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. AnkurGarg

    Evolution Mnemonics (to remember phylogeny of humans, etc.)

    Can anyone provide me with a list of simple mnemonics to learn phylogeny of horse,phylogeny of humans,geological times list and others?? Ty in advance !
  2. E

    Will future stars create new elements through evolution?

    I was thinking about this the other day, and I was curious about what future stars will contain for their cores. If I understand correctly, the first generation stars in the early universe didn't contain (or contained significantly less) metals. As stars evolved, they contained more metals (or...
  3. AnkurGarg

    Why aren't microspheres and protocells living beings?

    Why aren't microspheres and protocells considered as living beings? What I know is that they do reproduce and exhibit metabolism.. so they fulfill the basic criteria of living systems. I am really confused about it!
  4. M

    Evolution & DNA: Does It Exist In All Life?

    Does DNA exist in all living things...Humans, extremophiles, plant life?
  5. Graeme M

    Evolution of the Human Mind: Understanding Brain Development Over Time

    I got to wondering about the development of the human brain, and the consequent development of human intelligence (and to an extent the mind). I googled the question and after reading several articles, was left not much the wiser in regard to the development of 'intelligence'. Part of my problem...
  6. TrickyDicky

    Descriptions of time evolution: closed vs open systems

    The equivalence between descriptions of time evolution in QM are rigorously defined and proved for conservative systems as explained for instance among many other sources in Jauch's "Foundations of quantum mechanics" in the chapter 10. However, and an exception is the cited reference, it is not...
  7. Ygggdrasil

    Lokiarchaeota and the Evolution of Complex Cellular Life

    Biologists split life into two broad categories: prokaryotes and eukaryotes. Prokaryotes are relatively simple single-celled organisms and are split into two groups (bacteria and archaea). Eukaryotes, on the other hand, are much more complex cells containing specialized compartments such as...
  8. zonde

    Are photon probability amplitudes entangled in a two-filter setup?

    I have thought for some time that it is physically correct to treat photon source as time evolving rather than photon state (i.e. using Heisenberg picture rather than Schrodinger picture) so I was glad to find this picture in Feynman's book (QED: The Strange Theory of Light and Matter): In...
  9. virgil1612

    Evolution toward a white dwarf

    Hello, I will need to talk to students about the evolution of a solar-like star. We will look at a diagram like the following: It will be a descriptive presentation, no mathematics. I know pretty well what happens until the formation of the carbon core. The linear upper line happens because...
  10. A

    Prove evolution of Hubble parameter

    Homework Statement Prove that Homework Equations [/B]The Attempt at a Solution Without cosmological constant, one finds that where w is the ratio between pressure and density.[/B]
  11. excelsior

    Reading Recommendation - Sun / Stellar Evolution

    My apologies for starting a thread on a seemingly easy and searchable topic. But, alas, I've searched here, Amazon, google, Goodreads etc and wanted to get some recommendations. Specifically book suggestions on The Sun and / or Stellar evolution. I've ran across several intriguing textbooks...
  12. B

    Unlocking the Potential of Titan: Igniting Methane Oceans for Photosynthesis

    If a methane-filled planet or moon like Titan was pulled toward a star, as the methane warmed and became gaseous, would it be possible to ignite it, converting the methane oceans to H2O with a CO2 atmosphere, which could in turn cause photosynthesis to naturally occur? If it's possible, it...
  13. X

    Time Evolution for particle with potential suddenly removed

    Homework Statement This is a problem from my Statistical Mechanics book by Pathria. [/B] At ##t=0##, the ground state wavefunction of a one-dimensional quantum harmonic oscillator with potential ##V(x)=\frac{1}{2}\omega_0^2 x^2## is given by, \psi(x,0)=\frac{1}{\pi^{1/4}...
  14. wolram

    Dark Energy Evolution: Is $\Lambda$CDM Model the Best?

