Evolution

• Evolution


  Change over time, the process by which modern organisms have descended from ancient organisms
• Charles Darwin


  • Traveled as a naturalist on the HMS Beagle (22 years old)
  • Noticed similarities and differences among many organisms (finches, tortoises, armadillos, etc.)
  • Became convinced that organisms change over time
• Voyage of the HMS Beagle

  • Stopped in the Galapagos Islands (500 miles off the coast of Ecuador)

  
• Darwin's Observations

  • Many patterns of diversity
  • Found clues in the fossils he collected
  • The Galapagos Islands had a large influence on Darwin

  
• Darwin asked


  Is there a relationship between the environment & what an animal looks like?
• James Hutton (1785)


  • Proposed that Earth is shaped by geological forces that took place over extremely long periods of time
  • Estimated the Earth to be millions---not thousands---of years old
• Charles Lyell (1833)


  • Principles of Geology - explained how processes that changed the Earth in the past are the same processes that operate in the present
• If the earth can change over time


  Might life change as well?
• Jean-Baptiste Lamarck's Evolution Hypothesis (1809)

  • Tendency toward perfection
  • Use and disuse
  • Inheritance of acquired traits
• Thomas Malthus and Population Growth

  • Observed that human populations were increasing faster than the food supply
  • Food supplies increase linearly
  • Number of people increases exponentially
  • Overproduction and competition
  • Populations are limited by their environment
• Darwin noticed that all species tend to produce more offspring than can survive
• Darwin Presents His Case

  • Eventually published his findings in: On the Origin of Species
  • Credited with forming one of the most important theories in Biology- Evolution
• Alfred Russell Wallace (1823 – 1913)


  • Came to the same conclusions as Darwin, around the same time
  • Sent his ideas to Darwin, which prompted Darwin to write the book
• Evolution is a Theory

  A widely accepted idea, a general explanation for a broad range of well-tested data
• Darwin's view of Evolution

  • Inherited variation
  • Over-production
  • Competition for limited resources
• Fitness


  The ability of an organism to survive and reproduce in its specific environment
• Adaptation


  Any inherited characteristic that increases an organism's chance of survival
• Natural Selection


  • Survival of the fittest
  • The organism does not choose to adapt, he inherits specific traits that make him more likely to survive than others
• Organisms that are well adapted to their specific environment


  Will live long enough to reproduce
• Organisms that are poorly suited

  Will eventually die off
• Natural Selection is a VERY SLOW process
• Peppered moth during the Industrial Revolution

  • Peppered moths were white to hide against the white trees they lived on
  • Then the Industrial Revolution occurred, everything was covered in soot, the trees either died or turned black
  • Now the populations of Moths that survived and reproduced were black
• Reproduction and inheritance of more fit traits can lead to speciation over long periods of time
• Evidence of Evolution


  • Geologic Evidence
  • Geographic Distribution of Living Species
  • Anatomy
  • Embryology
  • Biochemistry
• Geologic Evidence


  • Rock Strata
  • Fossil records
• Superposition


  Lower layers form first, then newer layers on top (a type of relative dating)
• Fossils


  • Solidified remains/tracks of an organism
  • Some are from organisms that are now extinct
  • Shows that different organisms lived at different times
  • The closer the strata layers, the more similar the organisms tend to be
  • Can look at the half life of radioactive isotopes in rocks for absolute dating
• Fossils do not provide a complete history of the Earth, because not everything is fossilized
• Fossils show us that the animals alive today have not always been around
• Cladogram


  • one of several types of tree diagramsused in phylogenetics.
• Geographic Distribution of Living Species

  • Organisms that do not share a common ancestor develop similar physical features due to living under similar ecological conditions
  • New species form from a common ancestral species who is separated and then adapts to different environments
• Comparative Anatomy


  • Homologous structures
  • Analogous structures
  • Vestigial structures/organs
• Homologous structures


  Anatomically similar but used for different functions
• Analogous structures


  Features that serve identical functions and look somewhat alike, having very different embryological development and internal anatomy
• Vestigial structures/organs


  No longer in use or necessary for survival
• Vestigial structures/organs


  • Wings of ostriches, emus, flightless birds
  • Eyes on cave fish
  • Human appendix
  • Pelvic bone in whales
• Embryology


  • The early stages of different vertebrate embryos are very similar to each other, indicating a common ancestor
• Biochemistry


  • Looking at DNA and Protein sequences
  • DNA and amino acid sequences show that some species are more genetically similar than others
• Patterns of Evolution


  • Extinction
  • Adaptive Radiation (divergent evolution)
  • Convergent Evolution
  • Coevolution
  • Punctuated Equilibrium
• Extinction


  • 99% of all species that have ever lived are now extinct
  • Mass extinctions wiped out entire ecosystems in earth's history, clearing the way for the evolution of new organisms