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. Abhishek Sethi

    I Time evolution of a wave function

    Hi, I just completed my second year of my physics undergraduate degree. And recently did a course on Quantum Mechanics. I have a few questions regarding the basic theory and postulates, probably, because due to lack of full clarity. So, Consider a wave function ψ(x,o), which is well behaved and...
  2. bananabandana

    How Does Time Evolution Affect Quantum Operator Matrix Elements?

    Homework Statement [/B] For a general operator ## \hat{O}##, let ##\hat{O}_{mn}(t)## be defined as: $$ \hat{O_{mn}}(t) = \int u^{*}_{m}(x,t) \hat{O} u_{n}(x,t) $$ and $$ \hat{O_{mn}} = \int u^{*}_{m}(x) \hat{O} u_{n}(x) $$ ##u_{m}## and ##u_{n}## are energy eigenstates with corresponding...
  3. entropy1

    I Proof of unitarity of time evolution in Susskind's book

    In "The Theoretical Minimum" of Susskind (p.98) it says that if we take any two basisvectors |i \rangle and |j \rangle of any orthonormal basis, and we take any linear time-development operator U, that the inner product between U(t)|i \rangle and U(t)|j \rangle should be 1 if |i \rangle=|j...
  4. H

    How did egyptian mathematical fractions evolve in antiquity?

    There are certain explanations on how integers might have evolved, like for example "the wings of a bird to symbolize the number two, clover--leaves three, the legs of an animal four, the fingers on his own hand five."1 Seeing all these, and making experience short--abstract, can be said to have...
  5. I

    I Evolution style algorithm to determine EOM

    I had seen a documentary about an algorithm that uses notions of evolution to deduce the equation of motion of a system by sampling a variable connected with the system. For example, they used the double pendulum case where they sampled the position of the free end of the pendulum and arrived...
  6. Docscientist

    Virus Evolution: Predictions for the Future

    Will virus evolve into something else few decades from now?
  7. Kay Nanny Jay

    Coevolution, Convergent & Divergent Evolution, Adaptive Radiation

    pls can u say something on coevolution convergent and divergent evolution and adaptive radiation
  8. V

    A Evolution of Scalar Field: Equation Demonstration

    I'm looking for a demonstration of the equation governing the evolution of the scalar field: ## \Box \phi = \frac{1}{\sqrt{g}} \frac{ \partial}{\partial x^{\mu}} \sqrt(g)g^{(\mu)(\nu)} \frac{\partial}{\partial x^{\nu}} \phi=0## I used the lagrangian for a scalar field: ## L = \nabla_{\mu}\phi...
  9. Graeme M

    Current thinking on diet and brain evolution?

    I went to a talk on nutrition recently which led me to do some research. Of particular interest to me is just what early humans ate, but I've also found a lot of uncertainty around what led to the evolution of the human brain. There seem to be a variety of arguments, from the claim that meat...
  10. Aafia

    What is meant by "mode of existence"?

    According Zimmermann in 1953 "evolution is the transformation of the form and mode of existence" so I want want understand what is mode of existence ?
  11. gracy

    Modern self-assembly theory of evolution

    There is a sentence in the note of " modern self -assembly theory of evolution " as follows "The accepted model of protobiogenesis suggests that information or proto-information flowed from amino acids in the geochemical matrix to protein in the first organism." Please help me to comprehend...
  12. J

    I Unitary Time Evolution: Explaining Open Quantum Systems

    Hi, I am a bit confused about unitary time evolution, I understand that a closed quantum system can be explained by unitary time evolution which ensures that the probability of all possible outcomes is always 1. But for an open quantum system we can't in general explain it with a unitary time...
  13. durant35

    I Macroscopic wavefunction evolution

    Hi guys, I saw mr. Nugatory's post on one of the older threads which got me a bit conceptually confused so I wanted to ask you a question regarding it. This is the original quote: "For most macroscopic systems most of the time, the wave function evolves in a way that makes quantum effects like...
  14. S

    Are human actions part of evolution?

    Me and my friend were talking about human activities. She said that humans are creating pollution, killing so many animals creating an imbalance in food chain, global warming etc. In short we are making it worse for ourselves and other species. My reply was whatever humans do is a part of...
  15. I

    Position representation of coherent state and time evolution

    Homework Statement I ended up solving the problem as I was typing it up, I am posting what I did anyway as it took so long to type and might be useful to someone else. I am trying to figure out the position representation of a coherent state and it's time evolution. I should be getting a...
  16. M

    A Why use adiabatic evolution instead of cooling?

