Chapter 22: Descent with Modification

• Taxonomy


  scientific discipline concerned with naming and classifying the diverse forms of life
• Fossils


  a preserved remnant or impression of an organism that lived in the past
• Evolution


  defined broadly as: descent w/ modification; the idea that living species are descendants of ancestral species that were different from the present-day ones
• Strata


  rock layers formed when new layers of sediment cover older ones and compress them
• Darwin's Observations of Life

  1. Organisms are suited for life in their environments
  2. There are many shared characteristics of life
  3. The rich diversity of life
• Paleontology


  scientific study of fossils
• Catastrophism


  the principle that events in the past occurred SUDDENLY and were caused by different mechanisms than those operating today
• Uniformitarianism


  principle stating that mechanisms of change are constant over time
• Lamarck's Hypothesis of Evolution

  Based on 2 principles

  1. Use and Disuse: parts of the body that are used become larger & stronger, those that are not used deteriorate
  2. Inheritance of Acquired Characteristics: an organism could pass on these modifications to offspring
• Adaptation


  inherited characteristic of an organism that enhances its survival & reproduction in specific environments
• Natural Selection


  a process in which organisms w/ certain inherited characteristics are more likely to survive & reproduce than are organisms w/ other characteristics
• Artificial Selection


  the selective breeding of domesticated plants & animals to encourage the occurrence of desirable traits
• Natural selection can increase the match between organisms and their environment over time.
• If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.
• Individuals do not evolve. Populations change over time.
• Natural selection can only amplify or diminish heritable traits. Acquired characteristics cannot be inherited by offspring.
• Environmental factors change from place to place and over time. A trait that's favorable in one place or time may be useless or detrimental in other places or times.
• Homology


  similarity in characteristics resulting from a shared ancestry
• Homologous Structures


  structures in different species that are similar because of common ancestry
• Vestigial Structures


  a structure of marginal, if any, importance to an organism that are historical remnants of structures that had important functions in ancestors (ex: some snakes have remnants of the pelvis & leg bones)
• Evolutionary Tree


  a branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms (each branch point represents a common ancestor of all species that descended from it)
• Convergent Evolution


  evolution of similar features in independent evolutionary lineages (do NOT come from a common ancestor)
• Analogous


  having characteristics that are similar because of convergent evolution, NOT homology
• Biogeography


  the study of the past & present distribution of species; influenced by many factors, including continental drift
• Continental Drift


  the slow movement of the continental plates across Earth's surface
• Pangea


  supercontinent that formed near the end of the Paleozoic era, when plate movement brought all the landmasses of Earth together
• Endemic


  referring to a species that's confined to a specific, relatively small geographic area
• Aristotle thought that species were unchanging
• Paleontology was developed by a French scientist, Georges Cuvier. He noticed that the fossils in the older strata were more dissimilar than current life forms. He saw that from one layer to the next, some new species appeared while others disappeared.
• James Hutton said that Earth's geological features could be explained by gradual mechanisms still in operation today
• Galapagos Finches

  1. Volcanic islands near the equator
  2. Collected finches that were similar but seemed to be of different species
  3. Beaks were different due to different diets
  4. Darwin hypothesized that the Galapagos Islands were colonized by organisms that strayed from South America & then diversified
• Traits are inherited from parents to offspring
• All species are capable of producing more offspring than their environment can support
• Due to a lack of food or other resources, most of the offspring do not survive

  1. Individuals whose inherited traits give them a higher probability of surviving & reproducing in a given environment tend to leave more offspring than other individuals
  2. This unequal ability of individuals to survive & reproduce will lead to the accumulation of favorable traits in the population over generations
• Darwin saw a connection between natural selection & overproduction
• The Fossil Record

  1. Fossils show us that previous organisms differ from present day organisms
  2. Many species have become extinct
  3. Show evolutionary change in various groups of organisms
  4. Fossils can document the origins of new groups of organisms
  5. Early cetaceans
  6. Most mammals were terrestrial
  7. Fossils show the transition from life on land to the sea
• Embryological structures can compare early stages in development

  1. All vertebrate embryos have:
  2. Tail posterior to the anus
  3. Pharyngeal (throat) pouches that develop into gills or parts of the ears in throat
• We use continental drift to predict where fossils of different groups of organisms might be found
• Carolus Linnaeus: developed the two-part system of naming organisms called binomial nomenclature
• Darwin's concept of overproduction w/i a species was influenced by Thomas Malthus