Photosynthesis and It’s Role in Evolution By Jon Duval

Presentation Overview What is Photosynthesis The Actual Process ▫Light Dependent Reactions ▫Light Independent Reactions (Calvin Cycle) Evolution of Photosynthesis First Photosynthesis Impact on Earths Evolution ▫Formation of Earth ▫Earth’s Atmosphere

What is Photosynthesis Photosynthesis is the only significant solar energy storage process on Earth and is the source of all of our food and most of our energy resources.

Cont… used by autotrophic organisms converts light energy into chemical Carbon Dioxide and Water are synthesized into Carbohydrates (sugars) releasing Oxygen Energy supplied through photosynthesis provides energy needed for life to survive on earth. helps maintain atmospheric oxygen levels

The Actual Process Different for various species 2 main stages ▫Light dependent reactions ▫Light independent reactions (Calvin Cycle) Light energy absorbed by reaction centres ▫Proteins containing chlorophyll ▫Energy strips electrons from substances

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Chemical Formula Carbon Dioxide + Water -> Glucose + Oxygen

Cont. 4 smaller stages 1.Energy transfer in antenna chlorophyll 2.Electrons transferred in photochemical reactions 3.Electron transport chain and ATP synthesis 4.Export of stable products and carbon fixation

Light Dependent Reaction Photoreduction Capture light and store energy Light energy converted to chemical energy ▫ATP ▫NADPH They reduce CO2 into organic compounds

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Light Independent Reaction Calvin Cycle CO2 converted to glucose Occurs in stroma 3 main parts 1.Carbon fixation 2.Reduction reactions 3.Ribulose regeneration

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Evolution of Photosynthesis Much contorversy Oxygenic photosynthesis began early in earth’s history Not earliest metobolisms ▫Earliest are anoxygenic Stromatolites and microfossils present 3.5 billion years ago

Impact on Earth’s Evolution 3 living world domains ▫Archaea ▫Bacteria ▫Eukarya Photosynthesis only arose in bacteria

First Photosynthesis Only one photosystem originally Couldn’t oxidize water 3 main groups of extant photosynthesizing bacteria ▫Derived from same ancestral photosystem ▫Cyanobacteria ▫Green sulfur bacteria & heliobacteria ▫Purple bacteria & green nonsulfur bacteria

Impact on Formation of Earth First form of life to cause major impact Blue green algae created marine sediments Reduction of CO2 in atmosphere Began to produce O2 O2 molecules split by ultra violet light to create ozone UV sheild

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Sorces A Simpler Origin for Life by Robert Shapiro Evolution of Photosynthesis and its Environmental Impact by Lars Olof Bjorn The Evolution of the Earth by Claude J Allegre alchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/evolut ion_atm/&hl=en&gl=us&strip=1http://webcache.googleusercontent.com/search?q=cache:_Wy36iXKwysJ: alchange.umich.edu/globalchange1/current/lectures/Perry_Samson_lectures/evolut ion_atm/&hl=en&gl=us&strip=1