It is all driven by the Sun! Solar radiation is the primary energy source fuelling life on our planet. Photosynthesis underpins the primary production of the biosphere and sustains the vast majority of ecosystems, converting light into the chemical energy of organic matter.

In oxygenic photosynthesis, water serves as the electron donor, releasing molecular oxygen as a byproduct. The accumulation of oxygen roughly 2.4 billion years ago fundamentally transformed Earth’s atmosphere, driving the formation of the ozone layer and establishing the conditions necessary for life to colonize land.

Photosynthesis has played a monumental role in our daily lives. Coal, peat, petroleum, and natural gas are the fossilized remains of ancient flora and marine organisms accumulated over millions of years. Today, they serve as supplementary energy sources for humanity, powering the advancement of our civilization.

It is good to be children of the Sun! But what about those who live in perpetual darkness?

The Geological Footprint of Photosynthesis

Photosynthesis locks solar energy within organic matter. Over millions of years, this biomass transforms into various geological footprints of ancient life:

Wetland vegetation → Peat → Coal

Marine plankton and organic detritus → Petroleum and natural gas

Tree resin → Amber

Photosynthesis in the Ocean

Water absorbs light unevenly: red and orange wavelengths disappear near the surface, while blue light penetrates the deepest. To harvest the available spectrum, marine algae utilize specialized arrays of photosynthetic pigments:

Green Algae: Chlorophylls a and b, carotenoids

Brown Algae & Diatoms: Chlorophylls a and c, fucoxanthin

Red Algae: Chlorophyll a, phycobilins

Chloroplast vs. Cyanobacterium

Shared Characteristics:

• Double-membrane envelope
• Autonomous circular DNA
• Bacterial-type ribosomes
• Thylakoid/photosynthetic membranes

Distinct Identities:

• Chloroplast: An organelle of a eukaryotic cell.
• Cyanobacterium: An independent cell.

These similarities support the endosymbiotic theory, which states that chloroplasts evolved from ancestral cyanobacteria engulfed by a primitive eukaryotic cell.