    Hi everyone, For adibatic quantum computation one prepares the groundstate of a particular Hamiltonian and than adiabatically evolves the system to a problem Hamiltonian Hp which groundstate encodes the desired solution to a satisfiability problem. If the evolution takes place slowly the system...
  17. M

    A Computation time for adiabatic evolution

    Hi, my problem: following the adiabatic theorem we get an equation for the coefficients: \dot{a}_{m}=-a_{m} \langle{\psi_{m}} | \dot{\psi}_{m}\rangle - \sum_{n \neq m} \frac{\langle \psi_{m} | \dot{H}| \psi_{m}\rangle}{E_{n}-E_{m}} exp(\int_ 0^t E_{n}(t')-E_{m}(t') \, dt') we start in an...
  18. I

    Did tissues arise from other cells or cell differentiation?

    Hi I have a pretty specific question. It is in regards to tissues in multicellular organisms. Is there any information on how different cell grouping arose in multicellular organisms? I have some ideas from what I've so far read and learned: - Would this have happened because two different...
  19. C

    Other Book recommendations read for genetics, evolution, and neurobiology

    Hello everyone, So I'm a CS major college student. I've always been interested in biology, especially evolution and genetics; but recently I've been really interested in neurobiology. I read a lot from all kind of stuff and I thought I could read some books on these subjects. What I'm looking...
  20. Docscientist

    Organ Evolution: Classifying Organisms with Eyes

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  21. Docscientist

    Evolution: Understanding Our Common Ancestry with Chimpanzees

    What is the difference between saying "we evolved from chimpanzees" and "we and chimpanzees have a common ancestor"? The latter seems to be widely used.But don't they seem have a similar meaning? Thanks is advance,friends!
  22. J

    How did life emerge on Earth?

    Many people have claimed that evolution started life. I'd say it did not. Life started evolution. Before there is evolution, there must be life. Am I right?
  23. zawy

    Is the Moon responsible for reducing Earth's entropy and making life possible?

    Spontaneous negative entropy reactions can occur when the internal energy decrease is greater than the negative dS*T. dG=dU-dST is spontaneous if dG is negative. The moon is receiving at least 1E8 J/s from the loss of rotational energy from the Earth's water and air. A lot more rotational...
  24. A. Neumaier

    Ergodocity and unitary evolution

    [This thread split from https://www.physicsforums.com/threads/is-collapse-indispensable.854384/] I don't know a reference but I can indicate a proof. Ergodicity of unitary evolution of the wave function says that for given ##\psi_0## of norm 1, ##\psi(t)=e^{-itH}\psi_0## comes for some ##t##...
  25. Kitrak

    Why are Darwinian variations considered directional?

    I read that Darwinian mutations are considered as small and directional mutations. Why is that? Regardless of the type of mutation, a mutation (or a variation) is directionless- they are random. From what I understand, the direction is given to these variations through environmental and...
  26. HyperTechno

    Artificial Intelligence for human evolution

    Artificial Intelligence Technology can be used to develop intelligent Operation systems/ Management Systems for vehicles, buildings, factories, to control various systems.. etc. We can make robots out of it... and make intelligent equipment that improves the comfort ability of our day to day...
  27. Chronos

    Supermassive black hole evolution

    This paper; http://arxiv.org/abs/1601.05473, The Early Growth of the First Black Holes discusses the evolution of supermassive massive black holes [SMBH] as inferred from observations of high z quasars: which has provoked questions about the putatitve age of the universe and the time it allows...
  28. throneoo

    Time evolution of density profile

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  29. caters

    Humanoid Evolution: Dragon-Like Adaptability & Development

    Currently my humanoids have powers in their genetics but they all appear similar for a given gender, age, and height. My humanoids are 4 times as tall as a human and live on an earth-like planet that is 4 times bigger than earth(the size of neptune), and has 4 times as thick of an atmosphere...
  30. H

    Prove the time evolution operator is unitary

    How is (5.240b) derived? I get {U^{-1}}^\dagger(t, t_0)\,U^{-1}(t, t_0)=I instead. My steps: \begin{align}<\psi(t_0)\,|\,\psi(t_0)>&=\,<U(t_0, t)\,\psi(t)\,|\,U(t_0, t)\,\psi(t)>\\ &=\,<U^{-1}(t, t_0)\,\psi(t)\,|\,U^{-1}(t, t_0)\,\psi(t)>\\ &=\,<\psi(t)\,|\,{U^{-1}}^\dagger(t, t_0)\,U^{-1}(t...
  31. F

    How can morphological data accurately represent evolution?

    I was reading through the answer key of question 3 in an AP Biology free response (found here: https://secure-media.collegeboard.org/digitalServices/pdf/ap/ap15_biology_sg.pdf ), and it had this question: "Identify whether morphological data or amino acid sequence data are more likely to...
  32. zonde

    Unitary evolution and environment

    I have question about unitary evolution. As I understand it is assumed that unitary evolution concerns only quantum system and there are no changes in environment. First, I would like to ask if my understanding is correct? Second, from where comes this assumption? Does it comes with Schrodinger...
  33. D

    Conceptual questions on unitarity and time evolution

    From a physical perspective, is the reason why one requires that the norm of a state vector (of an isolated quantum system) is conserved under time evolution to do with the fact that the state vector contains all information about the state of the system at each given time (i.e. the...
  34. I

    Brain structure terminology consensus?

