Origins of Life & Hominid Evolution PDF

Earliest Ideas Spontaneous Creationism Generation Life arises from nonliving material Sudden appearance of life  So how did the Earth form? Most widely accepted hypothesis is Nebula Hypothesis Supporte...

Earliest Ideas Spontaneous Creationism Generation Life arises from nonliving material Sudden appearance of life  So how did the Earth form? Most widely accepted hypothesis is Nebula Hypothesis Supported by the Hubble Space Telescope Data: – Solar system formed from nebula (gas & dust) Early Earth Conditions 4.6 - 3.8 BYA - time on Earth was called the - Hadean Eon: – Frequently hit by asteroids & meteors – Earth molten planet, ~4 BYA cooling began & layers form – 1st atmosphere → ammonia, water vapor, & methane – O2 began to accumulate ~ 2 BYA Today’s Organic Molecule Hypotheses: suggests life arose gradually from inorganic molecules “building blocks” like amino acids forming first Amino acids combined to make complex polymers  Miller-Urey Experiment (1953) 1. Showed organic molecules can be made from inorganic compounds 2. Simulated early Earth conditions 3. Made amino acids  Sidney Fox (1964) 1. Built on Miller-Urey Experiment 2. Formed 12 amino acids 3. Demonstrated that amino acids could spontaneously form small peptides  Meteorite Hypothesis (1969) 1. Meteorite found in Austria had more than 90 amino acids, 19 that occur on Earth Amino acids could have … 1. Been here all along 2. Formed from early Earth’s materials 3. Arrived from meteors & asteroids 1. Iron-sulfide Bubbles Hypothesis Hydrothermal sea vents produce sulfur, mixes w/ water to make compartments of rock, may have housed 1st living cells as “membrane” Image result for hydrothermal vents 2. Lipid Membrane Hypothesis: 1. Liposomes form spheres from phospholipids 2. These may have been 1st cell membrane  RNA World Hypothesis Ribozymes are RNA molecules that can replicate & form proteins DNA can’t w/o enzymes (polymerase & helicase) RNA can form in a test tube from inorganic compounds BUT DNA stores info better & is more stable  Microbes Changed Conditions on Earth Oldest known fossils → cyanobacteria (3.5 BYA) – Formed stromatolites – Added Oxygen, 1st photosynthesis – Changed atmosphere Fossil stromatolites provide evidence of early colonies of life.  Eukaryotes Evolved by Endosymbiosis Endosymbiosis one organism inside another Lynn Margulis 1970’s, 1st to support Endosymbiotic Theory – Mitochondria & chloroplast – 1.5 BYA eukaryotes evolve – Evidence Includes: Own DNA & ribosomes Circular DNA like prokaryotes Copy themselves Same size as prokaryotes Theory of Endosymbiosis  The Story of Life on Earth: 1. Prokaryotic Anaerobic 2. Oldest known fossils marine cyanobacteria makes O2 3. Prokaryotic aerobic 4. Eukaryotic unicellular 5. Multicellular Life  Sexual Reproduction’s Impact Genetic variation is advantage Sexual reproduction led to evolution of complex multicellular life  Mammal w/ flexible hands & feet, forward looking eyes (depth perception), & large brain to body size Rotating shoulder joint, opposable thumbs  Prosimians oldest primate group (40 mya) Small & nocturnal Walking UPRIGHT required changes in skeletal anatomy Bipedal means walking on two legs Adaptive Advantages: Leave hands free for other things Higher reach into trees for foraging carrying infants, food, & using tools More energy efficient Predator avoidance Protecting infants Fossil Evidence Shows Change to Bipedal Locomotion Advantages: Leaves hands free for other things Allows for foraging Carrying infants, food, & using tools Predator avoidance Protection  Fossils of Hominids Most either Australopithecus or Homo genus Australopithecines lived 3-4 mya in Africa, small brains Homo genus evolved 2.4 mya H. habilis – 1st stone tools H. neanderthalensis – latest extinct group  Changes in the Human Skull Fossils Increased brain size in hominids Less protruding jaw, smaller Australopithecus Homo habilis Homo Homo sapiens afarensis neanderthalensis