What is Evolution: Definition and 731 Discussions

Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes that are passed on from parent to offspring during reproduction. Different characteristics tend to exist within any given population as a result of mutation, genetic recombination and other sources of genetic variation. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or rare within a population. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms and molecules.The scientific theory of evolution by natural selection was conceived independently by Charles Darwin and Alfred Russel Wallace in the mid-19th century and was set out in detail in Darwin's book On the Origin of Species. Evolution by natural selection was first demonstrated by the observation that more offspring are often produced than can possibly survive. This is followed by three observable facts about living organisms: (1) traits vary among individuals with respect to their morphology, physiology and behaviour (phenotypic variation), (2) different traits confer different rates of survival and reproduction (differential fitness) and (3) traits can be passed from generation to generation (heritability of fitness). Thus, in successive generations members of a population are more likely to be replaced by the progenies of parents with favourable characteristics that have enabled them to survive and reproduce in their respective environments. In the early 20th century, other competing ideas of evolution such as mutationism and orthogenesis were refuted as the modern synthesis reconciled Darwinian evolution with classical genetics, which established adaptive evolution as being caused by natural selection acting on Mendelian genetic variation.All life on Earth shares a last universal common ancestor (LUCA) that lived approximately 3.5–3.8 billion years ago. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, to fossilised multicellular organisms. Existing patterns of biodiversity have been shaped by repeated formations of new species (speciation), changes within species (anagenesis) and loss of species (extinction) throughout the evolutionary history of life on Earth. Morphological and biochemical traits are more similar among species that share a more recent common ancestor, and can be used to reconstruct phylogenetic trees.Evolutionary biologists have continued to study various aspects of evolution by forming and testing hypotheses as well as constructing theories based on evidence from the field or laboratory and on data generated by the methods of mathematical and theoretical biology. Their discoveries have influenced not just the development of biology but numerous other scientific and industrial fields, including agriculture, medicine and computer science.

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  1. M

    Significance of prokaryote evolution to enable multi-cellular life to exist?

    That is, if these cells even had anything to do with it. We're only going by the endosymbiotic theory.
  2. WaveJumper

    Evolution not completely random according to an experiment

    Evolution mutations not completely random according to an experiment I wondered for a while where to post this link, but since it will probably provoke questions on the origins of this new guiding mechanism of evolution, i decided it had to land here(it will be a matter of time till someone...
  3. C

    Time evolution from zero state

    Homework Statement Suppose the state of a single-mode cavity field is given at time t=0 by |\Psi(0) \rangle = \frac{1}{\sqrt{2}}(|n \rangle + e^{i\phi}|n+1 \rangle) where phi is some phase. Find the state |\psi(t)\rangle at times t > 0. Homework Equations I'm a little...
  4. T

    Time Evolution of Gaussian Wave packets

    Hi, I'm trying to derive a wave equation for a gaussian wavepacket for both the position (x) and the momentum (k), for a wave packet of width sigma, at some initial position x0 and with an initial momentum k0. Now I have worked out the initial wavepacket equation to be: psi(x) =...
  5. S

    Time Evolution of a Square Pulse - Fourier

    Hi There, A square pulse of light has the form f(x) = A exp(ik0x) for |x| < L/2 and f(x) = 0 everywhere else. I want to know how that pulse evolves overtime. I want to graph it in Mathematica. I did a Fourier transform to find the wave number spectrum, with the general form: F(k) =...
  6. B

    Biology: Evolution and variation

    What role do you think variations play in the process of evolution?
  7. N

    Evolution and the Second Law of Thermodynamics

    I'm not quite sure where to put this, in Physics or Biology. Mentors, please move this to the most appropriate location. A common argument put forth by creationists/intelligent design proponents is that evolution/abiogenesis violates the second law of thermodynamics, by causing a decrease in...
  8. DaveC426913

    Modern selection and evolution

    The general consensus I think is that evolution is still occurring in modern times but just being driven by different factors than geography, climate, predation, etc. But doesn't the process require time as well? Flora and fauna (including humans) evolve characteristics because of...
  9. M

    Could we do QM without time evolution ?

    could we do QM without time evolution ?? that is the idea, could we perform QM without referring to any coordinate called 'time' in the sense that the Hamiltonian and Schroedinguer equation would be H \Psi (x) =0 and time and energy only appear as the pair (p_0 , t) the idea is ...
  10. Fra

    Is the Subjective Interpretation of Probability Falsifiable?

