Evolution Definition and 733 Threads

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. E

    Is there any real scentisit (who is not creationism) reject evolution?

    Hello all, I was wondering if there is any modern real scientist (who is not creationism) rejects evolution based on purely scientific views? Because may be his religious beliefs obstruct his scientific view. I am interested in a highly credited person under this description. Thanks
  2. S

    What Are Some Common Questions and Misconceptions About Evolution?

    Hey guys I was in a discussion with my friend and I couldn't answers some questions about evolution .. and since I'm not that good in biology, I hope that I get some explained answers. Q1 : How can mutations produce organs ? Q2 : Do genetic mutations produce positive and negative changes ...
  3. H

    Defeating Evolution: How Unnatural Factors Weaken Adaptation

    Life forms adapt, and thereby strengthen, by countering detrimental influences. Given that man is increasingly less dependent on his (natural) body defence mechanisms, and more reliant on (unnatural) man-made solutions (pharmaceuticals), is it the logical conclusion that the biological...
  4. C

    The cause of evolution of human brain?

    Hello, I was interested in human consciousness, and I picked up Daniel Dennett's book "Consciousness Explained" and something he claims there got me thinking: He says that human brain evolved from chimp-size to homo-sapiens-size in a period after humans learned to stand on 2 feet, and before...
  5. W

    Chromosome Count Proves Evolution is Wrong

    I’m wondering if that is some kind of unscientific thinking masquerading as scientific thinking. Does the thinking appear to be scientific but is, in fact, faithless to science’s basic values and methods?This definition is indebted to Sagan, The Demon-Haunted World, p. 13. Because...
  6. Spinnor

    Interesting simulation of a spiral galaxy evolution.

    Hope you enjoy the following, http://www.youtube.com/watch?v=_Ssc1GsqHds&feature=player_embedded From, http://planetsave.com/2012/10/20/galaxies-trend-towards-more-ordered-disk-like-forms-over-time-upending-old-assumptions/
  7. S

    News Is Creationism Gaining Support in Congress?

    He calls evolution a lie from the "pit of hell", not to mention embryology and the Big Bang theory. http://www.huffingtonpost.com/huff-wires/20121006/us-congressman-creationism/
  8. S

    Effects of the earth's mass on evolution?

    Here's a question, though I'm not sure if it is suited to the biology section, since it might overlap physics and Earth science. Hell, i don't know; I'm an English major :smile: Forgive me if i make any foolish assumptions. To what extent has the Earth's mass affected the types of life that...
  9. D

    Long Term Evolution Experiment

    I haven't read the Nature article. However, the newspaper article had a sufficiently complete description to infer what they did to infer. The scientist kept frozen samples of the distant ancestors, i.e., the bacteria that were first placed in a flask. Samples were taken from the flask...
  10. B

    How Did the Moon's Orbit Evolve Over Time?

    Homework Statement Extrapolate the evolution of the Moon's orbit backwards in time. Use conservation of angular momentum for the Earth-Moon system to derive a variant of eq. 1. You may neglect solar tides in your calculations, but comment qualitatively on their effects. Assume that kt1/Q1 has...
  11. H

    Understanding SELEX to Systematic Evolution of Ligands

    Could someone explain SELEX (systematic evolution of ligands by exponential enrichment) or at least direct me to a good resource online because so far I have'nt found a decent explanation or website regarding SELEX online.
  12. D

    Time evolution operator in terms of Hamiltonian

    Homework Statement "Show that if the Hamiltonian depends on time and [H(t_1),H(t_2)]=0, the time development operator is given by U(t)=\mathrm{exp}\left[-\frac{i}{\hbar}\int_0^t H(t')dt'\right]." Homework Equations i\hbar\frac{d}{dt}U=HU U(dt)=I-\frac{i}{\hbar}H(t)dt The Attempt at a...
  13. M

