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Evolution and Natural Selection


Evolution and Natural Selection
u Charles Darwin’s theory of evolution is 1 of the 3 pillars of the science of zoology— the other 2 being Gregor Mendel’s theory of heredity and Louis Pasteur’s experiments disproving the theory of spontaneous generation.

u All 3 of these date to the middle decades of the 19th century. All 3 are backed up by decades upon decades of excellent work in experimental science. Only Darwin’s work remains controversial in popular culture, perhaps because it’s not really well understood.
u The theory of evolution as it is taught today was really laid out by a biologist named Ernst Mayr in the mid-20th century. He taught that Darwin’s theory was actually a system of 5 theories:
Evolution and Natural Selection

      That the living world is neither static nor cyclical but is undergoing perpetual change.
      That all living things descend from a common ancestor in a branching tree of life.
      That evolutionary processes produce multiplication of species by splitting and transforming older ones.
     That these processes happen very gradually by accumulation of l changes, not single large changes.
  That natural selection determines which changes are advantageous to a population of organisms, thus determining which organisms manage to reproduce and pass their features on to the next generation.
u For zoologists, natural selection is the most important part of this theory.
u A related process to natural selection is artificial selection, which is when humans intentionally direct the breeding of animals or plants. Whether we’re creating a Labradoodle or building a better banana, the idea is the same: The farmer, breeder, or scientist selects the desired trait and gets more of that trait in the next generation by giving certain organisms a reproductive advantage.
u In natural selection nature does the same thing, except the selection isn’t a conscious process. Nature isn’t deciding which traits to breed into the next generation; instead, when a series of mistakes occur in DNA replication, this gives rise to a change in the next generation of animals, and those that survive and reproduce best provide offspring that continue the selection process.
u Natural selection works on individuals within whole populations, not just on individuals in isolation, and it comes about because of the interaction of the individual within the population and its environment. If enough changes accumulate in a population, generation after generation, natural selection may create a whole new species over time.