Evolution didn't start 3.8 billion years ago but it may have started 13.7 billion years ago with big bang. We usually refer evolution to biological evolution but 13.7 billion years ago there were no biological evolution. There were only energy. So the story of evolution starts with energy. There weren't any chemical reaction as elements weren't evolved yet. In few minutes the nucleosystheis started with led to evolution of elements. It is late after evolution of stars and the formation of circumstellar environments which led to the start of chemical reaction. The disc around the stars from which planets and other heavenly objects formed and were the appropriate place for chemical reaction. Again energy and energy level is key in evolution. In earlier hot environment of big bang and nucleosynthesis processes in stars the chemical reaction weren't possible (Chemical reaction is the transfer of electron(s) and different pattern of sharing of electrons to bind the atoms/elements to make molecules or compounds and it all depends on the energy levels). The biological evolution on earth is very late to leave some evidence of its existence perhaps in 3.8 billion years age when earth was 0.7 billion years old. For 700,000,000 years the earth was without life.
How energy have driven the evolution?
Diversity and diversity within habitats and modes of life is clear evidence of evolution. Does this diversity indicate competition and natural selection or is it the result of a search for exploitation of available sources of energy? Following are some examples:
Ecosystem
Ecosystem is a delicate balance between physical, chemical and biological components of it. Top down control and bottom up control is very famous in trophic levels of a terresterial ecosystem like, lake, which have simple food chains. A change in one of these components affect others. Similarly inorganic and oganic cycles of chemicals and nutrients are dependent on each other. Even the relation of organisms among themselves are delicately balanced. Prey and predation is interdependant on each other. Change in predators affect on prey populations and sizes and similarly changes in prey population and sizes affect on predators. The effect of changes in one component of a food web can be observed throughout the food web. This delicacy of balance is all controlled by supply of energy (sunlight, temperature, nutrient supply, supply of gases, water and some essential minerals). Following we go for more examples in ecosystem,
Chemoautotrophs
The earlier life forms were chemoautotrophs which were getting their energy from inorganic molecules (oxidation of electron donating molecules in anaerobic environments) to expoite the carbon dioxide for synthesis of organic molecules. Because iron were frequent and free oxygen were rare in earlier hot crust (on hydrothermal vents) so earlier life forms exploiting these energy source (to get electron from Iron II by oxidizing them into iron III).
Glycolysis:
It is assumed that earlier oceans or water bodies were filled with organic compounds but free oxygen were rare. In this nutrient rich anoxic environment the led the life forms of that time to exploit this energy source by evolving a mechanism known as glycolysis. Glycolysis is a process of gaining energy by break down of glucose in anaerobic environment to lactic acid. Glycolysis is still used in all living cells.
Archaea
Archaea is famous for living in extreme environments and also in mild environments. Those groups of Archaea which live in extreme environments got the name of extremophile. Let's acidophile living in acidic environments, alkalophile living in alkaline environments, Halophiles living in saline environments and thermophile living in high temperature environments. Living in these extreme environments make Scientists think of their extraterrestrial origins. Why archae is adapted these extreme environments, have a very simple answer to exploit the energy of these environments.
Looking for energy:
From flagella, psuedopodia in unicellular organisms to position of mouth on the upper side and anterior of the animals indicate that energy is the primary drive of organims. Organisms with head protected by some sort of shield (exoskeleton, tentacles and cranium) have concentrated their main senses which detect food source in the head region and near their chief senses is provoided an apparatus for taking up of food (mouth). The shape of head depend on the main receptors which may be photorecptor, chemoreceptor, thermorecptor or sensors to detect sound or movements.
Symbiosis
Why organims are cooperating if the life is the result of competations. Symbiosis of organims led to the concept of Co-evolution. Why flowers specialized themselves (evolved) to attract the birds, insects, bats and animals? Mutualism, commensalism and parasitisms are evolution of organisms to exploit available energy by help of each other and even at the expense of each other.
Fungi
Fungi is a unique group that evolved a life habit, shared both by plants and animals. It evolved from a unicellular stem eukaryotes. Its nutrition mode is like animals by enzymatic digestion (unlike internal digestion in animals it has evolved an external digestion) and absorption. A diverse range of habitate and mode of life show the opportunistic natures of fungi. Fungi are important decomposers, active predators, parasites and also symbionts. These diversities and a life habit of between land and plants is not a signature of competition but instead struggles to exploite available sources of energy.
Herbivores, Carnivores and Decomposers
Certainly earlier life forms evolved autotrophy by which they could use gases, water and energy from sunlight to produce their food. Why then some life form evolved not to produce their food but consume food produced by photosynthetic organisms. This consumption is not an easy process. It requires a lot of specailization to break down the stored food and get energy out of it. Still some other organisms evolved to eat herbivores evolving the ability of predation besides digestion. And to complete the cycle another group of organisms to break down the dead bodies of all organisms to not only get energy for themselves but also provoide primary producers or photosynthetic organisms the essential elements they requires for prodcuing food. Are these opportunistic and cooperative mode of life indicating competition or a search for possible sources of energy and an escape from competition?
Homology
Homology is used as an evidence of common descent. Yes it is true but what organisms living in different evironments and with different adaptations still the same pattern of structures in the body? If we take the famous example forearms in vertebrates, A forearm in marine organisms like whale, organisms living on land like human, those fly in air like birds, those living on trees like monkeys, those living in mountains like volves, those living in poles like white bear, those living in tropics like tree frogs who have adopted so contrasting environments and doing different functions but still retained the same structures of bones. Though the length proportions of bones have modified according to the energy required by body size and environments in which they live but still the same structures and use of leverage for swimming, flight, climbing, running, defence, and complex works in case of human must have also have functional reasons beside common descent.
Gravity pull us when we move against it. Certainly organisms get their energy from metabolisms and the organs which functions require movements to get energy from external environments and make available for us. These movements require a support system. Though metabolism provoides the energy required for this support but organisms tends to be energy effcient, so they use the leverage system which use gravity itself to move against it.
Homology is the evidence of efficient use of energy besides common descent.
This was part of my effort to rethink evolution... Of course, it is not done yet... So feel free to criticize, suggest points or comment...
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