A Look at the Evolution Model

I readily admit that the following on evolution may be a bit dry but I tried to present the evolutionary model as fairly as possible and, as such, have used material from web sites which present evolution.

The Evolution Model

After doing a Google search of more than 200 entries on the internet, looking for a precise definition of the evolutionary model, I came up with only two sites that somewhat explain the evolutionary theory. They can be found at psychcentral.com/psypsych/Evolution#Scientific_theory and wiki.cotch.net/index.php/Evolutionary_theory. Both sites really only take in a segment of the whole evolutionary theory and do not lay out the entire theory in a nutshell. Many of the sites were defending their theories whether evolution or creation with a lot of rhetoric. Many other sites went through the history of the evolutionary theory quoting from Aristotle to Lamarck to Darwin to current refinements of the evolutionary theories. Evolutionists define evolution as a change in life forms all of which have a common ancestor. Most rest on Darwin's theories which have these elements in common.

Mutations. A change in genetic code known as a mutation consists of changes in the hereditary instructions contained within a gene. A mutation, the ultimate source of all genetic variation, must occur in reproductive cells to cause genetic change in offspring. The process of mutation involves random genetic change primarily due to chemical factors and ionizing radiation.

Gene Flow. The movement of genes from one population to another, describes the process of the loss or gain of genes in a population due to the emigration or immigration of fertile individuals, or the transfer of gametes, between populations. This process introduces new genes into a population resulting in populations becoming more similar to one another.

Genetic Drift. The process of genetic drift, dealing with chance preservation or extinction of particular genes, may be defined as a variation in the gene pool, a change in allele frequency, in a small population due to chance.

Natural Selection. The process of natural selection refers to the differential survival and reproduction of organisms as a result of their biological characteristics.

(The above was taken from www.bibarch.com/concepts/Origins/evolution.htm) To put all this into a simple package, life forms change with time because of mutations (which is a change or error in the genetic code), gene flow (where new genes are introduced into a different gene pool), genetic drift (where genes, by chance, disappear as in losing the master document and relying on photocopies of photocopies until much of the original information cannot be seen anymore), and natural selection (which is similar to survival of the fittest, where the thing which adapts the easiest to a new situation will survive) The above theory, as mentioned before, only takes in a portion of the whole evolutionary theory. It looks at only the portion that deals with living organisms. But where did the living organisms begin? Where did the Universe begin? To answer this we need to go to the Big Bang theory.

The Big Bang Theory

Presentation of the universe according to inflationary cosmology.

The Big Bang Theory is the dominant scientific theory about the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.

In 1927, the Belgian priest Georges Lemaitre was the first to propose that the universe began with the explosion of a primeval atom. His proposal came after observing the red shift in distant nebulas by astronomers to a model of the universe based on relativity. Years later, Edwin Hubble found experimental evidence to help justify Lemaitre's theory. He found that distant galaxies in every direction are going away from us with speeds proportional to their distance.

The big bang was initially suggested because it explains why distant galaxies are travelling away from us at great speeds. The theory also predicts the existence of cosmic background radiation (the glow left over from the explosion itself). The Big Bang Theory received its strongest confirmation when this radiation was discovered in 1964 by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery.

Although the Big Bang Theory is widely accepted, it probably will never be proved; consequentially, leaving a number of tough, unanswered questions.

Updated December 2, 1997. Contacts

To put this into simpler form, a "primeval atom" exploded which sent debris from the explosion out into the vastness of space from which all the stars, planets, and galaxies evolved from. As to where this "primeval atom" came from we will look at later. This theory may explain the origins of the universe but it does not explain the origin of life. One of the key natural laws is the law of biogenesis or, simply put, the law which states that life can only come from life. Obviously in a big bang situation life was not present. To answer this problem, evolutionists believe that in one instance, and one instance only, life came or began from non life. This is called the theory of abiogenesis or, in other words, outside of the law that life comes from life. The evolutionists believe that conditions existed on early planet earth where amino acids were created which then evolved into single cell organisms, which evolved progressively into higher and higher organisms through mutations, gene flows, gene drifts, and natural selection

Macro Evolution vs. Micro Evolution

Two terms of evolution need to be clarified. The evolution model contains both macro and micro evolution while the creation model only contains micro evolution. Macro evolution refers to a jump from one kind to another such as a reptile becoming a bird. Micro evolution, on the other hand, deals with changes within the same species. This can be explained by the various dog varieties or other animal varieties that have changed in appearance but are still the same species. There is no hard evidence that macro evolution has occurred, is occurring, or will occur.

