Bio Exam 2

• Birds were not the first feathered animals on Earth- dinosaurs were.
• The origin of birds from a lineage of reptiles is an example of macroevolution, evolutionary change above the species level.
• Earth formed about 4.6 billion years ago.
• Fossil stromatolites were formed by prokaryotes date back to 3.5 billion years ago.
• First stage of how life may evolved:

  The abiotic synthesis of small organic molecules, such as amino acids and nitrogenous bases.
• Second stage of how life may evolved:

  The joining of these small molecules into polymers such as proteins and nucleic acid.
• Third stage of how life may have evolved:

  The packaging of these molecules into "protocells"
• Fourth/final stage of how life may have evolved

  The origin of self-replicating molecules that eventually made inheritance possible.
• As a strong oxidizing agent, O2 tends to disrupt chemical bonds. Before the early photosynthetic prokaryotes added O2 to the air, Earth may have had a reducing atmosphere.
• Stanley Miller produced this model of the abiotic synthesis of organic molecules such as amino acids. 


  Model of abiotic synthesis

  
• The three stages that could have occurred

  on early Earth: abiotic synthesis of polymers, formation of protocells (assisted by clay), and self replicating RNA
• Natural selection could have acted on protocells that contained self-replicating molecules.
• Macroevolution: an evolutionary change above the species level.
• Macroevolution encompasses: the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery.
• Earth timeline: newest-oldest

  1. Hardean Eon (Earth created)
  2. Archaean Eon (appearance of prokaryotes and oxygen)
  3. Proterozoic Eon (evolution of plants and animals)
  4. Phanerozoic Eon (land plants and animals diversify)
• Colonization of land by "large" organisms did not start until 500 million years ago.
• Plants colonized land in the company of fungi. They have a symbiotic relationship.
• Today, the most widespread and diverse land animals are arthropods and tetrapods.
• Radiometric dating: based on the decay of radioactive isotopes (unstable forms of an element), and can date rocks and fossils.
• By dating rocks and fossils, scientist have established a geologic record of Earth's history.
• Carbon-12 to Carbon-14 ratio: we have the same ratio as the atmosphere. Once we die, carbon-12 does not change but carbon-14 is radioactive and we lose some at a steady rate known as half life.
• The fossil record: the sequence in which fossils appear in rock strata (rock layers=deeper the older), is an archive of evolutionary history.
• Geologic Record: based on the sequence and the ages of rocks and fossils, geologists have established the geologic history.
• In geologic records, eras and periods are seperated by major transitions in life-forms often caused by extinctions.
• The history of life on Earth has been shaped by plate tectonics.
• Earths crust is divided into giant, irregularly shaped plates that essentially float on the underlying mantel.
• 250 million years ago, plate movements brought all the previously separated landmasses together into the supercontinent Pangaea.
• The formation and split-up of Pangaea affected the distribution and diversification of organisms.
• Moving crustal plates cause continents to collide, pile up, and build mountain ranges, and produce volcanoes, and earthquakes that often occur at the boundaries of earths plates.
• The fossil record chronicles five mass extinctions when global environmental changes were so rapid and disruptive that 50% or more of Earth’s species were swept away in a relatively short amount of time.
• The Permian extinction is linked to the effects of extreme volcanic activity.
• The Cretaceous extinction, which included most dinosaurs, may have been caused by the impact of an asteroid.
• The loss of species that are now at critical risk of extinction would push our planet into a sixth mass extinction.
• The fossil record shows that it typically takes 5-10 million years for the diversity of life to return to previous levels.
• Permian Extinction occurred about 252 million years ago. It defines the boundary between the Paleozoic and Mesozoic eras. It claimed about 96% of marine animal species and at least 70% of terrestrial life. Widspread volcanic eruptions occured, and oxygen levels in the water dropped alot.
• The Cretaceous Extinction happened about 66 million years ago. We lost more then half of all marine species and many lineages of terrestrial plants and animals. Almost all dinosaurs went extinct.
• Adaptive radiation: brief periods of evolutionary change in which many new species evolve from a common ancestor.
• The origin of many new species often follows mass extinctions, colonization of new habitats, and the evolution of new adaptations.
• Adaptive Radiations Have Increased the Diversity of Life
• Evo-devo combines evolutionary and developmental biology. It is how slight genetic changes can become magnified into major morphological differences between species