    I am wondering if there is any consensus on the structure terminology of the brain. 1 - I've heard that the brain has the reptilian, mammalian(limbic) and neocortex parts that overall perform specific functions and evolved in that order. - On that note, would reptiles have had any really...
  35. A

    R136a defies Laws of Stellar Evolution

    At 265 SM, and age 1.7 Million years, at 163,000 Light Years Away in the R136 cluster, is R136a. But, it shouldn't be alive now. It should have exploded given the model of Solar Mass Evolution at 200,000-375,000 Years old of age. It's in it's Wolf-Rayet phrase, but it still shouldn't be alive...
  36. S

    Evolution of magnetic field in a Z-pinch?

    How does the magnetic field in a Z-pinch develop with time? Does it get stronger and stronger as the pinch contracts? How strong? Where can I read about it on an intermediate or perhaps advanced level? I'm looking for both books and articles. S.A.
  37. Sace Ver

    Evolution of Horses: Comparing the Foot to the Human Hand

    Would you consider the foot of the modern horse to be analogous or homologous to the hand of a human? I'm confused because I'm not quite sure. I don't really see how they look similar or if they are even used for a similar purpose.
  38. P

    Human Evolution-Bacteria Conjugation

    So evolution is based on the premise that successive mutations lead to phenotypic changes ultimately resulting in varied species. This despite the fact that many mutations in nature are actually deleterious to that species. The question I have then, is that if mammalian evolution produced...
  39. F

    Interaction picture - time evolution operator

    Hey all, I got some question referring to the interaction picture. For example: I have the Hamiltonian ##H=sum_k w_k b_k^\dagger b_k + V(t)=H1+V(t)## When I would now have a time evolution operator: ##T exp(-i * int(H+V))##. (where T is the time ordering operator) How can I transform it...
  40. Ygggdrasil

    Exploring the Ring of Life: Horizontal and Vertical Gene Transfer

    Since the time of Darwin, biologists have looked at the history of life as a tree showing how the common ancestor of all life gave rise to all extant species. However, as we have learned more about biology, we've found that organisms do not inherit genetic information from only their direct...
  41. Timelord88

    The first human : male or female

    We humans and chimpanzees had a common ancestor from which we seem to diverge. So that indicates that the common ancestor we had at some point gave birth to an offspring which would have slightly different features or mutations. So at some point in history of the common ancestor of humans and...
  42. Monsterboy

    The second law of thermodynamics and evolution

    Mod note: The link in the original post contained a link to a crackpot, anti-evolution website (against our rules) that discusses a rejected paper (also against our rules). This link has been removed. Here's a link to Retraction Watch that covers the same (retracted) paper...
  43. A

    Other What's the best highschool biology book?

    What's a good comprehensive book for a high school student on biology that has never studied the subject before? (Campbell seems to be college/university-level so I can't touch that)
  44. Amine Quentin

    Why are there no bones from the stages of monkey evolution?

    Why is there no bones of the stages of the evolution of monkeys? :oldconfused: As we have the bones of the stages of human evolution :oldconfused:
  45. Amine Quentin

    Evolution: Is It Fact or Fiction? | Biology Questions

    Hello Guys I'm not an expert in biology and do not know anything about I have some questions about evolution Is evolution fact and scientifically proven? And is there of biologists who say that evolution is wrong? Thank You
  46. K

    Differential equations time evolution

    Homework Statement Homework EquationsThe Attempt at a Solution Any help would be appreciated
  47. L

    Evolutionary theorist here

    I am an evolutionary theoretician, focusing on the dynamics of process that shape the generation of variation in organisms, including properties such as mutational robustness, the evolution of evolvability, and modularity in the genotype-phenotype map. My main mathematical area is development...
  48. A

    Evolution of Life-Supporting Elements

    Looking for research answering the following question: "What is the earliest point in time, in the Universe, that exoplanets comprised of life-sustaining elements such as carbon, water, etc. could have formed?" I've read that the earliest known stars likely formed about 500 million years after...
  49. AnkurGarg

    Vestigal organs definition clarification please

    Are temporary embryonic structures like gill clefts included under "Vestigeal organs"??
  50. M

    Properties of an evolved universe

    Hello All :) I've heard it proposed that a reason for the fine tuned nature of our universe in a way to allow the existence of complexity and life could be that the universe itself is the product of evolution in a multi-verse. I don't want to debate around the anthropological principle as I am...
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