bacteria. Gradually these bacteria transformed into algae by the acts of mutation or variation that might have occurred over the generations. Algae soon clumped together. As more and more ozone was formed in the upper atmosphere and the earth itself achieved its stable form of today, it cooled down, and due to the new ozone layer it was not bombarded by as much radiation and heat as it was before. This meant that the algae could come closer to the surface and flourish in the now cooler climate. The plant lineages have deep roots dating to the original dispersion of organisms onto land some 400 to 450 million years ago. These original plants were still tied somewhat to water, particularly for replication, just as amphibians were and are today. However, just as the reptilian lineage arose from the amphibians, terrestrial plants also developed from these early, water-tied terrestrial plants. And just as with the reptilian lineage, the truly great innovation was the development of methods by which sex and development were accomplished in the absence of standing water. Once the methods of asexual and sexual reproduction were established, the remaining part was to optimise the organism for maximum benefit from the environment. It is thought that fauna and flora have gradually become smaller or at least more dense and compact in comparison with more modern organisms. Perhaps this is because of the fact that the smaller size requires lesser energy to maintain and hence, increases the chances of survival.

In conjunction with plants developing from primitive bacteria, so did animals. As certain bacteria were made, according to their niches, to integrate a system of self-sufficiency, others were forced due to natural conditions to equip themselves with ingestion systems that could eat and derive energy from other organisms. Over time the complexity of the organisms increased. Multi-cellular organisms came into being. As time passed, this increasing complexity led to the development of primitive fish. Soon the population in the water grew to such an extent that the pressure for survival pushed the fish to find sources of nutrition outside the water. For this purpose, specialised systems had to be developed whereby the fish could breathe outside the water too. The first fish to develop lungs were the lobe-finned fish called ‘Crossopterygians’ and the lungfish called ‘Dipnoans’. At first these fish came out of the water for small periods of time to get food and rush back. But soon these time periods increased. This led to the creation of amphibians, who could live both on land and in water. These animals had almost fully developed lungs and the capability like modern frogs to breathe underwater through their skin. Their stronger skins also allowed them to withstand more heat and the perils of land life effectively. Limbs were perhaps perfected in this period of evolution. The tail was basically used for balance. As time went on, the nostrils of the amphibians became more pronounced and increasingly functional for breathing. They developed hands and feet with three or five digits and their backbones become stronger, allowing them to grow even bigger. Soon they developed eardrums and the ability to hear sound. Around 325,000,000 years ago the amphibians started to change into reptiles. These reptiles were faster, stronger and bigger than amphibians and more land-based. They developed stronger exoskeletons. Early reptiles were plant and insect eaters, but as their size grew, so did their ferocity. Another trait developed by reptiles was the ability to lay shelled eggs on land.

The next link in the evolutionary chain was that of the birds. When the survival-pressure grew too high for reptiles, they developed what resembled wings and took to the skies. They could reach higher parts of the trees and in doing so get the fruits that others could not. When the environmental pressures grew too much, the reptiles (cold-blooded as they are) needed a system with which they could regulate their internal environments effectively. This system was inherently present in mammals, which were warm-blooded.

Although it may seem that evolution always does the best for the organism, this might not be the case in all cases. The term overspecialisation refers to an organism becoming so evolved and suited to an environment that if it is removed from that environment it dies. And we can only hope that we as human beings have not become overspecialised or our dream of colonising other worlds will truly be a short-lived one.

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Written by redtribution

October 15, 2007 at 5:41 pm

3 Responses

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  1. Commendable for you to defend evolution so. Your descriptions are a bit on the very simple side, however. I wish you had provided some links to some good sites on evolution, say, like Berkeley’s Evolution Gateway:

    http://evolution.berkeley.edu/

    Good luck!

    Ed Darrell

    October 21, 2007 at 10:18 pm

  2. Mr. Ed,

    I realize that it is a simplistic explanation but that is by choice. Pakistan is a country where the whole concept of evolution is not really taken seriously – Half the population doesnt know what it is to begin with and the other half believes that Islamic Creationism is the way to go.

    In order to introduce the concept to the layman evolution must be over-simplified.

    However, I do agree with the point you raised that more links could have been added. I’ll look up some good ones and do that soon.

    Thank you for your kind interest,

    Regards,
    Mobeen Chughtai.

    redtribution

    October 22, 2007 at 11:05 pm


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