    Question about evolution of animal species

    Please explain something I don't understand about the evolution of animals that have sexual reproduction. I thought that being a separate species means an animal will have sexual intercourse resulting in fertile offspring only if the partner is of the same species. I shall cite the giraffe...
  14. I_am_learning

    The Evidence Behind Human Evolution: Probability & Chance

    We know the exact age of Universe and the earth. We know when life began on earth. Is the formation of life a result of random grouping of atoms and molecules? Is evolution the outcome of random mutations? If so, is the chances of such series of random mutations resulting in formation of...
  15. P

    I am aware that physicists are trying to derive born rule from unitary evolution

    I am aware that physicists are trying to derive born rule from unitary evolution. Has there been any success? What is the current status of that program?
  16. M

    Theory of Evolution disproved? (satire)

    Muahahahaaa, have a look they have found a perfectly preserved hominid skeleton inside the gaping mouth of a dinosaur: http://www.nmsr.org/Archive.html I like the length they went to to make up a true-looking story. Love the perfectly clean black dinosaur skeleton, ha ha.
  17. SixNein

    News Don't want your kid learning about the evils of evolution? Move to Missouri

    A few day's ago, the great state of Missouri passed Amendment 2 which has a clause that specifically states http://www.sos.mo.gov/elections/2012ballot/fulltext_1.pdf Along with other religiously inspired text that was mostly already covered under existing law.
  18. L

    Dirac's Quantum Mechanics - the definition of the time evolution operator

    Dirac's "Quantum Mechanics" - the definition of the time evolution operator I'm reading Dirac's "Principles Of Quantum Mechanics" to learn more about the formal side of the subject. I have a question about the way he defines the time evolution operator in the book. Either there's a mistake or...
  19. M

    Nonlinear evolution of the quantum mechanical state vector

    Hi, My understanding that one of the postulates of quantum mechanics is that the vector describing the quantum mechanical state of a system evolves in a linear fashion. My question is how this can be reconciled with systems where the system evolves in a non-linear fashion for example systems...
  20. I

    How does a non-linear Schrodinger equation implies non-unitary evolution?

    Hi, I several times heard that one way to describe the collapse of the wave-function is to add non linearities in the Schrodinger equation (I know that this approaches are not convincing but that's not my point), however, I don't see why a non linear SE would imply loss of unitarity? As long...
  21. R

    Why do we consider the evolution (usually in time) of a wave function ?

    Why do we consider evolution of a wave function and why is the evolution parameter taken as time, in QM. Look at a simple wave function $\psi(x,t) = e^{kx - \omega t}$. $x$ is a point in configuration space and $t$ is the evolution parameter. They both look the same in the equation, then why...
  22. T

    Lingusitics Oddball question about linguistics wrt evolution of language

    Has anyone ever tried to establish an approx rate that languages evolve, in a similar way that genetic change was used to establish a molecular clock of sorts? (disclaimer: i know zero about linguistics) thanks someone.
  23. T

    Time Evolution Of A 1-D Gaussian Wave Packet Under The Gravitational Potential

    Hello Colleagues, I am curious about a problem in Quantum Mechanics that incorporates the evolution of a Gaussian Wave Packet under the Gravitational Potential. What I am interested in is equation (3) in the following paper: "On the quantum analogue of Galileo's leaning tower...
  24. D

    Is there a limit to evolution?

    Are Earthian biological systems, in their present state, more complex than they were 200 million years ago? Do evolutionary adaptations reach a limit in terms of they're effectiveness? Perhaps I can restate this question. If a species from 200 million years ago was transported to present...
  25. E

    When does helium fusion occur in an evolution of star?

