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Unit 3A Origins of life

Unit 3A Origins of life. Click me!!. What happened first. 1. The cosmic dust left over from the “Big Bang” helped form the Earth– 4.6 Billion Years Ago

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Unit 3A Origins of life

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  1. Unit 3A Origins of life Click me!!

  2. What happened first • 1. The cosmic dust left over from the “Big Bang” helped form the Earth– 4.6 Billion Years Ago • Big Bang Theory- the theory that the entire universe began condensed together and in an instant began to rapidly expand outward ~14 billion years ago. • The resulting “cosmic dust” or matter expanded, cooled, and with the help of gravity interacted to form the stars, galaxies, etc. • The early Earth was a land of molten rock and violent volcanic activityand its crust was not yet solidified.

  3. 4.2 Billion years ago • 2. The Formation of the Oceans • As the earth was forming, gasses were released from the molten core in volcanic activity. • These gasses formed a cloud around the earth and were held as an atmosphere by the earth’s gravity. • As the earth cooled and the crust solidified, the vapor condensed to liquid water and the rain began to fall. • It rained such an enormous quantity over millions of years that the oceans of the world were formed.

  4. . 4 billion years ago • 3. Primordial Soup • Inorganic molecules in the water and atmosphere are believed to have reacted in the presence of the enormous amounts of energy on the planet to produce small organic molecules. • With the accumulation of the small organic compounds, the oceans became a “primordial soup” in which protocells (early, incomplete, primitive cells) formed. • Over time, these protocells accumulated more molecules and could function as unicellular organisms.

  5. 3. Primordial Soup (Continued) • Evidence for the creation of primordial soup: • In 1953, Stanley Miller and Harold Urey did an experiment that showed that the inorganic molecules on primitive Earth could have combined to create organic molecules organic soup, gasses, lightning (electricity), oceans, rainfall, heat source

  6. 3. Primordial Soup (Continued) • From the primordial soup came protocells, then the first unicellular organisms. • The first organism is believed to have been: • Unicellular- made of one cell, multicellularity had not yet evolved • Anaerobic- there was no oxygen gas yet on the planet • Heterotrophic- it is easier to eat something than create food internally (photosynthesis had not yet evolved) • Prokaryotic- no internal membranes and no nuclear envelope- these are complex structures that had not yet evolved.

  7. 2.5 billion years ago • 4. The evolution of photosynthesizing organisms caused oxygen to enter the atmosphere. • Oxygen in the upper atmosphere formed ozone, which filtered UV light. • The presence of oxygen also meant that most environments were unsuitable for anaerobic prokaryotes. • Photosynthetic cyanobacteria and aerobic bacteria multiplied as new metabolic pathways evolved.

  8. 1.5-2 billion years ago • 5. EndosymbiontRecruitment • Most likely the eukaryotic cell evolved from the prokaryotic cell, acquiring its organelles gradually. • Mitochondria and chloroplasts may once have been prokaryotes that started to live inside other cells (endosymbiosis)

  9. 1 billion years ago • 6. Sexual Reproduction • It is not exactly known when multicellularity began but the first multicelledcreatures were likely microscopic. • Sexual reproduction would have its origins here and would have been an important first step toward the development of complex macroscopic organisms.

  10. 438 million years ago • 7. The first land organisms were plants! • Before this point all life existed in bodies of water. • The arrival of plants on land helped to form the soil, create habitats, further change the atmosphere, and create a food source. • This changed the surface of the Earth and made it livable for animals.

  11. 248 million years ago • 8. Reptiles & Mammals • The first reptiles appeared about286 - 360 million years ago • The first dinosaurs and mammals appeared about 200 mya. • Placental mammals appeared about100 mya.

  12. 175-225 million years ago • 9. The Continental Drift Theory • continents are part of the Earth’s crust that moves due to the fluid mantle layer below. • About 225 mya, the continents were joined to form one supercontinent called Pangea which then divided into two subcontinents. • This separated species and allowed for different environments and further speciation (evolution of one species into other species) Continental drift explains why some coastlines are mirror images of each other

  13. 2 million years ago • 10. Monkey-like primates appeared about 30 mya. • The first hominids (the great ape family of primates) appeared 2 – 6 mya • Humans appeared about 2 mya.

  14. Life on Earth 2 BYA 4 BYA 5 BYA 3 BYA 1 BYA Present Day 500 MYA

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