    Is Dark Energy a constant ? arXiv:1503.04923 [pdf, ps, other] Is there evidence for dark energy evolution? Xuheng Ding, Marek Biesiada, Shuo Cao, Zhengxiang Li, Zong-Hong Zhu Comments: 8 pages, 2 figures. Accepted for publication in the ApJL Subjects: Cosmology and Nongalactic Astrophysics...
  15. M

    How can I calculate the exponential of a non-diagonal matrix?

    Hello, I have a problem where I'm given the following H=-\frac{\hbar\Omega}{2}\sigma_x\quad\quad\quad\textrm{and}\quad\quad\quad\Psi(0)=\left|0\right\rangle\quad Where \sigma_x=\begin{pmatrix}0 &...
  16. Keith Mackie

    Two great fallacies in science

    The first is taught universally (as far as I can make out) at school and university, that Galileo discovered that all bodies (at least in vacuum) fall at the same rate. He didn't. He read it in Lucretius' great work of Roman science "De Rerum Natura" published about 60 BC. Lucretius followed...
  17. naima

    Time evolution of a state. (a missing t)

    Hi PF there is one thing that i cannot understand here. Please look at eqn 1068 I try to compute the first term (without ##V^\dagger##) I get something like ##c_f (t) =-i/\hbar exp [i(\omega + \omega_{fi})t/2] \frac{sin(\omega + \omega_{fi})t/2}{(\omega + \omega_{fi})/2} \}## Unlike eqn 1071...
  18. Calpalned

    Human evolution -- Neanderthals and Homo Erectus

    What differentiates a homo erectus from a neanderthal? They look very similar as they both lack chins and have brow ridges. To me, a neanderthal seems like a large brained homo erectus. Modern human skulls, on the other hand, look completely different. Thanks
  19. h6ss

    Is Evolution Slowing Down Due to Protective Mechanisms Against Mutations?

    Hey there, before I start I just want to point out that I'm a statistician and doesn't know much about biology. I've worked with artificial neural networks, which required a minor understanding of some biological concepts, but apart from that, my level of knowledge in biology is very limited. I...
  20. Pterosaur

    Has the Number of Galactic Revolutions Influenced Spiral Galaxy Formation?

    Greetings all, First time poster and an absolute neophyte, please forgive my utter cluelessness in advance. So I was reading "Why does the Milky Way rotate?" (http://phys.org/news/2015-02-milky-rotate.html), and it brought to mind a question that's niggled at me every so often when my...
  21. Suraj M

    Evolution, short term or long term adaptation?

    I had a small question, which one contributes more to evolution: 1)short term adaptation and heritable 2)long term adaptation and heritable ?
  22. Diploria

    Origin/fitness effect of brain coral's grooves?

    Hello, Brain corals, like my avatar's Diploria, get their moniker for visually obvious reasons. I wonder whether there are informed hypotheses how come they look that way. The answer to such a question would probably be partly a morphology/pattern formation story, and partly an adaptive story...
  23. B

    Calculate A's Evolution Over 1000 Generations with Mutation Probability

    Homework Statement A strand of length L begins life as all A's. Assume that each letter evolves independent of all the rest until today, 1000 generations later. Within each generation there is a ##\mu## probability that the letter mutates to either C, G, T. Finally, assume that once a letter...
  24. carllacan

    Obtain Time evolution from Hamiltonian

    Homework Statement A quantum system with a ##C^3## state space and a orthonormal base ##\{|1\rangle, |2\rangle, |3\rangle\}## over which the Hamiltonian operator acts as follows: ##H|1\rangle = E_0|1\rangle+A|3\rangle## ##H|2\rangle = E_1|2\rangle## ##H|3\rangle = E_0|3\rangle+A|1\rangle##...
  25. G

    Evolution or action potential.

    Action potential is defined as" the local voltage change across the cell wall as a nerve impulse is transmitted" Now my question is "why it happens? i.e.,why organism evolves?
  26. P

    Time-dep Hamiltonian commute with time evolution?

