theory of evolution

• Theory


  An explanation based on well-substantiated evidence that has been tested repeatedly and is what is accepted by the scientific community
• Evolution


  The gradual change in a population's genetic composition over successive generations
• Evolution provides an explanation for the changes observed in organisms throughout geological history when compared with those present today
• Evolution is based in theory
• Jean-Baptiste de Lamarck


  French naturalist, First evolutionist who believed that organisms change over time
• Lamarck's theories


  • Theory of Need
  • Theory of Use and Disuse
  • Theory of Acquired Characteristics
• Theory of Need


  Organisms change in response to the changes in their environment, Develop characteristics necessary for them to adapt in their environment
• Theory of Use and Disuse


  Organs that are not used will disappear while those that are constantly used will be developed
• Theory of Acquired Characteristics


  The acquired trait or structure will be passed on its offspring
• Charles Darwin


  British naturalist who proposed an entirely different mechanism to account for the evolution of species
• Darwin's voyage of the Beagle


  1. From 1831 to 1836, he was part of a survey expedition carried out by the ship HMS Beagle

  2. Over the course of his travels, Darwin began to see intriguing patterns in the distribution and features of organisms
• Darwin's observations in Galapagos Islands


  • Darwin found similar but nonidentical species of finches living on Galapagos islands
  • Each finch species was well-suited for its environment and role
• It took him 20 years to organize his data from his 5 week trip to Galapagos
• Darwin's finches


  Species that ate large seeds tended to have large, tough beaks, while those that ate insects had thin, sharp beaks
• The finches might have gradually adapted to local conditions (over many generations and long periods of time)
• These data led him to write a book "On the Origin of Species"
• Darwin is not the only one who had the idea of natural selection. Another scientist, Alfred Russel Wallace reached conclusions very similar to Darwin's at roughly the same time
• On The Origin of Species (1859)


  Wherein nature select organisms that will or will not survive based on their existing trait
• Natural Selection


  Individuals with the most favorable trait for an environment survive and pass on those traits to their offspring
• Natural Selection


  • Species Overproduction
  • Competition
  • Variation
  • Adaptation
  • Natural Selection
  • Speciation
• Species Overproduction


  Organisms tend to over reproduce, More offspring are produced than can survive
• Competition


  There is a struggle of existence and the survival of the fittest, Living space and food are limited
• Variation


  No two individuals of the same species differ in size, strength, and adaptive structures, The offspring in any generation will be slightly different from one another in their traits (color, size, shape, etc.), and many of these features will be heritable
• Adaptation


  It is the process of becoming better suited to the environment, It improves an organisms chance of survival
• Natural Selection


  Environment selects organisms that survived to be the parents of the succeeding generations
• Speciation


  Favorable adaptation gradually accumulate in the species and unfavorable ones disappear
• Lamarck's giraffe


  Neck elongate because of necessity since there are lots of competition with their food near the ground, These acquired characteristic is passed to their offspring
• Darwin's giraffe


  Before there are short necked, medium neck, and long necked giraffes, Because of competition on food, giraffe with longer necks are able to reach trees which allowed them to survive and reproduce
• Peppered moths


  • Before the industrial revolution in Britain, most peppered moths were of pale variety and were well camouflaged against birch tress that they like to sit on
  • Young mutant black coloring moths were easily eaten by birds, Therefore, pale moths were able to thrive than the black
  • Airborne pollution covered the birch tree bark with soot, Mutant black-peppered moths blended well on the darkened bark, However, the white variety became much more vulnerable to predators
• Lamarckism


  Early evolutionary theory proposed that individuals acquired characteristics during their lifetime that aided survival; these characteristics could then be inherited by offspring
• Darwinism


  It was later discovered by Charles Darwin that individuals born with traits that aided survival, were better suited to their environments and were therefore more likely to live long enough to reproduce and pass on those favourable traits