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Evolution. 15. The Big Idea. The theory of natural selection explains evolution and the diversity of life. Main Idea #1. Charles Darwin developed a theory of evolution based on natural selection. The 1st Scientific Hypothesis of Evolution.

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the big idea
The Big Idea

The theory of natural selection explains evolution and the diversity of life.

main idea 1
Main Idea #1
  • Charles Darwin developed a theory of evolution based on natural selection.
the 1st scientific hypothesis of evolution
The 1st Scientific Hypothesis of Evolution
  • French biologist Jean Baptiste de Lamarck offered the first complete explanation of evolution in 1809.
    • He was the first to argue that fossils were the remains of extinct animals.
    • His concept was transformational, meaning individuals transform their own traits in order to evolve.
  • Geologist Sir Charles Lyell - the principle of uniformitarianism.
  • Two parts:
  • laws of physics and chemistry remain the same throughout earth’s history
    • past geological events occurred by natural processes similar to those that observed today
  • He said Earth’s age must be measured in millions of years.
charles robert darwin 1809 1882
Charles Robert Darwin1809-1882
  • In 1831, Darwin sailed aboard the very small ship the HMS Beagle.
  • During his 5-year voyage, he collected a wide variety of flora and fauna from South America and surrounding islands.
  • He found long extinct fossils, including seashells in the Andes Mountains at an altitude of 13,000 feet.
  • He also witnessed earthquakes and severe erosion that helped to confirm his ideas about geology.
darwin the galapagos islands
Darwin & The Galapagos Islands
  • These volcanic islands are on the equator, 600 miles west of Ecuador.
  • Each island varied in tortoises, iguanas, mockingbirds, and ground finches.
  • The islands had similar climate, but varied greatly in vegetation.
  • Darwin inferred that island species originated in South America, and were modified over many years under the varying conditions of different islands.
darwin continued
Darwin (continued...)
  • Darwin conducted the remainder of his work at home in England, where all of his notebooks had been sent home ahead of him in October 1836.
  • His travel journal, The Voyage of the Beagle, was published three years later, but he continued his research on the evolution of species by natural selection.
  • Darwin first presented his ideas in a paper in 1844, but did not began writing the larger volume until 1856. By 1858, he had received a manuscript from Alfred Russel Wallace summarizing his ideas on natural selection.
  • Geologist Lyell was instrumental in convincing Darwin to publish a joint paper with Wallace.
  • Darwin’s book On the Origin of Species by Means of Natural Selection was published in 1859. All printed copies sold out in one day.
darwin s theory of evolution
Darwin’s Theory of Evolution
  • Darwin’s work actually included 5 separate theories
    • Perpetual Change is the basic theory of evolution on which the others are based stating that the world is constantly changing.
    • Common Descent (controversial theory) states that all forms of life descended from a common ancestor.
    • Multiplication of Species - species divide and split into different species, which can no longer interbreed
    • Gradualism - large differences actually originate from an accumulation of many smaller differences
    • Natural Selection - explains the selective processes of the environment, through a phenomenon called adaptation.
natural selection
Natural Selection
  • The Ideas Behind Natural Selection
      • Individuals in a population show variations.
      • Variations can be inherited.
      • Organisms have more offspring than can survive on available resources.
      • Variations that increase reproductive success will have a greater chance of being passed on.
types of evidence of evolution
Types of Evidence of Evolution
  • Fossil Record
  • Comparative Anatomy
      • Homologous Structures - similar structures inherited from a common ancestor
      • Vestigial Structures - structures that are reduced forms of functional structures in other organisms; get smaller over generations
      • Analogous Structures - structures that have similar function, but not similar shapes; not inherited from a common ancestor
evidence continued
Evidence (continued...)
  • Comparative Embryology - many embryos share characteristics that are not alike in the adult form
  • Comparative Biochemistry - the more closely related two species are, the more amino acid sequences they will share
  • Geographic Distribution - evolution may be closely linked to climate and geographical characteristics
  • Speciation is the evolutionary process by which new biological species arise.
    • Allopatric speciation - a physical barrier divides one population into one or more populations
        • mountain ranges, lava flows, channels between islands, wide rivers
        • believed to be the most common type of speciation
    • Sympatric speciation - no physical barrier separates the populations
        • the ancestor species and new species live side by side
types of evolution
Types of Evolution
  • Chemical Evolution - formation of organic molecules from inorganic substances
      • primordial soup; chemicals in the early ocean giving rise to organic, and eventually, living matter
  • Organic Evolution - changing of a species into something different by the accumulation of small changes over time