    Hi all, I'm attempting to prove that i \frac{d \xi (t)}{dt}=[\xi(t),H(p,q ; t)] where the Hamiltonian is explicitly time-dependent, in general. We also have some unitary U(t) which generates time-evolution. I wrote up a quick proof but realized afterward that I had assumed that H and...
  27. S

    Observational data for evolution of Hubble rate

    Is there any observational data available for evolution of Hubble rate? To give some context, read the dark energy FAQ by Sean Caroll here. He says: "If the universe is decelerating, the Hubble constant is decreasing. If the Hubble constant is increasing, the universe is accelerating. But...
  28. T

    The Power of Weakness: Tracing Human Evolution

    Is physical weakness the catalyst that started Human evolution?
  29. P

    Adiabatic evolution and floquet theorem

    Hello everybody, I'm trying to understand if is possible to say something about the Floquet exponents, in the limit of a very slow changing on time. I try to explain. Given the differential equation $$ \dot{\vec{v}}(t) = A(t) \vec{v}(t) $$ with $$ A(t+T)=A(t) $$ a monodromy matrix is given...
  30. Y

    Why are humans attracted to good looking mates?

    It may not be the general case but this is what it seems from experience. But what's the reason? Do looks indicate health or any other desirable characteristics?
  31. Manraj singh

    Evolution and theory of conservation of energy

    Life started from a single cell, right? And now we have countless number of cells on our planet. So is this like new matter being created? So there is more energy on the planet as of now? How is the energy on the planet being conserved? I possibly framed the question wrong, but I hope you...
  32. Xenosum

    Time Evolution of the Complex Scalar Field

    Homework Statement Consider the Lagrangian, L, given by L = \partial_{\mu}\phi^{*}(x)\partial^{\mu}\phi(x) - m^2\phi^{*}(x)\phi(x) . The conjugate momenta to \phi(x) and \phi^{*}(x) are denoted, respectively, by \pi(x) and \pi^{*}(x) . Thus, \pi(x) = \frac{\partial...
  33. M

    Quantum system time evolution

    Homework Statement A quantum system has Hamiltonian H with normalised eigenstates ψn and corresponding energies En (n = 1,2,3...). A linear operator Q is defined by its action on these states: Qψ1 = ψ2 Qψ2 = ψ1 Qψn = 0, n>2 Show that Q has eigenvalues 1 and -1 and find the...
  34. B

    Time evolution, Hamiltonian

    Homework Statement A magnetic field pointing in ##\hat{x}##. The Hamiltonian for this is: ##H= \frac{eB}{mc}\begin{pmatrix} 0 & \frac{1}{2}\\ \frac{1}{2} & 0 \end{pmatrix}## where the columns and rows represent ##{|u_z\rangle, |d_z\rangle}##. (a) Write this out in Dirac...
  35. M

    Succinct Definition of Biological Evolution

    Anyone exposed to academic rigor would find the use of the term "biological evolution" to be rather vague. There is something about Darwin and common descent and then it starts to get somewhat vague. Is there a definitive definition of "biological evolution"? I offer this in the spirit...
  36. D

    A few conceptual questions on time evolution of quantum states

    Hi guys, Sorry if this isn't quite the right place to post this, but I have a few conceptual questions that I'd like to clear up about time evolution of a quantum state. Firstly, what is the exact argument for the evolution operator \hat{U}\left(t,t_{0}\right) being independent of the initial...
  37. Q

    Boundaries of Time in The Evolution of The Universe

    Given The Hawking-Hartle state is an initial state of the very early universe If the universe very far in the future asymptotically approaches 0K, what is the name of this final state of Maximum Entropy Does time stop at Maximum Entropy final state of the universe Given the assumption that...
  38. D

    Unitary time evolution - products of consecutive evolutions

    Hi all, I was wondering if anyone could clarify my understanding of unitary time evolution of quantum states, in particular for products of time evolution's: Suppose we know state of a quantum system at t=t_{0}, given by \vert\psi\left(t_{0}\right)\rangle, then to determine its state at...
  39. V