    A frequently seen opinion, for example expressed by Popper in reflecting over what he calls the "the fundamental problem of chance in his classic "The logic of scientific discovery", is to reject the subjective interpretation of probability because he thinks it is not falsifiable. This really...
  11. P

    Is there an alternative to evolution?

    hey folks, i'm just curious. are there any biologists who don't accept the theory of evolution? if yes, how do they scientifically explain the diversity of species (other than believing in Intelligent Designing stuff)? cheers
  12. L

    Evolution Bibliography: Expert Texts for Advanced Readers

    Evolution bibliography [Urgent] Hi, I'm writing an article for my college magazine. As always, I'm already behind the deadline. I need to include a very basic bibliography on evolutionary theory. I've included Richard Dawkins's The Selfish Gene and The Extended Phenotype as introductory...
  13. D

    Could hedgehogs evolving to avoid cars be a sign of ongoing evolution?

    My knowledge of biology is very limited and I know just the basics, so please enlighten me. This evolution phenomenon has started way way back in the past and as a result, today we see varieties of species including humans. My question is: are WE (present species) still being evolved and...
  14. L

    QM: time evolution in an infinite well

    Homework Statement http://img379.imageshack.us/img379/1864/screenshothw4pdfapplicamd7.png Homework Equations H|\psi > = E_n |\psi > The Attempt at a Solution About part 1 of the question: I can find the eigenfunctions of psi_1 by comparing coefficients with the well known...
  15. D

    Wavefunction Evolution Problem: Solving for \phi_1

    Problem Describe the evolution in time of \phi_1 = A \sin \omega t \cos k(x+ct). Attempt at Solution We have that \partial^2 \phi_1 / \partial x^2 = -Ak^2 \sin \omega t \cos k(x+ct) \partial \phi_1 / \partial t = A \sin \omega t (-kc \cdot \sin k(x+ct)) + A \omega \cos \omega t \cos...
  16. D

    Calculating Time Evolution of Density Matrix

    Hi, I am trying to calculate the time evolution of a density matrix. Like if there is a mixed state with 50% of |x, 0> and 50% of |y, 0>. After time t due to time evolution, the kets become: |x,t>= e^(-i/h Ht) |x,0> and so on. Is it ok to use these kets instead of the original ket to...
  17. V

    Religion = product of evolution ?

    First, sorry for any grammar errors because English is my second language. This thread got me thinking about atheism and evolution: http[:]//www[.]physicsforums.com/showthread[.]php?t=124428 From the most of replies in that thread I came to conclusion that people who don't believe in GOD...
  18. S

    Did fruit flies evolve differently in zero gravity?

    I heard a long time ago (im 18, so perhaps "a long time ago" lacks perspective, I guess I was 12 or something at the time) about an experiment that would have a colony of common fruit flies or mayflies onboard the space station to see how they evolved in a (as good as) zero gravity environment...
  19. E

    Schrodingers Cat and time evolution

    There have been countless discussions about the thought experiment about Schrodinger's cat in a box, and how to describe the state of the cat before and after the box is opened, leading to all sorts of bizarre notions like a half dead/half alive cat inside the box, and I certainly don't fully...
  20. V

    Superwind phase in stellar evolution

    why is there very rapid mass loss in the superwind phase. my notes simply say "because the envelope attains positive binding energy". Firstly, how can binding energy be positive by definition?! Secondly, I am not entirely sure what the lecturer is talking about? what makes the envelope...
  21. V

    Stellar Evolution: After Hydrogen Exhaustion

    why after hydrogen exhaustion (of low mass stars) does the the core become isothermal. (according to my notes) I mean, after exhaustion, its all helium, and it keeps on contracting right? So by the virial therem it must heat up (so by definition, it is NOT isothermal)! Indeed it must do so...
  22. W

    Is a squeezed state keeping as a squeezed state in its evolution?

    we well know that, a coherent state keeps to be a coherent state in its evolution does similar conclusion hold for a squeezed state?
  23. D