    When does helium fusion occur in an evolution of star? Well, i just need help in this confusing part of a star's life. First of all, when the sun finishes the H-fuel at core, why doesn't it immediatly use the H-fuel on the surface.. And then another doubt is, what causes the expansion of the...
  26. E

    The stellar evolution. Low Mass stars

    Well, this topic is driving me crazy so any answers or replies should preferably be detailed and in an easy way.. My question is i want a sum up of the evolution of a low mass star... I will give my answer and tell me where are the dropouts.. Let me begin,With a protostar accreting hydrogen in...
  27. H

    Modular construction of genomes allows rapid evolution

    Hi, I read the following recently in a book on genetics: The modular construction of genomes has allowed the relatively rapid evolution of biological complexity. I could'nt understand what the modular construction of genomes mean. Is it referring to genes which make up a genome?
  28. E

    Exploring the Evolution of Low Mass Stars

    In my book, it is written that in an evolution of a star, specifically the sun, IT will run low on hydrogen fuel but will have produced so much energy that it will expand slightly... Once H- fuel is used, the star will start fusing helium nuclei. This complex process can cause an explosion that...
  29. T

    Evolution of universe with differing SOL

    I have seen discussions of universes with different numbers of spatial dimensions, universes without a strong arrow of time, universes with differing physical constants, etc. but I was wondering (here it comes, you are wondering) (LOL) would our universe be substantially similar with a...
  30. K

    The time evolution operator (QM) Algebraic properties

    Homework Statement The hamiltonian for a given interaction is H=-\frac{\hbar \omega}{2} \hat{\sigma_y} where \sigma_y = \left( \begin{array}{cc} 0 & i \\ -i & 0 \end{array} \right) the pauli Y matrix Homework EquationsThe Attempt at a Solution So from the time dependant schrodinger...
  31. aleemudasir

    Is Evolution Thermodynamically Possible?

    Is evolution(biological) feasible thermodynamically? Why and why not?
  32. G

    How Does the Delta Emerge in the Time Evolution Operator's Exponential Form?

    If you have some Hamiltonian represented by a 2x2 matrix ## H = \left( \begin{array}{cc} 0 & \Delta \\ \Delta & 0 \end{array} \right) ## And you want to use the time evolution operator ## U = \exp ( - \frac{i}{\hbar} H t ) ## it says that ## U = \exp (- \frac{i \Delta}{\hbar} t) ## Why...
  33. P

    Perception, Intelligence and Evolution

    At what point does perception enter the process of evolution. Are all the mechanisms of evolution 'blind'? In other words, it seems that a tremendous power is ignored - an organism can perceive their environment so why doesn't evolution capitalize on this instead of relying on random mutations...
  34. StevieTNZ

    Evolution of Photons from Bell-States to Separable States

    Hi there, I know in this article - http://arxiv.org/ftp/arxiv/papers/1203/1203.4834.pdf - the authors discard the clicks at H at output b" with V at output c" (and vice versa), saying they are seperable states regardless of whether the decision to perform a bell-state measurement on photons #2...
  35. M

    What if the theory of evolution was determined to be false?

    Let's assume the theory of evolution was determined by scientists to be false and all of us accepted the idea that some supernatural being directly has created and continues to create species, with the exception of artificial selection. (This idea is a form of...
  36. 0

    Does Evolution has a role on beauty of Wood Duck bird?

    Does Evolution has a role on beauty of "Wood Duck" bird? Hey there, Lately I had a debate with a person on internet on whether beauty of Wood Duck has any relation to Evolution or not. At first he claimed that Evolution has nothing to do with beauty of species, and only narrow-minded...
  37. Y

    Evolution Homework - Genetic Variation

    Homework Statement 2. About 1 in 200 Amish are homozygous recessive for Ellis-van Crevald syndrome, which causes short stature, extra fingers and toes, and several other characters. A) What % of Amish people are likely to be heterozygote carriers for the disorder? B) If the...
  38. B

    How Are New Traits Generated in Evolution?

