Gen Bio 4Q

• The Earth is about 4.5 billion years old and contains Zircon crystals as the oldest materials found in the crust.
• Formation of the Earth

  1. Collisions of many meteorites

  2. Cooling and solidification of the surface into crust

  3. Erosion, sedimentation and volcanic activity

  4. Formation of small protocontinents that grew to current size and shape about 2.5 billion years ago
• Life on Earth began about 3.8 billion years ago with single celled organisms such as cyanobacteria and stromatolites.
• Evolution of life forms

  1. Multicellular life forms evolved much later, starting with arthropods more than 500 million years ago

  2. Land plants evolved 475 million years ago

  3. Forest plants evolved 385 million years ago

  4. Mammals started evolving into existence 180 million years ago

  5. Homo sapiens only 200,000 years ago
• Geologic Time Scale (GTS)

  A system of chronological dating that relates geological strata (stratigraphy) to time, used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history
• Divisions of the Geologic Time Scale

  • Eon (largest division spanning one billion years)
  • Era (division spanning tens to hundreds of millions of years, distinguished by extinction events and appearance of new life forms)
  • Period (division spanning no more than one hundred million years, characterized by a single type of rock system)
  • Epoch (smallest division characterized by distinctive organisms)
• The geologic time scale is established using fossil forms that occur in rocks.
• Important Events in the Geologic Time Scale (in million years ago)

  • 4600 - Origin of Earth
  • 3800 - Earliest life forms
  • 3500 - First bacteria and archaea
  • 2400 - 'Great oxidation event' - oxygen started to build up in the atmosphere
  • 2300 - Ice age - Earth freezes over
  • 2000 - First eukaryotes
  • 900 - First multicellular organisms
  • 770 - Ice age - Earth freezes over
  • 540 - First chordates (with backbone), including the primitive ones
  • 510 - First fish
  • 450 - Major extinction
  • 420 - First plants and animals on land
  • 370 - First amphibians
  • 365 - Major extinction
  • 315 - First reptiles
  • 250 - Major extinction, including most marine animals
  • 225 - First dinosaurs
  • 200 - Major extinction
  • 180 - First mammals
  • 150 - First birds
  • 130 - First flowering plants
  • 65 - Major extinction, including dinosaurs
  • 2 - First humans (genus Homo)
  • 5 - Extreme global warming
• RECALL ON EARTH'S HISTORY AS MEANS TO UNDERSTAND MACROEVOLUTION
• Macroevolution

  Genotypic changes in a population level through time
• Paleozoic Era

  Era of "old life", lasted from about 542 million to 251 million years ago, many species of organisms lived in the Earth's oceans, not many species on land until middle of the era, amphibians and reptiles lived on land, many species of insects existed by the end of the era
• Macroevolution

  Can be seen over a few generations, used interchangeably with the term speciation
• Mesozoic Era

  Era of "middle life", began about 251 million years ago and ended about 65 million years ago, reptiles were the dominant organisms, including dinosaurs, small mammals and birds also evolved during the later parts
• Macroevolution

  Creation of new species and taxonomic groups, Diversification of species (divergent evolution), Accumulation of traits due to series of microevolution

  
• Cenozoic Era

  Era of "recent life", began about 65 million years ago and continues to the present, mammals became more dominant after dinosaurs went extinct
• Macroevolution: Patterns in the history of life
• Holocene Epoch


  The current period of geologic time, also called the Anthropocene Epoch due to global changes caused by human activity, began 12,000 to 11,500 years ago at the close of the Paleolithic Ice Age
• Macroevolution


  The study of evolutionary changes occurring at the level of species and above, explores the broader patterns and processes of evolution over long periods of time

  
• The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch (with the more recent time sometimes called Anthropocene) as a result of human activity.
• Speciation


  The formation of new species
• The Geologic Time Scale provides data with regards to evolutionary successions, thanks to discovered fossils that date back to a specific time in the geological time scale.
• Macroevolution generally refers to evolution above the species level

  
• Through the Geologic Time Scale, we have discovered animals that have existed billions or millions of years ago, most of which are already extinct.
• There are no firsthand accounts to be read, instead we reconstruct the history of life using all available evidence: geology, fossils, and living organisms (similarities)
• Evolution is the unifying principle for all the biological sciences, providing an explanation for the differences in structure, function, and behavior among life forms, and includes the change in characteristics of populations through generations.
• Basic evolutionary mechanisms like mutation, gene flow (migration), genetic drift, and natural selection are at work and can help explain many large-scale patterns in the history of life
• Evolution is a gradual process that occurs when the genetic composition of a population changes over successive generations, and the changes that occur are inheritable.
• Due to evolution, there is a diversity of organisms on Earth that are able to adapt to new environments.
• Classification of life: Taxonomical groups go from the most inclusive to more exclusive (species level)
• Uniformitarianism


  The principle that the same natural laws and processes that operate in the universe now have always operated in the universe in the past and apply everywhere in the universe
• Speciation events are seen thru Phylogenetic tree/cladograms
• Lamarckian Evolution

  Proposed by Jean-Baptiste Lamarck, the theory of evolution based on inheritance of acquired characteristics, where the bodies of living organisms were modified through the use or disuse of certain parts based on the need of the organism to adapt to an ever changing environment, and these modified parts were then inherited by the offspring
• Understanding phylogenies is a lot like reading a family tree
• Lamarck's theory of evolution was later displaced by Darwinism.
• When a lineage splits (speciation), it is represented as branching on a phylogeny
• Darwin-Wallace Evolution

  The mechanism of evolution accepted by many, proposed by Charles Darwin and Alfred Russel Wallace, based on natural selection where individuals with favorable variations are more likely to survive and reproduce, passing on their traits to offspring
• Phylogenies trace patterns of shared ancestry between lineages
• A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor
• Clades are nested within one another — they form a nested hierarchy
• Lamarck's Theory/ Lamarckian Evolution

  Environment requires greater use of that body part--> gets bigger as a result . Less use-/ not required-> deteriorated/ disappear