Evolution

• Lamarckism was proposed by French biologist Jean Baptiste Lamarck at the beginning of the 19th century
• Lamarckism


  • New Needs
  • Use and disuse
  • Inheritance of acquired traits
  • Speciation
• George Buffon challenged the idea that the earth was older than 6000 years and that organisms changed over time in response to environmental pressure and random events
• The theory of evolution is based on the idea that all species are related and gradually change over time
• Use and disuse in Lamarckism

  Continually using a structure or process leads to its enlargement or more development
• Speciation in Lamarckism


  New characters acquired and transmitted to the next generation accumulate over generations, leading to the formation of a new species
• Lamarck's theory cannot account for all the observations made about life on Earth, as it implies that all organisms would gradually become complex and simple organisms disappear
• Lamarckism


  The theory of evolution based on the principle that physical changes in organisms during their lifetime, such as greater development of an organ or a part through increased use, could be transmitted to their offspring
• Major theories of evolution

  • Lamarckism
  • Darwinism
  • Neo Darwinism
• For many years Europeans believed that earth and organisms had been created about 6000 years ago and stayed unchanged
• Significance of Lamarckism: 1. It was the first comprehensive theory of biological evolution. 2. It explains the existence of vestigial organs in animals due to their continuous disuse. 3. It explains the development of strong jaw muscles and claws in carnivores due to their continued extra use. 4. It stimulated other biologists to look for the mechanism of organic mechanism
• New Needs in Lamarckism

  Changes in environmental factors lead to the origin of new needs in living organisms, which require special efforts like changes in habits or behavior to fulfill
• Inheritance of acquired traits in Lamarckism


  Traits changed or acquired during an individual's lifetime could be passed on to its offspring
• Lamarck's theory implies that all organisms would gradually become complex and simple organisms disappear
• Darwinism theory of evolution was forwarded by Charles Darwin and Alfred Russell Wallace in 1858
• The body changes resulting in phenotypic changes do not affect the genes in the gametes which give rise to the new generation
• Darwin explained that individuals of the same species are not identical
• Origin of Species

  In the course of long periods of time, the best-fitted and suitable individuals survived and adjust to the nature, new adaptations appear in organisms
• Darwin's evidence came from a visit to the Galapagos Islands
• Darwin's observations summarized in 5 main ideas

  • Geometric increase (Fecundity)
  • Variation
  • Struggle for existence
  • Survival of the fittest/Natural selection
  • Origin of Species
• Darwin's evolution theory

  • Natural selection is the key for evolution
• Lamarck believed that species started out simple and consistently moved towards complexity or closer to perfection
• Lamarck's Theory of inheritance of acquired traits was disproved because modifications brought about in an individual are not always transferred to the next generation
• Lamarck's theory was disproved because it cannot account for all the observations made about life on Earth
• Darwin studied the finches found on the different islands and noted similarities and differences
• Survival of the fittest/Natural selection

  Those members of a species that are better adapted to the environment will survive
• Individualistic adaptations and changes among some living beings have enabled them to sustain and multiply at a faster rate than others
• Behavior patterns of organisms

  Can be neutral, advantageous, or disadvantageous and may be used as a factor by natural selection
• Darwin's theory of natural selection

  Those members of a species that are best adapted to their environment will survive and reproduce in greater numbers than others less well adapted
• Mutations


  Important in introducing variation into populations
• Gene pool


  Refers to all alleles of all the genes found in the organism
• Neo-Darwinism Theory of Evolution is a revised version of Darwin’s theory of evolution by means of natural selection
• Advantageous behavior in geese

  Following 'mother goose' provides a survival advantage as the young goslings will be fed and protected. Goslings that do not show this behavior pattern are much less likely to survive
• Neo-Darwinism Theory of Evolution

  • Combines Darwin’s original theory, genetic theory, and ethology (animal behavior)
• Advantageous behavior


  • Imprinting in geese. Young geese (goslings) ‘imprint’ upon the first moving object that they see after hatching, and follow it everywhere
• Gene mutations


  • Neutral - the mutation will have generally no harm or benefit to the organism, Advantageous - frequency of an advantageous gene (allele) increases in the gene pool of a population, Disadvantageous - frequency of such a gene will decrease, and eventually disappear from the gene pool
• An advantageous allele of a gene


  Individuals with the advantageous allele will survive to reproduce in greater numbers, pass on their advantageous allele in greater numbers, increase the frequency of the advantageous allele in the gene pool of the population in the next generation
• Antibiotic resistance


  • A modern example of selection in action