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Emma van Schalkwyk English 72 cards

Cards in this deck (72)

  1. 1EvolutionA change in the gene pool from population to population
  2. 2Gene poolThe total of all the alleles present in a population at any one time
  3. 3Phylogenic TreeA phylogenetic tree is a diagram that represents evolutionary relationships among organisms.
  4. 4MacroevolutionEvolutionary changes on a large scale that occur over extended periods of time involving whole groups of species
  5. 5MicroevolutionSmall scale changes within gene pool over populations
  6. 6Analogous StructuresSimilar features that have evolved independently in unrelated species due to similar environmental pressures
  7. 7Homologous StructuresShow similarity in characteristics
    resulting from a common ancestry but different functions
  8. 8Molecular BiologyDNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
  9. 9DNAThe molecule containing all of the genetic information of an organism
  10. 10Nuclear DNANuclear DNA refers to the
    genetic material found in the nucleus of a cell
  11. 11Mitochondrial DNAMitochondrial DNA (mtDNA)
    found in the mitochondria can also be analysed to determine relatedness and when species diverged.
  12. 12BiogeographyThe study of the geographical distribution of species.
  13. 13Allele FrequencyThe percentage of each allele in a gene pool
  14. 14Founder EffectA new population is established by a small number of individuals from an original larger population
  15. 15Natural SelectionNatural selection is the process where individuals best adapted to their environment will survive AND reproduce and pass these favourable alleles to their offspring
  16. 16Disruptive SelectionDisruptive Selection favours both
    extremes at the expense of the average.
  17. 17Stabilising SelectionStabilising Selection favours the
    intermediate phenotype (have the highest fitness) and selects against two extreme phenotypes:
  18. 18Directional SelectionDirectional Selection favours the
    phenotype of one extreme over the average or other extremes.
  19. 19Migration/Gene FlowGene flow is the movement of alleles between populations
  20. 20ImmigrationImmigration is the entracnce of an organism/group of organisms into a population, resilting in new allele combinations.
  21. 21EmmigrationEmmigration is when an organism/group of organisms leave a population, resulting in a loss of alleles from the original population.
  22. 22Favourable PhenotypeA phenotype that is favourable will be selected for and the alleles become established in the gene pool as the individual’s chance of survival AND successful reproduction are increased.
  23. 23Unfavourable PhenotypeA phenotype that is harmful is unlikely to become established, as it will be selected against, due to the individual’s chances of survival AND successful reproduction being reduced.
  24. 24Genetic DriftGenetic drift is the random changes in allele frequencies due to chance.
  25. 25Fixed AllelesFixed as the only allele present in the gene pool (frequency = 100%)
  26. 26Lost AllelesLost from the gene pool (frequency = 0%)
  27. 27Selection PressuresSelection pressures are factors
    which affect an organism’s fitness or ability to survive and reproduce in an environment.
  28. 28Population BottleneckPopulation bottleneck is a significant reduction in the size of a population often due to a catastrophic event or human impact (e.g. hunting, volcanic eruption)
    The small sample that survives are unlikely to be representative of the original gene pool by chance.
  29. 29Non-Random MatingIn non-random mating, organisms may prefer to mate with others of the same genotype or of different genotypes.
  30. 30Assortive MatingAssortive mating is an individual’s preference to mate with partners who are phenotypically similar to themselves.
  31. 31Genetic DiversityThe differences in genetic make-up of a gene pool.
  32. 32Sexual ReproductionSexual reproduction occurs when the sperm from the male parent fertilizes an egg from the female parent, producing an offspring that is genetically different.
  33. 33FertilisationFertilisation is the process in which the nucleus of a sperm cell fuses with the nucleus of an egg cell to produce a zygote.
  34. 34MutationA permanent change to the DNA base sequence of an organism.
  35. 35Independent AssortmentThe alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
  36. 36Crossing OverThe exchange of DNA between paired homologous chromosomes (one from each parent) that occurs during the development of egg and sperm cells (meiosis).
  37. 37SegregationThe separation of paired alleles (versions of a gene) during gamete formation (meiosis) so that each gamete (sperm or egg) carries only one allele of each pair.
  38. 38Alllopatric SpeciationAllopatric speciation is the
    formation of new species from ancestral species when original gene flow was stopped by a geographical barrier.
  39. 39Stage 1The parent population expands its range and occupies a new part of the environment.
  40. 40Stage 2Gradual formation of geological barriers (formation of rivers/mountains) may isolate parts of the population
