Evolution

• For life to begin, there must be carbon, which is the main component of macromolecules like carbohydrates, lipids, proteins, and nucleic acids
• The Miller-Urey Experiment aimed to create organic molecules from inorganic ones, with the hypothesis that organic molecules needed for life came from inorganic molecules
• Miller and Urey created an environment similar to early Earth, introducing energy with an electric spark, resulting in the formation of organic compounds like amino acids
• The Endosymbiotic Theory suggests that Chloroplasts and Mitochondria developed from small prokaryotic cells that once lived inside other prokaryotic cells
• Charles Darwin observed subtle differences in organisms during his visit to the Galapagos Islands
• Organisms appeared to be physically adapted to their environments
• Adaptations are characteristics or traits that allow organisms to best fit in their environments
• Darwin proposed that changes result from natural selection, where organisms best suited to the environment will survive and pass on their genes to future generations
• Darwin's ideas helped form the Theory of Evolution by Natural Selection, where evolution occurs through genetic change in a population over time
• Evolution is defined as genetic change in a population over time
• Population is a group of organisms
• Species is a group of similar organisms that can interbreed and produce fertile offspring
• Evolution occurs by natural selection, where beneficial traits (i.e., genes) will survive and be passed on to future generations
• Variation is the genetic differences in individuals due to environmental pressures
• Darwin's 3 Conditions Necessary for Natural Selection to Result in Change:

  • Over-Production of Offspring: more offspring are produced than will survive, ensuring at least some survive to reproduce
  • Individuals are different: some inherited characteristics help individuals survive
  • Some individuals are more suited for their environment, and these will survive and reproduce
• Individuals with beneficial adaptations are more likely to survive to pass on their genes
• Adaptation is a physical or behavioral trait that improves an organism's fitness or survival
• Natural selection: organisms with traits best suited to the environment survive and reproduce
• Mechanisms assisting evolutionary change:

  • Random mutation: creates allele variations through inheritable genetic changes
  • Gene flow: migration in or out of a population introduces more alleles; less flow leads to less variety
  • Sexual selection: choosing mates based on traits like attractiveness or strength
  • Genetic recombination: new allele combinations in gametes through processes like crossing over and independent assortment
  • Genetic drift: random change in gene frequency, affecting small populations and leading to a decrease in diversity
• Example of natural selection: Giraffes with longer necks are more likely to survive and reproduce, while those with shorter necks are less likely to live
• Example of sexual selection: A peacock may prefer to mate with a male peacock with colorful and full feathers over one with less colorful feathers
• The Theory of Evolution is based on the idea that living things are related, exhibit diversity due to natural selection and adaptation, and have evolved through common ancestors
• Darwin's idea of Descent with Modification states that all species have evolved from a common ancestor
• Four types of evidence support the Theory of Evolution:

  1. Fossils show species have changed over time

  2. Organisms of the same species separated by a physical barrier undergo geographic isolation

  3. Behavioral differences in a new group may lead to reproductive isolation

  4. Comparing similar physical traits to determine possible common ancestry, known as Homologous Structures
• Homologous Structures are structures with the same form but different functions, indicating a shared ancestry
• Vestigial structures are structures that no longer function as they do in other species, possibly indicating shared ancestry
• All organisms have DNA containing the same 4 bases: A-T, C-G
• Embryos of different species show similar stages of development, suggesting a common ancestor
• Many species have similar DNA sequences and proteins, pointing to a common ancestor
• Humans, apes, and monkeys are all primates
• Humans are believed to have evolved differently from other primates from an unknown common ancestor - another hominid
• Primate evolution traits that helped hominids succeed:

  • Opposable thumb
  • Bipedalism: walking on two feet, providing a visual advantage and hands free to use tools
  • Larger brain relative to body size
  • Advanced social interactions
• Primate evolution includes the order of mammals with flexible hands, forward-facing thumbs, enlarged brains relative to body size, and advanced social interactions
• Australopithecus afarensis, part of the primate family, had opposable thumbs, walked upright, used tools, and had complex language
• Homo erectus had a larger brain, smaller jaw and teeth, and a change in skull shape that allowed for grasping and handling objects, indicating more sophisticated communication and social structure
• Homo sapiens have a smaller, less protruding jaw and greater skull capacity, allowing for a larger brain and the development of language