Evolution connection: Photosynthesis II
Learning goals:
Students will understand that 1) consistency in the reactions of photosynthesis
across the tree of life is explained by inheritance from a common ancestor, and 2) C4
and CAM photosynthesis have evolved convergently many times.
For the instructor:
This short slide set explains uniformity and variation in the process of photosynthesis
across all life using evolutionary theory. To integrate it best, use these slides
immediately after you’ve discussed C4 and CAM carbon fixation. Alternatively, you
could incorporate your lecture material on the processes of C4 and CAM fixation into
this slide set. This slide set could be shortened, if you wish, by cutting slides 8, 10,
and 11.
Each of the following slides comes with a sample script for the instructor. To review
this script, download the PowerPoint file and view the Notes associated with each
slide.
Evolution Connection slideshows are provided by Understanding Evolution
(understandingevolution.org) and are copyright 2011 by The University of California
Museum of Paleontology, Berkeley, and the Regents of the University of California.
Feel free to use and modify this presentation for educational purposes.
Evolution connection: Photosynthesis II
“That’s a lot of reactions. How many sets of these chemical
reactions do we need to memorize?”
Not many. All plants use the same set of reactions (or slight variations
on these) to photosynthesize.
Why is that?
Pterosperma photo by David Patterson and Bob Andersen and licensed via Creative
Commons.Pediastrum photo by Luis Fernandez Garcia and licensed via Creative Commons.
Moss photo by Charles Webber © California Academy of Sciences. Fern photo by
Gerald and Buff Corsi © California Academy of Sciences. Douglas Fir photo © Br. Alfred
Evolution connection: Photosynthesis II
… because of common ancestry
Photosynthesis
begins to evolve
Evolution connection: Photosynthesis II
… and endosymbiosis
Photosynthesis
begins to evolve
Evolution connection: Photosynthesis II
… followed by diversification
Plants
Photosynthesis
begins to evolve
Evolution connection: Photosynthesis II
Because of common ancestry, the reactions of photosynthesis are
largely consistent across all plants. But there are a few variations on
the theme …
Cyanobacterium engulfed
by common ancestor of
green plants
Evolution connection: Photosynthesis II
C4 photosynthesis
CO2
high O2
concentration
PEP carboxylase fixes
carbon efficiently
C4
low O2
concentration
RUBISCO completes
photosynthesis
Corn photo by Doug Wilson/USDA
Evolution connection: Photosynthesis II
C4 photosynthesis involves specific adaptations
PEP carboxylase
mesophyll
cells
bundle-sheath
cells
anatomical
chemical
Cellular photo provided by Paul Schulte. PEP carboxylase image from Three-dimensional
structure of phosphoenolpyruvate carboxylase: A proposed mechanism for allosteric inhibition
PNAS 1999 96 (3) 823-828; doi:10.1073/pnas.96.3.823
Evolution connection: Photosynthesis II
C4 photosynthesis among the angiosperms
Phylogeny based on Sage, R. F. (2004). The evolution of C4 photosynthesis. New
Phytologist. 161: 341-370.
Evolution connection: Photosynthesis II
C4 photosynthesis leaf morphologies
Illustration adapted from Kadereit, G., Borsch, T., Weising, K., and Freitag, H. (2003).
Phylogeny of Amaranthaceae and Chenopodiaceae and the evolution of C4 photosynthesis.
International Journal of Plant Sciences. 164: 959-986.
Evolution connection: Photosynthesis II
PEP carboxylase for C4 photosynthesis
before duplication
after duplication
serves ancestral function
serves ancestral function
free to evolve a new function—
like C4 photosynthesis
Evolution connection: Photosynthesis II
CAM photosynthesis also evolved convergently
Pineapple photo by Enid Leff © California Academy of Sciences; aloe photo by Zoya Akulova
and licensed via Creative Commons; yucca photo by Robert Sivinski and licensed via Creative
Commons; cactus photo by Gary Monroe and licensed via Creative Commons.
Evolution connection: Photosynthesis II
Björn, L. O., and Govindjee. (2009). The evolution of photosynthesis and
chloroplasts. Current Science. 96: 1466-1474.
Kadereit, G., Borsch, T., Weising, K., and Freitag, H. (2003). Phylogeny of
Amaranthaceae and Chenopodiaceae and the evolution of C4 photosynthesis.
International Journal of Plant Sciences. 164: 959-986.
Sage, R. F. (2004). The evolution of C4 photosynthesis. New Phytologist. 161:
341-370.
Svensson, P., Bläsing, O. E., and Westhoff, P. (2003). Evolution of C4
phosphoenolpyruvate carboxylase. Archives of Biochemistry and Biophysics.
414: 180-188.