  41. 41Stage 3The isolated population(s) may be subjected to quite different selection pressures.These selection pressures will favour those individuals with traits suited to each environment.Allele frequencies for certain sub-species change, forming sub-species.
  42. 42Stage 4Each separated sub-species undergoes changes in its genetic makeup and behaviour. This will prevent mating with individuals from other populations.
  43. 43Sympatric SpeciationSympatric speciation is where two
    populations are in the same area and gene flow is stopped by a non-geographical barrier.
  44. 44Niche DifferentiationNiche differentiation (or resource partitioning) refers to the process by which natural selection drives competing populations into different patterns of resource use or different niches.
  45. 45PolyploidyPresence of 3 or more sets of chromosomes in a body cell. Polyploidy is an importance process in the evolution of many plant species, as changes in the number of sets of chromosomes between generations can lead to instant speciation through reproductive isolation
  46. 46Cause of PolyploidyFailure of chromosomes to seperate during meiosis because the 'spindle' doesn't form properly. Causes instant speciation as polyploids cannot reproduce with the parent species due to the difference in chromosome count. The resulting organism is therefore genetically and reproductively unique (new species)
  47. 47Autopolyploidyinvolves the multiplication of the entire genome within a single species.
  48. 48Allopolyploidywhen the sets of chromosomes originate from two or more ancestral species.
  49. 49Non-DisjunctionA failure of homologous chromosomes or sister chromatids to separate properly during cell division, specifically during meiosis. This results in gametes with an abnormal number of chromosomes
  50. 50SpeciesA group of organisms that can potentially interbreed with one another to produce viable, fertile offspring
  51. 51InterbreedingDifferent species do not interbreed because there is some kind of barrier to gene flow between them.
  52. 52Ring SpeciesOccurs when two apparently different species in one area are joined by a series of geographical and structural intermediates.
  53. 53ClineA gradual change in phenotypic characters from one part of a species range to another. Usually associated with environmental factors such as temperature or altitude and latitude
  54. 54DemesA species usually exists as distinct populations may be separated
    geographically. These local
    interbreeding populations are called demes.
  55. 55Reproductive Isolating MechanismA reproductive isolating mechanism is a barrier that prevents two organisms from differing species from mating and producing fertile offspring. They prevent gene flow.
  56. 56Prezygotic Isolating MechanismsThese act before fertilization to prevent successful reproduction
  57. 57Geographical IsolationResults from physical barriers such as mountains, rivers and oceans.
  58. 58Temporal IsolationDifferences in activity or breeding times (day, season, year)
  59. 59Gametic IsolationThe sperm and egg are not compatible – they can’t fuse and form a viable zygote
  60. 60Behavioural IsolationCourtship rituals and behaviour
    signals are species specific. These
    behaviours ensure mating within species.
  61. 61Habitat IsolationDifferent species may occupy different habitats with the same geographical area
  62. 62Structural IsolationStructural differences in the anatomy of reproductive organs prevent the delivery or
    acceptance of gametes
  63. 63Postzygotic isolating MechanismsThese act after fertilisation to prevent successful reproduction.
  64. 64Hybrid BreakdownThe first generation offspring (F1) are fertile, but the second generation (F2) are infertile or inviable.
  65. 65Hybrid SterilityEven if two species mate and produce offspring, the offspring may be sterile.
  66. 66Hybrid InviabilityA zygote is formed but fails to develop properly.
  67. 67Convergent EvolutionEvolution of similar adaptive features in originally different species because they are under similar selective pressures.
  68. 68Divergent EvolutionDivergent evolution is where two or more species form from a common ancestor.
  69. 69Adaptive RadiationAdaptive radiation is when multiple species arise, relatively quickly, from a common ancestor due to exploiting different niches.
    More common in periods of major environmental change.
  70. 70Co-EvoltutionThe term coevolution is used to describe cases where two (or more) species reciprocally affect each other’s evolution.
  71. 71GradualismSelection and variation that happens more gradually. Very gradually, over a long time, the population changes. Change is slow and consistent. Gradual change in intermediates due to constant selection pressure. No major change in form is selected for. The ancestral species no longer exists.
  72. 72Punctuated EquilibriumLong periods of stasis (no change) with short bursts of rapid change resulting in the formation of new species.
    Caused by environmental changes or new availability of niches

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Flashcards on Untitled, created by Emma van Schalkwyk on 12/05/2025.
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