AP Biology

AP Biology Notes: The Origin of Life and Natural Selection

Three Things to Know about The Origin of Life and Natural Selection

  1. It is thought that the chemical components of life on Earth originated through radiation and storms. These compounds became increasingly complex, forming protobionts and, ultimately, living organisms.
  2. According to Darwin, species evolve via natural selection, in which animals with certain traits are more likely to survive and reproduce, passing on those traits.
  3. Selection can be stabilizing (median is encouraged), directional (the norm shifts toward one extreme), or disruptive (extremes are favored over the norm).

Key Topics–The Origin of Life and Natural Selection

Remember that the AP Biology exam tests you on the depth of your knowledge, not just your ability to recall facts. While we have provided brief definitions here, you will need to know these terms in even more depth for the AP Biology exam.

Origin Hypothesis

  • Protobionts: Metabolically active protein clusters that inaccurately reproduce; possible evolutionary precursors to prokaryotic cells

Darwin and Natural Selection

  • Charles Robert Darwin (1809-1882): Naturalist who came up with the theory of evolution based on natural selection
  • Jean-Baptiste de Lamarck (1744-1829): Naturalist who studied evolution and classified invertebrate organisms; Lamarck produced several theories of evolution including Philosophie Zoologique; best known for his incorrect theory of inheritance of acquired characteristics
  • Theory of evolution: Theory that organisms have developed over time to produce current biomes
  • Natural selection: Process by which organisms best adapted to their environment survive to pass their genes on through offspring; idea pioneered by Charles Darwin
  • The Origin of Species: Charles Darwin’s book in which he expressed his theory that species evolve through natural selection
  • Fitness: The ability of an organism to contribute its alleles and, therefore, its phenotypic traits to future generations
  • Stabilizing selection: Selection that maintains the same mean in a phenotypic distribution by removing individuals from both phenotypic extremes
  • Directional selection: Favors organisms within a population that have one extreme variation of a trait Disruptive (diversifying) selection: Favors organisms within a population with extreme variations of a trait over those with moderate variations

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