Mar 05, 2016 Evolution of Life on Earth. Evolutionary Biology is the study of history of life forms on earth. Homology indicates common ancestry. In the context of biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different species.
Published online 2015 Dec 12. doi: 10.1016/j.sjbs.2015.11.012
PMID: 26858553
1.âIntroduction
Biology literally means âthe study of lifeâ. Life Sciences attempts to untie the living things mysteries from the working of protein âmachinesâ, to the growth of organism from a single cell to the majesty and intricacy of whole ecosystem. Questions about life sciences are as diverse and fascinating as life itself like; how a single cell knows to build up complex organism? How interpretation of genetic information takes place?
How the properties of organism are affected due to gene mutation? How ecosystem changes due to climate?
What can human genetic variation tell us about the history of human evolution and migration? Evolution is the change in heritable traits of biological populations over successive generations. Evolutionary processes give rise to diversity at every biological organization level. All life on earth shares a common ancestor known as the last universal ancestor. In the mid-19th century, Charles Darwin formulated the scientific theory of evolution by natural selection, while in the early 20th century the modern evolutionary synthesis integrated classical genetics with Darwinâs theory of evolution by natural selection through the discipline of population genetics. Evolution is a cornerstone of modern science, accepted as one of the most reliably established of all facts and theories of science, based on evidence not just from the biological sciences but also from anthropology, psychology, astrophysics, chemistry, geology, physics, mathematics, and other scientific disciplines, as well as behavioral and social sciences.
2.âTheory of evolution on Earth
Today life diversity on earth is the result of evolution. On Earth life began at least 4 billion years ago and it has been evolving every year. In the beginning all living things on earth were single celled organism, after several years multicellular organism evolved after that diversity in life on earth increased day by day. Here in the figure shows the history of life on earth (Fig. 1).
Timeline for history of life on Earth.
DNA (deoxyribonucleic acid) is the double helix structure shown in Fig. 2. Its duplicate copies have coded information coiled up in almost all of the 100,000,000,000,000 (one hundred trillion) cells in your body. In human DNA has 46 segments; 23 segments received from father and 23 from mother. Each DNA contains exclusive information that determines what you look like, your personality and how your body cell is to function throughout your life.
Depictions of Saturn, DNA, and the Ark.
If one cell whole DNA was uncoiled and stretched out then it would be six feet long. Its detailed structure could not be seen due to its thin structure even under electron microscope. If all the coded information from one cell of one person were printed on books then it would fill a library of four thousand books and if the whole body DNA were positioned continuously, it would extend from here to Moon more than 500,000 times. If one set of DNA from each individual who still lived were placed in a pile, the final pile would weigh less than an aspirin.
3.âGeneric information
Different Scientists gave different information about genetic evolution like; Carl Sagan who showed by using simple calculation that how one cellâs value of genetic information approximates four thousand books of written information while volume of each book would have 50 cubic inches (Sagan, 1977). 1014 cells are present in each adult individual. About 800 cubic miles have been worn from the Grand Canyon. According to that if each cell in one individualâs body was reduced to four thousand books then they would fill the Grand Canyon 98 times.
From earth the moon is 240,000 miles. If the human cell DNA were prolonged out and linked, it would be more than 7 feet long. If the entire DNA in one individualâs body were located back-to-back, it would enlarge to the moon 552,000 times.
The weight of DNA in human cell is 6.4 Ã 10â12 g and almost less than fifty billion individuals lived on earth, if one copy of DNA from living individual were taken it is enough to define the physical characteristics of all those inhabitants in microscopic aspect and would weigh only, which is less than the weight of 1 aspirin.
According to Hoyle and Wickramasinghe, biochemical systems are exceptionally composite, so much so that the possibility of their being shaped from side to side haphazard shuffling of simple organic molecules is remarkably small, to a position certainly where it is inertly different from zero (Hoyle and Wickramasinghe, 1999). Life cannot have a random beginning, like monkeyâs troops thundering on typewriter could not be able to produce Shakespeare work. For the realistic cause entire visible universe is not vast adequate to hold the essential monkey hordes, essential typewriters, and surely the baskets for waste paper required for the deposition of wrong attempts. The same is true for the living matter.
The simple truth is not mentioned by Hoyle and Wickramasinghe that even a few correct words typed by monkeyâs hordes would decompose long before a whole sentence of Shakespeare was completed. In the same way, a small number of correct amino acids sequences would decay long before a protein was completed, not to point out that thousands of proteins must be at their proper place in a living cell. At last the most composite condition of all is the occurrence of working DNA (Vogel, 2001). They also state that our intelligence must reflect a vastly superior intelligence, even the tremendous idealized limit of God. They also believe that life was created by some intelligence somewhere in outer space and latter was transported to the Earth. All point mutations that have been studied on the molecular level turn out to reduce the genetic information and not to increase it (Storz, 2002).
