chapter 8

• Scientific hypothesis


  Statement that provides 1 possible answer to a question, or 1 possible explanation for an observation
• Hypotheses


  Tested to determine their validity through experiments, observation, etc...
• Scientific theory


  Hypotheses that lead to successful predictions and explanations are synthesized into a statement that explains and makes successful predictions about observations
• Empirical studies


  Involve observation/ experiment to form ideas and hypotheses about nature
• John Ray


  • 1st scientist to carry out empirical studies of the natural world
  • Developed a classification system for plants/ animals based on anatomy and physiology
  • Later extended by Carolus Linnaeus
  • Helped scientists recognize and think about similarities/ differences between organisms
• Georges-Louis Leclerc, Comte de Buffon


  • Challenged the idea that life forms are unchanging
  • His 44-volume Histoire Naturelle compiled his understanding of the natural world
  • Noted similarities between humans and apes and thought they might have a common ancestor, suggesting that species change over time
  • Suggested that Earth was much older than 6000 years
  • His ideas were revolutionary for his time
• Fossil


  Preserved remains of a once-living organism (preserved in amber, dry caves)
• Mary Anning


  • Fossil hunter–most important discovery was the 1st plesiosaur (aquatic reptile)
  • Her work was acknowledged by Georges Cuvier, making her respectable
• Georges Cuvier


  • Credited with developing the science of paleontology – study of ancient life by examining fossils
  • Found that deeper (older) stratum→more dissimilar to species from today
  • Found evidence that new species appeared and others disappeared over time (showed that species could become extinct)
• Catastrophism


  Cuvier proposed that Earth experienced many destructive natural events in the past
• Charles Lyell


  • Rejected catastrophism–proposed based on the work of James Hutton
  • Uniformitarianism: geological processes operated at the same rates in the past as they do today
  • Theorized that slow, subtle processes could happen over a long time–resulting in changes
  • Forces that build and erode mountains are no different today than they were in the past
  • Floods in the past had no greater power than today–inspired by Darwin and others
• Jean-Baptiste Lamarck


  • In his book Philosophie Zoologique, he outlined his ideas about changes in species over time
  • Thought that species increased in complexity over time, until they achieved a level of perfection
  • Hypothesized that organisms would become better adapted to their environments
  • Idea of inheritance of acquired characteristics
  • Suggested use and disuse: body parts not used would eventually disappear
  • Gave a hypothesis for how inheritance of characteristics from 1 gen to the next might happen
  • Noted that an organism's adaptations to the environment resulted in characteristics that could be inherited by offspring
• Evolution by natural selection


  Life has changed, and continues to change, during Earth's history
• Evolution


  Process of genetic change in a population over time
• Darwin observed that flora and fauna in Beagle were distinct from those in England and Europe. Ex. Rodents in South America were structurally similar to each other but different from rodents on other continents.
• Darwin observed fossils of extinct animals, such as the armadillo-like glyptodont, that looked similar to living animals.
• Finches and other animals seen on the Galapagos Islands resembled those on the west coast of South America. The islands formed at about the same time and have similar abiotic conditions.
• Galapagos species (such as tortoises and finches) looked identical at first, but they varied slightly between islands. Each type of Galapagos finch was adapted to eating a different type of food based on the size and shape of its beak.
• Through his experience with artificial selection (breeding pigeons and studying breeds of dogs and varieties of flowers), Darwin knew that traits could be passed on from parent to offspring and that sexual reproduction resulted in many variations within a species.
• Alfred Russel Wallace


  • Reached conclusions that were similar to Darwin's
• Thomas Malthus


  • Proposed that populations produced more offspring than their environments (Ex. their food supply) could support→populations reduced by starvation or disease
• Survival of the fittest

  Individuals with traits that helped them survive in their environments were more likely to survive to pass on these traits
• Natural selection


  Process by which individuals with favourable traits are more likely to survive and reproduce, passing on those traits to future generations
• Darwin proposed that all life descended from unknown organism
• Descent with modification


  Darwin's theory that populations change gradually over time, with new species emerging and others becoming extinct
• Darwin did not use the word evolution in the original edition of The Origin of Species, instead speaking of descent with modification
• Natural selection does not demonstrate progress; it has no set direction
• The Origin of Species, Darwin assembled facts that previously seemed unrelated and was 1st to publish the idea that life had changed over long periods
• Biologists, geologists, geographers, and paleontologists provided info that supported the theory of evolution by natural selection
• Fossil record


  Sedimentary rock with fossils provides a record of the history of life by showing the kinds of species that were alive in the past
• Fossils in young layers of rock (recent periods–closer to the surface) are more similar to species alive today than those in deeper strata
• Fossils appear in chronological order in the rock strata–probable ancestors for a species are found in older rocks
• Not all organisms appear in the fossil record at the same time–shows successive evolution of groups (kingdom) of species
• Transitional fossil


  Fossil that shows links between groups of organisms and shares characteristics common to 2 now separate groups–link the past with the present
• Transitional fossils


  • Basilosaurus and Dorudon (ancient whales with tiny hind limbs but led an entirely aquatic life)
  • Pakicetus and Rodhocetus (filled gaps in the fossil record of whales)
• Archaeopteryx


  • Fossil of a previously unknown dinosaur called Atrociraptor was discovered (similar to Archaeopteryx)
  • Fossils of Archaeopteryx show a transitional stage in the fossil record because this species had characteristics of both reptiles (dinosaurs) and birds
• Biogeography


  Study of the past and present geographical distribution of organisms
• Geographically close environments (desert and forest) are more likely to be populated by related species
• Animals found on islands often closely resemble animals on the closest continent
• Fossils of the same species can be found on the coastline of neighbouring continent