Origin of life Biogenesis living organisms come from

Origin of life • Biogenesis – living organisms come from other living organisms. • Concept was proved by Francesco Redi’s experiment, 1668. • Flies come from flies. • Ie. Lay eggs which grow into maggots. • No spontaneous generation.

Big Bang Theory – our planet and solar system developed from a huge explosion. When – 4. 6 billion years ago.

Earth – 4. 6 Billion years ago. Surface covered with hot seas and hot molten rock. • Steam rises into atmosphere and forms huge clouds • Steam cools, condenses and falls to Earth in violent thunder storms. • On land, huge violent volcanoes erupt & release gases. •

Oparin’s Hypothesis (1936, Russian scientist) Alexander Oparin believed that life began spontaneously in the seas. • He proposed the following ideas based on ideas of early conditions on Earth. • 1. The early atmosphere & oceans contained ammonia (NH 3), water vapor (H 2 O), methane (CH 4) and hydrogen (H 2) gases. 2. Lightning, heat from the earth and UV light split these compounds into individual atoms of Carbon, Hydrogen, Oxygen and Nitrogen.

3. These atoms recombined to form small organic molecules. 4. Over time, these molecules accumulated into a primordial soup that could reproduce. 5. These molecules were the first life on Earth.

1953 – Stanley Miller & Harold Urey test Oparin’s hypothesis.

Findings of Miller Urey Expt. 1. Collected organic molecules after a few days. 2. Hypothesized that it took millions of years for cells to form from these organic molecules. 3. The first cells were called protocells. They are not true cells but do have a membrane and can grow and reproduce.

Prokaryotes • First true cells developed 3. 5 mya. • Do not have a nucleus. • No oxygen in atmosphere so most likely were heterotrophic. – fed off living organic compounds. • Known as archaebacteria • Photosynthesizing cells, cyanobacteria developed 3 mya. • Cyanobacteria is responsible for developing oxygen in the atmosphere.

Pasteur’s Experiment • Disproves spontaneous generation ideas.