As Murray Eden reported that it is our contention that if ârandomâ is given a serious and crucial interpretation from a probabilistic opinion, then the randomness assumption is greatly improbable and a sufficient scientific theory of evolution has to wait for the finding and clarification of new natural laws like physical, physico-chemical, and biological (Eden, 1967). I. After clearing up the above to a scientific symposium, Hoyle said that evolution was similar with the possibility that âa tornado sweeping through a junk-yard might assemble a Boeing 747 from the materials therein.
According to Ohnoâs likable term is junk DNA that traps and no doubt dispirited a generation of researchers from studying the huge amount of important âjunkâ DNA that did not code for proteins (Ohno, 1972). This study made an insightful point that if all the DNAs of human, mice and other organisms were useful then after so many mutations that build up in hundreds of millions of years then those species become extinct.
In different species non coding DNA differs more as compared to protein coding DNA. If we find a particular protein coding gene in human then we find nearly the same gene in mice and that rule just does not work for narrow elements. The biggest mistake in the history of molecular biology is the failure to recognize the importance of introns (Mattick, 2003).
In transcription regulation, replication, RNA processing, translation and protein degradation non coding RNAs play an important role. Recent studies show that non coding RNAs are more important and abundant as compared to those initially imagined. The term junk DNA which is used is the reflection of our ignorance, non gene sequence also has their regulatory role (Birney, 2012).
Fig. 3 shows that macroevolution would need a rising change in the complication of definite traits and organs while the microevolution is involved only in horizontal changes with no rising complications. Most of the creationists agree that natural selection occurs but it does not result in macroevolution.
Macroevolution vs. microevolution.
Today, the most accepted theory of life on Earth is evolution, and there is a vast amount of evidence supporting this theory. However, this was not always the case. Evolution can be described as a change in species over time. Dinosaur fossils are significant evidence of evolution and of past life on Earth. Before taking into consideration that how life began, first of all we understand the term organic evolution. It is naturally occurring and beneficial change that produces rising and inheritable complication. If the offspring of one form of life had a different and improved set of vital organs then this is called macroevolution, but the microevolution does not increase the complexity. By one or more mutation only size, shape and color are altered (Taubes, 2009). Microevolution can be thought of as horizontal change, while macroevolution would involve vertical beneficial change in complexity. So the combination of microevolution and time will not produce macroevolution. Evolutionists have the same opinion that microevolution takes place. Since the start of history a minor change has been observed. But become aware of how frequently evolutionists give confirmation for microevolution to hold up macroevolution. It is macroevolution which requires new abilities and rising complication, resulting from new genetic information and is the center of the creation-evolution argument (Maher, 2012).
4.âThe key parts of the theory of evolution
4.1. Top 5 misconceptions about evolution4.1.1. It is just a theory
In everyday language theoryâ might mean a hunch or a guess. For scientists theory refers to a well supported explanation.
Scientific theories and scientific laws are often confused.
4.1.2. Fittest survival
Is this accurate for Darwinâs theory of Natural Selection?
Fact 1 â Population tends to remain stable.
Fact 2 â Organisms reproduce more offspring than could be supported.
Interference 1 â Not all the offspring live long enough to reproduce.
Fact 3 â Resources are limited
Fact 4 â Individuals within population differ in individuality.
Fact 5 â Inherited characteristics are more.
Interference 2 â There will be differential survival and reproduction.
This is Natural Selection.
Interference 3 â Over time these differences will shift the makeup of the population.
This is decent with modification. Evolution will occur.
4.1.3. Humans descend from Apes
4.1.4. No one was there and It cannot be Proven
Evidence of evolution
Journals publish evidence
4.1.5. Darwin was wrong
4.2. The origins of life
In the process of evolution a series of natural changes cause species to arise, familiarize yourself to the environment, and turn out to be extinct.
Evolution=Change
By the process of biological evolution all species originated. The term species refers to a group who can reproduce their fertile offspring. Scientist classify the species with two scientific name first is genus name and second is species name like humans referred as Homo sapiens. In populations, there are variations or differences between individual members because of the variety of genes (alleles). Examples are skin color in humans, coat color in foxes. When there is a change in genes inherited from parents to offspring in different proportions then evolution occurs. These variations in genes arose for either (1) recombination of alleles when they sexually reproduce or (2) mutations.
Mechanism of evolution occurs by different ways
Recombining genetic material can happen in three ways.
Mutations are usually neutral or harmful. Sometimes they can be beneficial if the environment is under a state of change.
These variations lead to adaptations. Adaptations are traits that aid a populationâs chance of survival and reproduction (Hoyle, 1981).