Animal Evolution

Classification

More scientists have started to base evolutionary studies more on genetics, botanists and zoologists classified organisms into different categories based on their physical characteristics. This ordering of organisms into groups based on similarities and differences is called classification. In the 18th and 19th centuries leading naturalists identified and named newly discovered plants and animals. These European biologists believed that plants and animals including humans had been created in their present form so they did not seek explanations for the patterns of similarities and differences between organisms. However one important 18th Century naturalist was Karl von Linne (1707-1778), a Swedish botanist and medical doctor. In 1735 Carolus Linnaeus (the Latinised form of his name) published a book called systema naturae in which he outlined his scheme for classifying all known and unknown organisms according to the greater or lesser extent of their similarities. This book was very influential and the Linnaean system of classification was widely accepted by the early 19th century and is still the basic framework for taxonomy today.

Tax Taxonomy is a term coined by Augustin Pyramus de Candolle in 1813 and is the study of the principles and methods of classification.

Linnaean System depends upon the hierarchical structure in which organisms are grouped. According to this system the animals belonging to the higher level, need not necessarily be similar to its other members, but the members of the lower levels are very similar and can reproduce. The typical hierarchical system of classification is:

- Kingdom

- Phylum (Division is used here for plants)

- Class

- Order

- Family

- Genus

- Species

- Variety (for plants)

One of the best sites on the web detailing the animal evolution comes from the University of Waikato web site.

These are excerpts from University of Waikato school of science and engineering in New Zealand. I include them only to prove my point that evolution is taught as fact.

The Ediacaran animals

Between 620 and 550 million years ago (during the Vendian Period) relatively large, complex, soft-bodied multicellular animals appear in the fossil record for the first time. While found in several localities around the world, this particular group of animals is generally known as the Ediacaran fauna, after the site in Australia where they were first discovered.

The Cambrian "explosion" and the Burgess Shale

The Ediacaran animals disappear from the fossil record at the end of the Vendian (544 million years ago). In their place we find representatives of almost all the modern phyla recognised today: sponges, jellyfish and corals, flatworms, molluscs, annelid worms, insects, echinoderms and chordates, plus many "lesser" phyla such as nemertean worms. These "modern" organisms appear relatively quickly in the geological time scale, and their abrupt appearance is often described as the "Cambrian explosion" however, bear in mind that the fossil record of the "explosion" is spread over about 30 million years. I keep taking things out of brackets because it is interesting relevant and memorable

A foot on the land

Whatever their origins, animals may have ventured onto land early in the Cambrian. Previously scientists believed that animals did not begin to colonise the land until the Silurian (440 - 410 million years ago). However, the 2002 discovery of the footprints of animals that scuttled about on sand dunes about 530 million years ago has changed this view. These animals were arthropods, and resembled centipedes about the size of crayfish. They probably didn't live on land, instead coming ashore to mate or evade predators. At this time the only land plants appear to have resembled mosses

The earliest vertebrates

Animals continued to diversify in the Ordovician seas (505 - 440 million years ago). They were mostly invertebrates, including graptolites, which were stick-like branching colonies of tiny animals, together with brachiopods, trilobites, cephalopods, corals, crinoids and conodonts. We now place the conodonts with the chordates, but for a long time they were known only by their tiny, but very common, teeth.

Appearance of the fish

Like the conodonts, fish are members of the chordate phylum because they display certain defining characteristics: a dorsal stiffening rod called the notochord, a dorsal nerve cord, pharyngeal gill slits and a tail that extends beyond the anus. However, fish are placed in the subphylum Vertebrata, because they also show the development of skeletal features such as a backbone, skull, and limb bones.

The jawless fish

Agnathans, or jawless fish, were the earliest fish: an excellent fossil of Haikouichthys ercaicunensis dates back about 530 million years, to the Cambrian. Previously the earliest-known agnathans were dated to around 480 million years ago. Agnathans have traditionally been placed with the vertebrates due to the presence of a skull, although the modern forms such as hagfish lack a vertebral column. The earliest agnathans were Ostracoderms. They were bottom-feeders and were almost entirely covered in armour plates. When the sharks and bony fish began to evolve, around 450 million years ago, most ostracoderms became extinct. Only the lineage that produced the modern hagfish and lampreys survived.

