In this page, I will talk about the three big questions of a philosophical nature about biology which in my other webpage I mentioned but I will talk about in detail and in my other blogposts where each blog will describe each of the questions separately but for now I will talk about the three questions and how each questions relates to one another.
What is Life?
We are surrounded by a variety of life forms, whether they are microbes, plants, fungi, and animals and every biology textbook will usually give a definition of life based on what all life forms have in common such as the fact that all life is composed of one or more cells, use matter and energy for biological processes, reproduce and evolve by natural selection and other evolutionary mechanisms, and so on but what is it that distinguishes life from non life? Before biology became a science, everyone who has seen a chick hatch from a egg, watch a caterpillar turn into a butterfly, or see a flower blossom from a bud, cannot help but notice that these properties of life are completely different from the behavior of inaminate objects such as rocks and also another thing not to notice about life is that unlike rocks which if you ever threw one it follows a definite path under the influence of gravity, but when you see birds flying whether they are migrating or finding a place to shelter, you cannot fail to notice that they have a goal that they are pursuing which is something not evident in inanimate things. In fact it is tempting to think that the difference between life and nonlife is something that is powered by a “life force” and that is the basis behind the belief of what is called “vitalism” or the belief that life is powered by some mystical force which makes life go but now we know that such a belief is really unscientific and that there is no evidence of a “life force” but we know that life is powered by the same form of energy that is present in the universe notably two forms of electromagnetic energy, visible light and chemical energy and that life is composed of the same elements as non life notably carbon, oxygen, hydrogen, nitrogen, phosphorous, and sulfur, also a part of the same physical universe.
Life is also related to one another because at the level where all the properties of life are still present, cells, the internal structures in the form of molecules like DNA and protein are universal in all life forms and that all of life uses the same genetic code and the DNA can be transcribed into RNA which is translated into protein which is present in all life forms found so far. This is indicated by the fact that all of life is descended by a common ancestor a long time ago and as revealed by Darwin that life evolves into new and more complex forms that are better adapted into new environments and indeed when you study life whether at the cellular level there is a degree of complexity that rivals even non life. A crystal is a simple structure composed of a few atoms are linked together in a pattern but a life form is composed of several atoms joined together in various polymers usually DNA, RNA, and proteins and are arranged in a very specific order such as cell membranes composed of phospholipids along with special proteins that can allow substances in and out, and that all chemical reactions in the cell are catalyzed by a specific set of proteins called enzymes. Indeed this is complicated compared to the crystal.
It is a well know fact that life begets life but the process of reproduction which allows offspring to be identical to its parent is also an imperfect process, some of the offspring will be different than its parents and this difference will allow the offspring to adapt to novel situations such as a better ability to find food or hide from predators, and it is these tiny changes, as realized by Darwin which is favored by natural selection and gradually will result in changes in the population which will evolve into new species.
Here is a paradox that is worth considering. The universe is governed by the second law of thermodynamics. What is the second law of thermodynamics? The first of law of thermodynamics states that energy can be converted into various forms but the total amount is constant. Energy is neither created nor destroyed but can change into one form into another. The universe originated in the Big Bang 15 billion years ago and all the energy present ever since that one cosmic event, is available in many forms such as galaxy formation to our sun providing the energy for the biosphere. Life depends on electromagnetic energy in the form of visible light for the process of photosynthesis utilized by the class of organism called photoautrophs or in other words all the cyanobacteria, algae, and green plants which are the foundations of all terrestrial ecosytems and ocean surfaces and in the process of photosynthesis, oxygen is released and carbohydrates are manufactured so electromagnetic energy or visible light is converted into chemical energy in the form of carbohydrates and a universal energy donor called ATP in a process that is so complex that even our technology has yet to catch but has been favored by natural selection for 2 billion years.
While the first law says that all the energy is constant and interchangeable, the second law says about the quality of energy and there is a difference between energy that can do work and energy that is useless. This is embodied in another quantity called entropy. What is entropy? Entropy is basically the amount of energy that has been converted into a useless form. An example is when you throw a rock, all the atoms in the rock are moving in the same direction but when the rock hits the ground, all the atoms jostle randomly and it is this random movement that is called heat, which is a form of kinetic energy but it is a random process unlike work exerted on the rock where all the atoms move coherently in whatever direction the rock is moving. All energy conversions will end up in heat and so the atoms are disorganized and it is the disorganization that is called entropy and what science says is that the universe is increasing entropy or that less and less energy is available for work and disorganization increases which is the entropy.
