6 LESSON_Q3

• Creationism


  The belief that all forms of life were already created in their present form and have remained unchanged since the beginning of time
• Carolus Linnaeus


  The Father of Taxonomy who initially believed that all organisms appeared on Earth in their present form and never changed
• Evolutionism


  The theory that life on Earth has evolved over time
• George Louis Leclerc


  • Suggested that life on Earth was 75,000 years old and that men had descended from apes
• Erasmus Darwin


  • Said the Earth was millions of years old and that species did evolve, even if he could not explain how
• Jean-Baptiste de Lamarck


  The first evolutionist to publicly defend his ideas, believed that organisms had evolved constantly, from inanimate to animate organisms and on to humans, based on a continuous chain of inherited characteristics passed from parents to offspring
• Catastrophism


  The theory that evolution was driven by violent catastrophic events or "revolutions" that had contributed to extinction of old species and the development of species to replace them in the newly created environment
• Uniformitarianism


  The theory that evolution had been influenced by slow changes since the beginning of time in the shape of the terrestrial surface that could not be perceived in a single human lifetime
• Charles Lyell


  Developer of the uniformitarianism theory
• Lamarckism


  Jean Baptiste de Lamarck's theory that organisms change over time in response to their environment, and that these acquired characteristics can be inherited by offspring
• Lamarck's theories


  • Theory of Need - organisms change in response to their environment and develop characteristics to adapt
  • Theory of Use and Disuse - organs not in use will disappear while organs in use will develop
  • Theory of Acquired Characteristics - acquired traits can be inherited by offspring
• Many scientists rejected Lamarck's theories as they understood that changes in cell or body structure do not necessarily lead to changes in genetic information
• Darwinian Theory


  Charles Darwin's theory of evolution based on natural selection, which is different from Lamarck's theories
• Darwin's theory of natural selection

  • Selection favours the survival of organisms with advantageous traits that allow them to better adapt to their environment
  • Organisms with less suitable traits are eliminated due to lack of resources
• Darwin was influenced by the work of Thomas Malthus, who argued that overpopulation and competition for limited resources drives natural selection
• Alfred Russel Wallace independently developed similar ideas about natural selection, which he shared with Darwin
• Darwin published his groundbreaking work "On the Origin of Species" in 1859, presenting his theory of evolution by natural selection
• Natural selection


  The process by which organisms with advantageous traits are more likely to survive and reproduce, leading to changes in a population over time
• Natural selection


  Leads to survival of the fittest - the preservation of the most well-suited individuals in a population
• Variations among individuals in a population increase the chances of survival, as organisms with the best-suited traits are more likely to adapt and reproduce
• Organisms that are best adapted to their environment will continue to reproduce, leading to shifts in the abundance of different traits and potentially increasing biodiversity over time
• Darwin's concept of natural selection


  • Traits are often heritable
  • More offspring are produced than can survive, leading to competition
  • Offspring vary in their heritable characteristics
• Darwin did not just propose that organisms evolved. He also proposed a mechanism for evolution: natural selection.
• Darwin's concept of natural selection


  • It was elegant and logical, and it explained how populations could evolve (undergo descent with modification) in such a way that they became better suited to their environments over time.
• Traits are often heritable

  • In living organisms, many characteristics are inherited, or passed from parent to offspring.
• More offspring are produced than can survive


  • Organisms are capable of producing more offspring than their environments can support. Thus, there is competition for limited resources in each generation.
• Offspring vary in their heritable traits


  • 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.
• The process of natural selection

  1. Variation

  2. Inheritance

  3. High rate of population growth

  4. Differential survival and reproduction
• Natural selection


  Genetic mutations that are beneficial to an individual's survival are passed on through reproduction. This results in a new generation of organisms that are more likely to survive to reproduce.
• Example of natural selection


  • Evolving long necks has enabled giraffes to feed on leaves that others can't reach, giving them a competitive advantage.
• If you took 1,000 giraffes and measured their necks, they're all going to be slightly different from one another. Those differences are at least in part determined by their genes.
• The ones with longer necks may leave proportionally more offspring, because they have fed better and have maybe been better in competing for mates because they are stronger.
• Natural selection can cause microevolution
• Fitness


  A measure of how well organisms survive and reproduce, with emphasis on "reproduce".
• Fitness depends on the environment
• Natural selection can act on traits controlled by many genes
• Stabilizing selection


  • Intermediate phenotypes are more fit than extreme ones.
• Directional selection


  • One extreme phenotype is more fit than all the other phenotypes.
• Disruptive selection


  • Both extreme phenotypes are more fit than those in the middle.
• About 200 years ago, many people believed that the Earth was only 6,000 years old.