    Causal Evolution of Wave Function and Gravity

    I read in my textbook that the wavefunction of a particle evolves causally when unobserved. but isn't it constantly being observed or detected in some sense by its gravitational effects?
  24. M

    Evolution: 24 myths and misconceptions

    Evolution: 24 myths and misconceptions The following myths are debunked: - Everything is an adaptation produced by natural selection - Natural selection is the only means of evolution - Natural selection leads to ever-greater complexity - Evolution produces creatures perfectly...
  25. DaveC426913

    How Quickly Can Evolution Change a Species' Physical Characteristics?

    http://www.sciencedaily.com/releases/2008/04/080417112433.htm In 1971, biologists moved five adult pairs of Italian wall lizards from their home island of Pod Kopiste, in the South Adriatic Sea, to the neighboring island of Pod Mrcaru. “Striking differences in head size and shape...
  26. JK423

    Solve Evolution Operator: <J|U|E>=Exp[-iEt/h]*<J|E>??

    [SOLVED] Evolution Operator If U=Exp[-iHt/h] is the evolution operator, and H the hamiltonian one, i can't figure out how to derive the following equation. Let`s call |E> an eigenstate of H, E it`s eigenvalue and |J> a random basis. Then: <J|U|E>=Exp[-iEt/h]*<J|E>. ??
  27. A

    Time evolution and the Dirac Equation

    I have a question about the Dirac Equation. I know that if I have a given initial state in non-relativistic quantum mechanics, I can find the Fourier coefficients using that state, and then write down the wavefunction for any time. But if I have an initial state wavefunction (that is, the...
  28. N

    Time evolution of spin state

    Homework Statement An +x-polarized electron beam is subjected to magnetic field in the y-direction. What is the probablity of measuring spin +x after a period of time t. Homework Equations Time evolution operator U = e^{-i/\hbar \hat{H} t} The Attempt at a Solution Since the...
  29. Simfish

    Stellar Evolution: Pathways & Perturbations

    stellar evolution pathways...? I find this especially interesting since the trajectories of stars on the HR diagram are more or less based on this assumption. But obviously, small perturbations can lead to major changes in the long-run. But it seems that most of those changes involve only...
  30. 1

    Can dog breeding truly be considered evolution?

    I want to clairfy something: Is it true that without DNA mutations it would be impossible to start with a population of x wild wolfs and breed a chihuahua, or poodle? Lets say your only goal is to start with a very large population of wolfs who on average weigh 100 lbs, your goal is to create a...
  31. E

    News The Republican Candidates and Evolution

    In case you haven't already heard, when the Republican Candidates were asked, "Who doesn't believe in evolution?" 3 of them raised their hand. If you didn't see it, I attached the clip below...
  32. O

    Is Evolution Universally Driven by Self-Perpetuating Processes?

    How does evolution work? It seems that evolution has determined many of the circumstances of the world we find ourselves in. Here are a few examples: (1) Cosmologists tell us that our present astronomical universe --- a conglomeration of planets, stars and clustered galaxies, together with...
  33. P

    Evolution in a Bottle: Can Artificial Environments Create New Species?

    Is there any reason that evolution can't take place in an artificial environment? I contend that, just as hybrid swarms of plants in Nature can stabilize into new species, the process of prolonged hybridization can artificially create new species. I have been told that these hothouse plants...
  34. N

    Calculate time evolution of Schrodinger wave equation

    [SOLVED] Calculate time evolution of Schrodinger wave equation Homework Statement At time t=0 particle is in state: \psi\left(x\right)=\sqrt{2}A\phi_{1}(x)+\frac{A}{\sqrt{2}}\phi_{2}(x)+A\phi_{3}(x) where \phi_{n}(x) are eigenfunctions of 1-D infinite potential well. a) Normalize...
  35. D

    Evolution of blood clotting mechanism

    I'm currently reading this article by Ken Miller on a plausible account of how the blood clotting mechanism in vertebrates might have evolved. There's some things I don't understand but which I hope someone here will explain to me: Here's the article...
  36. M

    What is the relationship between evolution, statistics, and social engineering?

    Let me preface this by saying that economist Gregory Clark argues in "A Farewell To Alms" that one of the factors for the success of the industrial revolution was evolutionary in nature: disease killed off poorer members of the society and their position was taken over by sons of the wealthy who...
  37. Z

    Galaxies in filaments; a different evolution?