Here is the paradox. Life forms are evolving into new complex forms and are continuing to do so and has been doing so for 3.5 billions of years. How can the complexity of life occur in a universe where entropy is increasing? As will be thoroughly explained in future blog posts, life is not really violating any laws of physics and the second law is no exception. As I will make it clear, it is because of the second law that life can exist in the first place.
What is the Origin of Life?
Since life is considered a physical process that takes in matter and energy, carry out metabolism, reproduce, and evolve, the life that we know on this earth is continuously producing itself and as long as there is a flow of matter and energy, life will continue to evolve to exploit whatever it is it depends in its own environment. Many if not all lineages of species of organisms are evolving into more complex forms are better able to adapt and life has been doing this, despite being in a universe dominated by the second law which is the opposite , more and more disorder occurring in the universe, and have been doing so for about 3.5 billions of years. Around 4.5 billions of year, our planet condensed out of the interstellar matter from which the sun and the other planets also condensed out of. The planet was at first, a hot and lethal place, where no life of any kind was present but after 3.5 billions of years, somehow atoms of carbon, oxygen, nitrogen, phosphorous, and sulfur somehow came together to form the systems capable of metabolism, formation of a membrane that could separate a network of specific chemical reactions from the rest of the environment , along with the ability to reproduce, and once that threshold from non life to life was crossed, life, as we know it, began to evolve into the various forms that we see today as well as in the fossil record.
What is agreed upon is that for there to be reproduction, variation, and metabolism which are part of life, there must be a flow of matter, in the form of carbon, oxygen, and nitrogen and a few other elements, especially carbon since it is one of the few elements that can form a large variety of compounds along with a specific kind of energy such as chemical energy and light energy. As long as the flow of energy continues whether in the form of iron sulfide compounds from hydrothermal vents at the deep or visible light on the earth surfaces. life is able to metabolize and reproduce making evolution possible.
Just how exactly did the conditions came together to form the first biological systems capable of evolution and metabolism? Ever since 1952 when Stanley Miller and Harold Urey conducted the first abiotic experiment in which water vapor, ammonia, methane, and hydrogen gas were subjected to energy flow in the form of an electric charge and after the first few weeks, organic compounds notably amino acids were produced, and many versions of the same experiment revealed that as long there are hydrogen and carbon based compounds, it is relatively easy to synthesize amino acids, sugars, even nucleotides the building blocks of DNA although it is very difficult to fully synthesize from scratch a DNA molecule capable of replicating itself. In addition recent evidence suggests that the early earth had an atmosphere that was mostly carbon dioxide and nitrogen but virtually no oxygen and it is very difficult to synthesize any amino acids and nucleotides where the mixture contains carbon dioxide.
The origin of life is part of the problem of the nature of life and once you know what it is, if there is any criteria, of separating life from non life then you realize that at one point in the distant past, life came from non life in a very special and unique way and since life as we know it depends on carbon, water, and energy then somehow these three combine together to form the system known as life so if the nature of life is a combination of information in the form of a genetic code and energy in the form of what is called a coupled metabolism then that combination had to have been present in order for life to have gotten started.
Is Life Common throughout the Universe?
This question has far more questions than there are answers. Is life only a unique property of our planet the result of a process or processes that is so unique that is so unlikely to be common or since the same elements that make up life are so widespread and also the same energy is also present in the universe that whenever conditions are permissible then new patterns of life are inevitably. In the past several years, science has revealed that planets are common throughout our galaxy wherever there is star formation and also the same elements of life are also common, that is carbon, oxygen, and nitrogen are abundant and in addition even amino acids and sugars are present in meteorites, and in interstellar clouds respectively so it is not impossible to say that life can form wherever and whenever certain specific conditions permit it. Of course, no hard evidence of any life form outside of earth has been found so far, but with the nature and origin of life as a guide, then this question becomes a valid scientific question to consider and will also be the subject of future blog posts where I will discuss about the science of astrobiology or the study of life in the cosmos where I will combine both the two previous questions into the question of whether or not life is a natural phenomenon of the universe.
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U.S Fish and Wildlife Service Coral Reef at Palmyra Station https://www.flickr.com/photos/usfwshq/8425324548/in/photolist-ad3p91-9MfzYB-9MekHF-9Mh72m CC BY 2.0
abbamouse Digital Earth https://www.flickr.com/photos/abbamouse/4309898643/in/photolist-7yRmHi-dwZHYM CC BY-SA 2.0
David DeHetre orion nebula october 5 2010 https://www.flickr.com/photos/davedehetre/5054113321/in/photolist-8GBDNR-5NVXv5 CC BY 2.0