A single individual does not change by the result of evolution, while it causes the change by inherited means of growth and development that are specified for a population. When the parent inherits these changes to the offspring then they become common in that population and as a result offspring inherit those genetic characteristics for probability of survival, capability to give birth which will work until the environment changes. Eventually, the genetic changes can modify a species overall way of life, like what it eats, how to grow, how it can live. As new genetic variations in early ancestor populationâs preferential new abilities to become accustomed to environmental changes and so altered the human behavior causes the human evolution (John, 2007).
5.âConclusion
Science should forever support conclusions on what is seen and reproducible. So what is observed? We see variations in lizard and birds. If macroevolution occurred in between forms they never as fossils.
An alert viewer can typically see astonishing discontinuities in these claimed upward changes, as well as in the drawing above. From the time of Darwin, different excuses made by evolutionists that why the world and our fossil museums are not spilling over with intermediates. Evolution is a scientific theory in biological sciences, which explains the emergence of new varieties of living things in the past and present. Evolution accounts for the conspicuous patterns of similarities and differences among living things over time and across habitats through the action of biological processes such as mutation, natural selection, symbiosis and genetic drift. Evolution has been subjected to scientific testing for over a century and has been again and again confirmed from different fields.
Footnotes
Peer review under responsibility of King Saud University.
A Windows 8 DVD is not included. The system can be restored via a recovery partition. Travelmate p253 drivers.
References
Articles from Saudi Journal of Biological Sciences are provided here courtesy of Elsevier
This timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth. In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization, from kingdoms to species, and individual organisms and molecules, such as DNA and proteins. The similarities between all present day organisms indicate the presence of a common ancestor from which all known species, living and extinct, have diverged through the process of evolution. More than 99 percent of all species, amounting to over five billion species,[1] that ever lived on Earth are estimated to be extinct.[2][3] Estimates on the number of Earth's current species range from 10 million to 14 million,[4] of which about 1.2 million have been documented and over 86 percent have not yet been described.[5] However, a May 2016 scientific report estimates that 1 trillion species are currently on Earth, with only one-thousandth of one percent described.[6]
While the dates given in this article are estimates based on scientific evidence, there has been controversy between more traditional views of increased biodiversity through a cone of diversity with the passing of time and the view that the basic pattern on Earth has been one of annihilation and diversification and that in certain past times, such as the Cambrian explosion, there was great diversity.[7][8]
Extinction[edit]
Visual representation of the history of life on Earth as a spiral
Species go extinct constantly as environments change, as organisms compete for environmental niches, and as genetic mutation leads to the rise of new species from older ones. Occasionally biodiversity on Earth takes a hit in the form of a mass extinction in which the extinction rate is much higher than usual.[9] A large extinction-event often represents an accumulation of smaller extinction- events that take place in a relatively brief period of time.[10]
The first known mass extinction in earth's history was the Great Oxygenation Event 2.4 billion years ago. That event led to the loss of most of the planet's obligate anaerobes. Researchers have identified five major extinction events in earth's history since:[11]
(Dates and percentages represent estimates.)
Smaller extinction-events have occurred in the periods between these larger catastrophes, with some standing at the delineation points of the periods and epochs recognized by scientists in geologic time. The Holocene extinction event is currently under way.[12]
Factors in mass extinctions include continental drift, changes in atmospheric and marine chemistry, volcanism and other aspects of mountain formation, changes in glaciation, changes in sea level, and impact events.[10]
Detailed timeline[edit]
In this timeline, Ma (for megaannum) means 'million years ago,' ka (for kiloannum) means 'thousand years ago,' and ya means 'years ago.'
Hadean Eon[edit]
4000 Ma and earlier.
[15][21]'Remains of biotic life' were found in 4.1 billion-year-old rocks in Western Australia.[22][23]This is when life most likely arose.[37]Commencement of plate tectonics with old marine crust dense enough to subduct.[20]Palaeozoic Era[edit]
542 Ma â 251.0 Ma and contains the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods.
With only a handful of species surviving today, the Nautiloids flourished during the early Paleozoic era, from the Late Cambrian, where they constituted the main predatory animals.[58]
Haikouichthys, a jawless fish, is popularized as one of the earliest fishes and probably a basal chordate or a basal craniate.[59]
Ferns first appear in the fossil record about 360 million years ago in the late Devonian period.[60] [66]
Mesozoic Era[edit]
Utatsusaurus is the earliest-known form of an ichthyopterygian.
From 251.4 Ma to 66 Ma and containing the Triassic, Jurassic and Cretaceous periods.
[who?]adapt more rapidly and effectively than others[who?].
Major extinctions in terrestrial vertebrates and large amphibians. Earliest examples of armoured dinosaurs
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