Listen to Episode 145 on PodBean, YouTube, Spotify, or wherever you listen to your favorite podcasts!
We live in a solar-powered world. This episode, we discuss the process that provides the energy that every organism on the planet relies on, as well as the oxygen that characterizes the atmosphere that allows life as we know it to thrive: Photosynthesis.
In the news
These plesiosaurs seem to have frequented freshwater habitats
Evidence from inner ear bones suggests a late origin for mammal warm-bloodedness
It seems whale sharks are omnivorous
Bone-crushing dogs identified at the Gray Fossil Site
Photosynthesis is a chemical reaction that takes place in the cells of certain organisms. Broadly speaking, it’s pretty straightforward: photosynthesizers take in carbon dioxide and water from the environment and harness the energy of sunlight to convert those substances into sugars (food), releasing oxygen as a waste product.
If you happen to be an organism that eats food and breathes oxygen, you can see why photosynthesis is so important. It’s an incredible innovation of evolution that takes in energy from our cosmic companion (the sun) and makes it available to nearly every living thing on Earth.
There are, in fact, multiple flavors of photosynthesis. Oxygenic photosynthesis is the classic version, but anoxygenic photosynthesis, typically seen in certain bacteria, uses compounds other than water (such as hydrogen sulfide) and doesn’t produce oxygen. The most common version of oxygen photosynthesis is called C3 photosynthesis, named for the three-Carbon compounds important in the process, but there are other strategies: some plants, notably grasses, use C4 photosynthesis, a version that expends more energy for a more efficient metabolism; and others, notably plants in hot, dry habitats, use CAM photosynthesis, a strategy that allows them to take in gases at night and perform sun-powered reactions during the day.
Within the cells of photosynthesizers, the molecules responsible for harnessing light are pigment molecules, the most famous of which is chlorophyll, the same pigment that gives most photosynthesizers their characteristic green color. But not all photosynthesizers are green! Different colors can come from different pigments used for light-catching, or from other color-producing features in the same organism. In plants, most photosynthesis takes place in the chlorophyll-containing structures (chloroplasts) of the leaves.
The oldest evidence for photosynthesis is about the same age as the oldest evidence of life on Earth, nearly 4 billion years old. The earliest well-known fossils, structures called stromatolites, were formed by mats of photosynthesizing bacteria. This process is about as old as life itself.
The paleobiological record of photosynthesis (technical, open access)
If you enjoyed this topic and want more like it, check out these related episodes:
- Episode 57 – The Evolution of Flowering Plants (Angiosperms)
- Episode 38 – Grass
- Episode 135 – Seeds
- Episode 73 – Trees
We also invite you to follow us on Twitter, Facebook, or Instagram, buy merch at our Zazzle store, join our Discord server, or consider supporting us with a one-time PayPal donation or on Patreon to get bonus recordings and other goodies!
Please feel free to contact us with comments, questions, or topic suggestions, and to rate and review us on iTunes