What is Evolution: Definition and 724 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. uxioq99

    Exploring Solutions to Spin Evolution Equations

    By the statement of the question, a solution must take the form ##\begin{pmatrix} \Psi_1 \\ \Psi_2 \end{pmatrix}## and the energy operator will be as per usual ##\hat{E} = i\hbar \frac{\partial}{\partial t}##. I am confused by the fact that ##S_y = \frac{\hbar}{2} \begin{pmatrix} 0 & -i \\ i & 0...
  2. R

    I Understanding diagrams of the late stages of stellar evolution

    Hi, I have an upcoming exam in astrophysics. We have been told to make sure we study all figures and tables, s.t. we are able to explain them. However, I ran into these figures below, in my lecturer's PowerPoint and I do not know where they originate and aren't presented in my book. I'm having...
  3. jedishrfu

    Recent Article on the Evolution of a Theory of Covid Origins

    https://theintercept.com/2023/01/19/covid-origin-nih-emails/
  4. LittleSchwinger

    A Why unitary evolution?

    The usual justification for why the evolution of physical systems is unitary in quantum mechanics involves arguments like "probabilities must sum to 1" or similar arguments that apply equally to any CPTP map. I'm just curious what justifications people here would use for selecting out unitary...
  5. H

    I Global evolution of a Bell pair of photons

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  6. James1238765

    I Time evolution of the electromagnetic wavefunction on a lattice

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  7. S

    I Deviations of conservation laws in cosmological evolution?

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  8. R

    On the origin and the evolution of information in the Universe

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  9. Astronuc

    B Evolution of planetary system around a white dwarf

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  10. J

    Why do scientists call evolution a "theory"?

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  11. BillTre

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  12. Astronuc

    Formation and evolution of the Great Lakes in US/Canada border

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  13. DennisN

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  14. A

    Why do we consider Neanderthals a different species than humans?

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  15. Lren Zvsm

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  16. L

    Medical Evolution of people within a generation?

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  17. tworitdash

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  18. D

    A Evolution of Quantum state

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  19. Viishnu

    Searching for a book like Evolution of Physics or Physics for the Inquiring Mind

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  20. D

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    • deepalakshmi
    • Thread
    • Coherent Coherent state Evolution Quantum entanglement Quantum optics State Time Time evolution Vacuum
    • Replies: 2
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  21. T

    Evolution and preservation of endangered animals

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  22. D

    A Evolution of cat states

  23. D

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  24. M

    I ##\Lambda##CDM: Evolution of the population of galaxies

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  25. F

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  26. C

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  27. stephen8686

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  28. jk22

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  29. Demystifier

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  30. Astronuc

    Billion-year-old fossil, a missing link in the evolution of animals?

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  31. K

    I Evolution of a Boltzman distribution

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  32. pinball1970

    Human brain evolution

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  33. CptXray

    I Coherent state evolution - nonlinear Hamiltonian

    Given the hamiltonian: \hat{H} = \hbar \omega_{0} \hat{a}^{+}\hat{a} + \chi (\hat{a}^{+}\hat{a})^2, where ##\hat{a}^{+}##, ##\hat{a}## are creation and annihilation operators. Find evolution of the state ##|\psi(t) \rangle##, knowing that initial state ##|\psi(0)\rangle = |\alpha\rangle##...
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  34. Llukis

    I The time evolution of a Hamiltonian

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  35. S

    I Evolving laws of physics?

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  36. LCSphysicist

    Evolution of state/system

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  37. BillTre

    Update on Dog Evolution

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  38. Someone_physics

    A Conditional time evolution entropy and the experimenter?

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  39. Nick tringali

    The Obstetrical Conundrum: Fontanelles & Human Birth Canals

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  40. T

    B Question about the s-process and r-process in stellar evolution

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  41. C

    COVID The Evolution of the SARS-COV-2 virus

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  42. A

    Evolution — information increase and entropy

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  43. J

    I Energy in the Hamiltonian formalism from phase space evolution

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    • Jaime_mc2
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  44. Buzz Bloom

    Evolution of the hymen

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  45. S

    Binnig's fractal evolution applied to multiple universes?

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    • Suekdccia
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    • Replies: 1
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  46. A

    Math-probability and theroy of evolution

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  47. J

    Writing: Input Wanted What are the Consequences of a Longer PETM?

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  48. Amaterasu21

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  49. Leonardo Machado

    A Boundary conditions in the time evolution of Spectral Method in PDE

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  50. A

    Are these “flaws of evolution”?

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