    Homogeneous gravity field time evolution position and momentum operato

    Homework Statement I am trying to solve Problem 21 from this sheet: Homework Equations The equation describing the time evolution of operators is given in the problem. The Attempt at a Solution I have found the commutators of the position and momentum operator with the...
  40. I

    Finding the Time Evolution of a Particle in a Divided Box

    Homework Statement A box containing a particle is divided into a left and right compartment by a thin foil. The two orthonormal base kets |L> and |R> stand for the particle being in either the left or the right compartment, respectively. Hence, any state ket in our system can be...
  41. edpell

    Evolution: Could speciation in humans happen by choice?

    I think "physics" forum is not the place to find a discussion on evolution. I am hoping someone can point me to a place where evolution is discussed. Let me be clear I do not want a discussion of whither evolution is real. I am looking for a group of people ALL of who accept evolution to discuss...
  42. binbagsss

    Quantum Mechanics - Time evolution operator , bra ket states.

    The question is to calculate the time evoution of S_{x} wrt <\Psi(t)\pm l where <\Psi\pm (t) l= ( \frac{1}{\sqrt{2}}(exp(^{+iwt})< \uparrow l , \pm exp(^{-iwt})< \downarrow l ) [1] Sx=\frac{}{2}(^{0}_{1}^{1}_{0} ) Here is my attempt: - First of all from [1] I see that l \Psi\pm (t) > = (...
  43. P

    Although the wrong theories contributed to scientific evolution

    Dear friends, I am writting a simple essay about the mechanisms of scientific evolutions, where I would like to point out the main driving forces that induce scientific progress. I would like to give simple examples from history of science (e.g Physics, Astrophysics, Mathematics, etc.)...
  44. V

    Regarding human evolution and evolution in general

    I spoke to someone that said that the reason we know humans originated from evolution is because there is no other scientifically possible explanation. I originally thought the reason we knew humans originated from evolution because we had explicit evidence of human evolution. Although now that...
  45. K

    What are the Current Debates in Evolutionary Science?

    I'm curious about what debates are currently going on within the scientific community. Are there still things about evolution that scientists don't understand or agree upon? Links/sources would be greatly appreciated!
  46. X

    Time Evolution operator in Interaction Picture (Harmonic Oscillator)

    Homework Statement Consider a time-dependent harmonic oscillator with Hamiltonian \hat{H}(t)=\hat{H}_0+\hat{V}(t) \hat{H}_0=\hbar \omega \left( \hat{a}^{\dagger}\hat{a}+\frac{1}{2} \right) \hat{V}(t)=\lambda \left( e^{i\Omega t}\hat{a}^{\dagger}+e^{-i\Omega t}\hat{a} \right) (i)...
  47. P

    What's the probability of a similar evolution on a different planet?

    Although I have taken Discrete Mathematics I am really bad with probability and would appreciate your insight in this. I had a discussion with a friend about aliens. So the question that arose is what is the probability that aliens on a different planet somewhere look similar to an animal...
  48. X

    Time Evolution of Hydrogen Atom in a Magnetic Field

    Homework Statement A hydrogen atom is prepared in its ground state with spin up along the z-direction. At time t = 0 a constant magnetic field ##\vec{B}## (pointing in an arbitrary direction determined by ##\theta## and ##\phi##) is turned on. Neglecting the fine structure and terms...
  49. K

    Which language to use for evolution simulation

    Hi guys, my friend and i are planning on creating an evolution simulation. We are however, trying to balance between the amount of time to write code and the amount of time our simulation will take to run, and how fast it runs(the simulation is in real time). So, what programming language do you...
  50. TrickyDicky

    What is the impact of nonperturbative effects on time-dependent quantum theory?

    If I haven't understood this tricky stuff very badly when the Hamiltonian is time independent, then Schrödinger’s equation implies that the time evolution of the quantum system is unitary, but for the time-dependent Hamiltonian one must add some mathematically "put by hand" assumptions (although...
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