    Evolution is the passing of genetic traits from species to their offspring and the natural selection of evolution occurs because certain species die out when they are unable to cope with their environment and the surviving species continue to pass on their genetic traits, which serves as...
  39. T

    Cosmological models - Evolution of Inhomogenity

    Homework Statement I'm working on a project to find evolution equations for a cosmological model, where the following propagations equations are known, \dot{\mu}=-\Theta\mu \dot{\Theta}=-\frac{1}{3}\Theta^{2}-2\sigma^{2}-\frac{1}{2}\mu...
  40. D

    How to Find the Time Evolution of a Polarized Cavity Mode in Quantum Mechanics?

    Homework Statement Suppose that a particular x-polarized cavity mode is described, at time t = 0, by the state |ψ(0)> = (1/√2)(|n> + |n+1>) Find |ψ(t)> for t > 0. This is best done in the Schrodinger picture. Evaluate the expectation of the electric field operator Ex and the uncertainty...
  41. R

    Reproduction and Human evolution

    Hey, I recently watched a video on YouTube by Kenneth Miller, The collapse of Intelligent Design. One of the things he brought up in the lecture was a comparison between. Human and chimpanzee genome. What was specifically said was that we had 23 pairs of chromosomes while the chimp and all...
  42. S

    How Does Field Operator Evolution Hold in QFT?

    This is a doubt straight from Peskin, eq 2.43 ∅(x,t) = eiHt∅(x)e-iHt. This had been derived in Quantum Mechanics. How does this hold in the QFT framework? We don't have the simple Eψ=Hψ structure so this shouldn't directly hold. I'm sorry if this is too trivial
  43. D

    Calculating Averages in a Unidimensional Quantum System

    Homework Statement Hi, i would to resolve this problem of quantum mechanics. I have hamiltonian operator of a unidimensional system: \hat{H}={\hat{p}^2 \over 2 m}-F\hat{x} where m and F are costant; the state is described by the function wave at t=0 \psi (x, t=0)=A e ^{-x^2-x} where A is...
  44. G

    Question: How do symmetries and time evolution interact in quantum mechanics?

    My question is the following: when in quantum mechanics one introduces symmetry, says that a states and observables transform both, in order to mantain mean values intact (kind of like a change of coordinate system), i.e.: |\psi>\rightarrow U|\psi> and O\rightarrow UOU^\dagger...
  45. andrewkirk

    Question about evolution of a wave function

    As I understand it, where a system’s Hamiltonian is not time-dependent, the wave function of a system that is in state psi(0) at time t=0 evolves as: psi(t) = sum, over all eigenvalues E of operator H, of exp(-i*E*t / hbar) * <E|psi(0)> * | E> If the eigenvalues are continuous it is an...
  46. B

    Simple Question : Taste of Vegetables and Evolution.

    Hi, All: Please forgive my ignorance of much (most ) of this topic--and biology in general. Basically, I'm puzzled as to why most people do not find the taste of vegetables naturally attractive, despite vegetables being benefitial, maybe even necessary for a healthy life. It...
  47. Ivan Seeking

    How Did North Long Beach Transform Over the Decades?

    When I was very young, North Long Beach, Ca., was a very nice, very clean, very safe, very calm, completely white, middle-class suburb of Los Angeles. In the late 1960s and early ‘70s it began to deteriorate as slums in SW Los Angeles expanded and neighboring communities turned into slums. Then...
  48. E

    Atomic/Physic description of life, growth and evolution

    I have no idea where this topic belongs since it combines physics and biology. Is there a way to describe life, growth, and evolution in terms of Atoms or Physics. Or are they two completely different things?
  49. B

    3-10 points why you believe in the theory of evolution and big bang

    Can you give me 3-10 points why you believe in the theory of evolution and/or the big bang? this is independant of any other theories. I'd like it numbered. and just brief points, like a topic and brief explanation of why this makes you believe evolution and/or the big bang to be true. I'll...
  50. B

    Commutation of Hamiltonian and time evolution operator

    Can anyone explain how the time evolution operator commutes with the Hamiltonian of a system ( given that the the Hamiltonian does not depend explicitly on t ) ?
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