Colonisation of the land

Fish continued to evolve during the Silurian period (440 - 410 million years ago). At the same time some groups of plants and animals took a major step as they colonised the land for the first time. We are not sure why this advance occurred, but it was probably the result of competition in the marine ecosystems, plus the opportunity to escape predators and the availability of new terrestrial niches.

Arthropods, which had ventured temporarily onto land 100 million years earlier, were the first animals to become more permanent colonists. Fossil footprints made in the sandy flats surrounding temporary lakes dating back about 420 million years have been found in Western Australia.

The arthropods were pre-adapted to life on land. By the time they moved ashore, they had already evolved lighter bodies and slim, strong legs that could support them against the pull of gravity. Their hard outer exoskeletons provided protection and would help to retain water, although the development of a waxy, waterproof cuticle was necessary for efficient water conservation.

Spiders, centipedes and mites were among the earliest land animals. Some of them were giants: the largest was Slimonia, the size of a man and a relative of the scorpions. This animal was still too big and too heavy and the walking legs too small to venture onto land for any length of time and so they lived in marginal marine (deltaic) environments.

The evolution of amphibians

By the Devonian period two major animal groups dominated the land: the tetrapods (4-legged terrestrial vertebrates) and the arthropods, including arachnids and wingless insects. The first tetrapods were amphibians, such as Ichthyostega, and were closely related to a group of fish known as lobe-finned fish e.g. Eusthenopteron . Once thought to be extinct, the coelacanth is a living representative of this group.

Colonisation of the land

Fish continued to evolve during the Silurian period (440 - 410 million years ago). At the same time some groups of plants and animals took a major step as they colonised the land for the first time. We are not sure why this advance occurred, but it was probably the result of competition in the marine ecosystems, plus the opportunity to escape predators and the availability of new terrestrial niches.

The arthropods were pre-adapted to life on land. By the time they moved ashore, they had already evolved lighter bodies and slim, strong legs that could support them against the pull of gravity. Their hard outer exoskeletons provided protection and would help to retain water, although the development of a waxy, waterproof cuticle was necessary for efficient water conservation.

Early reptiles and the amniotic egg

One of the greatest evolutionary innovations of the Carboniferous period (360 - 268 million years ago) was the amniotic egg, which allowed early reptiles to move away from waterside habitats and colonise dry regions. The amniotic egg allowed the ancestors of birds, mammals, and reptiles to reproduce on land by preventing the embryo inside from drying out, so eggs could be laid away from the water. It also meant that in contrast to the amphibians the reptiles could produce fewer eggs at any one time, because there was less risk of predation on the eggs. Reptiles don't go through a larval food-seeking stage, but undergo direct development into a miniature adult form while in the egg, and fertilisation is internal.

By 125 million years ago the mammals had already become a diverse group of organisms. Some of them would have resembled today's monotremes (e.g. platypus and echidna), but early marsupials (a group that includes modern kangaroos and possums) were also present. Until recently it was thought that placental mammals (the group to which most living mammals belong) had a much later evolutionary origin. However, recent fossil finds and DNA evidence suggest that the placental mammals are much older, perhaps evolving more than 105 million years ago. Note that the marsupial and placental mammals provide some excellent examples of convergent evolution, where organisms that are not particularly closely related have evolved similar body forms in response to similar environmental pressures.

Taking wing: Archaeopteryx and the origins of the birds

In 1861 an intriguing fossil was found in the Jurassic Solnhofen Limestone of southern Germany, a source of rare but exceptionally well-preserved fossils. Given the name Archeopteryx lithographica the fossil appeared to combine features of both birds and reptiles: a reptilian skeleton, accompanied by the clear impression of feathers. This made the find highly significant as it had the potential to support the Darwinians in the debate that was raging following the 1859 publication of "On the origin of species".

While it was originally described as simply a feathered reptile, Archaeopteryx has long been regarded as a transitional form between birds and reptiles, making it one of the most important fossils ever discovered.