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Evolution

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Mechanisms and evidence of evolution, plus human evolution.

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Evolution

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  1. 1Evolution
    The change in the heritable characteristics of biological populations over successive generations
  2. 2Darwin's most famous book on evolution
    On the Origin of Species, which first set out the theory in detail
  3. 3Four observable facts that establish evolution by natural selection
    (1) More offspring produced than can survive; (2) Traits vary among individuals; (3) Different traits confer different rates of survival and reproduction; (4) Traits can be passed from generation to generation
  4. 4Last universal common ancestor (LUCA)
    The common ancestor shared by all life on Earth (including humanity), which lived approximately 3.5–3.8 billion years ago
  5. 5Main evolutionary processes
    Genetic drift, natural selection, mutation, and gene flow
  6. 6Genotype
    The complete set of genes within an organism's genome (genetic material)
  7. 7Phenotype
    The complete set of observable traits that make up the structure and behaviour of an organism
  8. 8What molecule encodes genetic information?
    DNA (deoxyribonucleic acid), a long biopolymer composed of four types of bases
  9. 9Gene
    A portion of a DNA molecule that specifies a single functional unit
  10. 10Chromosome
    A long strand of DNA within cells; the specific location of a DNA sequence within a chromosome is known as a locus
  11. 11Alleles
    Different forms of a DNA sequence at a locus that vary between individuals
  12. 12How can new alleles be created?
    Through mutations in DNA sequences, which can alter the trait that a gene controls
  13. 13Example of peppered moth evolution
    Peppered moths exist in white and black morphs, demonstrating variation within a population that can be subject to selection
  14. 14Fixation in population genetics
    When a new allele either disappears from the population or replaces the ancestral allele entirely
  15. 15Mutation
    Changes in the DNA sequence of a cell's genome; the ultimate source of genetic variation in all organisms
  16. 16What proportion of mutations in coding regions of protein-coding genes are deleterious?
    About half are deleterious, the other half are neutral, and a small percentage confer a fitness benefit
  17. 17How can gene duplication contribute to evolution?
    Extra copies of genes provide raw material for new genes to evolve; one copy can acquire a new function while the other maintains the original function
  18. 18Human eye example of gene duplication
    The human eye uses four genes to sense light (three for colour vision, one for night vision), all descended from a single ancestral gene
  19. 19De novo gene birth
    The generation of entirely new genes from previously noncoding DNA
  20. 20Exon shuffling
    When small parts of several genes are duplicated and recombine to form new combinations with new functions
  21. 21Example of mutation affecting piglet coloration
    Wild boar piglets have camouflage stripes, but mutations in the melanocortin 1 receptor (MC1R) disrupt this pattern, causing different colorations in pig breeds
  22. 22asexual vs sexual reproduction regarding genes
    In asexual organisms, genes are inherited together (linked); in sexual organisms, offspring contain random mixtures of parents' chromosomes through independent assortment
  23. 23Homologous recombination
    A process in sexual organisms where DNA is exchanged between two matching chromosomes
  24. 24Two-fold cost of sex
    First described by John Maynard Smith: (1) only one sex can bear young in dimorphic species; (2) any individual passes on only 50% of genes to offspring
  25. 25Red Queen hypothesis
    An explanation for sexual reproduction as a means to enable continual evolution and adaptation in response to coevolution with other species in an ever-changing environment
  26. 26Gene flow
    The exchange of genes between populations and between species, which can be a source of new variation
  27. 27What can cause gene flow?
    Movement of individuals between populations (e.g., mice between inland and coastal areas, or pollen between plant populations)
  28. 28Horizontal gene transfer
    The transfer of genetic material from one organism to another organism that is not its offspring; most common among bacteria
  29. 29How does horizontal gene transfer contribute to antibiotic resistance?
    When one bacteria acquires resistance genes, it can rapidly transfer them to other species
  30. 30Bdelloid rotifers an example of
    Eukaryotic organisms that have received a range of genes from bacteria, fungi, and plants through large-scale gene transfer

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