    Might galaxies in filaments http://pil.phys.uniroma1.it/twiki/bin/view/Pil/GalaxyStructures" for spirals? An extented flattened curve means more DM further out; the original discovery route of DM.
  38. M

    Time evolution of spherical harmonics

    Homework Statement At t=0, a given wavefunction is: \left\langle\theta,\phi|\psi(0)\right\rangle = \frac{\imath}{\sqrt{2}}(Y_{1,1}+Y_{1,-1}) Find \left\langle\theta,\phi|\psi(t)\right\rangle. Homework Equations \hat{U}(t)\left|\psi(0)\right\rangle =...
  39. vincentm

    News Evolution Vs. Intelligent Design in Florida

    http://blog.wired.com/wiredscience/2007/12/evolution-battl.html Why? :confused: They had their butts kicked in Dover, PA. And have been proven wrong, that ID is not a science. So why do they persist?
  40. E

    Evolution Function: A Clue to Understanding Self-Similarity

    I am reading a paper about self-similar.but this concept,evolution function,really troubled me.and i have seached wiki,but it didn't work.can anyone explain it wisely or provide a clue about it.
  41. L

    New Finding Challenges History of Evolution

    I got this link from someone: http://www.buzzle.com/editorials/10-27-2004-60892.asp I'm suspicious as no other science website has this as a main story, and it's strangely under the "editorial" directory. Give me your thoughts. Fact or fiction?
  42. C

    Given the initial state, Ican find the time evolution wave function right?

    Homework Statement At t=0, the particle is in the eigenstate S_x , which corresponds to the eigenvalues -\hbar \over 2 The particle is in a magnetic field and its Hamiltonian is H=\frac{eB}{mc}S_z . Find the state at t>0. Homework Equations Eigenstate of the Sx is...
  43. T

    How will the tragedy of the HIV epidemic effect human evolution?

    I believe I read the Black Death or Black Plague that effected Europe created a noticeable genetic bottlenecking in Europeans. HIV is still relatively new, but has anyone heard or have any ideas how HIV may effect human genetics and culture?
  44. D

    How Does a New Species Reproduce After Macro-Evolution?

    Okay I have a question. In micro-evolution, traits change among the same species, enough of these changes leads to macro-evolution. What is macro-evolution other than a different name and a series of small changes? A change big enough so that the new organism is no longer of the same species...
  45. DaveC426913

    Darwin vs. Evolution: An Overview of Theories & Myths

    I've just finished reading Darwin's Origin of Species - A Biography and I realize I'm not much closer to understanding the subtleties of evolutionary theory. At least, I think I'm not. What Darwin brought to the world, while it rocked the foundations of biology, was not his alone. The concept of...
  46. M

    Epidemic models which incorporate disease evolution

    I was wondering if anyone knew anything about epidemic models which take into account the ability of a disease to mutate. Basically I’m curious if there are any existing models which could predict how a rapidly changing disease might affect the progression of an epidemic, or how slower...
  47. A

    Evolution Qs: How Would We Evolve Physically & Mentally?

    This is a very general set of questions but sincere the same. If humans evolve to become telepathic, how would we have enough self control not to speak our private thoughts or accidentally insult others? Assuming we did gain enough self control during our evolution, what about the mentally...
  48. P

    Discover the Evidence for Evolution: Recommended Books and Articles

    can anyone recommend any good books or online articles that cover all the evidence in favor of evolution? I found this so far: http://www.talkorigins.org/faqs/comdesc/ it seems very long and detailed, considering I have very little background in biology. Is it a good site, nonetheless?
  49. J

    Help Historical evolution of understanding of SR

    I realize that the understanding of physics and the perferred description or mathematical representation of our understanding evolves over time. So I have a feeling that the answer to my question is strongly a mix of history and physics. Please, when at all possible add some of the historical...
  50. S

    Is Evolution Truly Flawed?

    Personally i don't think evolution is stupid. I was watching a documentary with this title out of interest. You can watch the full documentary here: h**p://tv-links.co.uk/video/9/5566/8296/53218/76984# (If you copy and paste the link and replace the *s with ts it should work, if not...
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